BS ISO 12789-1-2008 Reference radiation fields - Simulated workplace neutron fields - Characteristics and methods of production《参考辐射区域 模拟工作场所中子区域 生产特性和方法》.pdf

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1、BRITISH STANDARDBS ISO 12789-1:2008Reference radiation fields Simulated workplace neutron fields Part 1: Characteristics and methods of productionICS 17.240g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g

2、55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS ISO 12789-1:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2008 BSI 2008ISBN 978 0 580 60927 5National forewordThis British Standard is the UK implementation of ISO 1278

3、9-1:2008. It supersedes BS ISO 12789:2000 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee NCE/2, Radiation protection and measurement.A list of organizations represented on this committee can be obtained on request to its secretary.This publication do

4、es not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsReference numberISO 12789-1:2008(E)INTER

5、NATIONAL STANDARD ISO12789-1First edition2008-03-01Reference radiation fields Simulated workplace neutron fields Part 1: Characteristics and methods of production Champs de rayonnement de rfrence Champs de neutrons simulant ceux de postes de travail Partie 1: Caractristiques et mthodes de production

6、 BS ISO 12789-1:2008ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Simulated workplace neutron fields . 3 5 General requirements for the production of simulated workplace neutron spectra . 3 6 Characterization of simulated workplace

7、 neutron fields 4 7 Fluence to dose-equivalent conversion coefficients 6 8 Sources of uncertainty. 7 9 Expression and reporting of uncertainties 7 Annex A (informative) Examples of simulated workplace neutron fields 8 Bibliography . 22 BS ISO 12789-1:2008iv Foreword ISO (the International Organizati

8、on 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 been established ha

9、s 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 standardization. Inte

10、rnational 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 for voting. Publica

11、tion 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 all such patent rig

12、hts. ISO 12789-1 was prepared by Technical Committee ISO/TC 85, Nuclear energy, Subcommittee SC 2, Radiation protection. This first edition of ISO 12789-1 cancels and replaces ISO 12789:2000, of which it constitutes a minor revision. ISO 12789 consists of the following parts, under the general title

13、 Reference radiation fields Simulated workplace neutron fields: Part 1: Characteristics and methods of production Part 2: Calibration fundamentals related to the basic quantities BS ISO 12789-1:2008vIntroduction ISO 8529-1, ISO 8529-2 and ISO 8529-3, deal with the production, characterization and us

14、e of neutron fields for the calibration of personal dosimeters and area survey meters. These International Standards describe reference radiations with neutron energy spectra that are well defined and well suited for use in the calibration laboratory. However, the neutron spectra commonly encountere

15、d in routine radiation protection situations are, in many cases, quite different from those produced by the sources specified in the International Standards. Since personal neutron dosimeters, and to a lesser extent survey meters, are generally quite energy-dependent in their dose equivalent respons

16、e, it might not be possible to achieve an appropriate calibration for a device that is used in a workplace where the neutron energy spectrum and angular distribution differ significantly from those of the reference radiation used for calibration. ISO 8529-1 describes four radionuclide-based neutron

17、reference radiations in detail. This part of ISO 12789 includes the specification of neutron reference radiations that were developed to closely resemble radiation that is encountered in practice. Specific examples of simulated workplace neutron source facilities are included in Annex A, for illustr

18、ation. BS ISO 12789-1:2008blank1Reference radiation fields Simulated workplace neutron fields Part 1: Characteristics and methods of production 1 Scope This part of ISO 12789 gives guidance for producing and characterizing simulated workplace neutron fields that are to be used for calibrating neutro

19、n-measuring devices for radiation protection purposes. Both calculation and spectrometric measurement methods are discussed. Neutron energies in these reference fields range from approximately thermal neutron energies to several hundred GeV. The methods of production and the monitoring techniques fo

20、r the various types of neutron fields are discussed, and the methods of evaluating and reporting uncertainties for these fields are also given. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cit

