© ISO 2016 Measurement of radioactivity Measurement and evaluation of surface contamination — Part 2 Test method using wipe test samples Mesurage de la radioactivité — Mesurage et évaluation de la con[.]
INTERNATIONAL STANDARD ISO 7503-2 Second edition 2016-01-15 Measurement of radioactivity Measurement and evaluation of surface contamination — Part 2: Test method using wipe-test samples Mesurage de la radioactivité — Mesurage et évaluation de la contamination de surface — Partie 2: Méthode d’essai utilisant des échantillons d’essai de frottis Reference number ISO 7503-2:2016(E) © ISO 2016 ISO 7503-2:2016(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2016, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2016 – All rights reserved ISO 7503-2:2016(E) Contents Page Foreword iv Introduction v Scope Normative references Terms and definitions, symbols and abbreviations Sources of surface contamination Objectives o f the surface contamination evaluation Strategy Methods for evaluating surface contamination Wipe test material Instrumentation 9.1 General 9.2 Liquid scintillation counters 10 Calibration 10.1 Calibration of installed instruments 10.2 Calibration of portable instruments 11 Guidelines on wipe test sampling 11.1 General 11.2 Guidelines on sampling removable tritium contamination 12 Measurement procedure 13 Evaluation of measurement data f f f f f f 13.3 Application of ISO 11929 14 Wipe test uncertainties 15 Test report Bibliography 11 Terms and definitio ns Symb o ls and ab b reviated terms C alculatio n o the activity p er unit area o r meas urement res ults o ins talled ins truments C alculatio n o the activity p er unit area o r meas urement res ults o p o rtab le ins truments © ISO 2016 – All rights reserved iii ISO 7503-2:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso.org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the meaning o f ISO specific terms and expressions related to formity assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary in formation The committee responsible for this document is Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies, and radiological protection , Subcommittee SC 2, Radiological protection This second edition cancels and replaces the first edition ( ISO 7503-2:1988), which has been technically revised ISO 7503 consists of the following parts, under the general title Measurement of radioactivity — Measurement and evaluation of surface contamination : — Part 1: General principles — Part 2: Test method using wipe-test samples — Part 3: Apparatus calibration iv © ISO 2016 – All rights reserved ISO 7503-2:2016(E) Introduction ISO 7503 gives guidance on the measurement of surface contamination This International Standard is applicable to many situations where radioactive contamination can occur Contamination arises from the release o f radioactivity into the local environment In most circumstances, the release is inadvertent but, on occasion, may be deliberate Although the purpose and scope o f the investigation may di ffer, the approaches taken to measure the levels and extent o f the contamination are essentially similar Radioactive contamination can arise from a number of activities or events such as the following: — routine laboratory use o f radiochemicals; — medical treatments; — industrial applications; — transport accidents; — equipment mal functions; — malevolent incidents; — nuclear accidents Without process knowledge or documentation, it is not always possible to identi fy or distinguish the different radionuclides constituting a surface contamination, and the evaluation of such contamination cannot be made on a quantitative basis Instead o f using instruments with nuclide specific calibrations, it may be necessary to use other instruments which are fit for such a purpose However, there may be cases (e.g a contaminated fuel material transport container) where the radionuclide or the radionuclide mixture can be clearly characterized A sur face contamination evaluation exceeding a pure qualitative assessment o f fixed and removable sur face contamination may then be needed Moreover, following requirements laid down in national regulations and in international conventions, a measured sur face contamination activity per unit area has to be compared with surface contamination guideline values or surface contamination limits Sur face contamination guideline values are radionuclide-specific