1、Designation: C1831/C1831M 17Standard Guide forGamma Radiation Shielding Performance Testing1This standard is issued under the fixed designation C1831/C1831M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide identifies appropriate test methods for deter-mining the sufficiency of radiological shielding for hot cellsand shielded
3、 enclosures.1.2 After constructing or modifying radiological shielding,it is necessary to verify that shielding performance meets orexceeds the shielding performance requirements. This is typi-cally accomplished using sealed test sources of much lessactivity than the design basis. This allows for mo
4、difications orcorrection of any discrepancies identified before the commis-sioning of the hot cell.1.3 The guidance and practices recommended by this guideare applicable to both new and existing shielded facilities andenclosures for evaluating shielding suitability and locating theexistence of shine
5、 paths or other shielding anomalies that resultfrom design, manufacture, or construction.1.4 Two types of testing may be performed.1.4.1 Shielding performance verification testing providesevidence that the shielding configuration is sufficient formeeting established performance criteria and for iden
6、tifyingdeficiencies in the shielding configuration or components thatmay not have been addressed during design. Test results areexpected to demonstrate that shielding performance meets orexceeds design criteria, not match the dose rates predictedanalytically.1.4.2 Shielding performance verification
7、testing identifiesshielding deficiencies (hot spots) in the installed configurationrelative to adjacent shielding but does not demonstrate com-pliance with any quantitative shielding performance require-ment.1.5 Performance testing should be specified and performedto assess shielding adequacy with s
8、ources in all criticallocations.1.6 Requirements for shielding performance testing shouldbe clearly defined in design basis or procurement documenta-tion.1.7 This guide is not applicable to neutron radiation shield-ing performance evaluations.1.8 UnitsThe values stated in either SI units or inch-pou
9、nd units are to be regarded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in noncon-formance with the standard.1.8.1 Units for total activity should
10、 be given in Becquerel(Bq) or curies (Ci).1.8.2 Units for dose rate as measured during testing shouldbe given in Sieverts (Sv/h) or rad/h.1.8.3 Distances and locations should be provided in centi-metres or inches.1.9 This standard does not purport to address all of thesafety concerns, if any, associ
11、ated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.10 This international standard was developed in accor-dance with internationally rec
12、ognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C859 Terminology Re
13、lating to Nuclear Materials3. Terminology3.1 For terms not defined in this guide, see TerminologyC859.3.2 Definitions:3.2.1 angular response sensitivity, nthe ability of aninstrument or detector to detect radiation based on the angle ofincidence of the radiation on the instrument or detector.1This g
14、uide is under the jurisdiction of ASTM Committee C26 on Nuclear FuelCycle and is the direct responsibility of Subcommittee C26.14 on Remote Systems.Current edition approved Nov. 1, 2017. Published November 2017. DOI:10.1520/C1831_C1831M-17.2For referenced ASTM standards, visit the ASTM website, www.
