PWR secondary water chemistry guidelines in Japan - Purpose and technical background

This paper introduces the purpose, technical background and framework of preliminary secondary water chemistry guidelines for Japanese PWRs. Addition, the differences in bases of parameter settings between the Japanese and overseas guidelines are discussed.

Progress in Nuclear Energy 114 (2019) 121–137 Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene PWR secondary water chemistry guidelines in Japan - Purpose and technical background T Hirotaka Kawamuraa,∗, Yasuhiko Shodab, Takumi Terachic, Yosuke Katsumurad, Shunsuke Uchidae, Takayuki Mizunof, Yusa Muroyag, Yasuo Tsuzukih, Ryuji Umeharai, Hideo Hiranoj, Takao Nishimurab a Central Research Institute of Electric Power Industry, Japan Mitsubishi Heavy Industry, Ltd, Japan c Institute of Nuclear Safety System, Inc, Japan d University of Tokyo, Japan e Tohoku University, Japan f Mie University, Japan g Osaka University, Japan h Japan Nuclear Safety Institute, Japan i Japan Nuclear Safety Institute, Japan j Central Research Institute of Electric Power Industry, Japan b A R T I C LE I N FO A B S T R A C T Keywords: Guidelines PWR Secondary water chemistry System component integrity Steam generator Stress corrosion cracking Flow accelerated corrosion In the more than 40 years of operational history of pressurized water reactors (PWRs) in Japan, sustainable development of water chemistry technologies has resulted in the world's highest secondary system component integrity; additionally, secondary system components, especially steam generator (SG) tubing, with excellent material integrity have been developed to prevent leakage of radioactive contamination from the primary to the secondary system and to maintain the heat removal function of the secondary system Although reasonable control and diagnostic parameters for water chemistry are utilized by each PWR owner, the specific values are not shared To ensure reliable PWR operation and to achieve the highest safety level, relevant members of the Standards Committee and the related committee organized by the Atomic Energy Society of Japan (AESJ) decided to establish water chemistry guidelines for PWRs The Japanese PWR secondary water chemistry guidelines provide strategies for improving material integrity and the heat removal function The guidelines also provide reasonable “action levels” for control parameters and “control values” and “diagnostic values” for multiple parameters, and they stipulate the responses when these levels are exceeded Specifically, “conditioning parameters” are adopted in the guidelines Good operational practice conditions are also discussed with reference to long-term experience This paper introduces the purpose, technical background and framework of preliminary secondary water chemistry guidelines for Japanese PWRs Addition, the differences in bases of parameter settings between the Japanese and overseas guidelines are discussed Introduction To increase the safety and reliability for the operation of light watercooled nuclear power plants, careful and reliable water chemistry control is one of the key issues For this, plant water chemistry should be controlled by the water chemistry experts based on the suitable water chemistry guidelines There are many water chemistry guidelines ∗ prepared by many organizations, e.g., Electric Power Research Institute (EPRI) in US (Fruzzetti, 2004), Vereinigung der Groβkesselbesitzer (VGB) in Germany (Neder et al., 2006) and Électricité de France (EDF) in France (Odar and Nordmann, 2010) On the other hand, the major features of a plant's water chemistry depend on its' unique construction materials and operational histories This means that the water chemistry guidelines should include common Corresponding author E-mail address: kawamuh@criepi.denken.or.jp (H Kawamura) https://doi.org/10.1016/j.pnucene.2019.01.027 Received 28 October 2018; Received in revised form 20 December 2018; Accepted 25 January 2019 Available online 14 March 2019 0149-1970/ © 2019 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/) Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al features while ensuring the flexibility required for each plant In the Standard Committee of the Atomic Energy Society of Japan (AESJ), the water chemistry guidelines have been prepared Those for BWR water chemistry and PWR primary water chemistry are now in press Those target values and technical background have been introduced in the previous paper (Kawamura et al., 2016) The water chemistry guidelines for PWR secondary water chemistry is now on the final stage of editing processes, which will be published after public review One of the major objectives and roles of PWR secondary water chemistry control are to ensure the secondary coolant system components integrity, especially steam generator (SG) tubing, to prevent leakage of radioactive contamination from the primary to secondary systems and to maintain the heat transfer efficiency for steam generation In the PWR secondary coolant system, the structural materials contact with the secondary water under a high-temperature and high-pressure environments Degradation in the system component are due to corrosion affected by the following secondary water parameters, e.g., pH, conductivity, presence of impurities, and dissolved oxygen content Notably, if inappropriate water chemistry management occurs for a prolonged time, stress corrosion cracking (SCC) propagates through the wall of the SG tubes, and coolant with radioactive species may leak from the primary system to the secondary system in the SG and potentially leak out of the station Some of corrosion products might accumulate on heater tube surface, which results in decreasing heat transfer efficiency and then decreasing plant efficiency In addition, wall thinning of secondary coolant pipes caused by flow-accelerated corrosion (FAC) is an important safety issue for plant workers because wall thinning will cause possible large amount of steam leakage from the secondary coolant piping However, changes in water chemistry as a material corrosion control technique often result in change in the integrity of the various secondary system component materials due to different corrosion mechanisms Thus, the various issues must be solved harmoniously through a comprehensive understanding of the plant system Due to the complexity of the water chemistry, which affects several corrosion mechanisms of secondary system components, various sustainable developments and improvements in water chemistry technologies have been applied to commercial PWRs based on plant systems, material design and operational experiences to achieve high-reliability performance of secondary system components and highly effective heat-exchange performance Those backgrounds are also involved in the PWR secondary water chemistry guidelines “Control values”, “diagnostic values” and “action levels” for multiple parameters are also provided in the Japanese PWR secondary water chemistry guidelines The concept of these values are same as the Japanese PWR primary water chemistry guidelines (Kawamura et al., 2016) Specifically, the concept of a “conditioning parameter”, such as the hydrazine (N2H4) content and pH of the feed water, is adopted in the Japanese PWR secondary water chemistry guidelines These guidelines lead to the optimum water chemistry parameters and protocols for Japanese PWRs to assist in self-discipline and sustainable safety improvements and to provide strategies to improve material integrity and heat-exchange performance A further goal is to create more human resources for developing water chemistry experts, including those of the next generation This paper introduces the purpose, technical background and framework of the secondary water chemistry guidelines for Japanese PWRs Additionally, the differences and the bases of parameter settings between the Japanese and the EPRI and VGB guidelines (Fruzzetti, 2004), (Neder et al., 2006) are discussed supplemented with chemical additives To scavenge dissolved oxygen and maintain an adequate reducing condition in the secondary coolant system, hydrazine (N2H4) is added to the secondary water Ammonia or ethanol amine (ETA) is also injected into the coolant to maintain a suitable pH and increase the corrosion resistance of the secondary system components Recently, sophisticated chemical injection control has been carried out using multiple pH-control agents such as ETA, dimethylamine (DMA) and 3-Methoxypropylamine (MPA) in US PWRs to ensure the long-term integrity of the secondary system material However, Japanese PWR utilities emphasize reliability rather than efficiency, and therefore simple operation using single pH-control agents has been carried out Concurrent achievement of reliability and efficiency is targeted by eliminating copper-based alloys and adapting high pH operation 2.2 Objectives of water chemistry PWRs have experienced various corrosion problems, such as intergranular attack (IGA), SCC of nickel-based alloy tubing in the SG and stainless steel piping, and FAC of carbon steel To overcome these problems, it has been widely recognized that secondary water chemistry is very important for the safe and reliable operation of PWRs The primary objectives of PWR secondary water chemistry control are as follows: (1) To mitigate coolant-assisted corrosion and ensure the material integrity of the secondary system components (2) To maintain heat exchange performance 2.3 Necessity of water chemistry guidelines PWR secondary system management is charged with generating safe, reliable, and low-cost electric power Management is periodically faced with a choice of either keeping a unit available to generate power to meet short-term system demands or maintaining good control of chemistry to help ensure the long-term integrity of the secondary system components, and to improve power generation and balance-ofplant (BOP) Based on the PWR operational history of more than 40 years in Japan, Japanese PWR utilities have made huge efforts to maintain reactor and component integrity and improve power generation as well as to pursue corrosion risk reduction Japanese PWR utilities have voluntarily implemented secondary water chemistry precautions to obtain the highest reliability In the implementation process, secondary water chemistry experts have discussed the operating rules for PWR secondary water chemistries based on state-of-the-art scientific understanding as well as the field experiences of Japanese PWRs To ensure secondary system safety, assurance of the material integrity of the secondary system