IEC TR 62971 Edition 1 0 201 5 1 0 TECHNICAL REPORT Radiation instrumentation – Radiation sources used in i l l icit trafficking detection standards – Guidance and recommendations IE C T R 6 2 9 7 1 2[.]
I E C TR 62 ® Edition 201 5-1 TE C H N I C AL RE P ORT colour i n sid e Rad i ati on i n s tru m en tati on – Rad i ati on s ou rces u s e d i n i l l i ci t traffi cki n g d ete cti on IEC TR 62971 :201 5-1 0(en) s tan d ard s – G u i d an ce an d recom m en d ati on s T H I S P U B L I C AT I O N I S C O P YRI G H T P RO T E C T E D C o p yri g h t © I E C , G e n e v a , S wi tz e rl a n d All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or IEC's member National Committee in the country of the requester If you have any questions about I EC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local I EC member National Committee for further information IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch Ab ou t th e I E C The I nternational Electrotechnical Commission (I EC) is the leading global organization that prepares and publishes I nternational Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i ca ti o n s The technical content of IEC publications is kept under constant review by the IEC Please make sure that you have the latest edition, a corrigenda or an amendment might have been published I E C Catal og u e - webstore i ec ch /catal og u e The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad I E C pu bl i cati on s s earch - www i ec ch /search pu b The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications E l ectroped i a - www el ectroped i a org The world's leading online dictionary of electronic and electrical terms containing more than 30 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C G l os sary - s td i ec ch /g l oss ary More than 60 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st Pu bl i s h ed - webstore i ec ch /j u stpu bl i sh ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u stom er S ervi ce C en tre - webstore i ec ch /csc If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C TR 62 ® Edition 201 5-1 TE C H N I C AL RE P ORT colour i n sid e Rad i ati on i n s tru m e n tati on – Rad i ati on s ou rce s u s ed i n i l l i ci t traffi cki n g d e tecti on s tan d ard s – G u i d an ce an d recom m en d ati on s INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 3.280 ISBN 978-2-8322-2958-3 Warn i n g ! M ake su re th a t you obtai n ed th i s pu bl i cati on from an au th ori zed d i s tri bu tor ® Registered trademark of the International Electrotechnical Commission –2– I EC TR 62971 : 201 © I EC 201 CONTENTS FOREWORD Scope Norm ative references Terms and definitions, abbreviations and symbols Terms and definitions Abbreviations and sym bols Background List of relevant standards Source suppliers Nuclear Material (N M) sources and m aterials of interest 4 Neutron sources Surrogate materials and efforts Materials Efforts Sim ulated gamm a spectra versus real spectra Use of N aturall y Occurring Radioactive Material (N ORM ) General requirem ents NM Metals or oxides 1 Spheres or plates 1 Source encapsulation 1 Bibliograph y Figure – 241 Am-Be energy distribution Figure – Low resolution RGPu (blue trace) and WGPu spectra com parison 1 Table – I EC N M I EC TR 62971 :201 © I EC 201 –3– INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON R AD I AT I O N I N S T RU M E N T AT I O N – R AD I AT I O N S O U RC E S U S E D I N I L L I C I T T R AF F I C KI N G D E T E C T I O N S T AN D ARD S – G U I D AN C E AN D RE C O M M E N D AT I O N S FOREWORD ) The I ntern ation al Electrotechni cal Com m ission (I EC) is a worl d wid e organi zation for stan dardization com prisin g all n ation al electrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all questions concerni ng stan dardi zati on in the el ectrical and electronic fields To this end an d in ad dition to other acti vities, I EC publishes I nternational Stan dards, Techn ical Specifications, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) and Guid es (h ereafter referred to as “I EC Publication(s)”) Thei r preparation is entrusted to technical comm ittees; any I EC National Comm ittee interested in th e subject d ealt with m ay partici pate in this preparatory work I nternati onal, g overnm ental an d non governm ental organ izations liaising with the I EC also partici pate in this preparation I EC collaborates