1、Designation: D5411 10Standard Practice forCalculation of Average Energy Per Disintegration ( E) for aMixture of Radionuclides in Reactor Coolant1This standard is issued under the fixed designation D5411; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice applies to the calculation of the averageenergy per disintegration (E)
3、for a mixture of radionuclides inreactor coolant water.1.2 The microcurie (Ci) is the standard unit of measure-ment for this standard. The values given in parentheses aremathematical conversions to SI units, which are provided forinformation only and are not considered standard.1.3 This standard doe
4、s not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Stan
5、dards:2D1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD3370 Practices for Sampling Water from Closed ConduitsD3648 Practices for the Measurement of RadioactivityD7282 Practice for Set-up, Calibration, and Quality Controlof Instruments Used for Radioactivity Measurements2.2 Code
6、of Federal Regulations:10 CFR 100 Reactor Site Criteria33. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminology D1129.4. Summary of Practice4.1 The average energy per disintegration, E(pronounced Ebar), for a mixture of radionuclides is calculated from thek
7、nown composition of the mixture. Eis computed by calcu-lating the total beta/gamma energy release rate, in MeV, anddividing it by the total disintegration rate. The resultant Ehasunits of MeV per disintegration.5. Significance and Use5.1 This practice is useful for the determination of theaverage en
8、ergy per disintegration of the isotopic mixture foundin the reactor-coolant system of a nuclear reactor (1).4The Evalue is used to calculate a site-specific activity limit for thereactor coolant system, generally identified asAlimiting5 K/EwhereK = a power reactor site specific constant (usually in
9、therange of 50 to 200).The activity of the reactor coolant system is routinely mea-sured, then compared to the value of Alimiting. If the reactorcoolant activity value is less thanAlimitingthen the 2-h radiationdose, measured at the plant boundary, will not exceed anappropriately small fraction of t
10、he Code of Federal Regula-tions, Title 10, part 100 dose guidelines. It is important to notethat the measurement of the reactor coolant system radioactiv-ity is determined at a set frequency by use of gammaspectrometry only. Thus the radionuclides that go into thecalculation of Eand subsequently Ali
11、mitingare only those thatare calculated using gamma spectrometry.5.2 In calculating E, the energy dissipated by beta particles(negatrons and positrons) and photons from nuclear decay ofbeta-gamma emitters. This accounting includes the energy1This practice is under the jurisdiction of ASTM Committee
12、D19 on Water andis the direct responsibility of Subcommittee D19.04 on Methods of RadiochemicalAnalysis.Current edition approved June 1, 2010. Published December 2010. Originallyapproved in 1993. Last previous edition approved in 2005 as D5411 05. DOI:10.1520/D5411-10.2For referenced ASTM standards,
13、 visit the ASTM website, www.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.3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Ph
14、iladelphia, PA 19111-5094, Attn: NPODS.4The boldface numbers in parentheses refer to a list of references at the end ofthis practice.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.released in the form of energy released from extra-n
15、ucleartransitions in the form of X-rays, Auger electrons, and conver-sion electrons. However, not all radionuclides present in asample are included in the calculation of E.5.3 Individual, nuclear reactor, technical specifications varyand each nuclear operator must be aware of limitationsaffecting th
16、eir plant operation. Typically, radioiodines, radio-nuclides with half lives of less than 10 min (except those inequilibrium with the parent), and those radionuclides, identi-fied using gamma spectrometry, with less than a 95 % confi-dence level, are not typically included in the calculation.However
17、 the technical requirements are that the reportedactivity must account for at least 95 % of the activity afterexcluding radioiodines and short-lived radionuclides. There areindividual bases for each exclusion.5.3.1 Radioiodines are typically excluded from the calcula-tion of Ebecause United States
18、commercial nuclear reactorsare required to operate under a more conservative restriction of1 C (37 kBq) per gram dose equivalent131I (DEI) in thereactor coolant.5.3.2 Beta only emitting radio isotopes (for example,90Sror63Ni) and alpha emitting radioisotopes (for example,241Amor239Pu) which comprise
