ANS 6.4.2-2006 Specification for Radiation Shielding Materials《辐射屏蔽材料的规范》.pdf

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1、ANSI/ANS-6.4.2-2006specification for radiationshielding materialsANSI/ANS-6.4.2-2006ANSI/ANS-6.4.2-2006American National StandardSpecification for RadiationShielding MaterialsSecretariatAmerican Nuclear SocietyPrepared by theAmerican Nuclear SocietyStandards CommitteeWorking Group ANS-6.4.2Published

2、 by theAmerican Nuclear Society555 North Kensington AvenueLa Grange Park, Illinois 60526 USAApproved September 28, 2006by theAmerican National Standards Institute, Inc.AmericanNationalStandardDesignation of this document as an American National Standard attests thatthe principles of openness and due

3、 process have been followed in the approvalprocedure and that a consensus of those directly and materially affected bythe standard has been achieved.This standard was developed under procedures of the Standards Committee ofthe American Nuclear Society; these procedures are accredited by the Amer-ica

4、n National Standards Institute, Inc., as meeting the criteria for AmericanNational Standards. The consensus committee that approved the standardwas balanced to ensure that competent, concerned, and varied interests havehad an opportunity to participate.An American National Standard is intended to ai

5、d industry, consumers, gov-ernmental agencies, and general interest groups. Its use is entirely voluntary.The existence of an American National Standard, in and of itself, does notpreclude anyone from manufacturing, marketing, purchasing, or using prod-ucts, processes, or procedures not conforming t

6、o the standard.By publication of this standard, the American Nuclear Society does not insureanyone utilizing the standard against liability allegedly arising from or afterits use. The content of this standard reflects acceptable practice at the time ofits approval and publication. Changes, if any, o

7、ccurring through developmentsin the state of the art, may be considered at the time that the standard issubjected to periodic review. It may be reaffirmed, revised, or withdrawn atany time in accordance with established procedures. Users of this standardare cautioned to determine the validity of cop

8、ies in their possession and toestablish that they are of the latest issue.The American Nuclear Society accepts no responsibility for interpretations ofthis standard made by any individual or by any ad hoc group of individuals.Requests for interpretation should be sent to the Standards Department atS

9、ociety Headquarters. Action will be taken to provide appropriate response inaccordance with established procedures that ensure consensus on theinterpretation.Comments on this standard are encouraged and should be sent to SocietyHeadquarters.Published byAmerican Nuclear Society555 North Kensington Av

10、enueLa Grange Park, Illinois 60526 USACopyright 2006 by American Nuclear Society. All rights reserved.Any part of this standard may be quoted. Credit lines should read “Extracted fromAmerican National Standard ANSI0ANS-6.4.2-2006 with permission of the publisher,the American Nuclear Society.” Reprod

11、uction prohibited under copyright conventionunless written permission is granted by the American Nuclear Society.Printed in the United States of AmericaForewordThis Foreword is not a part of American National Standard “Specification for RadiationShielding Materials,” ANSI0ANS-6.4.2-2006.!The need fo

12、r this standard was identified in mid-1977 by Working Group ANS-6.4.At that time, it was recognized that an increasing number of different material0design shielding concepts were being introduced into nuclear power plants tosolve neutron and gamma-ray streaming problems. For protection against neu-t

13、ron streaming, materials varying from water-filled rubber bags, rubber balls,special concretes, treated plastics, and silicone gels were proposed, while lead-filled silicone rubber and gels were proposed for gamma-ray streaming. Withsuch a variety of materials, some only a year or two after initial

14、commercialintroduction, a clear need was discerned to standardize the specification of thesematerials to assist the material manufacturer in the type of information he orshe needs to provide to the user.The focus of the working groups initial work was to orient the standard towardthe reporting requi

15、rements used by material suppliers rather than toward thepreparation of specifications by designers and end users. This focus has beenmaintained through the development of this standard as that representing thetrue needs of nuclear power plants in this area. The standard was reaffirmed in1997 and ag

16、ain in 2004, at which time a working group was appointed andcharged with revision of the standard.Working Group 6.4.2 of the American Nuclear Society Standards Committee hadthe following membership at the time of this revision:R. E. Faw Chair!, IndividualC. C. Graham, AmerenUE Callaway PlantS. J. Ha

17、ynes, Sandia National LaboratoriesT. M. Lloyd, EnergySolutionsJ. D. Olson, Black the word “should” is used to denote arecommendation; and the word “may” is usedto denote permission, neither a requirementnor a recommendation. To conform with thisstandard, materials that are to be consideredfor use as