components, particularly, the SG tubing integrity, to prevent radioactive contamination from the primary to secondary leakage and to maintain the heat-removal function of the primary system are related strongly to the nuclear safety principles of “confining sources of radiation risks” and “protecting people and the environment from radiation” Pipe wall thinning control is related to labor safety principles Both sets of principles are important to the operation of PWRs from the viewpoint of safety and reliability Therefore, to ensure nuclear safety, continuous integrity of the secondary system component material based on appropriate water chemistry control techniques is required However, changes in the water chemistry as a material corrosion control technique should be performed to maintain the integrity of the various different secondary system component materials, which have different corrosion mechanisms Thus, the various issues must be solved PWR secondary water chemistry guidelines 2.1 PWR secondary coolant The secondary water in the PWR is an alkaline solution 122 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al controlled water chemistry and should be factors that are likely to affect the corrosion performance of secondary system materials ● The concentrations of impurities, iron and copper in secondary water should be kept to practical and achievable minimum levels ● All action levels should be consistent with the technical specifications of the plant, and should be based on quantitative information about the effects of the water chemistry on the corrosion behavior of components In the absence of quantitative data, prudent and achievable action level values should be determined by expert consensus harmoniously through a comprehensive understanding of the plant system Standardized water chemical guidelines from the viewpoints of secondary system safety and reliability have not yet been established In the guideline establishment process, it is important that experts in the nuclear safety, plant life management (PLM) and water chemistry fields share information and discuss the guidelines to ensure consistency with each other's knowledge and thereby ensure PWR secondary system safety, maintenance of coolant system component integrity, and highpower-generation effectiveness The goal should be to extend the operating life of the secondary system components and maintain heat exchange performance while providing an acceptable level of unit availability Water chemistry parameters in the start-up and shutdown processes are also defined in the guidelines in addition to power operation because the secondary system component integrity and heat exchange improvement are influenced by the deposition and release of corrosion products which are affected by changes in coolant temperature and reactor pressure 2.4 Guideline definitions and philosophy The objectives of the secondary water chemistry guidelines are to simultaneously assure the material integrity of the secondary system components and improve the heat-exchange performance To achieve these objectives, suppressing material corrosion in the secondary system and reducing corrosion product release and deposition on the SG tubes are key issues The AESJ PWR Secondary Water Chemistry Guidelines are applicable only to the recirculating SG and cover the secondary coolant system and make-up water system Fig shows the targets of the PWR secondary water chemical system in the guidelines Similar definitions are used for the chemistry parameters in all systems The parameters can be categorized as control, conditioning, and diagnostic parameters, and they are set for all PWR operation modes The following framework was used to establish the parameters 2.4.1 Plant status of PWR With respect to the water chemistry parameters, these guidelines define the plant status in the four operating modes shown in Table 1, and they consider the thermal and hydraulic conditions and their effects on the chemical environment Typical plant status modes and operations in Japanese PWRs are shown in Fig 2.4.2 Concept of control, conditioning and diagnostic parameters As mentioned above, the key purpose of the secondary water chemistry is the elimination of impurities except for chemical additives to reduce corrosion product and to ensure secondary coolant system component integrity Fig shows an example of the concept of control, conditioning and diagnostic parameters for the SG blowdown water and feed water and at the outlet of condensate water during power operation according to the PWR secondary water chemistry guidelines The concept of control, conditioning and diagnostic parameter definitions are the same as that in the PWR primary water chemistry guidelines (Kawamura et al., ● Each control parameter has three action levels that are defined to ensure the long-term integrity of the secondary system materials ● The conditioning parameter is defined by the hydrazine (N2H4) content and pH of the feed water ● The diagnostic parameters are defined to complement the overall Fig Targets of the PWR secondary water chemical system in the guidelines 123 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Operational status modes in a PWR secondary coolant system Plant Status Reactor Condition Remarks Start-up Power Operation Shutdown Outage/Wet Layup (Clean-up) Critical to power operation Reactor critical Power descent to shutdown Shutdown to coolant temperature < 100 °C Covers the period of increasing pressure before power operation Covers the period from power up to the beginning of the shutdown process Covers the period from power descent to heat removal using an SG Covers the period from shutdown to start-up Purification of the feed water and condensate water systems and deaeration before start-up are also included in this period chemistry guidelines (Kawamura et al., 2016) When the water chemistry parameters deviate from the action levels, water chemistry experts should ensure that the optimal water chemical conditions are recovered within the set time Requirements for the action levels are the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 2016) In the guidelines, the ideas of recovering from deviations in the control parameters are the same to ensure secondary coolant system component integrity and to improve heat-exchange performance 2.4.3 Control parameters The control parameters are selected to ensure that overall water chemistry allows optimal plant operation, and the parameters are the water quality limits for ensuring the long-term reliability of the materials In addition, the control parameters are selected based on their importance according to the state-of-the-art scientific understanding and extensive Japanese PWR field experience Moreover, the parameters are selected based on the availability of detection methods that are reliable, sensitive and accurate when used in PWR secondary systems When the water quality is outside the safe limits, suitable countermeasures should be taken to maintain plant system reliability For the control parameters, the following values are defined (2) Recovering from Action Levels and Requirements The basic concept of recovering from the secondary water chemical deviations is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) If it is foreseeable that the values will go down immediately within Action Level by a power descent, then the operating status can be continued 2.4.4 Conditioning parameters Conditioning parameters are key parameters associated with chemical additives, such as the pH and N2H4 used to maintain appropriate feed water quality Conditioning parameters are not stipulated in the EPRI and VGB guidelines (Fruzzetti, 2004), (Neder et al., 2006) (1) Action Levels Three action levels are defined as the chemical conditions that require immediate evaluation and corrective actions The definitions of the action levels are the same as that in the PWR primary water Fig Typical plant status conditions and operations for Japanese PWR secondary systems 124 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Fig Example of the concept of control, conditioning and diagnostic parameters in the PWR secondary water chemistry guidelines Action levels and are not stipulated for pH because the direct effect of protons in the secondary coolant has not been clarified When the pH does not recover from action level 2, impurities must be identified, and remedial action should be taken The monitoring frequency is weekly because the pH depends on the feed water pH, which is checked daily, as shown in Table The secondary coolant properties can affect intergranular attack and stress corrosion cracking (IGA/SCC) and pitting corrosion in the presence of small amounts of oxygen and/or oxidant IGA/SCC has appeared on the secondary side of nickel-based alloys within SG tubes/ tube support plate (TSP) crevices and SG tubes/tube sheets (TS) because sodium and sulfate ions (Na+ and SO42−) are concentrated in the crevices (Tsuruta et al., 1995), (Shoda et al., 1996), (Kawamura and Hirano, 2000) The impurities are slightly dissolved in the secondary coolant due to ion exchange resin degradation in the condensate polisher Sodium and chloride can also be present in the secondary coolant due to sea water ingress from a leaking condenser tube Chloride can form acid chlorides in crevices, and acid chlorides may be a major factor in the denting of SG tubes and pitting corrosion on ferric materials (EPRI, 1983a), (EPRI, 1982), (Von Nieda et al., 1980) The presence of oxidants can promote the formation of acidic conditions in crevices Thus, the sodium, sulfate, and chloride concentrations are stipulated as control parameters because they are harmful species that adversely affect the long-term integrity of the nickel-based alloys used for SG tubes and other structural materials According to the crevice calculation code provided by Mitsubishi Heavy Industry, the relationship between the pH300C and sodium concentration for crevice concentration factors of (a) 107 and (b) 105 at a simulated SG tube support plate crevice is shown in Fig The sodium concentrations are μg/L and 50 μg/L for concentration factors of 107 and 105, respectively, at a drilled-type and a broached egg crate (BEC)type TSP crevice with pH300C = 10, respectively Based on Figs and 6, action levels and for sodium are set to > μg/L (> ppb) and > 50 μg/L (> 50 ppb), respectively Action level is set to > 300 μg/L (> 30 ppb) for concentration factors of 105 at a BEC-type TSP crevice with pH300C = 10.5, which was calculated considering thermally treated alloy 600 (alloy TT600) Even if condenser leakage occurs, the feed water can be