15、astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis int
16、ernational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) C
17、ommittee.13.2.2 Bremsstrahlung radiation, nelectromagnetic radia-tion produced by the deceleration of a charged particle whendeflected by another charged particle, typically an electron byan atomic nucleus.3.2.2.1 DiscussionThe moving particle loses kineticenergy, which is converted into a photon be
18、cause energy isconserved.3.2.3 buildup factor, nfor radiation passing through amedium, the buildup factor is the ratio of the total value of aspecific radiation quantity (direct and scattered) measured asabsorbed dose at any point within that medium to the contri-bution to that quantity from the inc
19、ident uncollided radiationreaching that point.3.2.3.1 DiscussionThe buildup factor increases with in-creased shielding thickness and is higher for low atomicnumber materials.3.2.4 encapsulated source, nsealed source strong enoughto maintain leak tightness under the conditions of use for whichthe sou
20、rce was designed and also under foreseeable mishaps.3.2.4.1 DiscussionIt is radioactive material that is perma-nently sealed in a capsule or closely bonded and in a solidform.3.2.5 Geiger-Mller counter, GM, ntype of particle detec-tor that measures ionizing radiation.3.2.5.1 DiscussionThe radiation-
21、sensing element is aninert gas-filled Geiger-Mller tube (usually containing helium,neon, or argon with halogens added) at a low pressure thatbriefly conducts an electrical charge when a particle or photonof radiation makes the gas conductive by ionization. GMsdisplay the number of ionization events,
22、 typically in “counts-per-second.” The GM tube can detect the presence of radiationbut not its energy, which determines the ionizing effect.Instruments that make use of an energy compensated GM tubeare capable of displaying absorbed dose.3.2.6 ionization chamber, nbeta-gamma radiation meteruseful fo
23、r direct measurement of exposure and dose rates,determining shielding effectiveness, checking sourcecontainers, monitoring radiation areas, and checking resultsfollowing decontamination procedures.3.2.6.1 DiscussionThe unit contains an ion chamber thatconverts directly from ion chamber current to do
24、se rate.3.2.7 manipulator through tube, npenetration providedspecifically for installation of a master-slave manipulator.3.2.7.1 DiscussionTypically, a hole with a diameter of acertain size depending on the manipulator being used thatpasses horizontally though the shield wall above the operators.3.2
25、.8 penetration, nlocations where utilities,instrumentation, or processes pass through the shield wall.3.2.9 sealed source, nradioactive source that has beenenclosed within a sealed container that prevents loss ofmaterial, spread of contamination, and maintains the geometryof the radioactive material
26、.3.2.10 shielding performance evaluation testing, ntestingthat assesses the uniformity in shielding performance.3.2.10.1 DiscussionIt is useful for locating void spacesthat may reside in the shielding system.3.2.11 shielding performance verification testing, ntestingused to demonstrate that shieldin
27、g meets or exceeds theperformance requirements established in the design basis orprocurement documents.3.2.12 skyshine, nradiation that is scattered by the atmo-sphere or adjacent structures above a radiation source to pointson the ground around the outsider perimeter.3.3 Definitions of Terms Specif
28、ic to This Standard:3.3.1 biological shielding, vfor purposes of this guide, itis the radiation-absorbing shield used to protect personnel fromthe effects of nuclear particles or radiation.3.3.2 source location volume, nspecifies the zone thesource is expected to occupy within the shielded enclosure
29、.4. Summary of Guide4.1 The test source(s) is positioned within the shieldedenclosure and the dose rate is measured at established locationsusing a calibrated instrument.4.2 It is important that test acceptance criteria reflect the testsource and not the design basis source term.5. Significance and
30、Use5.1 Shielding performance testing should be performed toverify analytical predictions of shielding effectiveness, com-pliance with design requirements, and determine the loca-tion(s) of shielding deficiencies that may require either supple-mental shielding, design modification, or changes to oper
31、atingmethods and procedures to resolve.5.2 Dose rates higher than adjacent shielding may beexpected in the vicinity of master-slave manipulator penetra-tions as a result of cable or tape clearance requirements withinthe mechanisms where they pass through the shield walls. Thisis true even with suppl
32、emental shielding installed in themanipulator through tube.5.3 Similar to manipulator penetrations, when sources areplaced directly in front of penetrations and gaps resulting fromaccess doors or panels, radiation levels directly on the otherside of the gaps or penetrations may be higher than levels
33、 inadjacent shielding or analytical predictions. If these test con-figurations are representative of how the shielded enclosurewill actually be operated (that is, the test configuration isrepresentative of engineered source and normally occupiedwork locations) than the additional expense of designin
