BS ISO 18589-6-2009 Measurement of radioactivity in the environment - Soil - Measurement of gross alpha and gross beta activities《环境中放射性的测量 土壤 总α和总β活性的测量》.pdf

1、BS ISO18589-6:2009ICS 13.080.01; 17.240NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMeasurement ofradioactivity in theenvironment SoilPart 6: Measurement of gross alphaand gross beta activitiesThis British Standardwas published under theauthority of the Stand

2、ardsPolicy and StrategyCommittee on 30 April2009. BSI 2009ISBN 978 0 580 53279 5Amendments/corrigenda issued since publicationDate CommentsBS ISO 18589-6:2009National forewordThis British Standard is the UK implementation of ISO 18589-6:2009.The UK participation in its preparation was entrusted to T

3、echnicalCommittee NCE/2, Radiation protection and measurement.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Com

4、pliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 18589-6:2009Reference numberISO 18589-6:2009(E)ISO 2009INTERNATIONAL STANDARD ISO18589-6First edition2009-03-01Measurement of radioactivity in the environment Soil Part 6: Measurement of gross alpha and gross beta ac

5、tivities Mesurage de la radioactivit dans lenvironnement Sol Partie 6: Mesurage des activits alpha globale et bta globale BS ISO 18589-6:2009ISO 18589-6:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed

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10、22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2009 All rights reservedBS ISO 18589-6:2009ISO 18589-6:2009(E) ISO 2009 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms, definitions and symbols 1 4 Pri

11、nciple. 2 5 Chemical reagents and equipment . 2 6 Procedure 3 7 Expression of results . 5 8 Test report . 8 Annex A (informative) Preparation of calibration sources with plutonium 239. 10 Bibliography . 12 BS ISO 18589-6:2009ISO 18589-6:2009(E) iv ISO 2009 All rights reservedForeword ISO (the Intern

12、ational Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work 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 b

13、een 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 of electrotechnical sta

14、ndardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies f

15、or voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention 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 a

16、ll such patent rights. ISO 18589-6 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 2, Radiation protection. ISO 18589 consists of the following parts, under the general title Measurement of radioactivity in the environment Soil: Part 1: General guidelines and definitio

17、ns Part 2: Guidance for the selection of the sampling strategy, sampling and pre-treatment of samples Part 3: Measurement of gamma-emitting radionuclides Part 4: Measurement of plutonium isotopes (plutonium 238 and plutonium 239 + 240) by alpha spectrometry Part 5: Measurement of strontium 90 Part 6

18、: Measurement of gross alpha and gross beta activities BS ISO 18589-6:2009ISO 18589-6:2009(E) ISO 2009 All rights reserved vIntroduction ISO 18589 is published in several parts for use jointly or separately according to needs. Parts 1 to 6 concerning the measurements of radioactivity in the soil hav

19、e been prepared simultaneously. These parts are complementary and are addressed to those responsible for determining the radioactivity present in soil. The first two parts are general in nature. Parts 3 to 5 deal with nuclide-specific measurements and Part 6 with non-specific measurements of gross a

20、lpha or gross beta activities. Additional parts can be added to ISO 18589 in the future if the standardization of the measurement of other radionuclides becomes necessary. BS ISO 18589-6:2009BS ISO 18589-6:2009INTERNATIONAL STANDARD ISO 18589-6:2009(E) ISO 2009 All rights reserved 1Measurement of ra

21、dioactivity in the environment Soil Part 6: Measurement of gross alpha and gross beta activities 1 Scope This part of ISO 18589 provides a method that allows an estimation of gross radioactivity of alpha- and beta-emitters present in soil samples. It applies, essentially, to systematic inspections b

22、ased on comparative measurements or to preliminary site studies to guide the testing staff both in the choice of soil samples for measurement as a priority and in the specific analysis methods for implementation. The gross or radioactivity is generally different from the sum of the effective radioac

23、tivities of the radionuclides present since, by convention, the same alpha counting efficiency is assigned for all the alpha emissions and the same beta counting efficiency is assigned for all the beta emissions 2 Normative references The following referenced documents are indispensable for the appl

24、ication of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 31-9, Quantities and units Part 9: Atomic and nuclear physics ISO 11074, Soil quality Vocabulary ISO/IEC 17025

25、, General requirements for the competence of testing and calibration laboratories ISO 18589-1, Measurement of radioactivity in the environment Soil Part 1: General guidelines and definitions ISO 18589-2, Measurement of radioactivity in the environment Soil Part 2: Guidance for the selection of the s

26、ampling strategy, sampling and pre-treatment of samples 3 Terms, definitions and symbols For the purposes of this document, the terms, definitions and symbols given in ISO 18589-1, ISO 11074 and ISO 31-9 and the following symbols apply. m Mass of the test portion, expressed in kilograms a Activity p

27、er unit of mass, expressed in becquerel per kilogram A, AActivity of the standard in the and calibration sources, expressed in becquerel tgSample counting time, expressed in seconds BS ISO 18589-6:2009ISO 18589-6:2009(E) 2 ISO 2009 All rights reservedt0Background counting time, expressed in seconds

28、ts, tsCalibration and sources counting time, expressed in seconds rg, rgGross count rate per second, from the and windows, respectively r0, r0Background count rate per second, from the and windows, respectively rs, rsCalibration count rate per second, from the and windows, respectively , Counting ef

29、ficiency for alpha and beta, respectively Alpha-beta cross-talk, percentage of count going into window from the calibration source ()ua Standard uncertainty associated with the measurement result U Expanded uncertainty, calculated by ( )Ukua= with k = 1, 2, expressed in becquerel per kilogram a* Dec