demineralized within 24 h after sodium detection using a condensate demineralizer system On the other hand, sodium contamination has been caused by human error during chemical 2.4.5 Diagnostic parameters The concept of diagnostic parameters is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 2.4.6 Recommended values The concept of recommended values is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 2.4.7 Monitoring frequency The concept of monitoring frequency is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 2.5 Example of PWR secondary water chemistry guideline values and settings for control parameters and recommendations As mentioned previously in the paper, action level and recommended values are defined for self-disciplined safety improvement In this section, some examples of action levels and recommended values are shown for PWR power operation 2.5.1 SG blowdown water during power operations Table shows the control and diagnostic parameters and recommended values for SG blowdown water during power operations pH can be a harmful parameter that adversely affects the long-term integrity of secondary system components via general corrosion and FAC of the carbon steel used for the SG support plates, feed water systems, and bleeding and drain lines, and corrosion product release and deposition due to material corrosion in the secondary system Ammonia attack of condenser tubes made of copper alloy has been observed Fig shows SCC initiation mapping for SG tubing made of alloys MA600 (mill-anneled alloy 600), TT600 (thermally treated alloy 600), and TT690 (Yashima, 1995) SCC initiates at pH300C < or pH300C > 10 Fig shows an example of the effect of pH on magnetite (Fe3O4) dissolution Fe3O4 easily forms on the surface of carbon steel and stainless steel under the reducing conditions present in a PWR secondary system The dissolution of Fe3O4 increases at pH < 9.8 at 25 °C, as shown in Fig Based on the data, action level for pH is set to < at 25 °C, as shown in Table The pH represents the balance between the anion and cation concentrations in the secondary coolant 125 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Control and diagnostic parameters for SG blowdown water during power operations in the Japanese, EPRI, and VGB guidelines Period Parameters Japanese Guideline EPRI Guideline (Fruzzetti, 2004) VGB Guideline (Neder et al., 2006) Start-up to 100% Reactor Power > 30% Reactor Power 100% Reactor Power Action Levels pH at 25 °C Cation Conductivity, mS/m (μS/cm) Sodium, μg/L Sulfate, μg/L Chloride, μg/L Level Value 3 3 – 5b > 50b,c > 300b > 10 > 100b,e – > 10 > 100 Recom-mended value Frequency – Weekly – – ≤1 Dailyd ≤2 Dailyf ≤2 Dailyd Action Levels Level Value 3 3 – – – – >1 >4 >5 > 50 > 250 > 10 > 50 > 250 > 10 > 50 > 250 – – – Frequency Action Levels Level Value – Normal operating values: < 9.5 Continuous >1 >2 >7 > 50 > 100 > 500 Normal operating values: < 10 Continuous Daily Daily Normal operating values: < 10 – b > 2000 b Total Radioactivity, Bq/cm 3 – – – – Monthly g – – – Note a In Japanese PWRs, Na, SO4 and Cl concentrations in SG secondary water should be monitored instead of cation conductivity because cation conductivity reflects the sum of the effects of impurities b These values are defined based on experimental corrosion data c When the value is over action level 2, the cause should be sea water ingress If ingress can be detected and the leakage line can be isolated, the polluted secondary water can be cleaned up by condensate demineralizer within 24 h d Continuous monitoring should be recommended if a continuous monitoring system is implemented Ion chromatography is semicontinuous monitoring and an optional analysis method The frequency should be increased if evidence of sea water ingress is noted e Action level of sulfate is treated in the same manner as for chloride f Continuous monitoring should be recommended if a continuous monitoring system is implemented Ion chromatography is semicontinuous monitoring and an optional analysis method g Continuous monitoring should be adopted if using an SG blowdown water monitor dependent on the feed water pH and conductivity, as shown in Table Additionally, to check the water quality trend, continuous monitoring should be recommended if an on-line monitoring system is implemented The frequency should be increased if sea water ingress into the secondary system is noted According to the crevice calculation code provided by Mitsubishi Heavy Industry, the relationship between pHt and sulfate concentration for 105 as a concentration factor at a simulated SG tube support plate crevice is shown in Fig As shown in the figure, the sulfate concentration is 120 μg/L (120 ppb) for a concentration factor of 105 at crevice pH300C = The maximum concentration factor of sulfate is estimated to be 105 in the test solution with sulfuric acid (Tsuruta et al., 1995), (Shoda et al., 1996), (Kawamura and Hirano, 2000) Based on Figs and 7, action level for sulfate is set to > 100 μg/L (> 100 ppb) Action level is set to 1/10 of action level 2, i.e > 10 μg/L (> 10 ppb) Action level for sulfate is not stipulated because the effect of sulfate on SG material corrosion is not clear When sulfate does not recover from action level 2, it is necessary to identify the impurities, and take appropriate remedial actions The recommended value for sulfate is ≤ μg/L (≤2 ppb) because there are no data showing an adverse effect on coolant system component integrity at this level The monitoring frequency of sulfate is daily for the same reason as for sodium Fig shows the effect of chloride on the corrosion rate of alloy 600 using a boiling heat transfer test loop In Japanese PWRs (Atomic Energy soceity Of Japan, 2000), pitting corrosion cannot easily occur because the SG secondary side is maintained under reducing conditions Even if some oxidants are present in the SG secondary side, the effect of Fig SCC initiation region for SG tubing (Yashima, 1995) additive injection, leading to a rapid increase in the sodium concentration in the SG blowdown water and plant shutdown in some overseas PWRs Large amounts of sea water leakage can be detected by a salt detector When the sodium concentration does not recover from action level 2, appropriate remedial actions should be taken The recommended values for sodium are ≤1 μg/L (≤1 ppb) because data not show an adverse effect on the coolant system component integrity at this level The monitoring frequency is daily because sodium is 126 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Fig Relationship between the Fe ion concentration and pH (JIS B 8223: 2015) necessary to identify the impurities and take remedial action The recommended values for chloride are ≤2 μg/L (≤2 ppb) because there are no data showing an adverse effect on the coolant system component integrity at this level The monitoring frequency of chloride is daily for the same reason as for sodium Total radioactivity is an important parameter and can be used as an index to check primary coolant leakage The total radioactivity is chloride ions on alloy 600 corrosion is very small with a maximum chloride level of 0.1 mg/L (0.1 ppm) On the other hand, the possibility of pitting corrosion increases for chloride levels over mg/L, as shown in Fig Based on the test results, action levels and are set to > 100 μg/L (> 100 ppb) and > 2000 μg/L (> 2000 ppb), respectively Action level is set to 1/10 of action level 2, i.e., > 10 μg/L (> 10 ppb) When chloride does not recover from action level 2, it is Table Control and diagnostic parameters for feed water during power operations in the Japanese, EPRI and VGB guidelines Period Parameters Japanese Guideline EPRI Guideline (Fruzzetti, 2004) VGB Guideline (Neder et al., 2006) Start-up to 100% Reactor Power > 30% Reactor Power 100% Reactor Power Action Levels Level Hydrazine, μg/L Dissolved Oxygen, μg/L Copper, μg/L Lead, μg/L pH control agent, mg/L Conductivity, mS/m (μS/cm) Iron, μg/L Dispersant, μg/Li 3 3 3 3 Recom-mended value Frequency Action Levels Value < 50 – – – >5 – > 1c – – > 10 – – – – – – – – – – – – – – – Daily – Weeklyb – Weekly – Monthlyd Plant-specifice Appropriate a f Plant-specifice Dailya ≤5h Weekly – – Level Value 3 3 3 3 < 8xCDP [O2] or < 20 – – >5 > 10 – >1 – – – – – Plant-specific – – – – – >5 – – Plant-specific – – Frequency Action Levels Level Value Continuous Normal operating values: > 20 Continuous 3 3 Normal operating > 1.5 (> 15)g >5 > 20 > 100 – – – – – – < 9.8 – – values 3 – – – – – – Weekly – Daily – Weekly Daily – – Note a Continuous monitoring should be recommended Inlet water monitoring at a deaerator is an alternative analysis method b Weekly monitoring is enough to detect the water quality changes because the vacuum in the condenser, the temperature of the deaerator, Do in the condenser pump, and the hydrazine concentration at the outlet of the high-pressure feed water heater are monitored daily c If copper alloys are used in the secondary system, such as condenser tubes d Lead material is not used in Japanese PWR systems, although it is known to be the cause of PbSCC e Plant-specific administrative limits should be established Values are defined based on the plant design, component material and water chemistry f Required as appropriate during power operation g Cation conductivity is set to > 0.2 μS/cm in the VGB guidelines h Value is defined based on the plant design, component material and water chemistry i Dispersant is not employed in Japanese PWRs 127 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Conditioning parameters for feed water during power operations Conditioning Parameters pH at 25 °C Hydrazine, μg/L Conditioning Value a Plant-specific Plant-specificb Frequency Dailyb Dailyb Note a Plant-specific administrative limits should be established Values are defined based on the plant design, component material and water chemistry b Continuous monitoring should be recommended Inlet water monitoring at the deaerator is an alternative analysis Fig Relationship between the corrosion rate of alloy 600 and the Cl concentration (Atomic Energy Society of Japan, 2000) recommended if using an SG blowdown water monitor Table also shows the control and diagnostic parameters for SG blowdown water during power operation in the EPRI (Fruzzetti, 2004) and VGB guidelines (Neder et al., 2006) The pH is not stipulated within control parameters in the EPRI guidelines and is stipulated as normal operating values, i.e < 9.5, in the VGB guidelines because multiple pH control agents such as ETA, dimethylamine (DMA) and 3-methoxypropylamine (MPA) are employed in US and EU PWRs In these guidelines, the cation conductivity