19、 a small fraction of the activity,should not be included in the E-bar calculation. These isotopesare not routinely analyzed for in the reactor coolant, and thustheir inclusion in the E-bar calculation is not representative ofwhat is used to assess the 10 CFR 100 dose limits. Tritium, alsoa beta only
20、 emitter, should not be included in the calculation.Tritium has the largest activity concentration in the reactorcoolant system, but the lowest beta particle energy. Thus itsdose contribution is always negligible. However its inclusionin the E-bar calculation would raise the value of Alimiting,yield
21、ing a non-conservative value for dose assessment.5.3.3 Excluding radionuclides with half-lives less than 10min, except those in equilibrium with the parent, has severalbases.5.3.3.1 The first basis considers the nuclear characteristicsof a typical reactor coolant. The radionuclides in a typicalreact
22、or coolant have half-lives of less than 4 min or havehalf-lives greater than 14 min. This natural separation providesa distinct window for choosing a 10-min half-life cutoff.5.3.3.2 The second consideration is the predictable timedelay, approximately 30 min, which occurs between the releaseof the ra
23、dioactivity from the reactor coolant to its release to theenvironment and transport to the site boundary. In this time, theshort-lived radionuclides have undergone the decay associatedwith several half-lives and are no longer considered a signifi-cant contributor to E.5.3.3.3 A final practical basis
24、 is the difficulty associatedwith identifying short-lived radionuclides in a sample thatrequires some significant time, relative to 10 min, to collect,transport, and analyze.5.3.4 The value of E-bar is usually calculated once every 6months. However, anytime a significant increase in the activityof t
25、he reactor coolant occurs, the value of E-bar should bereassessed to ensure compliance with 10 CFR 100. Suchreassessment should be done any time there is a significant fueldefect that would alter the Evalue and affect Alimiting. The twopossible causes to reassess the value of Ewould be:(1) A signifi
26、cant fuel defect has occurred where the noblegas activity has increased.(2) A significant corrosion product increase has occurred.For the case of a fuel defect, the plant staff may need to includenew radionuclides not normally used in the calculation of Esuch as239U and239Np.6. Interferences6.1 The
27、analytical determination of the radionuclides usedfor this calculation is made by gamma ray spectrometry.Commercially available software is generally used to performthe spectrum analysis and data reduction. However there canbe significant number of interferences from gamma ray emit-ters with multipl
28、e gamma ray emissions. The user mustcarefully select the appropriate interference free gamma rayenergy for each radionuclide in order to determine accuratelythe activity of each radionuclide. As a specific example56Mn(t12 = 2.6 h) has a gamma ray energy of 847 keV and134I(t12 =53 min) also has a gam
29、ma ray energy of 847 keV. The 847 keVgamma ray is also the most abundant for each of theseradionulcides. It would be inaccurate to use the 847 keVgamma ray for the determination of either of these radionu-clides.7. Sampling7.1 If samples are collected for analysis in support of thispractice they sho
30、uld be representative of the matrix, be ofsufficient volume to ensure adequate analysis, and be collectedin accordance with Practices D1066, D3370, and D3648.7.2 In addition to the requirements of 7.1, if samples ofreactor coolant are required in support of this practice, theyshould typically be col
31、lected only after a minimum of 2effective full-power days and 20 days of power operation haveelapsed since the reactor was last subcritical for 48 h or longer.Individual nuclear operator technical specifications (or now formany plants called “technical requirements”) vary and shouldbe reviewed to de
32、termine specific requirements.8. Calibration and Standardization8.1 Any calibrations and standardizations required in sup-port of this practice should be in accordance with the appli-cable sections of Practices D3648 and D7282 and in accor-dance with the manufacturers specifications for the gammaspe
33、ctrometry system used.9. Procedure9.1 Conduct all analyses in support of this practice inaccordance with the applicable sections of Practice D3648.9.2 Perform sufficient gamma isotopic analyses of the liq-uid, gaseous, and suspended fractions of the sample to ensurethat at least 95 % of the coolant
34、activity due to gamma emittingisotopes has been quantified. Samples should be analyzed atapproximately 0.5 h, 2 h, 24 h, and 7 days following samplecollection. Multiple sample analyses are required to ensureaccurate quantification of the longer-lived isotopes because ofmasking caused by the high ini