and thus require complex radionuclide-specific calibrations o f measurement equipment Calibration quality assurance is crucial in order to avoid non-detection (i.e type II decision errors) leading to incorrectly assuming compliance with given sur face contamination guideline values or limits Evaluation o f sur faces contaminated by a mixture o f radionuclides with known ratios requires respectively proportionated calibration factors ISO 7503 is concerned with the measurement and estimation o f radioactivity levels It does not provide advice on decommissioning, planning and surveillance techniques Sur face contamination is specified in terms o f activity per unit area and the limits are based on the recommendations by the International Commission on Radiological Protection (ICRP 103) This part o f ISO 7503 deals with the evaluation o f sur face contamination by indirect measurement using a wipe test © ISO 2016 – All rights reserved v INTERNATIONAL STANDARD ISO 7503-2:2016(E) Measurement of radioactivity - Measurement and evaluation of surface contamination — Part 2: Test method using wipe-test samples Scope ISO 7503 (all parts) and ISO 8769 are addressed to the people responsible for measuring the rad io ac tivity pre s ent on s ol id s u r face s T h i s p a r t o f I S O 75 appl ie s to the eva luation o f conta m i nation on s u r face s i n term s o f ac tivity p er u n it are a b y an i nd i re c t me tho d o f me a s u rement T h i s p ar t o f I S O 75 i s appl ic able to wel l- defi ne d s u r face s , s uch a s tho s e o f e qu ipment a nd containers of radioactive materials, sealed sources and buildings or land T h i s p ar t o f I S O 75 c an b e u s e d for l ab orator y a nd e qu ipment/i n s ta l lation control a nd faci l itie s , for reme d iation and mon itori ng ac tivitie s to comply with rele a s e criteria This part of ISO 7503 also refers to institutions/authorities controlling nuclear material transports or material/equipment clearance according to national legislation guideline values or international convention limits This part of ISO 7503 f es not apply to contamination o the skin, clothing or lo ose material, s uch as gravel NOTE Direct evaluation of surface contamination from alpha-emitters, beta-emitters and photon emitters is dealt with in ISO 7503-1 The calibration of instruments for the evaluation of radioactive surface contaminations is dealt with in ISO 7503-3 Normative references T he fol lowi ng i nd i s p en s able c u ments , i n whole or i n p ar t, are normatively re ference d i n th i s c u ment a nd are for its appl ic ation For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c u ment (i nclud i ng any amend ments) appl ie s ISO 8769, Reference sources — Calibration of surface contamination monitors — Alpha-, beta- and photon emitters ISO 9698, Water quality — Determination of tritium activity concentration — Liquid scintillation counting method ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measurements o f ionizing radiation — Fundamentals and application ISO 18589-2, Measurement of radioactivity in the environment — Soil — Part 2: Guidance for the selection of the sampling strategy, sampling and pre-treatment of samples ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories IEC 60325, Radiation protection instrumentation — Alpha, beta and alpha/beta (beta energy >60 keV) contamination meters and monitors © ISO 2016 – All rights reserved ISO 7503-2:2016(E) Terms and definitions, symbols and abbreviations 3.1 Terms and definitions For the pu rp o s e s o f th i s c ument, the fol lowi ng term s a nd defi nition s and tho s e given i n I S O 75 -1 apply 3.1.1 removable sur face contamination rad io ac tive materia l th at c an b e remove d contact, wiping, or washing from s u r face s b y non- de s truc tive me a n s , i nclud i ng c as ua l N o te to entr y: I t s hou ld b e no te d th at u nder the i n fluence o f moi s tu re , chem ic a l s , e tc , or a s a re s u lt o f cor ro s ion or d i ffu s io n , fi xe d co nta m i n ation m ay b e come remo vab le or vice vers a without a ny hu m a n ac tion Fu r ther more , s u r face conta m i n atio n s m ay de c re a s e due to e vap oration a nd vo l ati l i z ation No te to entr y: I t s ho u ld b e emp s i z e d th at the ratio b e twe en fi xe d a nd remo vab le co nta m i n atio n c a n va r y over ti me , a nd th at s ome de c i s io n s , s uch