BS ISO 21238-2007 Nuclear energy Nuclear fuel technology Scaling factor method to determine the radioactivity of low and intermediate-level radioactive waste packages generated at .pdf

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1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Scaling factor method to determine the radioactivity of low- and intermediate-level radioactive was

2、te packages generated at nuclear power plantsICS 27.120.30Nuclear energy Nuclear fuel technology BRITISH STANDARDBS ISO 21238:2007BS ISO 21238:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2007 BSI 2007ISBN 978 0 580 50829 5Amend

3、ments issued since publicationAmd. No. Date Commentscontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 21238:2007.

4、The UK participation in its preparation was entrusted to Technical Committee NCE/9, Nuclear fuel cycle technology.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a Reference

5、 numberISO 21238:2007(E)INTERNATIONAL STANDARD ISO21238First edition2007-04-15Nuclear energy Nuclear fuel technology Scaling factor method to determine the radioactivity of low- and intermediate-level radioactive waste packages generated at nuclear power plants nergie nuclaire Technologie du combust

6、ible nuclaire Mthode des ratios pour dterminer la radioactivit des colis de dchets de faible et moyenne activit produits par les centrales nuclaires BS ISO 21238:2007ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Terms and definitions. 1 3 Principle. 3 4 Sampling 3 5 Evaluation methodo

7、logy for scaling factor 4 Annex A (informative) Practices and examples of application of scaling-factor method 8 Bibliography . 23 BS ISO 21238:2007iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The wor

8、k of 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-governme

9、ntal, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The m

10、ain task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. A

11、ttention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21238 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 5, Nuclear fu

12、el technology. BS ISO 21238:2007vIntroduction Burial disposal of low- and intermediate-level radioactive waste has been practiced in several countries. Before disposal, the radioactivity of specific nuclides in waste packages have to be declared in accordance with limits and criteria derived from sa

13、fety assessment of the disposal facility. Some of these nuclides are difficult to measure from the outside of the waste packages, because they are beta or alpha emitting nuclides. There are a number of activity determination methods. The scaling-factor method is widely applied in order to evaluate t

14、hese difficult-to-measure nuclides. The scaling-factor method is based on a correlation between easily measurable gamma emitting nuclides and difficult-to-measure nuclides. This International Standard presents guidelines on the empirical scaling-factor method for evaluating the radioactivity of nucl

15、ear power plants low and intermediate level waste. BS ISO 21238:2007blank1Nuclear energy Nuclear fuel technology Scaling factor method to determine the radioactivity of low- and intermediate-level radioactive waste packages generated at nuclear power plants 1 Scope This International Standard gives

16、guidelines for the common basic methodology of empirically determining scaling factors to evaluate the radioactivity of difficult-to-measure nuclides in low- and intermediate-level radioactive waste packages. This International Standard gives common guidelines for the scaling factors used in the cha

17、racterization of contaminated wastes produced in nuclear power plants with water-cooled reactor. This International Standard is also relevant to other reactor types, such as gas-cooled reactors. Methodologies for determining scaling factors based on theoretical considerations (i.e. not based on expe

18、rimental measurement) are not covered by this International Standard. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 difficult-to-measure nuclide nuclide whose radioactivity is difficult to measure directly from the outside of the waste pack

19、ages by non-destructive assay means EXAMPLE Alpha emitting nuclides, beta emitting nuclides, and characteristic X-ray emitting nuclides. 2.2 key nuclide gamma emitting nuclide whose radioactivity is correlated with that of difficult-to-measure nuclides and can be readily measured directly by non-des

20、tructive assay means NOTE Also called “easy-to-measure nuclide” or “marker nuclide”. EXAMPLE 60Co and/or 137Cs. 2.3 scaling factor factor or parameter derived from mathematical relationship used in calculating the radioactivity of difficult-to-measure nuclide from that of key nuclide determined from

21、 sampling and analysis data 2.4 waste package product of conditioning that includes the waste form and any container(s) and internal barriers (e.g. absorbing materials and liner), as prepared for handling, transportation, storage and/or disposal NOTE Adapted from IAEA Radioactive Waste Management Gl

22、ossary. 2003 Edition1. BS ISO 21238:20072 2.5 representative sample sample taken from a process of the material in that process or that quantity of material which is considered to possess the average characteristics of the material NOTE 1 Adapted from ISO 921:19972. NOTE 2 Samples of waste are used

23、to determine the scaling-factor parameters for the target waste stream. A representative sample is meant to closely resemble the characteristic nuclide content and activity proportions of the target waste stream. 2.6 composite sample mixture of samples from different containers such that the mass ra

24、tio of the samples is equal to the ratio of the material masses contained in the containers NOTE Adapted from ISO 921:19972. EXAMPLE Series of samples taken over a given period of time and weighted by collection rate; or a combined sample consisting of a series of discrete samples taken over a given

25、 period of time and mixed according to a specified weighting factor, such as stream flow or collection rate. 2.7 corrosion product nuclide nuclide produced by activation of corrosion products temporarily deposited on in-core surfaces EXAMPLE 60Co, 63Ni. 2.8 fission product nuclide nuclide produced e

26、ither by fission or by the subsequent radioactive decay of nuclides thus formed NOTE Adapted from ISO 921:19972. EXAMPLE 137Cs, 90Sr. 2.9 alpha emitting nuclide nuclide emitting an alpha particle when it decays EXAMPLE Most actinides and transuranic nuclides. 2.10 transuranic nuclide nuclide with at

27、omic numbers above 92 2.11 dry active waste solid waste generated in various waste streams in a nuclear power plant, including protective clothing, replaced equipment, parts, plastics, polyvinyl chloride sheets, and high efficiency particulate air filters removed during plant operation and maintenan

