Neutron emission spectra induced by 14.6-MeV incident neutrons, retrieved from ENDF/B-V, are graphically compared with experimental data by Hermsdorf et al. and Clayeux and Voignier. The elements selected for the comparisons include Na, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Ni, Cu, Nb, W, and Pb. In addition to comparing the evaluated total neutron emission spectra with experimental data, individually evaluated spectra from contributing reactions are presented. Only a few of the evaluated spectra were found to agree well with the measured spectra, namely, those evaluations which utilized advanced nuclear model codes with precompound effects and competing binary and tertiary reactions. Recommendations for removing several defects in most evaluations are made. 3 figures

Fu, C.Y.

Hetrick, D.M.

Larson, D.C.

UNT Digital Library

mmJfi{JfjlU 8 * = •* ? T?5 S : ? I s >3 1 '. = ° s * £ j§ % c t i I § I 5"By acceptance of this article, the publisher or recipientacknowledges the U. S. Government's ritht to retain anon-exclusive, royalty-free license in and to any copyrightcovering the aTtickfmr. ::-jnFACc FOR b 1 2 <; • PAGE-- iTO TS-; copyMASTERf NEUTRON EMISSION SPECTRA INDUCED BY 14-MeV NEUTRONS FROM THEEVALUATED NUCLEAR DATA FILE (ENDF/B-V)"-~A CRITICAL REVIEW\D. M. Hetrick, D. C. Larson, and C. Y. FuOak Ridge National LaboratoryOak Ridge, Tennessee 37830, USANeutron emission spectra induced by 14.6-MeV incident neutrons, retrieved from ENDF/B-V,are graphically compared with experimental data by Hermsdorf et al.1 and Clayeux and Voignier.2The elements selected for the comparisons include Na, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Ni, Cu,Nb, W, and Pb. In addition to comparing the evaluated total neutron emission spectra withexperimental data, individually evaluated spectra from contributing reactions are presented.Only a few of the evaluated spectra were found to agree well with the measured spectra;namely, those evaluations which utilized advanced nuclear model codes with precompound effectsand competing binary and tertiary reactions. • Recommendations for removing several defects inmost evaluations are made. j j! |[ENOF/B-V, neutron emission spectra, 14.6 MeV, nuclear model codes.]Introductioni Graphical comparisons of ENDF/B-V neutron emissionspectra with experimental data induced by 14-MeV inci-dent neutrons are presented. The elements chosen forthe comparisons are those considered important forfusion reactor applications and include Na, Hg, Al, Si,Ca, Ti, V, Cr, Fe, Ni, Cu, Nb, W, and Pb. On eachgraph, individually evaluated emission spectra from ;'contributing reactions and total emission spectra from:the ENDF/B-V files are shown. Thus, disagreement with. the experimental data, if any, may be attributed to• specific evaluated spectra. Experimental data arejavailable only for the total emission spectra.j Deficiencies in the ENDF/B-V neutron emissionI spectra for several materials are uncovered and dis-jcussed.| Experimental Data] Experimental data given by Hermsdorf et al. 1 and !I Clayeux and Voignier2 were utilized for this work. j: There are numerous other data sets available, but sincej they are generally in agreement with data of Hermsdorf,iet al. , they have been left off the plots for the pur--I pose of clarity. However, the data of Clayeux and iVoignier have been included since they have been used ]! frequently for evaluation work, and since they some- \times differ significantly from the data of Hermsdorf ;'et at."and others, we felt it useful to include them >for comparison. In addition, the energy-intergratedcross sections obtained from the data of Clayeux andI Voignier are much larger than the calculated results,due to the large intensity of low energy neutronsI indicated in their work.j In their report, Hermsdorf et al. presented the !j laboratory angular distributions of secondary neu- ij trons integrated over 1.0-MeV energy intervals. We !i have fitted a series of Legendre coefficients by least-I squares to tJie angular data for elements Na, Mg, Al, :j Si, Ca, Ti, V, Cr, Fe, Ni, Cu, Nb, w, and Pb for each •j energy interval given. For each energy interval, the ;integrated cross section was computed for different \polynomial