21、ed applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 8529-1:2001, Reference neutron radiations Part 1: Characteristics and methods of production ISO 8529-2:2000, Reference neutron radiations Part 2: Calibration fundamentals of radi

22、ation protection devices related to the basic quantities characterizing the radiation field ISO 8529-3:1998, Reference neutron radiations Part 3: Calibration of area and personal dosimeters and determination of response as a function of energy and angle of incidence ISO/IEC 98:1995, Guide to the exp

23、ression of uncertainty in measurement (GUM) 3 Terms and definitions For the purpose of this document, the following terms and definitions apply. NOTE 1 The definitions follow the recommendations of ICRU Report 51 8and ICRU Report 33 4. NOTE 2 Multiples and submultiples of SI units are used throughou

24、t this part of ISO 12789. 3.1 neutron fluence dN divided by da, where dN is the number of neutrons incident on a sphere of cross-sectional area da: ddNa = NOTE The unit of the neutron fluence is metres raised to the negative 2 (m2). BS ISO 12789-1:20082 3.2 neutron fluence rate d divided by dt, wher

25、e d is the increment of neutron fluence in the time interval dt: 2dddddNtat = NOTE The unit of neutron fluence rate is metres raised to the negative 2 times seconds raised to the negative 2 (m2s1). 3.3 spectral distribution of the neutron fluence Ed divided by dE, where d is the increment of neutron

26、 fluence in the energy interval between E and E + dE: ddEE = NOTE The unit of the spectral distribution of the neutron fluence is metres raised to the negative 2 times reciprocal joules (m2J1). 3.4 ambient dose equivalent H*(d) at a point in a radiation field dose equivalent at a point in a radiatio

27、n field that would be produced by the corresponding expanded and aligned field in the ICRU sphere at a depth, d, on the radius opposing the direction of the aligned field NOTE 1 For strongly penetrating radiation, a depth of 10 mm is currently recommended. NOTE 2 The unit of ambient dose equivalent

28、is joules times reciprocal kilograms (Jkg1) with the special name of sievert (Sv). 3.5 personal dose equivalent Hp(d) dose equivalent in soft tissue at an appropriate depth, d, below a specified point on the body NOTE 1 For strongly penetrating radiation, a depth of 10 mm is currently recommended. N

29、OTE 2 The unit of personal dose equivalent is joules times reciprocal kilograms (Jkg1) with the special name of sievert (Sv). NOTE 3 ICRU Report 39 5defines the mass composition of soft tissue as: 76,2 % O; 10,1 % H; 11,1 % C; 2,6 % N. NOTE 4 In ICRU Report 47 7, the ICRU has considered the definiti

30、on of the personal dose equivalent to include the dose equivalent at a depth, d, in a phantom having the composition of ICRU tissue. Then, Hp(10) for the calibration of personal dosimeters is the dose equivalent at a depth of 10 mm in a phantom composed of ICRU tissue, but of the size and shape of t

31、he phantom used for calibration (a 30 cm 30 cm 15 cm parallelepiped). 3.6 neutron-fluence to dose-equivalent conversion coefficient hdose equivalent divided by neutron fluence Hh= NOTE 1 The unit of the neutron-fluence to dose-equivalent conversion coefficient is the sievert times square metres (Svm

32、2). NOTE 2 Any statement of a fluence to dose-equivalent conversion coefficient requires the statement of the type of dose equivalent, e.g. ambient or personal dose equivalent. BS ISO 12789-1:200834 Simulated workplace neutron fields The neutron fluence spectra for a number of neutron fields have be

33、en available for some time 9, 10. Neutron fluence spectra, measured at workplaces and in simulated workplace calibration fields, are included in a catalogue resulting from work sponsored by the European Commission 11. This catalogue also contains response functions for common detectors and dosimeter