should be stipulated as the control parameter instead of pH monitoring and monitored continuously In Japanese PWRs, on the other hand, cation conductivity is not stipulated as a control and/or diagnostic parameter, and action level for pH is stipulated based on the SCC initiation mapping for the nickel-based alloy (Fig 4) and the effect of pH on Fe3O4 dissolution (Fig 5) When the pH is over action level 2, the cause should be sea water ingress and impurities in the chemical additives because sea water is used as the condenser coolant in all Japanese PWRs pH monitoring is also categorized in the Japanese guidelines to check for the ingress of impurities other than sodium, sulfate and chloride into the secondary coolant Ingress can be detected using a salt detector at the condensate hot well When sea water leaks into the secondary coolant system from the condenser tube, the leakage line should be isolated and the polluted secondary water should be cleaned up using condensate demineralizer within 24 h In the VGB guidelines, the sodium concentration was stipulated as the control parameter, and both sulfate and chloride in SG secondary water were set as normal operating values, i.e., < 10 μg/L (< 10 ppb) On the other hand, in the EPRI and Japanese guidelines, the impurity concentrations should be monitored separately, i.e., sodium, sulfate and chloride, instead of cation conductivity because cation conductivity reflects the sum of the effects of the impurities, and it is difficult to separate the effects of each impurity In the EPRI guidelines, the action levels of sodium, sulfate and chloride are stipulated based on the field experience in US PWRs In the Japanese guidelines, the action levels of sodium and chloride are larger than those in the EPRI guidelines, but they are defined based on many kinds of experimental corrosion data (Figs 4, 5, 7, and 8) The Japanese guidelines stipulate daily checking frequencies for sodium, sulfate and chloride for SG blowdown water, and continuous monitoring should be recommended using some kinds of semicontinuous monitoring, such as ion chromatography and optional analysis The monitoring frequency should be increased if evidence of sea water ingress is noted In the Japanese guidelines, the total radioactivity is stipulated as a diagnostic parameter and should be monitored continuously using the Fig Relationship between the pH300C and Na concentration for concentration factors of (a) 107 and (b) 105 at a simulated SG tube support plate crevice Fig Relationship between the pHt and SO4 concentration in a NaOH solution for a 10−5 mist carry-over rate at a simulated BEC-type tube support plate crevice stipulated as a diagnostic parameter because it does not affect secondary system material integrity The monitoring frequency is monthly for the same reason However, continuous monitoring should be 128 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Fig Effect of hydrazine on the corrosion potential of alloy 600 (Fruzzetti, 2000) SG blowdown water monitor In the EPRI and VGB guidelines, the total radioactivity is not stipulated within the control parameters and/or diagnostic parameters 2.5.2 Feed water during power operations Table shows the control and diagnostic parameters and recommended values for the feed water during power operations The water is sampled at the outlet of a high-pressure feed water heater Hydrazine is stipulated as a control parameter because hydrazine is injected into the PWR secondary coolant as an oxygen scavenger to reduce oxygen levels in the secondary coolant and to suppress SG tube corrosion Fig shows the effect of hydrazine on the corrosion potential (electrochemical corrosion potential, ECP) of alloy 600 (Fruzzetti, 2000) Based on the data, action level is set to < 50 μg/L (< 50 ppb) because this value is the limit to suppress oxidant formation in the secondary system Action levels and and recommended values are not stipulated The monitoring frequency is daily because reducing conditions should be maintained during power operation Continuous monitoring should be recommended if an on-line monitoring system is implemented Inlet water monitoring at the deaerator can be an alternative analysis method The dissolved oxygen (DO) content is set as a control parameter because it is a harmful parameter that adversely affects IGA/SCC and pitting and crevice corrosion of SG tubes by increasing the corrosion potential of nickel-based alloys, as shown in Fig 10 (Kishida et al., 1987) Action level is set to > μg/L (> ppb) because this concentration is the monitoring limit of the implemented continuous monitoring system Action levels and and the recommended values are not stipulated The monitoring frequency is weekly to check the reducing conditions Continuous monitoring should be recommended if an on-line monitoring system is implemented The copper concentration is also stipulated as a control parameter because copper ions and copper oxide increase the ECP of carbon steel, stainless steel, and nickel-based alloys as oxidants, and copper is a harmful species that adversely affects the long-term integrity of these materials Based on test results (Kishida et al., 1987) and Japanese PWR operating experiences, action level is set to > μg/L (> ppb) The value may be stipulated if copper alloys are implemented in the secondary system Action levels and and recommended values are not stipulated The monitoring frequency is weekly because the concentration changes in copper are very small during power operation Continuous monitoring should be recommended if an on-line monitoring system is implemented A control parameter for lead is also stipulated to monitor contamination in the SG even though lead-induced SCC (PbSCC) has not been experienced and lead materials are not installed in Japanese Fig 10 Effect of oxidant on the ECP of alloy 600 (Kishida et al., 1987) PWRs On the other hand, PbSCC has been experienced in some overseas PWRs due to lead shielding blocks left in the secondary system after a refueling outage Experimental data for PbSCC indicate that lead levels should be as low as possible (Takamatsu et al., 1997), (Staehle, 2005), (Fruzzetti, 2006a), (Fruzzetti, 2006b) However, the effect of lead on the SCC has not been clarified The lead level should be recommended to be as low as possible Fig 11 shows the effect of lead on SCC of nickel-based alloys (Staehle, 2005) A lead concentration < 0.1 mg/L (< 0.1 ppm) is not harmful for PbSCC In an SG crevice, the concentration factor of lead is estimated to be for 1% of the SG blowdown rate in a commercial Japanese PWR In the guidelines, the concentration factor is set to 10 as a conservative estimate Based on this knowledge, action level is set to > 10 μg/L (> 10 ppb) Action levels and and recommended values are not stipulated The monitoring frequency is monthly because the dominant changes in lead concentration are caused by leaving lead shielding blocks in place after periodic inspections The lead concentration in the feed water should be checked when the NH3 chemical additive is changed to another manufacturing lot because lead may be present in the additive The concentration of a pH control agent such as ammonia (NH3) or ethanol amine (ETA) is stipulated as a diagnostic parameter because an 129 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Fig 11 Effect of lead on the SCC of a nickel-based alloy (Staehle, 2005) guidelines Lead is not stipulated as a control parameter in the EPRI and VGB guidelines because the lower limit of the lead concentration that affects the PbSCC of nickel-based alloys has not been clarified Lead is not included as an additive in any materials in Japanese PWR systems However, a negligible amount of lead may be included in the NH3 chemical additive when the additive is changed to another manufacturing lot The pH control agent is stipulated as a control parameter in the EPRI and VGB guidelines to check the concentration of the injected pH control agent In the Japanese guidelines, on the other hand, the pH control agent is stipulated as diagnostic parameter because the pH control agent should be selected according to the plant design, component material and water chemistry Conductivity is not stipulated as a control and/or diagnostic parameter in the EPRI guidelines In the VGB guidelines, on the other hand, conductivity is stipulated as a control parameter to check the concentration of the injected pH control agent In the Japanese guidelines, conductivity is stipulated as a diagnostic parameter to monitor the concentration of the injected pH control agent Iron is stipulated as a control parameter in the EPRI guidelines to check the iron concentration In the Japanese guidelines, on the other hand, iron is stipulated as a diagnostic parameter because the value is defined based on the plant design, component material and water chemistry, and the recommended value, i.e., ≤5 μg/L (< ppb), is the same as in the EPRI guidelines In the VGB guidelines, iron is not stipulated as a control and/or diagnostic parameter The dispersant is stipulated as a control parameter in the EPRI guidelines because the dispersant is employed in US PWRs In the Japanese guidelines, on the other hand, the dispersant is not stipulated as a diagnostic parameter because dispersant is not employed in Japanese PWRs The conditioning parameters in these guidelines are original and are not stipulated in the EPRI and VGB guidelines The pH and hydrazine concentration are stipulated as conditioning parameters because they are additives in the secondary coolant and should be controlled based on the plant design, component material and water chemistry Table shows the conditioning parameters for the feed water during power operations pH is a parameter that adversely affects the general corrosion and FAC of the carbon steel used for the feed water system and bleeding and adequate concentration is needed in the feed water The pH control agent should be selected according to the plant design, component material and water chemistry The recommended value should also be defined as a plant-specific administrative limit based on the plant design, component material and water chemistry The monitoring frequency should be appropriate to check the concentration of the pH control agent injected into the secondary coolant during power operation Conductivity is stipulated as a diagnostic parameter to monitor the concentration of the injected pH control agent The recommended value should be defined as a plant-specific administrative limit according to the plant design, component material and water chemistry The monitoring frequency is daily to check the concentration