a s tho s e rel ate d to cle a nce , s hou ld b e b a s e d on to ta l ac tivity with the p o tenti a l to b e come remo vab le o ver ti me , no t j u s t the a mou nt th at i s removab le at the ti me o f a s u r ve y 3.1.2 wipe test te s t to de term i ne i f removable contam i nation i s pre s ent th rough wipi ng the s u r face with a d r y or we t materia l, fol lowe d b y eva luation o f the wip e materi a l for removable contam i nation N o te to entr y: T he t yp e o f w ip e te s t, we t o r d r y, ne e d s to b e a s s e s s e d b y a co mp e te nt p e rs o n I n s o me i n s ta nce s (e g tr i tiu m co nta m i n atio n) a we t wip e m ay b e p re fer re d I n o the rs , i t m ay b e mo re p rac tic a l o r ad vi s ab le to u s e a d r y wip e 3.1.3 wiping e fficiency ratio o f the ac tivity o f the rad ionucl ide s remove d from the s u r face b y one wip e s ample to the ac tivity o f the radionuclides of the removable surface contamination prior to this sampling N o te to entr y: T he wip i n g e ffic ienc y i s de fi ne d b y the εw where fo l lowi ng rel ation s h ip : a = R aT aR i s the ac tivity o f the rad ionucl ide s remove d b y wip e te s t; aT i s the to ta l removable ac tivity o f the rad ionucl ide s pre s ent on the wip e d are a N o te to entr y: I n prac tice , it i s a l mo s t i mp o s s ib le to me a s u re the to ta l a mou nt o f removab le ac tivity o n the s u r face; a nd i n mo s t c a s e s , a va lue for “wip i n g e ffic ienc y” c a n no t b e a s s e s s e d b ut c a n o n l y b e e s ti m ate d N o te to entr y: For i mp or ta nt co mb i n ation s o f co nta m i n a nt a nd s u r face m ater i a l , the wipi ng e ffic ienc y c a n b e de ter m i ne d e xp er i menta l l y u s i ng the me tho d o f “e xh au s tive remova l b y rep e titive wip e te s ts ” T he s tep - b y- s tep aT add ition o f the remove d ac ti vitie s re s u l ts i n a n app roxi m atio n o f the to ta l removab le ac tivity ( aR) ac ti vity remo ve d b y the fi rs t wip e te s t ( N o te to entr y: c a n then b e rel ate d to yield the wipi n g e ffic ienc y ), to which the T he me tho d o f “e xh au s ti ve remova l b y rep e titive wip e te s ts ” i s on l y app l ic ab le i f it c a n b e gu a nte e d th at e xac tl y the s a me a re a i s wip e d on e ach o cc a s io n a nd e xac tl y the s a me p re s s u re i s m a i nta i ne d u n i for m l y over the a re a wip e d M ore o ver, re s u lts o f th i s me tho d a re o n l y va l id of a surface and are not transferable to other surface structures for a s p e c i fic n atu re a nd s tr uc tu re 3.1.4 tritium surface contamination to ta l ac tivity o f tritiu m ad s orb e d up on and ab s orb e d i nto the s u r face © ISO 2016 – All rights reserved ISO 7503-2:2016(E) 3.1.5 removable tritium sur face contamination fraction of surface contamination which is removable or transferable under normal working conditions Note to entry: It should be noted that a) under external influences o f a chemical nature (e.g moisture, corrosion) or o f a physical nature (e.g ambient pressure or temperature changes, vibration, impact, expansion and contraction), and also as a result of The state is reversible multiple times, di ffusion, the total tritium activity may be trans formed into removable contamination or non-removable b) tritium sur face contamination may be volatile or contain volatile fractions which may volatilize under normal working conditions - this also contributes to the removable contamination and should be evaluated appropriately (see also Clause 7), and c) as a result o f di ffusion o f tritium into the sur face structure, removal o f the tritium sur face contamination by exhaustive wipes may be without e ffect as the removed tritium contamination may be replaced in short time (see also Clause 7) 3.1.6 indirect evaluation o f removable tritium sur face contamination evaluation o f the removable tritium activity by means o f a wipe test Note to entry: Any wipe used for tritium can only be analysed reliably using liquid scintillation counting Direct measurements o f tritium contaminated wipes may have large uncertainties or are not possible 3.2 Symbols and abbreviated terms For the purposes o f this part o f ISO 7503, the following symbols and those given in ISO 7503-1 apply: ε w wiping e fficiency aR activity o f the radionuclides removed by wipe test in Bq aT total removable activity o f