orders to obtain the total differential Icross section. The integral obtained from the order ithat gave the best visual fit to their data (gen- Ierally 1 ' 3 ) was compared with the evaluated data, iGraphical results are presented in Fig. 1-3. The jerror bars shown in these figures correspond to the ierrors given in the report by Hermsdorf et al. plus jtheir estimated 10% systematic error. • jThe data of Clayeux and Voignier were taken directly,from tables in their report. Whereas Hermsdorf et al., \I obtained cross sections from the bombardment of the mater-terials by 14.6-MeV neutrons, Clayeux and Voignier's| data were given for 14.0-MeV neutrons. The data ofjClayeux and Voignier for the elements Mg, Al, Si,.Ca,Fe, Ni, Cu, and Pb were used in this paper.ENDF/B-V FilesIn Figs. 1-3 the differential cross sections ;i versus outgoing neutron energy are plotted for all! reaction types that produce secondary neutrons. In all| figures, the incident neutron energy was 14.6 MeV. Thedifferential cross section for each reaction type was ;obtained from iIas given in Ref. 3. Here o(E) is the cross section forincident energy E as given in File 3 of the ENDF/B-V :library, m is the neutron multiplicity, and p(E-*E') jrepresents the energy distribution for the secondary ;particle. The energy distribution is broken down intopartial energy distributions,3 iNKP(E-E') = I pk(E)k=l K(2)where fk(E->E') represents the distributions of thesecondary neutron energies E1 calculated from datagiven in File 5 of the library. At a particular indent neutron energy E,NKI Pk(E) = 1 , (3)k=l K Iwhere pfe(E) is the fractional probability that the dis-tributifin fk(E->E') applies at E. NK is the number of:partial distributions, and, with the exception of 'reaction types for the elements Ni, W-182, W-183, W-184,and W-186, is equal to 1. jThe energy distributions fk(E-»E1) are described bydifferent analytic formulations? Each formulation, ior energy distribution law, has an identification num-ber (LF number) associated with it.3 Note in Figures,1-3 that the curves are shown for evaluated emissionspectra from all of the contributing reactions. Datafrom the (n,n') discrete curves were taken from theinelastic level excitation cross sections in File 3 ofthe ENDF/B-V files. For each excited state of an ele-ment, the cross section was calculated for the incidentenergy by interpolation and the outgoing neutron energywas calculated by subtracting the reaction Q-value fromthe incident energy. These results were combined into1.0-MeV bins. Figures 1-3 display the total differ- ,jntial j:ross section obtained by summing the curves viaMTMMtlMI IF mt MCUMENT It UNUDITfO1- \u PRiNT 31 ,"CH 3 \'2 X 11 PAGE TO75:--COPY:linear-linear interpolation from all neutron-producingI reactions present in the evaluation. This total neu- •itron emission cross section is compared with the data >•of Hermsdorf et al.1 and Clayeus and Voignier.2 iiI Discussions and ConclusionSodium (Fig. 1)i! The evaluation is in reasonable agreement with thedata of Hermsdorf. However, outgoing neutrons with', energies greater than 6.5 MeV are under-estimated byabout 30%, indicating the lack of a precompound com-ponent. Only the cross section of the discrete level;at 0.44 MeV was given in ENDF/B-V at En = 14.6 MeV.Magnesium (Fig. 1)I'. The data of Clayeux and those of Hermsdorf are in;disagreement, with the evaluation lying approximately ;between them. The evaluation somewhat underestimates j! (see Ref. 4) a 14-MeV pulsed sphere measureinent per- :formed at Livermore, indicating that the Hermsdorf dataare probably correct. The evaluation also underesti- ;mated this data set at most neutron energies by 302 to: 40%, and would benefit by the inclusion of a precom- jpound component. I, Aluminum (Fig. 1) j' For this material, the two data sets shown.; are in good agreement. However, there are too fewi neutrons below 2 MeV in the evaluation. This may be! caused by omission of neutrons from the (n.pn) and! (n,an) reactions. The evaluation also overestimatesi the number of neutrons with energies greater than 6i MeV.