of the pH control agent injected into the secondary coolant Continuous monitoring should be recommended at the inlet of the deaerator Inlet water monitoring at the deaerator is an alternative analysis method Iron oxide affects the heat transfer of SG tubes via scale adhesion on the tube surface and scale blockage within the TSP crevice A diagnostic parameter for iron is stipulated to suppress the above phenomenon The recommended value is set to ≤5 μg/L (< ppb), and the value is defined based on the plant design, component material and water chemistry The monitoring frequency is weekly to check the iron concentration in the feed water Table also shows the control and diagnostic parameters for the feed water during power operation in the EPRI (Fruzzetti, 2004) and VGB guidelines (Neder et al., 2006) Hydrazine is stipulated as a control parameter in the EPRI and Japanese guidelines However, action level for hydrazine is higher in the Japanese guidelines than in the EPRI guidelines because < 50 μg/L (< 50 ppb) is the limit to suppress oxidant formation in the secondary system In the EPRI guidelines, action level for hydrazine is set to maintain reducing conditions and to maintain hydrazine at greater than eight times the condensate dissolved oxygen in the condensate polisher demineralizer (CDP) or 20 μg/L (< 20 ppb) The value is set based on field experience in US PWRs On the other hand, hydrazine is stipulated as normal operating values, i.e., > 20 μg/L (< 20 ppb), in the VGB guidelines Action level for DO in the Japanese guidelines is set to > μg/L (> ppb) and is more conservative than in the EPRI and VGB guidelines Action level for copper is the same value in the EPRI and Japanese 130 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Control and diagnostic parameters for condensate water during power operations in the Japanese, EPRI and VGB guidelines Period Parameters Japanese Guideline EPRI Guideline (Fruzzetti, 2004) VGB Guideline (Neder et al., 2006) Start-up to 100% Reactor Power > 30% Reactor Power 100% Reactor Power Action Levels Level Cation Conductivity, mS/m (μS/cm)a Recom-mended value Frequency Value > 0.03 (> 0.3) – Continuousc Action Levels Level Value – – 3 – – – – > 10 > 30 – Frequency Normal operating values – < 0.02 (< 0.2) – – Continuous – – < 0.02 b > 0.05 (> 0.5) b Sodium, μg/La,b Dissolved Oxygen, μg/Ld 3 – > 10 > 20 – – – – – Continuousc – Daily Note a At least one of the parameters should be selected based on the implemented monitors in each plant b If sodium is monitored continuously, sodium should be > 10 μg/L at action level and > 20 μg/L at action level c Continuous monitoring should be recommended During monitoring sensor maintenance, a salt detector at the condensate hot well or manual analysis should be used as an optional analysis method d In the EPRI guidelines, dissolved oxygen in condensate water is monitored adequately during < 5% reactor power operation It is a diagnostic parameter if copper alloys are not implemented in the secondary system monitoring for cation conductivity should be adopted Sodium is monitored continuously if a salt detector is implemented During monitoring sensor outage for maintenance, a salt detector at the condensate hot well or manual analysis should be used as an optional analysis method Dissolved oxygen (DO) is stipulated as a diagnostic parameter because the DO monitor is effective for checking air in-leakage at the vacuum area in the condenser The recommended value is not stipulated, as shown in Table However, to maintain an appropriate level of DO in the condensate water, a recommended value should be considered if copper alloys are implemented in the vacuum area of the condenser and/or low-pressure feed water heaters The monitoring frequency is daily to check for air leakage into the secondary system Table shows a comparison of the diagnostic parameters for condensate water during power operations in the Japanese and EPRI guidelines Cation conductivity is not stipulated as a control and/or diagnostic parameter in the EPRI guidelines and is stipulated as normal operating values, i.e., < 0.02 mS/m, in the VGB guidelines In Japanese PWRs, on the other hand, cation conductivity and sodium are stipulated as control parameters, to detect sea water leakage and flow to the SG DO is stipulated as a control parameter in the EPRI guidelines and as normal operating values, i.e., < 0.02 μg/L (< 0.02 ppb), in the VGB guidelines In Japanese PWRs, on the other hand, DO is stipulated as a diagnostic parameter to monitor the water sampled at the outlet of a high-pressure feed water heater and to check air leakage into the secondary system drain lines The pH adversely affects ammonia attack on the condenser tube if copper alloy is implemented Hydrazine should be controlled to reduce the condensate and SG blowdown system polisher loads and to maintain the SG heat-transfer effectiveness The pH and hydrazine concentration are monitored at the outlet of a high-temperature feed water heater The monitoring frequencies for pH and hydrazine are daily because the pH is an important index of adequate injection of chemical additives and hydrazine is injected to maintain reducing conditions during power operation Continuous monitoring is preferable if an on-line monitoring system is installed Inlet water monitoring at a deaerator can be an alternative analysis method 2.5.3 Condensate water during power operations Table shows the control and diagnostic parameters and recommended values for condensate water during power operations The water is sampled at the outlet of the condensate pump Cation conductivity is affected by sea water leaking from the condenser tube The cation conductivity is set as a control parameter because SCC and pitting corrosion may be caused by a large amount of sea water leakage and flow into the SG In this case, the ruptured tube should be plugged and in extreme cases, power descent may be needed Action levels and are set to > 0.03 and > 0.05 mS/m, respectively, and 0.03 mS/m corresponds to the detection limit for changes in cation conductivity The value 0.05 mS/m corresponds to the sum of 0.03 mS/m and the maximum increase in cation conductivity of 0.02 mS/m caused by organic acid formation under high pH operation conditions with ETA Cation conductivity is also affected by the sodium chloride concentration in the feed water Therefore, for continuous sodium monitoring, the sodium concentration should be > 10 μg/L (> 10 ppb) at action level and > 20 μg/L (> 20 ppb) at action level Action level for the cation conductivity and sodium concentration are not stipulated because the cation conductivity includes the effect of dissolved carbon dioxide and impurity contamination in the condensate water, and the effect of contamination is difficult to eliminate When the cation conductivity or sodium concentration does not recover from action level 2, the impurities must be identified, and remedial action should be taken The recommended values for cation conductivity are not stipulated because data not show an adverse effect on the coolant system component integrity at this level Continuous 2.5.4 Make-up water during power operations Table shows the diagnostic parameters and recommended values for make-up water in the storage tank during power operations The make-up water is sampled from the storage tank Conductivity is stipulated as a diagnostic parameter because water purification in the make-up water treatment system is maintained by controlling the make-up water The possibility of exceeding the range of conductivity may be very small when the purification of make-up water is controlled adequately The recommended value is set to ≤0.1 mS/m based on the effect of dissolved carbon dioxide (CO2) The monitoring frequency is monthly because the possibility of exceeding the 131 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Diagnostic parameters and recommended values for make-up water at the storage tank during power operations Period Japanese Guideline EPRI Guideline (Fruzzetti, 2004) VGB Guideline (Neder et al., 2006) Start-up to 100% Reactor Power > 30% Reactor Power 100% Reactor Power Parameters Recommended Values Frequency Recommended Values Normal operating values Conductivity, mS/m (μS/cm) Sodium, μg/L Sulfate, μg/L Chloride, μg/L Dissolved Oxygen, μg/L ≤0.1 (≤1) ≤5 ≤10 ≤10 – Monthly Monthly Monthly Monthly – – – – – – – – – – – 2.5.5 Condensate demineralized water during power operations Table shows the control and diagnostic parameters and recommended values for condensed demineralized water during power operations The water is sampled at the outlet of the condensate demineralizer Conductivity is stipulated as a control parameter to monitor the clean-up capacity of the condenser and feed water quality Action level for conductivity is set to > 0.01 mS/m because the water quality can be recovered within that conductivity level, and the level has no adverse effect on the secondary system based on field experience in Japanese PWRs Action levels and and a recommended value for conductivity are not stipulated because no data show an adverse effect on the coolant system component integrity at this level The monitoring frequency is daily to check the clean-up capacity of the condenser and feed water quality Continuous monitoring for conductivity should be adopted if an on-line monitoring system is implemented During monitoring sensor maintenance, a salt detector at the condensate hot well or manual analysis should be used as an optional analysis method The sodium, sulfate and chloride concentrations are selected as diagnostic parameters because their concentration changes in the makeup water can be detected by on-line conductivity monitoring, and a plant operational change is not needed even when these impurities increase in the make-up water storage tank The recommended values of sodium, sulfate and chloride are set to ≤0.06 μg/L (≤0.06 ppb), ≤0.15 μg/L (≤0.15 ppb) and ≤0.15 μg/L (≤0.15 ppb), respectively, based on field experience in Japanese PWRs Although chloride may accelerate pitting corrosion of alloy 600 during the layup process (EPRI, 1983b), chloride is defined as a diagnostic parameter because chloride conductivity level may be very small when the make-up water purification is controlled adequately Conductivity is not stipulated as a control and/or diagnostic parameter in the EPRI guidelines In the VGB guidelines, conductivity is stipulated as a diagnostic parameter, and the value is set to < 0.1 mS/ m The sodium, sulfate and chloride concentrations are stipulated as diagnostic parameters because their concentration changes in the makeup water can