An assessment of the consequences of radiation doses due to the BDBA (beyond design basic accident) on the RSG-GAS research reactor has been done. The assessment was carried out to evaluate the KNS (Serpong Nuclear Area) EPZ (emergency preparedness zone) site after the reactor was operational for 30 years. The RSG-GAS research reactor is a 30MWt multipurpose reactor.
Progress in Nuclear Energy 140 (2021) 103927 Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene Assessment of dose consequences based on postulated BDBA (beyond design basic accident) A-30MWt RSG-GAS after 30-year operation P.M Udiyani, M.B Setiawan *, M Subekti, S Kuntjoro, J.S Pane, E.P Hastuti, H Susiati BATAN, Center for Nuclear Reactor Technology and Safety, Puspiptek Region Gd.80 Serpong, Tangerang Selatan, 15310, Indonesia A R T I C L E I N F O A B S T R A C T Keywords: Dose RSG-GAS BDBA Accident EPZ An assessment of the consequences of radiation doses due to the BDBA (beyond design basic accident) on the RSG-GAS research reactor has been done The assessment was carried out to evaluate the KNS (Serpong Nuclear Area) EPZ (emergency preparedness zone) site after the reactor was operational for 30 years The RSG-GAS research reactor is a 30MWt multipurpose reactor It is the largest research reactor in Indonesia RSG-GAS was built in the KNS Area in the Puspiptek complex which was put into operation in 1987 Previous estima tions of the radiological consequences were made on accidents which were postulated based on DBA conditions With the aging of the reactor, a study was carried out on the radiological consequences of the BDBA accident The ATWS (anticipated transient without scram) event caused the BDBA condition which resulted in the melted of fuel bundles Source term is estimated based on an inventory of melted fuel bundles, and fission products release through the reactor core, cooling system, reactor hall, and finally discharge to the environment through the reactor stack Radionuclide inventory is calculated by ORIGEN2.1 With the influence of weather, fission products are dispersed into the air and deposited to the surface of the soil on the site Weather and environmental data used are spatial analysis of ARC-GIS Consequences analysis was carried out in 16 wind direction sectors within a km radius using PC-COSYMA The calculation results show the largest dose is reached in a radius below 500 m with the direction of the wind to the South The radiation dose is below the dose limits for the exclusion and beyond exclusion area Consequences of BDBA accident dose at RSG-GAS does not require countermeasure like sheltering, evacuation nor relocation Introduction The RSG-GAS research reactor was built in 1983 This research reactor is located in the Serpong Nuclear Area (KNS) Puspiptek It reached its first critical level in July 1987 In March 1992 the reactor operated at a nominal power of 30 MW The permit to extend the operation until 2030 was issued by Bapeten Indonesian nuclear regu latory body, on December 6, 2020 RSG-GAS is a pool type reactor designed as a medium power research reactor (30 MW) It is located in the Center for Science and Technology Research (PUSPIPTEK) Serpong, South Tangerang This site is located at 6◦ 21′ 40′′ south latitude, 106◦ 39′ 57′′ east longitude and about 60 m above sea level The reactor site is surrounded by several villages and the Cisadane river as the western boundary Puspiptek area which has an area of 3.5 square kilometer It is located in Setu village, Cisauk sub-district, Tangerang district, Banten province The Puspiptek area is about 27 km southwest of the metropolitan city of Jakarta, and the distance from the site to the sea area, namely the Java Sea, is about 36 km The type of fuel is a plate with low uranium enrichment (19.75 %) In the year of 2005, its fuel - which was originally Uranium Oxide – was changed to Uranium Silicide (U3Si2–Al) The number of fuel elements in the reactor core is 40 fuel elements (FEs) and control elements (CEs) (BATAN, 2019) Coolant and moderator of reactors is light water (H2O) with a Berylium reflector RSG-GAS is a multipurpose reactor used mainly for neutronical, thermohydraulic, reactor safety system, power reactor research, and radiation protection It is also used for the pro duction of radioisotopes and silicon dopping, advanced material irra diation and for Neutron Activation Analysis (NAA) The operation of the RSG-GAS has the consequence of radioactive discharge into the environment Radioactive releases into the environ ment from the operation of nuclear reactors occur under normal or abnormal operating conditions Radioactive releases through the reactor stack will spread in the atmosphere and deposited to the ground surface * Corresponding author E-mail address: setiawan@batan.go.id (M.B Setiawan) https://doi.org/10.1016/j.pnucene.2021.103927 Received 21 January 2021; Received in revised form 25 June 2021; Accepted August 2021 Available online 14 August 2021 0149-1970/© 2021 The Authors Published by Elsevier Ltd This is an (http://creativecommons.org/licenses/by-nc-nd/4.0/) open access article under the CC BY-NC-ND license P.M Udiyani et al Progress in Nuclear Energy 140 (2021) 103927 With the influence