the radionuclides present on the wiped area in Bq ar activity per unit area o f the removable contamination o f the wiped sur face in Bq·cm –2 aw activity o f the wipe sample in Bq wiped surface area in cm2 Sw C(A) ind activity calibration factor for wipe sample in (Bq·cm –2 )/s−1 Sources of surface contamination A sur face can be contaminated with naturally occurring or man-made radionuclides The main natural radionuclides are 40 K and radionuclides originating from 238 U and 232 Th decay series Natural radioactivity may vary considerably from one type o f natural material to another (e.g building materials) Laboratories that intentionally handle naturally occurring radioactive material, such as radium or thorium, should anticipate surface contamination from these radionuclides The sources o f sur face contamination by man-made radionuclides can arise from a number o f activities such as the following: — routine laboratory use o f radio chemicals; — medical treatments; © ISO 2016 – All rights reserved ISO 7503-2:2016(E) — industrial applications; — transport accidents; — equipment mal functions; — malevolent incidents; — nuclear accidents O b j e c t i v e s o f t h e s u r f a c e c o n t a m i n a t i o n e v a l u a t i o n The ultimate goal is to protect the worker and the general population from direct and indirect radiation exposures, such as inhalation, ingestion, skin contact, and skin absorption pathways This is done by measuring surface contamination to assess the impact of release and to prevent resuspension and remobilization of radioactive materials Radiation protection depends on knowledge o f the sur face activity and o f the removable fraction o f activity The removable fraction may vary over time (see Clause ) and should be depending on the intent of the surface contamination characterization conservatively applied, Prior to any measurements, qualified and experienced radiation pro fessionals should develop the required program of work to ensure that the best possible information is gathered to characterize the type and spread o f contamination Strategy A strategy for the determination o f sur face contamination is normally established by qualified individuals that have appropriate experience and expertise in the measurement and assessment of sur face contamination The strategy should be based on — random and/or systematic screening[1][2][7] , — check of critical positions (e.g storage areas of radioactive sources, door handles, or the surfaces of any container or building in which radioactive materials are stored), and — complete monitoring of the surface A remediation monitoring process (e.g Reference [7 ]) or a systematic monitoring strategy as outlined in ISO 18589-2 may be the basis for the specification o f sur face contamination measuring points in a laboratory, on an extended container or on a site Such strategies, however, not replace a complete monitoring of surfaces, on which radioactive contaminations are assumed A strategy for sur face contamination control at an operating facility may also be the analysis and identification o f critical operational sequences potentially leading to sur face contamination Methods for evaluating surface contamination The applicability and the reliability o f direct measurement or indirect evaluation o f sur face contamination are strongly dependent on the particular circumstances [e.g the physical and chemical form o f the contamination, the adherence o f contamination on the sur face (fixed or removable), the accessibility o f the sur face for measurement or the presence o f inter fering radiation fields] Direct measurement as dealt with in ISO 7503-1 is used when the sur face is readily accessible, reasonably clean and when no inter fering radiation, such as a high background, is present Direct measurement is used to establish the presence o f both fixed and removable contamination © ISO 2016 – All rights reserved ISO 7503-2:2016(E) Indirect evaluation o f sur face contamination is more generally applicable when the sur faces are not readily accessible because o f di fficult location or configuration, where inter fering radiation fields adversely a ffect contamination monitors or when methods o f direct measurement with standard instrumentation are not available (e.g tritium) Also, the indirect method cannot assess fixed contamination, and, due to the uncertainty associated to the wiping e