be predicted from on-line monitoring data of conductivity, and a plant operational change is not needed even when the concentration of impurities increases in the make-up water storage tank Although chloride may accelerate pitting corrosion of alloy 600 during the shutdown process, chloride is defined as a diagnostic parameter because pitting cannot easily occur under reducing conditions (Staehle, 2005) The recommended values of sodium, sulfate and chloride are set to ≤5 μg/L (≤5 ppb), ≤10 μg/L (≤10 ppb) and ≤10 μg/L (≤10 ppb), respectively, which are the same as action level for SG blowdown water during operation The monitoring frequencies are monthly because their low levels should be monitored To check the trend of their concentrations, continuous monitoring should be recommended if an on-line monitoring system is implemented These impurities are not stipulated as control and/or diagnostic parameters in the EPRI guidelines DO is not stipulated as a control and/or diagnostic parameter or recommended value in the EPRI and VGB guidelines In Japanese PWRs, on the other hand, DO is not stipulated as a control and/or diagnostic parameter because DO should be controlled in the feed water Table Control and diagnostic parameters for condensate demineralized water during power operations in the Japanese, EPRI, and VGB guidelines Period Parameters Conductivity, mS/m (μS/cm) Sodium, μg/L Sulfate, μg/L Chloride, μg/L Japanese Guideline EPRI Guideline (Fruzzetti, 2004) VGB Guideline (Neder et al., 2006) Start-up to 100% Reactor Power > 30% Reactor Power 100% Reactor Power Action Levels Level Value 3 3 > 0.01 (> 0.1) – – – – – – – – – – – Recom-mended value Frequency – Dailya ≤0.06 Appropriateb ≤0.15 Appropriateb ≤0.15 Appropriateb Action Levels Level Value 3 3 – – – – – – – – – – – – Frequency – – – – Action Levels Level Value 3 3 – – – – – – – – – – – – Note a To check the trend of water quality, continuous monitoring should be recommended if a continuous monitoring system is implemented b It is required as appropriate when the conductivity of the secondary water at the condenser outlet is increased and the impurity concentration in the SG water changes greatly during power operation 132 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table Diagnostic parameters and recommended values for SG blowdown water during the start-up process Diagnostic Parameters Recommended Values Frequency Cation Conductivity, mS/m (μS/cm) Sodium, μg/L Chloride, μg/L Lead, μg/L ≤0.2 (≤2) ≤50 ≤100 ≤100 1 1 Table Diagnostic parameters and recommended values for feed water during the startup process timea timea timea timea Note a Check the recommended values prior to parallel in Diagnostic Parameters Recommended Values Frequency pH at 25 °C Conductivity, mS/m Hydrazine, μg/L Dissolved Oxygen, μg/L Plant-specifica Plant-specifica ≥50 ≤5 Appropriateb Appropriateb Appropriateb timec Note a Plant-specific administrative limits should be established Values are defined based on the plant design, component material and water chemistry b Required as appropriate based on the power generation during the start-up process c Check the recommended values prior to parallel in is monitored in the SG The monitoring frequencies are appropriate to evaluate the root cause of concentration changes To check the trends of their concentrations, periodic monitoring should be recommended if an on-line monitoring system is implemented Table Also shows the control and diagnostic parameters for condensed demineralized water during power operation in the EPRI (Fruzzetti, 2004) and VGB guidelines (Neder et al., 2006) Conductivity is not stipulated as a control and/or diagnostic parameter in the EPRI and VGB guidelines In the Japanese guidelines, on the other hand, conductivity is stipulated as a control parameter to check the clean-up capacity of the condenser and feed water quality Sodium, sulfate and chloride are not stipulated as control and/or diagnostic parameters in the EPRI and VGB guidelines In the Japanese guidelines, on the other hand, the concentrations of these impurities are stipulated as diagnostic parameters drain system, and SG The recommended values of pH and conductivity should be defined as a plant-specific administrative limit according to the plant design, component material and water chemistry The monitoring frequencies are appropriate for checking the values during the start-up process Hydrazine is injected into the PWR secondary coolant as an oxygen scavenger to suppress SG tube corrosion Hydrazine is stipulated as a diagnostic parameter to control adequate reducing conditions in the secondary side of the SG The recommended value of hydrazine is set to ≥50 μg/L (≥50 ppb), which corresponds to action level of hydrazine in the feed water during power operation as shown in Table to reduce oxygen to an adequate level in the secondary coolant The monitoring frequency of hydrazine is appropriate for checking the value during the process DO is also stipulated as a diagnostic parameter to check for adequate DO in secondary coolant reduction during the start-up process The recommended value of DO is set to ≤5 μg/L (≤5 ppb), which corresponds to action level of feedwater during power operation (Table 3) The monitoring frequency of DO is one time prior to parallel in to check the recommended value of DO in the secondary system 2.5.6 SG blowdown water during the strat-up process Table shows the diagnostic parameters and recommended values for SG blowdown water during the start-up process Cation conductivity, sodium, chloride and lead are stipulated as diagnostic parameters to the ingress of impurities into the SG during the start-up process During the parallel in from the step of the secondary coolant filling up the SG, it is difficult to concentrate impurities into SG crevices such as the tube support plate crevice and tube sheet crevice because the heat flux of the SG tube is very small during the process The recommended value of cation conductivity is set to ≤0.2 mS/m, which corresponds to ≤100 μg/L (≤100 ppb) as chloride and other impurities The recommended values of sodium and chloride are set to ≤50 μg/L (≤50 ppb) and ≤100 μg/L (≤100 ppb), respectively, which correspond to action level for sodium and chloride in SG blowdown water during power operation as shown in Table The recommended value of lead is set to ≤100 μg/L (≤100 ppb), which is ten times action level in the feed water during power operation as shown in Table The monitoring frequencies of cation conductivity, sodium and chloride are one time prior to parallel in (electric power generator start-up) because it is difficult to concentrate impurities into the SG crevice during the process The monitoring frequency of lead is one time prior to parallel in (electric power generator start-up) to confirm the removal of lead shield blocks after the periodic inspection Lead is not contained as an additive in any materials in Japanese PWR systems However, a negligible amount of lead may be found as contamination in the NH3 chemical additive Therefore, the lead concentration in the SG blowdown water should be checked carefully when the additive is changed to another manufacturing lot 2.5.8 Condensate water during the strat-up process Table 10 shows the diagnostic parameters and recommended values for condensate water during the start-up process The cation conductivity of the condensate water is also stipulated as diagnostic parameter to check salt contamination in the SG during the start-up process During the parallel in from the step of secondary coolant filling up the SG, it is difficult to concentrate sea water into the SG crevice because the heat flux of the SG tube is very small during the process The recommended value of cation conductivity is set to ≤0.03 mS/m The monitoring frequency of cation conductivity is one time prior to parallel in because it is difficult to concentrate impurities into the SG crevice during the process Continuous monitoring should be recommended if an on-line monitoring system is implemented 2.5.9 Feed water during the shutdown process Table 11 shows the diagnostic parameters and recommended values for the feed water during the shutdown process pH is stipulated as diagnostic parameter to check the adequate Table 10 Diagnostic parameters and recommended values for condensate water during the start-up process 2.5.7 Feed water during the strat-up process Table shows the diagnostic parameters and recommended values for the feed water during the start-up process pH and conductivity are stipulated as diagnostic parameters to check the adequate pH and secondary water quality during the start-up process because pH and conductivity are harmful parameters that adversely affect the long-term integrity of carbon steel, stainless steel, and nickel-based alloys, and corrosion product release and deposition by causing material corrosion in the feed water, condenser, bleeding and Diagnostic Parameters Recommended Values Frequency Cation Conductivity, mS/m (μS/cm) Sodium, μg/L ≤0.03 (≤0.3) ≤10 time time a a Note a Check the recommended values prior to parallel in Continuous monitoring should be recommended if a continuous monitoring system is implemented 133 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table 11 Diagnostic parameters and recommended values for feed water during the shutdown process Diagnostic Parameters Recommended Values Frequency pH at 25 °C Conductivity, mS/m (μS/cm) Hydrazine, μg/L Plant-specifica Plant-specifica ≥50 Appropriateb Appropriateb Appropriateb Table 13 Diagnostic parameters and recommended values for SG blowdown water during the outage/wet layup (clean-up) process Note a Plant-specific administrative limits should be established Values are defined based on the plant design, component material and water chemistry b Required as appropriate depending on the power generation during the shutdown process ≤0.03 (≤0.3) ≤10 timea timea ≥10 20 to 500b 50 to 500c Appropriatea Appropriatea Appropriatea – – – Appropriate Appropriate Appropriate With Ammonia Only Hydrazine (Without Ammonia) mixture of hydrazine and ammonia to maintain alkaline and reducing conditions For secondary coolant with ammonia, pH is stipulated as a diagnostic parameter to check for adequate pH during the outage/wet layup (clean-up) process because weak alkaline conditions with ammonia are effective to the long-term integrity of the structural material in the secondary system The recommended value of pH is set to > 10 to suppress the corrosion of carbon steel, stainless steel, and nickel-based alloys in the secondary system with ammonia The monitoring frequency of pH is appropriate for checking the