closel y with the I nternational Org ani zation for Stand ardi zation (I SO) in accordance with conditions determ ined by agreem ent between th e two organi zati ons 2) The form al decisions or agreem ents of I EC on technical m atters express, as n earl y as possi ble, an i nternati on al consensus of opi nion on th e rel evant su bjects since each technical com m ittee has representati on from all interested I EC N ational Com m ittees 3) I EC Publ ications have th e form of recom m endations for intern ational use an d are accepted by I EC Nati on al Com m ittees in that sense While all reasonable efforts are m ade to ensu re that th e tech nical content of I EC Publications is accu rate, I EC cann ot be h eld responsible for th e way i n which they are used or for an y m isinterpretation by an y en d u ser 4) I n order to prom ote intern ational u niform ity, I EC Nati onal Com m ittees und ertake to apply I EC Pu blications transparentl y to the m axim u m extent possible in th ei r n ation al and regional pu blicati ons Any di vergence between an y I EC Pu blication and th e correspond ing nati onal or regi on al publicati on sh all be clearl y i ndicated in the latter 5) I EC itself d oes not provide an y attestation of conform ity I n depend ent certificati on bodies provide conform ity assessm ent services and, in som e areas, access to I EC m arks of conform ity I EC is not responsi ble for an y services carri ed out by ind ependent certification bodi es 6) All users shou ld ensure that they h ave the l atest editi on of thi s publicati on 7) No liability shall attach to I EC or its directors, em ployees, servants or ag ents inclu din g in divi dual experts an d m em bers of its technical com m ittees and I EC N ational Com m ittees for any personal inj ury, property d am age or other dam age of any natu re whatsoever, wheth er d irect or indirect, or for costs (inclu di ng legal fees) and expenses arisi ng out of the publ ication, use of, or reliance upon, this I EC Publ ication or any other I EC Publications 8) Attention is drawn to the Norm ative references cited in this publication Use of th e referenced publ ications is indispensable for the correct applicati on of this publication 9) Attention is drawn to the possibility that som e of the elem ents of this I EC Publication m ay be th e subject of patent rig hts I EC shall not be held responsibl e for identifyi ng any or all such patent ri ghts The m ain task of I EC technical committees is to prepare I nternational Standards H owever, a technical committee m ay propose the publication of a technical report when it has collected data of a different kind from that which is norm ally published as an I nternational Standard, for exam ple "state of the art" I EC TR 62971 , which is a technical report, has been prepared by subcomm ittee 45B: Radiation protection instrumentation, of I EC technical committee 45: Nuclear instrum entation –4– I EC TR 62971 : 201 © I EC 201 The text of this technical report is based on the following docum ents: Enqui ry draft Report on votin g 45B/81 7/DTR 45B/821 /RVC Full information on the voting for the approval of this technical report can be found in the report on voting indicated in the above table This publication has been drafted in accordance with the I SO/I EC Directives, Part The comm ittee has decided that the contents of this publication will remain unchanged until the stability date indicated on the I EC website under "http: //webstore iec.ch" in the data related to the specific publication At this date, the publication will be • • • • reconfirmed, withdrawn, replaced by a revised edition, or amended A bilingual version of this publication may be issued at a later date I M P O RT AN T th at it – Th e co n ta i n s u n d e rs t a n d i n g c o l o u r p ri n t e r of ' co l ou r c o l o u rs i ts i n si de' wh i ch c o n te n ts l og o a re U s e rs on th e cover c o n s i d e re d sh ou l d p ag e to t h e re fo re of th i s be p ri n t p u b l i cati on u s e fu l th i s fo r i n d i c ate s th e d ocu m e n t c o rre c t u si n g a I EC TR 62971 :201 © I EC 201 –5– R AD I AT I O N I N S T RU M E N T AT I O N – R AD I AT I O N S O U RC E S U S E D I N I L L I C I T T R AF F I C KI N G D E T E C T I O N S T AN D ARD S – G U I D AN C E AN D RE C O M M E N D AT I O N S S cop e This Technical Report (TR) provides guidance and recom mendations regarding the