28、ce 2.12 homogeneous waste radioactive waste that shows an essentially uniform distribution of activity and physical contents EXAMPLE Flowable wastes such as concentrates, solidified liquids and spent resins, in which the radioactivity may reasonably be assumed to be uniformly distributed over the vo

29、lume or flowable wastes uniformly mixed with a solid matrix. 2.13 heterogeneous waste radioactive waste that does not meet the definition of homogeneous waste, including solid components and mixtures of solid components, such as dry active waste and cartridge filters BS ISO 21238:200733 Principle Th

30、e empirical scaling-factor method is a method for evaluating the radioactivity of defined difficult-to-measure nuclides from the radioactivity of key nuclides, based on the correlations between difficult-to-measure nuclides and key nuclides. To achieve this, it is important to understand the nuclide

31、 production mechanisms, the physico-chemical behavior of nuclides and observe radiochemical analysis data. Statistical calculation is a supplemental technique used for the quantitative evaluation of scaling-factor parameters from groupings of radiochemical data. The difficult-to-measure nuclides of

32、primary interest are those with very long half-lives that persist in a disposal site long after the period of institutional control. Their declarations are often important for the assessment of the health and safety of the disposal site. Some national programs for low-level radioactive-waste disposa

33、l establish specific limits on the concentrations of these nuclides in individual waste packages as well as on their total content in the disposal site. These are specific acceptance criteria which are set by the national regulatory system or waste management programs and are derived from the safety

34、 assessment of disposal facilities. The information about the activity concentration and total activity are also required for the transport of radioactive material. Scaling factors provide a mechanism for estimating the quantities of difficult-to-measure nuclides in individual waste packages based o

35、n limited radiochemical analysis of samples from the bulk waste stream. This is achieved by observing the consistent and reproducible relationships between individual nuclides in samples from a stream, which, with reasonable confidence, can be assumed to represent the entire stream. 4 Sampling 4.1 G

36、eneral Scaling factors in the context of this International Standard are based on a database of samples. Therefore, it is quite important to conduct appropriate sampling and create a database of analytical results. Described in 4.2.1 and 4.2.2 are two basic concepts employed for the collection of ra

37、dioactivity data that serve as the basis for the scaling-factor method. 4.2 Representative sampling Two common approaches to ensuring representative samples are homogenized sampling, accumulated sampling. 4.2.1 Homogenized sampling This sampling applies to waste that can be considered as homogeneous

38、. In order to ensure that the activity contained in the sample is uniformly distributed, the waste is sufficiently mixed before sampling or within the sample process. Satisfactory accuracy can be ensured even for scaling factors obtained from a small number of samples. a) Waste is uniformly stirred

39、and sampled from storage tanks. b) Composite samples can be prepared by proportionally mixing waste. 4.2.2 Accumulated sampling In this approach, waste samples are collected in suitable number or manner to represent the characteristic features of a population of waste samples. This is applicable to

40、both homogeneous waste streams and heterogeneous waste streams. BS ISO 21238:20074 4.2.3 Activity concentration range of waste samples When sampling a defined waste stream in the case of accumulated sampling, it is important to obtain radioactive waste samples having a wide range of activity concent

41、rations in order to ensure effective correlations between difficult-to-measure nuclides and key nuclides for waste from that stream. 4.3 Rejection of outliers If an outlier is found within analysis results, the cause should be identified and the outlier can be corrected or abandoned based on the stu

42、dy of distribution of data and origin of data. If the cause of such an outlier is not identified, statistical methods can be applied optionally for rejection of outliers. 4.4 Records of samples The following information should be recorded together with the measurement data of individual samples: sam

43、ple identification number; plant name; reactor identification and building identification; reactor type (e.g. boiling water reactor, pressurized water reactor, heavy water reactor, etc.); waste stream identification; type of waste (e.g. spent resin, concentrates, metal, smear, etc.); date of waste s

44、ampling; date of waste analysis; organization that conducted analysis; radioactivity and detection limits of each nuclide (the activity concentration of each nuclide should be corrected for decay to the generation date of waste); moisture content of the waste (to be measured if necessary for 3H eval

45、uation). 5 Evaluation methodology for scaling factor 5.1 Applicability of scaling-factor method The scaling-factor method relies on correlations or predictable relationships between nuclides. The crucial step is deciding whether a correlation exists, i.e. whether the scaling-factor method is applica

46、ble. The applicability of the scaling-factor method for a given difficult-to-measure nuclide and a key nuclide pair can be checked by either or both of the following ways: consider their production mechanism, physicochemical behavior and observation of their correlation diagrams; use statistical met

47、hods to check for existence of a correlation. BS ISO 21238:200755.2 Evaluation by linear relationship The radioactivity of the difficult-to-measure nuclide is predicted by multiplying its scaling factor by the concentration of the key nuclide. The scaling factor is determined as the geometric mean o

48、f analyzed values. dSFkaf a= (1) where adis the activity concentration of the difficult-to-measure nuclide in either activity per mass or activity per volume, e.g. expressed in Bq/kg or in Bq/m3; fSFis the scaling factor, see Equation (2); akis the activity concentration of the key nuclide in either

49、 activity per mass or activity per volume, e.g. expressed in Bq/kg or in Bq/m3. The geometric mean can be used to calculate scaling factors for the evaluation of activity concentrations in the following manner: SF d,1 k,1 d, k, d, k,()nii nnfaa aa aa= (2) where ak,iis the activity concentration of the key nuclide in sample i (i = 1n), e.g. expressed in Bq/kg if the activity is expressed per mass; ad,iis the activity concentration of the difficult-to-measure nuclide in sample i