18、 a radiation shield shall be evaluatedagainst the physical and nuclear properties thatthe standard sets forth. Accuracy of the deter-mined values shall be provided. Unless other-wise specified, it will be assumed that all valuesare at a pressure of 1 atm. Units used in spec-ifying properties shall b

19、e in the SI system asspecified in this standard but may be ex-pressed in other convenient units as well.3 Terms and definitionsThe following terms and definitions are pro-videdtoassureuniformunderstandingofthese-lectedtermsasareusedinthisstandard.Alargenumberofadditionaltermsthatareusedarede-finedin

20、thefollowingdocuments:“StandardTer-minology Relating to Methods of MechanicalTesting,” ASTM E6-06 1#;1!“Terminology Re-lating to Density and Specific Gravity of Solids,Liquids,andGases,”ASTME12-70R1991,with-drawn 1996!2#; “Standard Terminology of FireStandards,”ASTME176-05a3#;“StandardTer-minology R

21、elating to Rubber,” ASTM D1566-064#; “Cement and Concrete Terminology,” ACI-116R-00 R2005!5#;andGlossary of Terms inNuclear Science and Technology1986!6#.Arrhenius model: A model commonly used inaccelerated aging tests that relates the rate ofreaction of a material to temperature by a sim-ple expone

22、ntial function, r H11005 AexpH11002H90210kT!,where r is the reaction rate, A is a materialconstant frequency factor!, H9021 is the activationenergy of the material eV!, k is Boltzmannsconstant 0.8617 H11003 10H110024eV0K!, and T is theabsolute temperature K!.bremsstrahlung: Gamma radiation emitted b

23、yan electron when it is deflected by the Cou-lomb field of an atomic nucleus of charge Z;thefraction of energy radiated as photons by anelectron of initial energy E MeV! is approxi-mated numerically by ZE01000.equivalent test:Atest method utilized in placeof a standard or reference test that achieve

24、sthe same end result.induced radioactivity: Radioactivity due tothe interaction of an external neutron radia-tion field with the nuclides of a material.operating range: The range of values overwhich a parameter, indicative of environmen-tal conditions, is stated to vary during the ex-pected life of

25、a material as it performs itsintended function.photoneutron: Neutron released from anatomic nucleus in a photonuclear reaction witha gamma ray of sufficiently high energy. Thethreshold energy required of the gamma ray is;2 MeV for beryllium and deuterium but .8MeV for other elements.specific gravity

26、: For the purposes of this stan-dard, specific gravity is considered numeri-cally equal to density expressed in units g0cm3.trace element: An element found in smallquantities usually ,1%! within a material.trace radioactivity: Radioactivity due to traceamounts of naturally occurring radioisotopescon

27、tained within a material.1!Numbers in brackets refer to corresponding numbers in Sec. 8, “References.”14 Introduction and generaldescription4.1 IntroductionThepropertiesdiscussedinthisstandardarecon-sidered to be the most important ones for radi-ation shielding materials primarily as used innuclear

28、power plants; however, they should notbeviewedascomprisinganall-inclusivelist.In-cluded in Sec. 5 are the nuclear properties andin Sec. 6 are the general physical properties.Users of this standard should recognize that interms of the shielding function of a material,some properties are more importan

29、t than oth-ers because of the direct impact they have. In-cluded among these are density and the nuclearproperties. Other physical properties, e.g., sta-bility, strength, and fabrication, are needed todefine fully the conditions and capabilities ofcandidate materials but are of more peripheralintere

30、st to the shielding function. This stan-dard does provide guidance for the consider-ation of those more peripheral properties byreferencing examples of American Society forTesting and Materials ASTM! standards thatare available. However, there may be other stan-dards that provide a fundamental and m

31、oredetailed discussion of these properties and howthey are used. Such standards are properly theworking tools of engineering disciplines otherthan radiation shielding, and the ultimate de-cisions relating to such properties reside withthese other engineering disciplines.4.2 General descriptionInform

32、ation on the general description of amaterial such as its physical state, type, andintended use should be used in the initialidentification of potentially appropriate mate-rials for a specific application. Such informa-tion is generally supplied by material vendorsbut needs to be supplemented by the

33、 specificproperties discussed in this standard. Anyknown environmental restrictions shall beidentified.5 Nuclear properties of materials5.1 IntroductionThe selection of an appropriate shielding ma-terial is most strongly influenced by its nu-clear properties, i.e., its ability to provide therequired