availability and use of radiation sources that are needed when testing and evaluating instrum ents used for the detection of illicit trafficking of radioactive material The relevant standards are listed in Guidance includes the use of surrogate or replacem ent radioactive materials that could be m ore easil y obtained The obj ect of this Technical Report is to provide guidance to instrum ent m anufacturers, users, and testing organisations as to the selection and possible use of radiation sources, source surrogates and source simulation tools when testing and evaluating an instrument’s ability to detect and identify illicit trafficking of radioactive material N o rm a t i ve re fe re n c e s The following docum ents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, onl y the edition cited applies For undated references, the latest edition of the referenced docum ent (including an y amendments) applies I EC 60050-395 , in s tru m e n ta tio n : In te rn a tio n a l Ph ys ic a l Ele ctro te c h n ic a l ph en omen a, b a s ic Vo ca b u la ry c o n c e p ts , – in s tru m e n ts , Pa rt s ys te m s , 5: Nu c le a r e q u ip m e n t and de te cto rs T e rm s a n d d e fi n i t i o n s , a b b re vi a t i o n s a n d s ym b o l s T e rm s a n d d e fi n i t i o n s For the purposes of this docum ent, the following terms and definitions, as well as those given in I EC 60050-395 appl y n u c l e a r m a t e ri a l plutonium, except that with isotopic concentration exceeding 80 % in plutonium -238; uranium 233; uranium enriched in the isotope 235 or 233; uranium containing the m ixture of isotopes as occurring in nature other than in the form of ore or ore-residue; an y m aterial containing one or more of the foregoing Note to entry: Ad ditional details reg ardin g sou rce com position can be fou nd i n [ SOURCE: I AEA-TECDOC-1 31 -Septem ber 2002] DD DU HEU IAEA Ab b re v i a t i o n s a n d s ym b o l s Deuterium -Deuterium Depleted Uranium Highl y Enriched Uranium I nternational Atom ic Energ y Agency –6– NI ST NORM Np PMMA Pu RGPu NM WGPu 4 I EC TR 62971 : 201 © I EC 201 National I nstitute of Standards and Technology Naturall y Occurring Radioactive Material Neptunium Pol y m eth yl methacrylate Plutonium Reactor Grade Plutonium Nuclear Material Weapons Grade Plutonium Backgrou nd Li st of rel evan t stan d ard s The following standards are currentl y relevant to this Technical Report Each standard contains requirements for photon and neutron radiation emitting sources including those requirem ents for N M – I EC 62244, Ra dia tion protection in strum e n ta tion – In sta lled dia tio n m on itors for th e de tection of dioa ctive a n d spe cia l n ucle a r m a te ria ls a t n a tio n a l b orders – I EC 62327, Ra dia tion protectio n in strume n ta tion – Ha n d-h e ld in strum e n ts for the de tection a n d ide n tifica tio n of dion uclides a n d for th e in dica tio n o f a m b ie n t dose e quiva le n t te from p h oton dia tion – I EC 62401 , Ra dia tio n p rote ctio n in strume n ta tion – A la rm in g p erson a l dia tion devices (PRD) for detectio n of illicit tra ffickin g o f dioa ctive m a te ria l – I EC 62484, Ra dia tion p rote ctio n in strum e n ta tio n – Spectroscopy-ba se d porta l m o n itors use d for th e detection a n d ide n tifica tion of illicit tra ffickin g of dioa ctive m a te ria l – I EC 62533, Ra dia tion protectio n in strum e n ta tion – High ly se n sitive h a n d-he ld in strume n ts for p h oton de tection of dioa ctive m a teria l – I EC 62534, Ra dia tion protection in strum e n ta tion – Highly se n sitive h a n d-he ld in strume n ts for n e utron de tection of dioa ctive m a teria l – I EC 6261 8, Ra dia tion prote ctio n in strum en ta tion – Sp ectroscopy-b a sed a la rmin g Person a l Ra dia tion Devices (SPRD) for de tection of illicit tra ffickin g of dioa ctive m a teria l – I EC 62694, Ra dia tion pro tection in strum e n ta tion – Ba ckp a ck-typ e dia tion de tector (BRD) for th e de tection of illicit tra ffickin g of dioa ctive ma te ria l Sou rce su ppl i ers Several radioactive sources are required for testing to I EC standards Man y sources are commerciall y available for purchase I t is up to each individual organization to identify the manufacturer or supplier based on their specific needs N u cl ear M ateri al (N M ) sou rces an d m ateri al s of i n terest At the tim e of publication, the m aterials