fficiency, application o f this method results in conservative estimations Due to the inherent shortcomings of both the direct measurement and the indirect evaluation of surface contamination, in many cases, the use o f both methods in tandem ensures results which best meet the aims of the evaluation Tritium and its compounds are special case As a nuclide o f hydrogen, tritium has great mobility and may penetrate into a sur face (e.g along grain or crystal boundaries) to a depth that makes the indirect evaluation o f the tritium sur face contamination very di fficult This holds also for other mobile radionuclides In many cases, tritium contamination is present in the form o f contaminated water, which can evaporate, making the tritium airborne Because o f the ability o f tritium (as HT, T or HTO) to diffuse and substitute hydrogen against tritium in hydrogen containing compounds, tritium contaminations are found on and in the surface Therefore, special care shall be taken when evaluating tritium surface contamination The total sur face contamination cannot be accurately evaluated in any cases Indirect measurements per formed by dry or wet wipe tests generally provide only a “best guess” o f the removable sur face contamination at the time of collection Because of diffusion (e.g as HTO) into the surface, absorbed tritium contamination tends to replace the removable sur face contamination that was partially or totally removed by a decontamination process or by wet wipe tests There fore, a radiological hazard from volatile tritium may still remain Wipe test material The wipe material should be chosen to suit the purpose of the wipe test and surface to be checked (for example, filter paper for smooth sur faces, cotton textile for rough sur faces) Circular filter papers or circular cotton textile should pre ferably be used as the wipe material Expanded polystyrene [Polystyrene (PS) foam] [4] and cotton-tipped swabs can also be used as wipe material when appropriate If a wetting agent is used, it shall be compatible with the nature of the contamination to be sampled, and in case of liquid scintillation counting, the scintillation cocktail should be adapted to the applied wetting agent Instrumentation 9.1 General Measurements o f wipe samples are o ften carried out using well shielded, pulse-counting, installed laboratory instruments Portable surface contamination meters or monitors can also be used, but not in preference to well shielded installed laboratory instruments Characteristics and per formance o f the portable measuring instruments shall comply with IEC 60325 and be adapted to the measurement objectives Both instrument types shall be capable o f measuring activities below the levels o f the nuclide specific sur face contamination guideline values or limits set by national legislations or international conventions, to which the results of the contamination measurements are to be compared If a portable instrument is calibrated for the direct method of surface contamination evaluation, it is of value to calibrate it also for the indirect method (see ISO 7503-3) In the absence of interfering radiation © ISO 2016 – All rights reserved ISO 7503-2:2016(E) field s , p or table i n s tru ments may b e us e d to eva luate s ur face contam i nation when pre ferre d lab orator y instruments are not available If wipe tests with high activities are expected, a pre-measurement using an adequate portable measuring instrument is recommended to avoid contamination of installed instruments 9.2 Liquid scintillation counters Liqu id s c i nti l lation cou nti ng i s pri mari ly u s e d to cou nt low energ y b e ta s p ar ticle s and to a le s s er ex tent a lpha p a r ticle s C ou nti ng e fficiencie s range from % up to 10 % T he l iqu id s c i nti l lation me tho d i s most often used to measure H, 63 Ni, and 14 C A detailed description of the liquid scintillation counting technique is given in Reference [8] E m i s s ion c an b e de te c te d b y l iqu id s ci nti l l ation cou nti ng with var yi ng de gre e s o f e fficienc y dep end i ng on the following: the typ e and energ y o f em i s s ion ( X-rays and ton s may e s c ap e — from the s c i nti l lator without i nterac ti ng) ; — whe the r the s a mp le i s d i s s o l ve d i n the s c i nti l l ato r; i n the fo r m o f p a r ticle s ; o r re ta i ne d i n the w ip e m ate r i a l; — the e ffe c t o f chem ic a l s on the s