34、s in addition to fluence to dose-equivalent conversion coefficients. Measurements in nuclear power plants 12-15in the vicinity of transport casks containing spent fuel elements 14, 15, and in factories producing radionuclide neutron sources 15, 16and reprocessing fuel elements 17have demonstrated th

35、at neutron energy spectra in such environments can be described as a superposition of the following components: a high-energy component representing the uncollided neutrons, a scattered component with an approximately 1/Endependence (where Enis the neutron energy), and a thermal-neutron component. F

36、or these types of spectra, the design of simulated workplace neutron fields requires a knowledge and consideration of the components mentioned above because the relative fractions of these components can be very different in different situations. Other radiation environments can contain neutrons hav

37、ing much higher energies. For example, neutrons with energies greater than 10 MeV, contributing 30 % to 50 % of the ambient dose equivalent and personal dose equivalent, have been found in the vicinity of high-energy particle accelerators 18, 19and in aircraft flying at altitudes of 10 km to 15 km 2

38、0. Because of the characteristics of available neutron dosimeters and survey meters, it is difficult to obtain proper measurements in the workplace based on the calibration sources specified in ISO 8529-1 when the workplace spectrum differs markedly from the calibration source spectrum. This can res

39、ult in an inaccurate estimate of the dose equivalent when such devices are used. At least two possibilities exist for improving the situation. First, the neutron spectrum of the workplace field can be measured, and a correction factor calculated to normalize the energy-dependent response of the dete

40、ctor. Secondly, a facility can be constructed to produce a neutron field that simulates the energy spectrum found in the workplace. When this field has been properly characterized, it can be used for the direct calibration of personal dosimeters and survey meters. This latter approach has been emplo

41、yed at a number of laboratories, and this part of ISO 12789 gives guidance for producing and characterizing simulated workplace neutron spectra for the purpose of calibrating dosimeters and survey meters. The establishment of simulated workplace neutron spectra in the calibration laboratory is neces

42、sary because the laboratory setting offers the possibility of controlling the most influential quantities. The environmental parameters, such as temperature and humidity, can be maintained at a constant level. The materials used in the construction of the various pieces of equipment can also be spec

43、ified and controlled in the laboratory. The general layout as well as the sources of neutron scatter can also be controlled, or at least maintained constant, in the calibration laboratory. Simulated workplace neutron spectra that have been established in the calibration laboratory can be used to stu

44、dy the effects of changes in the neutron spectrum on the responses of personal dosimeters and survey meters. Dosimeter algorithms may also be tested with such sources used in conjunction with the other radionuclide sources recommended in ISO 8529-1. For these reasons, simulated workplace neutron fie

45、lds should be provided for the investigation and calibration of neutron personal dosimeters and survey meters that are used in any of the workplace locations mentioned above. 5 General requirements for the production of simulated workplace neutron spectra There are three basic methods for the produc

46、tion of simulated workplace neutron spectra. Irradiation facilities can be developed by making use of radionuclide neutron sources, accelerators and reactors. In each case, a variety of absorbing and scattering material can be placed between the primary source and detector in order to modify the ini

47、tial source spectrum and thus simulate a workplace neutron spectrum. In order to characterize the neutron fields generated in such facilities, it is necessary to measure and calculate the energy spectrum, and to determine the spectral and angular neutron fluence and dose equivalent rates at the refe

48、rence positions. BS ISO 12789-1:20084 it is also necessary to determine the field uniformity in the volume containing the detector. In some cases, this determination may be more amenable to a calculation rather than an experimental technique. The intensity of sources that are expected to vary with i

49、rradiation time (such as accelerators or reactors) shall be monitored. This monitoring shall intercept a known portion of the neutron field, measure an unused portion of the field or measure a parameter that has been proven to be directly proportional to the neutron output (such as the charged-particle beam current or the fluence rate of associated particles accompanying the reaction). If the fluence rate of the neutron field can be varied over a large range, as is often the case when using an