of interest include: – – – – Depleted Uranium (DU), Highl y Enriched Uranium (H EU), Reactor Grade Plutonium (RGPu), and Weapons Grade Plutonium (WGPu) Due to the availability of DU for testing, it will not be addressed in this Technical Report I EC TR 62971 :201 © I EC 201 –7– For I EC efforts, H EU has an enrichm ent of greater than 90 % 235 U and DU of no more than 0, % 235 U RGPu is defined as containing m ore than % 240 Pu, and WGPu having no m ore than % 240 Pu and not less than % 239 Pu Standardized test sources containing N M are sealed sources that are characterized by mass, isotope content, geometric shape (e g , spherical), and age The characterization should include chemical elem ents, not j ust radionucl ides 237 Np, 232 U , 233 U have been discussed as a possible material of interest, but due to very limited availability they will not be addressed further in this Tehcnical Report 4.4 Neutron sources Based on the m aterials of interest to be detected, a fission spectrum source is required at an em ission rate of 20 000 neutrons per second Therefore, each applicable standard requires the use of a 252 Cf source having an activity of approximatel y 85 kBq Neutron sources with higher emission rates such as those used for dosimetry or dosemeter calibration (i e , radiation protection instrument calibration) will produce more scattered neutrons because the source to detector distance m ust be increased to maintain the sam e fluence rate produced by the recom mended source Therefore, the use of a neutron source with much higher em ission rates is not recomm ended for illicit trafficking detection instrumentation 4.5 Su rrogate materials and efforts 4.5.1 M aterials – HEU HEU sources are required to produce the radiation test field for spectrometric or identification type instrum ents The am ount of 235 U depends on the requirements in the standard and instrum ent being tested Because the m ain photon energ y of 235 U is 86 keV, most em issions come from the surface of the source to a depth of approxim atel y mm (based on the 95 % infinite thickness emission rate) As a result, the quantity of a surrogate source can be reduced and still have the same emission as a much larger mass Surrogate H EU sources have been developed in the form of sealed stainless steel capsules containing porous graphite cylinders saturated with H EU oxide and in the form of thin wall hollow H EU spheres – Uranium Uran yl acetate m ay be used as a check source to verify uranium identification capabilities The chem ical compound can be purchased as a powder although there are man y different options as to its composition Uran yl acetate consists of 238 U and 235 U at 0, % to 0, % enrichm ent depending on the manufacturer Uran yl acetate is a toxic material – Plutonium radiation su rrogate A self-contained source of gamma-ray and neutron radiation suitable for use as a radiation source surrogate for WGPu has been developed (See Bibliograph y: U S Patent 7, 655, 935 B1 , Feb 2, 201 0) The surrogate source, which does not contain N M, was designed to produce a radiation spectrum sim ilar to that of WGPu over an energ y range from 59 keV to 61 keV This WGPu surrogate also em its neutrons having fluxes commensurate with gam ma radiation intensities employed The surrogate source consists of 33 Ba, 252 Cf, 37 Cs, 53 Gd, 57 Co, 55 Eu, 77m Lu, 1 Sn, 228 Th, 95 Zr in an assembl y Further details are available in the referenced patent This source is relevant for testing the identification capabilities of instrum ents with an energy resolution that is no better than % – Use of plated sou rces for handheld detection systems Sources m ade from the plating of 239 Pu or 235 U to a substrate were investigated as possible surrogates for larger sources that are used to test the identification function of handheld devices The investigation determined that the amount of material required m ay not be feasible for plated sources –8– I EC TR 62971 : 201 © I EC 201 – Neutron source The currentl y accepted em ission intensity for 252 Cf is 20 000 neutrons per second is used by the relevant standards Due to the short half-life of 252 Cf (2, 65 y), there has been much discussion in the standards community regarding the use of 241 Am -Be as a replacement The use of bare 241 Am-Be when testing illicit trafficking radiation detection system s that were built with m oderation included is not appropriate