value during the outage/ wet layup (clean-up) process For secondary coolant with ammonia, hydrazine is also stipulated as a diagnostic parameter to check for adequate reducing conditions in the secondary side of the SG The recommended value of hydrazine is set to 20–500 mg/L (20–500 ppm); 20 mg/L (20 ppm) hydrazine corresponds to twice the substitution of mg/L (8 ppm) as DO during the step of secondary coolant parallel in the SG The monitoring frequency of hydrazine is appropriate for checking the decrease in the hydrazine concentration during the outage/wet layup (clean-up) process For secondary coolant without ammonia, hydrazine is also stipulated as a diagnostic parameter to check for adequate reducing conditions in the secondary side of the SG The recommended value of hydrazine is set to 50–500 mg/L (50–500 ppm); 50 mg/L (50 ppm) hydrazine corresponds to 10 mg/L (10 ppm) as hydrazine during lay-up plus to times (20–30 mg/L as hydrazine) for substitution of mg/L (8 ppm) as DO during the step of secondary coolant parallel in the SG The monitoring frequency of hydrazine is appropriate for checking the value during the process Periodic analysis is recommended during the first 1–2 weeks to confirm the decreasing trend of hydrazine If the decreasing trend is sufficiently small, the appropriate frequency of monitoring can be decided Sodium, sulfate and chloride are stipulated as diagnostic parameters to check for impurities in the secondary water injected into the SG Until the parallel in from the step of secondary coolant injection into the SG, it is difficult to concentrate impurities into the SG crevice because the heat flux of the SG tube is very small Recommended values of sodium, sulfate and chloride are not stipulated because there are no data showing an adverse effect on the coolant system component integrity under the low temperature condition The monitoring frequencies of sodium, sulfate and chloride are appropriate for checking Table 12 Diagnostic parameters and recommended values for condensate water during the shutdown process Cation Conductivity, mS/m (μS/cm) Sodium, μg/L pH at 25 °C Hydrazine, mg/ L Note a Check the decreasing trend within 1–2 weeks during the outage/wet layup (clean-up) process If the decreasing trend is small, an appropriate check should be performed during the outage/wet layup (clean-up) process b Based on the field data during outage/wet layup, the initial decline in the concentration should be set, and the value should be within the recommended range for using ammonia c Based on the field data during outage/wet layup, the initial decline in the concentration should be set, and the value should be within the recommended range for without ammonia d When feed water is supplied from the make-up water storage tank, the purity of the make-up water should be checked 2.5.11 SG blowdown water during the outage/wet layup (clean-up) process Table 13 shows the diagnostic parameters and recommended values for SG blowdown water during the outage/wet layup (clean-up) process The guidelines stipulate two types of wet layup conditions One uses only hydrazine to maintain reducing conditions, and the other uses a Frequency Frequency Sodium, μg/L Sulfate, μg/Ld Chloride, μg/Ld 2.5.10 Condensate water during the shutdown process Table 12 shows the diagnostic parameters and recommended values for condensate water during the shutdown process Cation conductivity is also stipulated as a diagnostic parameter to check sea water contamination in the SG during the shutdown process Until the parallel in from the step of secondary coolant filling in the SG, it is difficult to concentrate the salt into the SG crevice because the heat flux of the SG tube is very small The recommended value of cation conductivity is set to ≤0.03 mS/m The monitoring frequency of cation conductivity is one time during the shutdown process because it is difficult to concentrate impurities into the SG crevice during the process Continuous monitoring is recommended if an on-line monitoring system is implemented Recommended Values Recommended Values d quality of the secondary coolant during the shutdown process because a weak alkaline condition is effective for the long-term integrity of carbon steel, stainless steel, and nickel-based alloys in the secondary system Conductivity is also stipulated as diagnostic parameter to check the adequate quality of the secondary coolant during the shutdown process because conductivity is a harmful parameter that adversely affects the corrosion of carbon steel, stainless steel, and nickel-based alloys in the secondary side The recommended values of pH and conductivity should be defined as plant-specific administrative limits according to the plant design, component materials and water chemistry Hydrazine is also stipulated as a diagnostic parameter to check for adequate reducing conditions in the secondary side of the SG The recommended value of hydrazine is set to ≥50 μg/L (≥50 ppb) to reduce oxygen to an adequate level in the secondary coolant The monitoring frequencies of pH, conductivity and hydrazine are appropriate for checking their values during the process Although chloride may accelerate pitting attack of alloy 600 during the layup process (EPRI, 1983b), chloride is not defined as a diagnostic parameter because pitting is not a problem (EPRI, 1983b) under reducing conditions or pH > 9.5 Diagnostic Parameters Diagnostic Parameters Note a Continuous monitoring should be recommended if a continuous monitoring system is implemented 134 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Table 14 Diagnostic parameters and recommended values for feed water or deaerator tank water during the outage/wet layup (clean-up) process Diagnostic Parameters Recommended Values Frequency Cation Conductivity, mS/m (μS/cm) Turbidity, mg/L Iron, μg/L Dissolved Oxygen, μg/L Sodium, μg/L Chloride, μg/L Lead, μg/L ≤0.03 (≤0.3) ≤1 ≤100 ≤50 ≤0.5 ≤0.5 ≤1 1 1 1 Table 15 Diagnostic parameters and recommended values for make-up water at the secondary high-purity storage tank during the outage/wet layup (clean-up) process timea timea timea timea timea timea timea Diagnostic Parameters Recommended Values Frequency Conductivity, mS/m (μS/cm) Sodium, μg/L Sulfate, μg/L Chloride, μg/L ≤0.1 (≤1) – – – Monthly Appropriatea Appropriatea Appropriatea Note a Check the value during SG layup and at the beginning of secondary cleanup Note a Monitoring frequency is one time during the clean-up process Check the recommended values prior to the step of feed water filling in the SG 2.5.13 Make-up water during the outage/wet layup (clean-up) process Table 15 shows the diagnostic parameters and recommended values for the make-up water at the storage tank during the outage/wet layup (clean-up) process Conductivity is also stipulated as a diagnostic parameter to check the adequate quality of the secondary coolant during the start-up process because conductivity is a harmful parameter that adversely affects the corrosion of carbon steel, stainless steel, and nickel-based alloys in the secondary side The recommended value of conductivity is set to ≤0.1 ms/m, which corresponds to the recommended value for the make-up water at the storage tank during power operation as shown in Table The monitoring frequency of conductivity is monthly Sodium, sulfate and chloride are stipulated as diagnostic parameters to check for impurities in the secondary water injected into the SG Recommended values of sodium, sulfate and chloride are not stipulated because there are no data showing an adverse effect on the coolant system component integrity under the low temperature condition The monitoring frequencies of sodium, sulfate and chloride are appropriate for checking the values during the process the values during the process 2.5.12 Feed water or deaerator tank water during the outage/wet layup (clean-up) process Table 14 shows the diagnostic parameters and recommended values for the feed water or deaerator tank water during the outage/wet layup (clean-up) process Cation conductivity is also stipulated as a diagnostic parameter to check for impurity contamination in the secondary coolant during the outage/wet layup (clean-up) process It is difficult for impurities to ingress into the SG crevice during the process because the SG is isolated from the secondary system The recommended value of cation conductivity is set to ≤0.03 mS/m The monitoring frequency of cation conductivity is one time during the process The cation conductivity is also confirmed to be within the recommended value prior to the step of secondary coolant filling in the SG Turbidity and total iron are stipulated as diagnostic parameters to check for the removal of rust in the feed water The recommended values of turbidity and total iron are set to ≤1 mg/L (≤1 ppm) and ≤100 μg/L (≤100 ppb), respectively, based on field experience in Japanese PWRs DO is stipulated as a diagnostic parameter to check for low levels in the feed water that not affect material corrosion The recommended value of DO is set to ≤50 μg/L (≤50 ppb), which corresponds to ten times the level of μg/L DO at the start of heat-up, which is equal to action level for the feed water during power operation as shown in Table Sodium and chloride are stipulated as diagnostic parameters to check the purification of the feed water The recommended values of sodium and chloride are set to ≤0.5 μg/L (≤0.5 ppb), which correspond to 0.5 μg/L (0.5 ppb) as the control value at the start of heat-up The monitoring frequencies of turbidity, total iron, DO, sodium and chloride are one time during the process, and sodium and chloride are checked to ensure that they are within the recommended values prior to the step of secondary coolant filling in the SG Lead is also stipulated as a diagnostic parameter to check for lead contamination in the secondary coolant during the outage/wet layup (clean-up) process The recommended value of lead is set to ≤1 μg/L (≤1 ppb), which corresponds to 1/10 of action level for lead in the feed water during power operation as shown in Table The monitoring frequency of lead is one time during the process, and lead is checked to ensure that it is within the recommended value prior to the step of secondary coolant filling in the SG Lead is not contained as an additive in any materials in Japanese PWR systems However, a negligible amount of lead may be present as a contaminant in the NH3 chemical additive Therefore, the lead concentration in the feed water or SG blowdown water should be checked carefully when the manufacturing lot of the additive is changed 2.5.14 Pure water at the outlet of the pure water production equipment