35、tial activity of short-livedD5411 102radionuclides in the sample. If interferences continue to be aconcern with the results of the analysis conducted on Day 7, itmay be necessary to conduct additional gamma isotopicanalyses of the sample at approximately 30 days after collec-tion.9.3 Sample fraction
36、s that are going to be stored for recount-ing (at 24 h, 7 days, or 30 days) should be preserved with atleast 2 mL of concentrated nitric acid per litre of sampleimmediately after the sample is taken to preserve the samplegeometry. This mitigates the precipitation of radionuclides oradhesion of radio
37、nuclides onto container walls.9.4 Tabulate the concentrations, uniformly measured inCi/cc (37kBq/cc) or Ci/g (37kBq/g), of all applicable gammaradioisotopes identified in the sample. Examples of the mostsignificant contributing radioisotopes to Eare:(1) Noble gas fission products:131mXe,131Xe,133mXe
38、133Xe,87Kr (others),(2) Soluble fission products:137Cs,134Cs,141Ce,140Ba,140La,92Sr (others),(3) Corrosion activation products:58Co,56Mn,54Mn,60Co,51Cr,59Fe,95Zr,95Nb (others),(4) Miscellaneous radionuclides:41Ar,24Na,18F,7Be (oth-ers), and(5) Reactor coolant suspended and particulate material(comm
39、only referred to as crud) will also have the activatedproducts in them and must be included in the calculationof E.10. Calculation10.1 Calculate the average energy per disintegration, E,inMeV according to the following equation:E5(i 5 1nAi* Ei!(i 5 1nAi(1)where:E = average energy per disintegration,
40、 MeV/disintegration,Ai= activity of the ith radionuclide uniformly measured,Ci/cc or Ci/g, andEi= isotopic energy emission for the ith radionuclide,MeV/disintegration.10.2 The values for AIare the measured activity levels of arepresentative sample in Ci/cc (37 kBq/cc) or Ci/g (37kBq/g), for each app
41、ropriate radionuclide identified in thesample (for example,60Co,133Xe,137Cs, etc.).10.3 The values for Eiare constant for each radionuclideand depend upon the decay scheme for that radioisotope. Eiiscalculated from the following equation:Ei5 Eibeta!1EiCE! 1 EiA! 1 Eigamma!1EiX! (2)where:Ei(beta) = t
42、he average, abundance weighted, beta en-ergy per disintegration, MeV/disintegration,Ei(CE) = the average, abundance weighted, conversionelectron energy per disintegration, MeV/disintegration,Ei(A) = the average, abundance weighted, Augerelectron energy per disintegration, MeV/disintegration,Ei(gamma
43、) = the average, abundance weighted, gammaenergy per disintegration, MeV/disintegration, andEi(X) = the average, abundance weighted, X-ray en-ergy per disintegration, MeV/disintegration.10.4 An example for the calculation of Eifor the disinte-gration of133Xe (EXe-133) follows.10.4.1 The decay scheme
44、 for133Xe (3) is given in Fig. 1.10.4.2 First, calculate EXe-133(beta).10.4.2.1 To determine each Ei(beta), multiply the averageenergy per disintegration for each beta emitted by its abun-dance and sum the products. The average beta energies for eachisotope may be found in the literature (3, 4). Or,
45、 it may beapproximated by multiplying the maximum beta particle en-ergy per transformation by a factor of one-third. Only one-thirdof the maximum beta energy is included in the calculationbecause the remaining two-thirds of the radionuclide decayenergy is dissipated by neutrino emission (5). Neutrin
46、os arevery high energy, chargeless particles that do not undergointeraction with matter like the human body. Therefore, theircontribution is ignored when considering the total energyavailable for absorption by a person at the site boundary of thenuclear facility.10.4.2.2 The average energies and abu
47、ndances of the majorbeta emissions for the decay of133Xe are (3):beta # Average Energy Abundance2 0.0751 MeV 0.69 %3 0.101 MeV 99.3 %10.4.2.3 Therefore, EXe-133(beta) is:EXe-133(beta) = (beta #2 average energy) * (beta 2 abundance) + (beta#3 average energy) * (beta 3 abundance)EXe-133(beta) = 0.0751
48、 * 0.0069 + 0.101 * 0.993,EXe-133(beta) = 0.101 MeV/disintegration.10.4.3 Next, calculate Ei(CE).10.4.3.1 Unlike beta particle emissions, conversion elec-trons are monoenergetic emissions and are not accompanied byneutrino emission. Therefore, their contributions to Ei(beta) isincluded at their full
49、 emission energy minus the binding energyof the emitted electron. Here again the abundance for eachtransformation is an included factor.10.4.3.2 The energies and abundances of the major conver-sion electron emissions for the decay of Xe-133 are (3):FIG. 1 Decay Scheme for133XeD5411 103CE # Energy AbundanceK-2 0.0450 MeV 53.3 %L-2 0.0753 MeV 8.14 %10.4.3.3 Therefore, EXe-133(CE) is:EXe-133(CE) = (K-2 energy) * (K-2 abundance) + (L-2 energy) * (L-2abundance)EXe-133(CE) = 0.0450 * 0.533 + 0.0753 * 0.0814,EXe-133(CE) = 0.0301 MeV/disintegration.10.4.
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