of weather and local meteorological conditions, this radioactive substance is spread and through various pathways of expo sure into the human body The Safety Analysis Report (SAR) document from the RSG-GAS and the study of the radiological consequences of the reactor operating in normal conditions and postulated DBA accidents have been carried out by several researchers (Udiyani et al., 2018a; Kuntjoro and Udiyani, 2005) The results of the study of the consequences of normal conditions are used as a basis for environmental monitoring of the KNS site While the results of the study of the consequences of the accident are used as a nuclear emergency in the KNS region In accordance with SAR and the Bapeten regulatory body considerations, nuclear emergency zones within the site and outside the site are monitored within a km radius A 500 m exclusion zone is determined and emergency areas outside the exclusion zone up to km The determination of the emergency zone is estimated based on the DBA accident postulation, which is an accident resulting from the melting of a bundle of fuel elements The assumption is that there has been an accident that is the damage of a set of fuel el ements (equal to 21 plates of the fuel element) The accident caused by a blockage of the cooling channel These accidents resulted fission product nuclides regardless of the cladding of fuel into the cooling system with a particular faction Part of the nuclide is released from the cooling water/ reactor tank into the reactor chamber Finally a small portion of radio nuclides can be released from the reactor chamber into the atmosphere (BATAN, 2019; Kuntjoro and Udiyani, 2005; Hastowo, 1996) Since the accident of the Dai-ichi Fukushima reactor, the IAEA and the regulatory body of the nuclear reactor owner re-review the safety of existing reactors and those are not yet operated The review was carried out by adding a study of radiation impacts to severe accidents or BDBA (Arjun et al., 2014; Mehbooba et al., 2015; Raimond et al., 2013) Learning from the Fukushima accident and the aging of the RSG-GAS which is already 30 years old, a study of the radiological conse quences to be included in the SAR were done based on the BDBA acci dent Based on the dissertation of Hudi Hastowo (1996) (Hastowo, 1996), BDBA conditions are surrounded by reactor thermohydraulic calculations based on the ATWS (Anticipated Transient Without Scram) ATWS is triggered by the blockage of the coolant flow in the fuel The simulation results obtained a state where fuel bundles melt (BATAN, 2019; Hastowo, 1996) Based on these conditions the inventory and source term of the BDBA accident are calculated With meteorological influences and site environmental data within a km radius, it can be determined the activity of fission products that are dispersed in the at mosphere and deposited on the surface of the site With various path ways that are adapted to local data and conditions, receipt of doses and emergency zoning can be estimated Calculation of inventory of fission products in fuel or reactor core using ORIGEN 2.1 (Rahgoshay and Hashemi-Tilehnoee, 2013; Obaidurrahman and Gupta, 2013; Setiawan et al., 2020; Kuntjoro et al., 2019) Meteorology and environmental data are processed with software for spatial analysis, ARC-GIS Estimation of radiologic consequences in the environment using PC-Cosyma software based on the atmospheric dispersion model (Udiyani et al., 2016; Udiyani et al., 2018b; Cao et al., 2000; Udiyani et al., 2019; European Commission, 1995) in the atmosphere, deposited on the ground surface, and through various pathways into the human body Zoning of nuclear emergencies is determined based on the receipt of public and environmental doses The methodological approach to calculating radiation consequences is shown in Fig 2.1 Radioactivity source term The source term calculation is based on a BDBA accident that was simulated in the RSG-GAS The worst accident condition which was simulated in the reactor thermo-hydraulic calculation based on the ATWS condition which was triggered by the blockage of the coolant flow in the fuel This condition causes fuel elements to melt (Hastowo, 1996) Calculation of inventory of fission products on melted fuels using ORIGEN 2.1 The calculation is done based on the neutral pa rameters of the fuel Fuel material from U3Si2Al; Cladding material from AlMg3; Channel width is 2.55 mm; The number of U-235 per element of fuel is 250 g; Fuel dimensions (0.54 x 62.75 × 600 mm); U-235 Enrichment is 19.75 %; Uranium density in fuel (2.96 g/cm3) With a new fuel management pattern, the five melting fuel elements are the F-26, F-31, F-32, F-36, and F-37 with burn-up respectively 37.94 %, 32.55 %, 44.82 %, 40.90 % and 20.81 % as seen in Fig (Setiawan et al., 2020; Kuntjoro et al., 2019) Radionuclide activity that can reach the reactor stack is obtained from the following equation: QS = Q1 + Q2 = (0.4 × f1 × f2 × f3 × A) + (0.6 × f1 × f2 × f3 × (1 − ηA ) × A) (1) Where A is an inventory activity (Bq); Q1 is radionuclide activity in cooling water (Bq); Q2 is radionuclide activity released into the reactor hall (Bq); f1 is radionuclide fraction that can escape from the fuel going to the