34、 attenuation of neutron radiation orgamma radiation, or both, per unit thicknesswithout creating deleterious nuclear, physical,or chemical side effects. These nuclear proper-ties are dependent on the isotopic compositionof the material.This section of the standard sets forth two al-ternate sets of d

35、ata requirements that serve todefine the nuclear properties of the candidateshielding material. One requirement applies tothe case where the supplier provides a com-plete elemental composition of the candidatematerial and is more fully described in Sec. 5.2.The alternative requirement applies when t

36、hesupplier provides attenuation and other nu-clear information directly, which is more fullydescribed in Sec. 5.3. The intent of the stan-dard is to encourage the material supplier touse the first alternative whenever practical.That the first alternative may also be advan-tageous from the viewpoint

37、of the material sup-plier is illustrated in Ref. 7#.5.2 Elemental compositionThe supplier shall provide a detailed materialcomposition; the data shall be in the format ofthe density of each element of the compoundg0cm3or kg0m3!. In the case of any elementwhose isotopes are not naturally abundant, su

38、chas depleted uranium, the composition of thiselement shall be subdivided into compositionby isotope. If lithium or boron is a componentof a neutron shield material, the isotopic abun-dance shall be provided since there is a largedifference in the neutron cross-section proper-ties between the isotop

39、es of these elements andsome variation in the naturally occurring iso-topic abundances in available material. Forshields containing an appreciable proportion ofhydrogen and where the neutron field to beshielded is largely thermal neutrons, it is alsoappropriate to indicate the molecular form inwhich

40、 the hydrogen atoms exist.5.2.1 Environmental considerationsThe elemental composition of the materialandisotopic breakdown for special elements such asin Sec. 5.2! shall be given along with the phys-ical and chemical conditions under which suchcompositionisapplicable.Theseconditionsmightbe temperatu

41、re, pressure, humidity, physicalform, age, etc. Variations of elemental composi-American National Standard ANSI0ANS-6.4.2-20062tionswiththeseconditionsshouldalsobegiven,either in accord with Sec. 5.2.4 of this standardor with a later section. The basis, i.e., type ofstandard or equivalent test, used

42、 in determin-ing the composition should also be provided.5.2.2 Trace elementsTrace elements can be very important in theselection of a shielding material if the materialis intended to be used in the presence of aneutron field. This importance stems from thevery large differences among the elements i

43、ntheir neutron interaction probabilitiescross sec-tions! that lead to the formation of activationproducts that emit gamma rays. Trace ele-ments, therefore, shall be provided by the sup-plier as part of the elemental composition ofthe material.2!5.2.3 Trace radioactivityTrace radioactivity is detrime

44、ntal when theshield material application is a low-level count-ing room, health physics laboratory, or analyt-ical laboratory. Examples of trace radioactivityisotopes are40K in concrete,204Pb in shieldingmaterials containing lead,209Bi in certain melt-able alloys, and numerous long-lived radioiso-top

45、es in thorium and uranium. Trace radioactiveisotope content shall be included in the compo-sition of materials intended to be used for suchapplications.5.2.4 Test documentationThe supplier should describe the laboratorymethods utilized to measure the material com-position or reference an existing in

46、dustry stan-dard procedure, such as those published by theAmerican National Standards Institute. Thephysical and chemical conditions existing atthe time of measurement should be stated. Insome cases, the weight percentages of the ele-mental constituents will remain constant overa wide range of tempe

47、rature, pressure, and otherenvironmental changes; in other cases, the ele-mental makeup will change e.g., loss of waterwith increasing temperature!. The suppliershould provide, in accordance with this sectionor later sections of the standard, definitive in-formation on how the composition varies ove

48、rthe operating range of temperature and pres-sure, in dry air versus immersed in water orother appropriate media!, and during agingseeSec. 6.4.1!.5.3 Nuclear dataAlternatively, in the absence of a detailed ele-mental composition, adequate nuclear data shallbe given to fully define the gamma-ray orne

49、utron shielding properties, or both, of thematerial, including attenuation characteris-tics, secondary radiation production, activationproperties, and residual radiation. Uncertain-ties in the defined properties should be sup-plied. The basis for the nuclear data shouldalso be provided.The intent of this standard is to encourage thematerial supplier to provide the elemental com-position of the material to the shield designer,rather than requiring a much more extensiveand complex nuclear data set needed as a sub-stitute for composition data as described inSecs. 5.3