since the monitors were designed specificall y for detection of fission spectrum sources Additional moderation would be required to ensure that the neutrons im pinging on the detector are similar to that from a fission spectra point source Figure shows an 241 Am-Be spectrum plotted in Letharg y form at normalized to one source neutron The spectrum is taken from I SO 8529-1 : 2001 For Lethargy plots, when the energy axis is logarithm ic and the ordinate axis is linear (as shown in Figure1 ), the area between an y two energies is directl y proportional to the number of neutrons emitted by the source between those energies 0, Leth argy per source neu rton 0, 0, 0, 0, 0, 0, 0, 0, 01 0, 1 10 Neutron en ergy (M eV) IEC Figure – 241 Am-Be energy distribution I t is not currentl y possible to m anufacture neutron sources from 241 Am-Be that provide an acceptable fission neutron spectrum Further investigation is needed to determine if it is possible to manufacture sources for the purpose of providing an alternative for 252 Cf Another possible source of fission spectrum neutrons is 244 Cm This radionuclide has an year half-life which is much longer than that of 252 Cf Manufacturing safety and availability of 244 Cm m akes this a less effective neutron source Another possible surrogate is through the use of a deuterium -deuterium (DD) generator that produces 2, MeV neutrons, which might be shaped by various shields to give a suitable spectrum This would be expensive, and there would need to be a way to verify reproducibility in output I t is therefore not recommended as a surrogate neutron source 241 Americium-Boron is also being investigated as a possible surrogate for 252 Cf due to the similar neutron spectra 4.5.2 Efforts – Semi-empirical method for performance evaluation of detection and radionuclide identification I EC TR 62971 :201 © I EC 201 –9– A semi-empirical (derived from experiment and observation rather than theory) perform ance appraisal method to anal yze the performance of radionuclide identification software has been developed This spectral injection technique is based on the anal ysis of random ized raw instrument m easured spectra The raw spectra are obtained from the high quality spectral m easurement of actual sources The process creates synthetic spectra for injection into the instrument–specific anal ysis software The m ethod also allows the use of synthetic spectra if raw spectra are not available This method provides a means to evaluate analysis software perform ance and to complement testing with actual sources This method does not include the detector and associated electronics Future I EC 62957-1 , Ra dia tio n m e th o d fo r p e rfo rm a n ce Pe rfo rm a n c e e va lu a tio n e va lu a tio n of o f in s tru m e n ts is being developed for this technique de te ctio n fe a tu rin g and in s tru m e n ta tio n dio n uc lide dio n uc lide – S e m i- e m p irica l ide n tifica tio n ide n tific a tio n in – s ta tic Pa rt 1: m o de , – Neutron field measurement Typicall y, a neutron source is m oderated by the surrounding m aterial as well as the surface below the source or detector These m oderating materials include air, the container holding the source (e g , vehicle, shipping container), and road or ground surface and m oisture level within those surfaces Measurements and model/calculations have shown that surrounding a 252 Cf source with high density polyethylene having a thickness of cm to cm is m ost representative of the operational environment 4.5.3 Simulated gamma spectra versus real spectra Sim ulated spectra are sometimes used to verify the functionality of instruments used to identify radionuclides Som e of the advantages of using simulated spectra include reduced time and budget required to m ake predictions of instrum ent response under different test conditions An example of the use of simulated spectra could be the characterization of an instrum ent’s response to sources that are shielded or m asked by different types of materials An actual experim ent may be unaffordable due to the large possible number of com binations and test cases The disadvantage of simulations is that it is difficult to produce spectra as obtained in an actual m easurem ent Simulations require the knowledge of m an y param eters, such as detector dim ensions, detector efficiency, source encapsulation, source activity, m aterials surrounding the detector