ci nti l l ator; — ab s orp tion of the em itte d l ight by colou r or op acity of the s ample b e fore it re ache s the tomu ltipl ier(s) ; — the orientation of the wipe in the sample vial B e c au s e o f the va r i ab le ge ome tr y o f wip e s NO TE i ntro duce d i nto the s a mp le vi a l , c a re i s ne ce s s a r y to achieve accurate measurement unless the wipe is made to dissolve in the scintillation cocktail, such as expanded fo a m] p ol ys tyrene [ Pol ys tyrene (P S ) 1 0 C a l C i a b l i r a b t i r a o t i n o n o f i n s t a l l e d i n s t r u m e n t s Installed measuring instruments (e.g liquid scintillation counters calibrated according to ISO 9698) shou ld be provide d with an accre d ite d trace able c a l ibration cer ti fic ate relati ng the i n s tr ument re s p on s e to the ac tivity on the wip e materi a l C a l i b r a t i o n o f p o r t a b l e i n s t r u m e n t s Por table i n s tr ument c a l ibration sh a l l b e done b y me an s o f re ference rad i ation s provide d b y re ference sources of known emission in accordance with ISO 8769 The portable instrument calibration should correspond to the calibration methods given in ISO 7503-3, Annex D 11 Guidelines on wipe test sampling 11.1 General D e te c tion and eva luation o f s u r face conta m i nation c an b e c arrie d out u s i ng one or more d r y or we t wipe samples When taking wipe samples from large areas, the following points shall be taken into consideration a) Outline the required area to wipe using string or tape, for example, 100 cm2 for surface contamination guideline values[2] or 300 cm for surface contamination limits[3] © ISO 2016 – All rights reserved ISO 7503-2:2016(E) b) If a wetting agent is used for moistening the wipe material, this wetting agent should not exude from the material WARNING — Since the contamination may be absorbed into the structure o f the wipe material or may be covered by residual moisture, the use o f a wetting agent may lead to a significant underestimation o f the contamination in the case of alpha-emitters c) The radioactive material should be dissolved or suspended in the wetting agent The wetting agent water should be used for tritium, dust and water-soluble compounds d) The wipe should be pressed moderately against the sur face to be checked, using fingertips or, pre ferably, by means o f a holder e) The entire area required by regulations shall be wiped f) After sampling, if using other methods than liquid scintillation counting, the wipe material shall be care fully dried in such a way that loss o f activity is prevented In case o f contaminations o f tritium, iodine isotopes or other volatile isotopes, drying o f the wipe material shall be omitted g) Use extreme caution when handling potentially contaminated wipe materials in order to prevent cross-contamination 1 G u i d e l i n e s o n s a m p l i n g r e m o v a b l e t r i t i u m c o n t a m i n a t i o n The guidelines for tritium given in this subclause are also valid for iodine or other volatile radionuclides Detection and evaluation of removable tritium contamination should be carried out using wet wipe samples Where tritium contamination is present in a particulate form which is insoluble in liquid scintillators (e.g metal hydrides), dry wipe materials may be used for tritium detection purposes The following points shall be taken into consideration when taking wipe samples a) If possible, the area to be wiped should measure 100 cm2 b) Where regulations permit larger areas to be wiped, such areas shall be used for sampling and their actual size shall be included in the calculation of the result in accordance with Clause 13 ; wiping o f very large areas with a single wipe should be avoided since the removal factor decreases with increasing area c) The wipe shall be pressed moderately against the sur face to be wiped, pre ferably by means o f a holder which is designed to ensure uniform and constant pressure d) The entire area of 100 cm2 or larger shall be wiped e) Unused wipe materials should be stored in a tritium free atmosphere f ) The use o f disposable gloves is recommended during wipe testing o f highly contaminated sur faces; changing o f gloves may be necessary to avoid cross-contamination o f samples 12 Measurement procedure The operating instructions for the instruments used for measuring the wipe samples shall be followed The background radiation level