34、g ormodifying the shielded enclosure should be considered if thatlocation is normally occupied and will result in a significantincrease of dose rates to personnel.5.4 Frames around shield windows may have a higherpotential for shielding deficiencies.5.5 Shield walls constructed of concrete may be su
35、bject tothe formation of void spaces that could result in diminishedshielding performance.5.6 Background radiation levels in the area where the dosemeasurement data are being gathered shall be monitored andtheir contribution to measured dose rates accounted for in thedata analysis as part of the tes
36、t report.C1831/C1831M 1726. Apparatus6.1 In HSE Ionizing Radiation Protection Series No. 7,Table 1, the recommended instrument for measuring gammaradiation dose rates is energy compensated GM counter,although an ionization chamber would be a viable alternative.36.2 Instrumentation used for dose rate
37、 measurements shallbe calibrated in accordance with the requirements of NCRP112.46.3 For shielding performance verification testing, traceablesealed calibration standards are preferred.6.4 If encapsulated calibrated standards with the total activ-ity or energy spectra desired are unavailable, then s
38、peciallyprepared sources may be used. Test sources of a knownisotopic composition and activity are required.6.5 The test source shall be selected specific to the facilityand in conjunction with input from the radiation experts for thespecific situation to be of sufficient activity to enable validmea
39、surements (that is, result in measurements within theinstruments span of calibration) and minimize exposure to testpersonnel making dose rate measurements.6.6 For shielding performance verification testing, sourceholders or other means shall be pre-placed in the shieldedenclosure to locate the sourc
40、e precisely and repeatedly whentest results are to be compared against analytically predictedvalues to demonstrate the shielding meets a specific perfor-mance requirement. The precision required for source place-ment accuracy will be a function of source strength and wallconstruction. Shielding anal
41、ysis will demonstrate the sensitiv-ity of expected dose rate measurements as a function of testsource location.6.7 When a source location volume within the biologicalshield is specified rather than specific engineered locations,provision should be included in the test apparatus to ensure thatthe sou
42、rce remains within that volume during testing.6.8 The use of multiple sources, different sources, or com-binations thereof within the same shielded enclosure duringtesting is acceptable.6.9 Test sources should be sealed and marked with a uniqueidentification number that provides traceability to isot
43、opiccomposition and a total activity value with an associatedreference date that would allow an analyst to decay the sourcebefore performing analysis used to establish test acceptancecriteria.6.10 Sources should be selected such that measured valuesare within the calibrated range of the instrument u
44、sed tomeasure dose rates.7. Procedure7.1 Detector orientation should be controlled to minimizethe effects of angular response on test results.7.2 All shielding performance testing should be performedusing an approved test procedure developed for the specificapplication.7.3 Background radiation level
45、s that could affect the testresults should be measured and recorded. When backgroundlevels are expected to vary, they should be measured andrecorded throughout testing.7.4 Shielding Performance Verification Testing:7.4.1 The calibrated source is placed in repeatable testlocation(s) for each penetrat
46、ion to be tested.7.4.2 Dose measurements are made at predeterminedlocations, typically in contact with the shielding and 30 cm 12in. away from the shielding being tested. Instrument readingsand location shall be recorded.7.4.3 Continue to reposition the source and take measure-ments until all data c
47、ollection has been completed.7.5 Shielding Performance Evaluation Testing:7.5.1 A source is positioned within the shielded enclosure,opposite the area to be evaluated.7.5.2 The instrument is used to measure dose rates in theregion of the source. The size of the region that can beevaluated without mo
48、ving the source may be determinedanalytically, as observed dose rates will be a function of sourceactivity and geometry relative to the detector.7.5.3 Regions in which an unexpected increase in measureddose occurs should be evaluated further to assess the reason forthe change. Dose rate increases ma
49、y indicate voids or deficien-cies that shall be addressed before commissioning the shieldedenclosure for use.8. Hazards8.1 Caution should be exercised around test sources toprevent unintended radiation exposures to personnel. Wherepractical, test sources should be placed remotely.8.2 For evaluation of sources in multiple locations, typicallysources are placed remotely using appropriate technology.9. Report9.1 The results of testing shall be documented in a writtenreport that includes a description of the shielding performancerequirement, test method, and find