cooler; f2 is radionuclide fraction that can release from the coolant to the reactor chamber; f3 = iodine fraction; and η = efficiency of reactor stack filters The values of f1 and f2 for noble gases are 1.0 and the Br nuclides are × 10− The value of f1 is 0.5 for iodine (element or organic) or other nuclides The f2 values for the Iodine element are × 10− and × 10− for organic Iodine The value of f for other nuclides is × 10− The release fraction f3 for iodine (element or organic) is 0.5 The efficiency of the stack filter for noble gases is 0.0 The efficiency of the stack filter for Br and Iodine elements is 0.99 and for organic iodine or other nuclides is 0.90 (BATAN, 2019; Kuntjoro and Udiyani, 2005) 2.2 Radioactivity and radiological concequences Estimates for radioactivity of atmospheric dispersion and surface deposition use the segmented Gaussian equation default from PCCosyma (European Commission, 1995) It uses a segmented Gaussian plume model which allows for hourly changes in the wind speed and direction, stability category and rainfall rate affecting the dispersing material The segmented plume model Musemet incorporated in PC-Cosyma was employed for the calculations; it is an improved linear Gaussian plume model, which assumes that the meteorological condi tions (wind direction, wind speed, stability category and rain intensity) are known and constant in subsequent time intervals of h (European Commission, 1995; Panitz et al., 1989) The segmented Gaussian plume model allowing of atmospheric conditions and wind direction will changes during plume travel This model derives the sequences of atmospheric conditions affecting the plume from a data file giving hourly averages for wind speed and di rection, stability category, precipitation intensity and mixing layer depth The linear Gaussian for atmospheric dispersion shown in following equation Methodology Study of the consequences of environmental and community has based on radiology atmospheric disperse (Pirouzmand et al., 2015; Birikorang et al., 2015; Abdelhady, 2013; Hirose, 2016) The calculation mechanism starts from the calculation of fuel inventory, and source term is calculated based on inventory data Fission products released to the primary cooling water system through the reactor pool passes to the reactor hall and reactor building It is assumed that fission products release into the atmosphere as source term without going through stack filters Due to the influence of meteorology, the plume formed is dispersed P.M Udiyani et al Progress in Nuclear Energy 140 (2021) 103927 Fig Methodology approach of radiological consequences calculation Q [ KNS Data were taken every hour for one year for 16 wind direction sectors Wind rose of KNS area is depicted in Fig 2πσy σ z μ / ( / ) ]{ [ / ] [ / ]} As seen in Fig 2, the dominant wind direction blows towards the 2 − y σy exp − 2((z − H)/σ z ) + exp − 2((z + H)/σz ) south (occurrence frequency is about 28 %) with a dominant speed (2) between 2.4 and 3.8 m/s (occurrence frequency is around %) Sta bilities: 29.0 % stability D; 26.0 % stability E; 18 % stability F, and 27 % Where X (x,y,z) = Concentration in the air (chi) on the x-axis, y, z (Bq.s/ stability C rain m ): Q = Source term (Bq): μ = Wind speed (m/s): σy = Horizontal Calculation of radiation doses through four main pathways are dispersion coefficient (m): σz = Vertical dispersion coefficient(m): H = external gamma and beta from cloud shine, external gamma from sur Effective height (m): y = Distance perpendicular to the wind (m): z = face ground, inhalation of cloud shine, and ingestion of contaminated Height above ground (m) food, as illustrated in Fig Local production data or agriculture and Generally, with respect to Gaussian dispersion modelling, atmo livestock such as grain products, leafy vegetable, non-leafy vegetable, spheric turbulence is classified by empirical turbulence-typing schemes root vegetable, milk, meat cow and sheep meat are taken for 16 wind The most widely used scheme is the one developed by Pasquill and directions for radius distances (500 m; 1.0 km; 1.5 km; 2.0 km; 2.5 km; Gifford (European Commission, 1995; Panitz et al., 1989), which assigns 3.0 km; 3.5 km; 4.0 km; and 4.5 km) the grade of atmospheric stratification to six diffusion categories Class A corresponds to very unstable conditions and is associated with small 2.3 Countermeasure mechanical but large thermal components of turbulence Class B is moderately unstable and Class C is slightly unstable Class D represents Anticipatory actions are carried out according to certain criteria and the neutral atmospheric conditions and turbulence is only due to the the time and duration of the action based on the dose exposed in the mechanical component Class E is moderately stable, and Class F cor location area A dose-based evacuation measure is taken if the com responds to thermally very stable conditions and the mechanical tur munity receives a total effective body dose >0.05 Sv, that is, the dose bulence tends to be damped by buoyant forces (Panitz et al., 1989) can cause non stochastic effects While sheltering is for receiving doses Meteorological data such as weather stability, wind direction, wind between 0.02 and