Table 16 shows the control and diagnostic parameters and recommended values for the outlet of the pure water production equipment The water is used for the make-up water Conductivity is stipulated as a control parameter to monitor the clean-up Action level of conductivity is set to > 0.02 mS/m because the water quality can be recovered within this conductivity level and the purity has no direct adverse effect on the secondary system Action levels and and the recommended value of conductivity are not stipulated because there are no data showing an adverse effect on the coolant system component integrity at this level The monitoring frequency of conductivity is daily or one time at mixed bed polisher (MBP) sampling time because pure water is used as make-up water Silica is stipulated as a diagnostic parameter because carryover of silica is very small and silicate precipitation on the turbine has not been experienced under normal steam conditions in PWRs, which is in Table 16 Control and diagnostic parameters for pure water at the outlet of the pure water production equipment Control Parameters Conductivity, mS/m (μS/cm) Silica, μg/L Action Levels Recommended Values Frequency > 0.02 (> 0.2) – – – – Daily or timea – – ≤20 Appropriateb Note a Required as appropriate during feed water treatment system operation b Monitoring of the condition of the feed water treatment system and the purity of the pure water is as required appropriate because the frequency should be defined based on the plant design, component material and water chemistry 135 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Summary contrast to observations under overheat steam conditions in thermal power The recommended value of silica is set to ≤20 μg/L (≤20 ppb) based on field experience in Japanese PWRs The monitoring frequency of silica is appropriate for checking the value This paper provides the technical background and framework for secondary water chemistry guidelines for PWRs; furthermore, this paper provides reasonable “control values”, “diagnostic values” and “action levels” for multiple parameters and stipulates the responses when these levels are exceeded Specifically, “conditioning parameters” are adopted in the Japanese PWR secondary water chemistry guidelines Good practices for operational conditions are also discussed with reference to long-term experience The guidelines provide strategies for improving secondary system component integrity and maintaining the heat removal function of the secondary system In addition, the differences and the bases of the parameter settings between the Japanese and the EPRI and VGB guidelines are clarified These guidelines are expected to be helpful as an introduction to safety and reliability during PWR plant operations 2.6 Water chemistry guidelines for improved water chemistry application Most Japanese PWR plants have already applied high pH control in the secondary coolant to reduce iron transportation into the SG and feed water pipe thinning Japanese PWR utilities have discussed high pH control to mitigate the corrosion of secondary system materials Chemistry strategy 3.1 Long-term strategy for PWR secondary controlled water chemistry The concept of the PWR secondary water chemistry guidelines for self-disciplined safety improvement follows the “Roadmap on R&D and Human Resources for Light Water Reactor Safety in Japan”, which provides nuclear safety visions and a technical basis for reconstruction after the Fukushima accident and was published by the Agency for Natural Resources and Energy (Agency for Natural Resources and Energy, 2015) A long-term strategy for controlling water chemistry had been discussed in the “Japanese R&D Road Map 2009 for Water Chemistry”, which was published by the Atomic Energy Society of Japan (AESJ) (Water Chemistry Division in AESJ), and the basic strategic scenario was not changed after the Fukushima-Daiichi nuclear accident Acknowledgments 3.1.1 High pH control To ensure the long-term integrity of secondary system materials, future challenges for PWR secondary water chemistry optimization, such as high pH control, will be addressed The primary objective of high pH control with a target pH of approximately 9.8 is the reduction of iron transfer to the SG Prior to the application of high pH control, copper alloy must be eliminated from the secondary system due to its high solubility in high pH conditions The typical pH control agent is ammonia, but some plants have chosen ETA to reduce corrosion in the two phase flow condition At present, 11 PWRs in Japan have already applied high pH control Supplementary data to this article can be found online at https:// doi.org/10.1016/j.pnucene.2019.01.027 We gratefully acknowledge Emeritus Professor Kenkichi Ishigure from the University of Tokyo; Yoshihumi Watanabe, Kotaro Takeda, and Toshiya Tezuka from Hokkaido Electric Power Co., Inc.; Nobuo Nakano from the Kansai Electric Power Co., Inc.; Nobuaki Ishihara, Hiroyuki Manabe, and Seitaro Mishima from Shikoku Electric Power Co., Inc.; Akira Takahashi and Yuuichi Koga from Kyusyu Electric Power Co., Inc.; and Kenji Hisamune and Yusuke Nakano from the Japan Atomic Power Company for their support and guidance Appendix A Supplementary data References Roadmap on R&D and Human Resource for Light Water Reactors Safety in Japan Agency for Natural Resources and Energy Handbook of Water Chemistry of Nuclear Reactor System Atomic Energy Society of Japan, pp 161 Cause of Denting, Vol and EPRI Report NP-3275 Laboratory Program to Examine Effect of Layup Conditions on Pitting of Alloy 600 EPRI Report NP-3012 PWR Steam-Side Chemistry Follow Program EPRI Report NP-2541 Fruzzetti, K., 2000 PWR Secondary Water Chemistry Guidelines – Revision EPRI Report 102134-R5 Fruzzetti, K., 2004 Pressurized Water Reactor Secondary Water Chemistry Guidelines –Revision EPRI Report 1008224-R6 Fruzzetti, K., 2006a Pressurized Water Reactor Lead Source Book: Identification and Mitigation of Lead in PWR Secondary Systems pp 2–53 EPRI Report 1013385 Fruzzetti, K., 2006b Pressurized Water Reactor Lead Source Book: Identification and Mitigation of Lead in PWR Secondary Systems pp 2-46–2-47 EPRI Report 1013385 Japanese government, 2015 Water Conditioning for Boiler Feed Water and Boiler Water April Kawamura, H., Hirano, H., 2000 Estimation of impurity concentration factor on boiling heat transfer surface using high temperature conductivity measurement technique Nucl Technol 129 (3), 398–406 Kawamura, H., Hirano, H., Katsumura, Y., Uchida, S., Mizuno, T., Kitajima, H., Tsuzuki, Y., Terachi, T., Nagase, M., Usui, N., Takagi, J., Urata, H., Shoda, Y., Nishimura, T., 2016 BWR water chemistry guidelines and PWR primary water chemistry guidelines in Japan - purpose and technical background - Nucl Eng Des 309, 161–174 Kishida, A., Takamatsu, H., Kitamura, H., et al., 1987 The causes and remedial measures of steam generator tube intergranular attack in Japanese PWR In: Proc 3rd Int Symp On Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, pp 465 Neder, H., Jurgensen, M., Wolter, D., Staudt, U., Odar, S., Schneider, V., 2006 VGB secondary and secondary side water chemistry guidelines for PWR plants In: Proc International Nuclear Plant Chemistry Conference, NPC2006, Paper 1.3, Jeju, Korea Odar, S., Nordmann, F., 2010 PWR and VVER secondary system water chemistry In: Advanced Nuclear Technology International Europe AB, ANT International Shoda, Y., Kadokami, E., Hattori, T., 1996 Examination of new bulk water molar ratio index for crevice environment estimation Water Chemistry of Nuclear Reactor Systems, vol pp 608 Bournemouth, UK Staehle, R.W., 2005 Clues and issues in the SCC of high nickel alloys associated with dissolved lead In: Proc 12th Int Symp On Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, pp 1163 3.1.2 Alternative to hydrazine In the near future, hydrazine use will be restricted in Japan because hydrazine is a known carcinogen Japanese PWR utilities have begun to discuss alternatives to hydrazine, such as carbohydrazide (CH6N4O) and diethylhydroxylamine ((C2H5)2NOH) However, hydrazine is an excellent oxygen scavenger and reducing agent and does not form organic species with adverse effects on the total organic carbon (TOC) concentration Efforts to develop alternative chemical additives should be required 3.2 Characteristics of the Japanese PWR secondary water chemistry guideline establishment system 3.2.1 Review of the draft As a technical standard of the Atomic Energy Society of Japan (AESJ), the draft of the PWR secondary water chemistry guidelines will be reviewed by experts not only in industry but also in academia The reviewing system is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 3.2.2 Satisfaction of regulatory criteria The revising system is the same as that in the PWR primary water chemistry guidelines (Kawamura et al., 2016) 136 Progress in Nuclear Energy 114 (2019) 121–137 H Kawamura, et al Von Nieda, G.E., Economy, G., Wootten, M.J., 1980 Denting in Nuclear Steam Generators – Laboratory Evaluation of Carbon Steel Corrosion under Heat Transfer Conditions NACE Corrosion 80 Japanese R&D Road Map 2009 for Water Chemistry Water Chemistry Division in AESJ Yashima, S., 1995 Genshiryoku Kogyo 41 (No.4), 62.Further reading “Strategic Energy Plan in Japan”, Japanese government, April 2014 http://www.enecho meti.go.jp/en/category/others/basic_plan/pdf/4th_strategic_energy_plan.pdf# search=%27Japanese+Strategic+Energy+Plan++Provisional+Translation%27 Takamatsu, H., Matsunaga, T., Migkin, B.P., Sarver, J.M., Sherburne, P.A., Aoki, K., Sakai, T., 1997 Study lead-induced stress corrosion cracking of steam generator tubing under AVT water chemistry conditions In: Proc 8th Int Symp on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, pp 216 Tsuruta, T., Okamoto, S., Kadokami, E., Takamatsu, H., 1995 IGA/SCC crack propagation rate measurement on alloy 600 SG tubing using a side stream model boiler In: The 3rd JSME/ASME Joint International Conference on Nuclear Engineering, pp 291 Kyoto, Japan 137 ... H., Shoda, Y., Nishimura, T., 2016 BWR water chemistry guidelines and PWR primary water chemistry guidelines in Japan - purpose and technical background - Nucl Eng Des 309, 161–174 Kishida, A.,... developing water chemistry experts, including those of the next generation This paper introduces the purpose, technical background and framework of the secondary water chemistry guidelines for Japanese... “conditioning parameter”, such as the hydrazine (N2H4) content and pH of the feed water, is adopted in the Japanese PWR secondary water chemistry guidelines These guidelines lead to the optimum water chemistry