and source that m ight be unknown to the user Therefore, software validation is required to understand the lim itations of the simulation 4.5.4 Use of Naturally Occurring Radioactive Material (NORM) I n several I EC standards, NORM is used to verify the identification response of spectrometric instruments The use of bulk or large quantities of NORM for standardized , routine testing is difficult due to non-reproducible isotopic composition between different NORM s and handling of bulk m aterial during testing To address this, a surrogate N ORM was developed that m akes use of 226 Ra and 232 Th (or 232 U) point sources surrounded by approxim atel y cm of polym eth yl m ethacrylate (PMMA) The PMMA increases the Compton contribution and reduces the x-rays and low energy gamm a-rays in the energ y spectrum m aking it appear as bulk m aterial (See Bibliograph y: Measurem ents for the Development of a Sim ulated N aturall y Occurring Radioactive Material, y, Volum e 1 (201 2)) The described configuration does not include 40 K nor does it create a reduction in the measured radiation field that may be caused by bulk m aterial The need to include 40 K should be determ ined prior to using the surrogate NORM material for testing Jo urn a l o f R e s e a rch o f th e Na tio n a l In s titute o f S ta n da rds and Te c h n o lo g Another possible surrogate NORM source is known as the “KUTH field verifier” This product was developed for the oil well logging industry as an aid in the calibration of down-hole gamm a-ray spectroscopy tools The device consists of 40 K, natural U , and 232 Th Both the natural U and 232 Th are in secular equilibrium No additional inform ation is available – 10 – 5 I EC TR 62971 :201 © I EC 201 G e n e l re q u i re m e n t s NM Table contains a list of the N M sources currently used in I EC standards Source strengths are typicall y given as a mass quantity for a given shape and m aterial type (m etal or oxide) The surface areas shown for H EU and DU are based on the center cross-section of a sphere for the stated m ass NOTE I n I EC 62327, the sou rce strength for testing is based on an am bient dose eq ui val ent rate of 0, µSv h –1 ( ± 30 %) Tabl e S o u rc e s – I EC N M Qu a n ti t y ( ± 20 %) cm ) DU 4, kg (46 HEU 237 g (6, cm ) RGPu ,4 g WGPu 252 Cf 15 g 2× 04 n eutrons s –1 For Pu (RGPu and WGPu), the am ount of 241 Am (ingrowth from the decay of 241 Pu) varies widel y for different Pu sources There is a need to lim it the am ount of low energy gam ma-ray emissions from 241 Am to ensure that test results are com parable when tests are perform ed using different Pu sources I n order to provide com parable results, the net count rate of the 60 keV line from the 241 Am is reduced to be no more than tim es greater than that of the net count rate from the 41 keV line for 239 Pu For exam ple, if the count rate from the 41 keV line is 00 counts per second then the count rate from the 60 keV line is less than or equal to 000 counts per second This ratio is based on spectral measurements made of various Pu sources Copper with more than 99 % purity or Cadm ium may be used as shielding material to reduce the 60 keV em issions An y dose rate m easurements should be made after the Pu source is surrounded by the m aterial used to shield 241 Am Current applicable I EC standards require the use of RGPu and WGPu to verify an instrum ent’s ability to identify radionuclides Figure shows a comparison between RGPu and WGPu spectra obtained using a sodium -iodide-based (N aI (Tl)) spectrometric instrument There are differences between the spectra which may allow an instrument to identify the plutonium enrichment, but this level of identification is not required in the relevant standards I t is therefore suggested that onl y one Pu m aterial be required for testing purposes Current availability indicates that WGPu be the required N M I EC TR 62971 :201 © I EC 201 – 11 – Livetim e: 300, sec Deadtim e: 0, 33 % Neutrons: NA 04 Cou nts 03 02 01 00 Livetim e norm alized 500 000 500 000 500 000 Energy (keV) IEC Figure – Low resolution RGPu (blue trace) and WGPu spectra comparison 5.2 Metals or oxides Test results have indicated that the difference between spectra from a m etal and those from an oxide is such that it would not prevent a typi cal spectrom etric instrument from identifying the material Oxides are typicall y easier to obtain but m ay be m ore difficult