in the area where the wipes are counted should be low and constant The following requirements shall be followed a) Before making a wipe measurement, the background count rate shall be determined at the place of measurement b) The background count rate shall be checked from time to time to account for changes in background levels © ISO 2016 – All rights reserved ISO 7503-2:2016(E) c) T he i n s tru ment s l l have a c u rrent c a l ibration s tatu s a nd s l l b e veri fie d u s i ng a s u itable che ck s ou rce Fre quenc y: dai ly more tha n % from for i n s tru ments i n fre quent us e, o ther wi s e b e fore e ach u s e D evi ation s o f the agre e d va lue s l l give ri s e to a re c a l ibration o f the i n s tru ment d) Instrument calibration factors suitable for the radionuclides to be measured should be available e) T he ge ome tr y cond ition s du ri ng a me a s u rement shou ld be identic a l to tho s e used du ri ng i n s tru ment c a l ibration For p or table i n s tru ments , they s hou ld b e as clo s e a s prac tic able to tho s e u s e d du ri ng i n s tr u ment c a l ibration; removable s p acers may b e u s e d for th i s pu rp o s e f) For methods other than liquid scintillation counting, the sensitive area of the detector shall be larger than the wipe sample g) If a wipe sample with alpha or beta emitters should be measured, alpha-beta pulse discrimination is required For the me as u rement o f wip e s ample s b y l iquid s ci nti l lation cou nti ng , the be complied with fol lowi ng re qu i rements s l l a) For water y wip e s ample s , appropriate s c i nti l lation co cktai l s are re qu i re d b) Tritiu m wip e s a mp le s shou ld b e place d i nto the cou nti ng vi a l a l re ady conta i n i ng an appropriate c) We t tritiu m wip e s ample s s l l b e pl ace d d i re c tly i n the s ci nti l l ation co cktai l amount of scintillation cocktail for ab out m i n prior to counti ng i n order to appro ach e qu i l ibrium d i s tribution o f the tritiu m ac tivity a nd dark adap tion d) Care should be taken that the introduction of the wipe sample into the scintillation cocktail does not cause excessive losses of light due to the mass of the material or to quenching effects, and does not introduce spurious scintillations due to brightening agents 13 Evaluation of measurement data 13.1 Calculation of the activity per unit area for measurement results of installed instruments Us i ng i n s ta l le d i n s tr u ments , the ac tivity p er u n it are a o f the removab le contam i nation o f the wip e d s u r face c an b e derive d from the ac tivity me a s u rement re s u lt o f the wip e materia l For i n s ta l le d i n s tru ments , the ac tivity p er u n it are a surface, expressed in Bq cm–2 ar = where aw Sw εw ar , i n rel ation to the ac tivity of the removable contamination of the wiped a w o f the wip e s ample, i s given b y Formu la (1) : aw (1) Sw ε w ⋅ i s the me a s u re d ac tivity o f the wip e s a mple i n B q; is the wiped surface area in cm2 ; i s the wipi ng e ffic ienc y D e term i n i ng the wipi ng e ffic ienc y exp eri menta l ly i nvolve s ti me a nd e ffor t Us ua l ly, a s er vative va lue o f ,1 i s u s e d wh ich as s u me s the wip e materi a l on ly picks up 10 % o f the ava i lable removable contamination[5] © ISO 2016 – All rights reserved ISO 7503-2:2016(E) 13.2 Calculation o f the activity per unit area for measurement results o f portable instruments Portable instruments calibrated according to ISO 7503-3, Annex D can be used to determine the activity per unit area ar of the removable contamination of the wiped surface, expressed in Bq cm–2 , according to Formula (2): a = C(A) ind ( ρ ρ0 ) (2) r where C(A) ind ρ g ρ ⋅ g − is the activity calibration factor in (Bq·cm−2 )/s−1 ; is the measured total count rate in s−1 ; is the background count rate in s−1 13.3 Application of ISO 11929 The calculation of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) according to ISO 11929 is given in ISO 7503-3, Annex F 14 Wipe test uncertainties The uncertainties in assessing the levels o f contamination from wipe tests are great and are a ffected by many factors including, but not limited to the following: — the type o f wipe material used; — the pressure applied by the person when making the wipe; — the area wiped; — the contamination distribution; — the porosity, chemical composition, texture and cleanliness o f the