30、ision threshold, expressed in becquerel per kilogram a#Detection limit, expressed in becquerel per kilogram ,aaLower and upper limits of the confidence interval, expressed in becquerel per kilogram 4 Principle Gross alpha and beta radioactivity are determined by using gas-flow proportional counting

31、or solid scintillation counting on a thin layer of fine soil on a planchette.1,2,3Gross alpha and beta determinations are not absolute determinations of the radioactivity of the sample but relative determinations referred to a specific alpha- or beta-emitter that constitutes the standard calibration

32、 source. These types of determinations are also known as the alpha index and beta index. 5 Chemical reagents and equipment 5.1 Degreasing solvent. 5.2 Fixer, for example cellulose nitrate (Parlodion1), up to 10 g/l in acetone. 5.3 Planchette, stainless steel, with a diameter adapted to the measuring

33、 apparatus. 5.4 Analytical balance, accurate to 0,1 mg. 5.5 Gas-flow proportional counter or solid-state scintillation counter (such as ZnS), designed to discriminate between the alpha and beta radioactivity. 1) Parlodion is an example of a suitable product available commercially. This information i

34、s given for the convenience of users of this part of ISO 18589 and does not constitute an endorsement by ISO of this product. BS ISO 18589-6:2009ISO 18589-6:2009(E) ISO 2009 All rights reserved 36 Procedure 6.1 Preparation of sources The preparation of sources involves the following stages. a) Clean

35、 the planchette (5.3) using a degreasing solvent (5.1). b) Evenly deposit a known mass of the test sample, m, prepared in accordance with ISO 18589-2 in order to obtain the thinnest possible layer with a surface deposit below 20 mg/cm2. c) The mass of the sample shall fall between the maximum and th

36、e minimum values of the calibration curve. d) Place the planchette on a horizontal surface. e) It is recommended to cover the deposit using the fixer (for example 10 ml of Parlodiondissolved in a 130 mm test dish) and leave it to evaporate at ambient temperature (take the same quantity of fixer as u

37、sed to prepare the standard sources). The purpose of this operation is to permanently fix a thin film on the surface of the sample on the planchette. The source is ready for the determination of the gross alpha and gross beta radioactivity indices using previously calibrated measuring equipment. The

38、 planchette should be suitably stored before measuring, to avoid any risk of contamination. IMPORTANT The self-absorption phenomena that depend on the matrix constituent as well as the thickness of the deposit tend to underestimate the gross radioactivity, especially the alpha radioactivity. It is d

39、ifficult to prepare thin sources with a uniform thickness, which shall be constant from one preparation to another. 6.2 Calibration 6.2.1 Principle The counting efficiency and associated uncertainty are determined using soil reference calibration sources4,5,6prepared by a) metrological bodies using

40、the reference soil supplied; b) the laboratory using soil of the same nature as the soil being analysed, whose homogeneity has been thoroughly evaluated. These soils become reference soils after spiking, separately, with calibrated alpha and beta solutions with sufficient activity to allow the activ

41、ity of the natural or artificial radionuclides present in the soil to represent less than 2 % of the total activity in the reference soils. Among the standard solutions available for artificial alpha-emitting radionuclides, 241Am and 239Pu are commonly selected. When 239Pu is used, it is necessary t

42、o take into account the presence of the 241Pu impurity. Among the standard solutions available for artificial beta-emitting radionuclides, 90Sr+90Y is commonly selected. Finally, among the natural standard solutions, Unatand 40K are commonly selected. An example of the method of the preparation of s

43、ources calibrated with plutonium to measure the gross -radioactivity is given in Annex A. A similar procedure may be implemented by spiking. The calibration sources shall be stored in a desiccator due to the hydrophilic nature of the soil. BS ISO 18589-6:2009ISO 18589-6:2009(E) 4 ISO 2009 All rights

44、 reservedIt is advisable to choose the alpha and beta windows so that the beta-alpha cross-talk is close to zero. Then it is sufficient to consider only the alpha-beta cross-talk correction factor. If this cannot be done, it is necessary to consider both the alpha-beta and the beta-alpha cross-talk

45、correction factors. 6.2.2 Procedure 6.2.2.1 Beta calibration The procedure for calibrating the counters is as follows. a) Deposit a thin layer of the reference soil following the procedure given in 6.1. b) Select the width of the alpha and beta windows. c) Select tsto collect at least 104counts in t

46、he beta window. d) Determine the count rate of the calibration source in its window. e) Verify that the count rate in the alpha window is zero or compatible with the equipment background count rate. f) Calculate the counting efficiency of the counter, dividing the recorded count rate by the activity

47、 of the calibration source as given by Equation (1): ()s0rrA= (1) 6.2.2.2 Alpha calibration The procedure for calibrating the counters is as follows. a) Deposit a thin layer of the reference soil following the procedure given in 6.1. b) Select the width of the alpha and beta windows. c) Select the t

48、sto collect at least 104counts in the alpha window. d) Determine the count rate of the calibration source in its window. e) Calculate the alpha-beta cross-talk correction factor, , as given by Equation (2): ssrr = (2) where sris the count rate in the beta window when the alpha calibration source is

49、measured. f) Calculate the counting efficiency of the counter by dividing the recorded count rate by the activity of the calibration source as given by Equation (3): ()s0rrA= (3) 6.3 Calibration curves In general, it is difficult to produce a sample source identical to the calibration source. To avoid self-absorption differences between them, it is convenient to construct a calibration curve of sample mass versus