to identify due to the presence of lower energy photons from scattering within the material 5.3 Spheres or plates NMs have a high density Most em issions come from the surface of the source to a depth dependent on the photon energy For exam ple, the depth for 85 keV is approxim atel y mm (based on the 95 % infinite thickness em ission rate), 5, mm for 400 keV, and 20, mm for MeV As a result, plates may be used instead of solid spheres For plates, the quantity of NM can be reduced and still have the sam e emission rate as the solid sphere of m uch greater mass 5.4 Source encapsulation Sealed sources are ideal for these types of applications Several sources were designed specificall y for testing against standards using stainless steel encapsulations (See Bibliograph y: N I ST Technical N ote, G a m m a -ra y e m ittin g test so urces for p orta l m on itors use d for h o m ela n d security) Due to the short half-life of m edical sources, stainless steel encapsulation m ay not be practical The use of epoxies to m ake a solid source for handling purposes is recomm ended The ph ysical design of the encapsulation should take into consideration m echanical requirements, safety, and ph ysical leakage Several sources used in I EC standards require specific construction due to their use and potential for damage – 12 – I EC TR 62971 :201 © I EC 201 Bibliography I SO 291 9: 201 2, R a dio lo g ic a l p ro te ctio n – S e a le d dio a ctive s o urc e s – G e n e l re q u ire m e n ts a n d cla s s ific a tio n I SO 4037-1 : 996, m e te rs and ch a c te ris tics and p ro te ctio n I SO 4037-3: 999, of X and a re a and p e rs o n a l re fe re n ce a fo r c a lib tin g fun c tio n dia tio n s th e ir re s p o n s e as a e n e rgy n g e s ga m m a a n d fo r de te rm in in g e n e rgy a n d a n g le dia tio n s as o f p h o to n s e m e te rs e n e rgy – and Pa rt 1: s e te R a dia tio n m e th o ds o ve r th e X and re fe re n ce th e ir re s p o n s e ga m m a fo r de te rm in in g fo r dia tio n m e te rs ga m m a a n d p ro du ctio n I SO 4037-2: 997, m e te rs X and fo r de te rm in in g re fe re n ce th e ir re s p o n s e s e m e te rs and fro m th e a o f p h o to n ke V to dia tio n s as fo r c a lib tin g fu n ctio n 1, o f p h o to n m e a s u re m e n t of – th e ir – 2: re s p o n s e as and Pa rt 3: a s e te D o s im e try Me V to s e m e te rs e n e rgy and Pa rt Me V a n d fo r c a lib tin g fu n ctio n s e m e te rs e n e rgy Me V s e te C a lib tio n fun c tio n of m e th o ds of o f in c ide n c e ISO 8529-1 : 2001 , R e fe re n c e n e u tro n dia tio n s – Pa rt 1: C h a c te ris tics and p ro ductio n ISO 8529-2: 2000, dia tio n Re fe re n c e p ro te ctio n ISO 8529-3: 998, s im e te rs de vic e s R e fe re n c e a n d de te rm in a tio n IAEA-TECDOC-1 31 -2002, dio a ctive n e u tro n re la te d to dia tio n s th e n e u tro n b a s ic dia tio n s o f re s p o n s e Pre ve n tio n as of a th e – Pa rt q u a n titie s – Pa rt fu n ctio n 2: C a lib tio n fun da m e n ta ls c h a c te ris in g th e 3: Ca lib tio n of a re a o f e n e rgy a n d a n g le in a dve rte n t m o ve m e n t and dia tio n and p e rs o n a l o f in c ide n c e illic it tra ffickin g of m a te ria ls ICRU Report 3, Ne u tro n Flu e n ce , Ne u tro n Sp e ctra a n d Ke rm a “Gamma-ray Test Sources for Portal Monitors Used for H omeland Security”, , Vol 1 3, N o , pp 08 – 1 , Decem ber 2004 Pro te ctio n of fie ld R a dia tio n D o s im e try “New Spherical Gamm a-ray and N eutron Emitting Sources for Testing of Radiation Detection I nstrum ents”, volume 1 4, pp 303-320, 2009 Na tio n a l In s titu te NI ST Technical N ote, o f Sta n da rds G a m m a - y e m ittin g a n d Te c h n o lo gy, te s t s o u rce s fo r p o rta l m o n ito rs us e d fo r h o m e la n d s e curity "Measurem ents for the Development of a Simulated N aturall y Occurring Radioactive M aterial ”, , Volum e 1 7, 201 Jo urn a l o f R e s e a rc h LA-U R-99-621 7, CAS 61 59-44-0 , o f th e Na tio n a l In s titute C a lib tio n o f th e Ura n yl a ce ta te , US Patent 7, 655, 935 B1 , D S NC o f Sta n da rds fo r th e Me a s ure m e n t o f dih ydra te Plu to n ium dia tio n a n d Te ch n o lo gy s u rro g a te _ 24 Cm a n d Pluto n iu m INTERNATIONAL ELECTROTECHNICAL COMMISSI ON 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 Switzerland Tel: + 41 22 91 02 1 Fax: + 41 22 91 03 00 info@iec.ch www.iec.ch