sur face Reference [6] demonstrates wiping efficiency can vary enormously and is almost impossible to assess accurately The uncertainties in the wiping e fficiency are an order o f magnitude larger than other uncertainties in the measurement Consequently, it has been common practice to allocate a value o f conservative 10 % to the wiping e fficiency, as essentially a “best guess” 15 Test report The test report has to conform to the requirements of ISO/IEC 17025 and has to contain the following information: — date; — location and sub-location; — type o f sur face; — instrument used, serial number; — re ference to the measurement and evaluation procedure used; — re ference o f the calibration standard employed; — identification o f the sample; © ISO 2016 – All rights reserved ISO 75 03 -2 : 01 6(E) — u n its i n wh ich the re s u lts are expre s s e d; — test result, a r ± u or a r ± U , with the associated k value C omplementar y i n formation, many o f wh ich are accord i ng to I S O 19 9, s hou ld b e i nclude d b enefit o f the u s er s uch as the a) wip e materi a l (d r y or wet) ; b) we tti ng agent; c) are a o f wip e; d) wipi ng e ffic ienc y e) i n s tru ment e fficienc y, c a libration date; f) re ference s ou rce: trace abi l ity o f s ou rce c a l ibration re s u lts; g) me a s u ri ng ti me s h) i n s tru ment re ad i ng o f the wip e s a mple; i) i n s tru ment re ad i ng o f the b ackground; j) no te s on the e xtent o f the conta m i nation; k) o ther ob s er vation s ( pre s ence o f vol ati le rad io ac tivity, e tc ) ; l) op erator ’s name; m) probabilities α, β for for s ample and b ackgrou nd; and (1 − γ) ; de ci s ion th re s hold and de te c tion l i m it; o) dep end i ng on the c u s tomer re que s t, there a re d i fferent ways to pre s ent the re s u lt: when the the i nd ire c t me a s urement (me as u re d or as s u me d) ; n) 1) for fol lowi ng: s u r face ac tivity concentration ar is compared with the decision threshold, in a r * when agre ement with I S O 19 9, the re s u lt o f the me a s urement s hou ld b e e xpre s s e d a s ≤ the re s u lt i s b elow the de ci s ion th re shold; 2) is compared with the detection limit, the result of when the result is below the detection limit If the detection limit exceeds the guideline value, it shall be documented that the method is not suitable for the measurement purpose when the s ur face ac tivity concentration ar ar# the me as u rement c an b e expre s s e d as ≤ 10 © ISO 2016 – All rights reserved ISO 75 03 -2 : 01 6(E) Bibliography [2] Report I.C.R.U 75 Sampling for radionuclides in the environment, Oxford University Press: Journal of the ICRU 2006, (1) U.S NUCLEAR REGULATORY COMMISSION Multi-Agency Radiation Survey and Site Investigation [3] IAEA SAFETY STANDARDS SERIES N o SSR-6 Regulations for the Safe Transport of Radioactive [4] S lobodien M.J., & Granlund R.W Extruded-Expanded Polystyrene - A Smear Material for Use in Liquid Scintillation Counting Health Phys 1974 July, pp 128–129 EAKINS J.D, & H UTCHINSON W P The Radiological Hazard from Tritium Absorbed on Metal Surfaces Part 2: The estimation ofthe Level ofTritium Contamination on Metal Surfaces by Smearing AERE-R-5988, 1969 Jung H., Kunze J.F., Nurrenbern J.D Consistency and efficiency of standard swipe procedures taken on slightly radioactive contaminated metal surfaces Health Phys 2001 May, pp S80–S88 IAEA SAFETY REPORTS SERIES No 72 Monitoring for Compliance with Remediation Criteria for [1] Manual (MARSSIM), Revision Report NUREG-1575, Rev.1; August 2000 Material - 2012 Edition International Atomic Energy Agency, Vienna, 2012 27 [5] [6] 80 [7] [8] Sites International Atomic Energy Agency, Vienna, 2012 L’Annunzi ata M.F Handbook o f Radioactivity Analysis Elsevier Academic Press, Third Edition, 2012 [9] ISO 31-0, Quantities and units — Part 0: General principles1) [10] ISO 31-9, Quantities and units — Part 9: Atomic and nuclear physics2) [11] ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM1995) [12] ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms (VIM) 1) Withdrawn This International Standard has been replaced by ISO 80000-1, Quantities and units — Part 1: General 2) Withdrawn This International Standard has been replaced by ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics © ISO 2016 – All rights reserved 11 ISO 75 03 -2 : 01 6(E) ICS 13.280 Price based on 11 pages © ISO 2016 – All rights reserved