| Silicon (Fig. 1)! The evaluated spectrum for silicon appears too low• in intensity from 6 to 8 MeV, but otherwise is in goodI agreement with both data sets.Calcium (Fig. 1)The two data sets shown are in sharp disagreementfor Ca. From the fact that a precompound component hasnot been included in the evaluation (see Ref. 5), it jmay be concluded that the evaluated spectrum is too |low from 4 to 10 MeV and the Clayeux data for Ca arein serious error.Iron (Fig.2)The evaluated spectrum is in good agreement withthe experimental data. The evaluation of various par-!tial neutron production spectra was based on an ad-vanced nuclear model analysis6 of several measuredtotal neutron production spectra.jCopper (Fig. 2)j . !The evaluated spectrum needs more high energy neu-I tron intensity between 8 and 13 MeV.1 Lead (Fig. 3)! There is good agreement between the evaluation andi the data. The evaluation had adequate data support,| and was coupled with a nuclear model analysis. TheI bump in the (n.n1) spectrum near 1 MeV reflects the use! of a giant dipole for the gamma-ray channels in thecalculation.JTitanium, Vanadium, Chromium, Nickel, Niobium, Tungsten! These materials appear to have similar deficien- !'cies in their neutron spectra. First,neutron intensity1in the (n,n') spectrum above the (n,2n) threshold is ]too high. This indicates that competition between the.Ineutron channels in the (n,2n) reaction and the gamma- j;ray channels in the (n.n'y) reaction does not seem toihave been properly considered. Second, there are too!few (or too many in the case of Nb) high energy neu-jtrons, indicating that precompound and/or direct inter-action effects have not been treated correctly in model(calculations or were based on inadequate estimates. It!appears that both deficiencies can be removed by usingjone of the recently developed nuclear model codes, iiGNASH8 or TNG9*10 An early version of TNG* was used forI the analysis of neutron spectra for Fe and Pb, showing!{reasonable success as evidenced in this report. !i From the discussions above we conclude that the jIENDF/B-V evaluations for the neutron spectra resultingifrom 14.6-MeV neutron interactions are reasonably goodifor Fe and Pb and fair for Na. Al, and Si. Further'evaluation is required for Mg, Ca, Ti, V, Cr, Ni.'Cu,;Nb, W-182, W-183, W-184, and w-186. From the nature ofthe deficiencies shown we recommend that advanced |'nuclear model codes8"10 employing precompound emissionI be used in future evaluations to assure consistency Iamong various partial cross sections and spectra and j|for extrapolating to energy ranges in which measure- Iiments have not been made. !*A multistep Hauser-Feshbach code with precompoundeffects.AcknowledgmentResearch sponsored by the U.S. Department ofEnergy, Office of Basic Energy Sciences, under contractNo. w-7405-eng-26 with Union Carbide Corporation.References1. D. Hermsdorf, A. Meister, S. Sassonoff, D.Seeliger, K. Seidel, and F. Shahin, Zentralinsti-tut fur Kernforschung Rossendorf Bei Dresden, ZfK277 (ii), (1975).2. G. Clayeux and J. Voignier, Centre d'Etudes deLimeil CEA-R-4279 (1972).3. D. Garber, C. Dunford, and S. Pearlstein, "DataFormats and Procedures for the Evaluated Nuclear iData File, ENDF," ENDF-102, BNL-NCS-50496 (1975).I4. M.K. Drake and M.P. Fricke, Defense Nuclear AgencyReport DNA 3479F (1975).5. C.Y. Fu, Atomic Data and Nuclear Data Tables 17,127 (1976). ~6. C.Y. Fu, "Development of a Two-Step Hauser-Feshbach Code with Precompound Decays and Gamma-• Ray Cascades: A Theoretical Tool for CrossSection Evaluations," Conf. Proc. Nuclear CrossSections and Technology, Washington, D. C. 1975,NBS-SP-425, p. 328 (1975).7. C. Y. Fu, private communication (1978).I! 8. E. D. Arthur and P. G. Young, "Cross Sections in !| the Energy Range from 10 to 40 MeV calculated withthe GNASH Code," Symp. on Neutron Cross Sectionsfrom 10 to 40 HeV, Brookhaven National Laboratory,Upton, New York, 1977, Eds. M. K. Bhat and S.Pearlstein, BNL-NCS-50681, p. 467 (1977).•'IT:H_ PV-rA9. C. Y. Fu, "Multi-Step Hauser-Feshbach Codes withPrecompound Effects: A Brief Review of Currentand Required Developments and Applications up to40 MeV," ibid, p. 4S3 (1977).10*10. C. Y. Fu, A Consistent Nuclear Model for Com- ipound and Precompound Reactions with Conservationof Angular Momentum," to be published in theproceedings of this conference. jID1 i—i—i—I rEN = 14.6 HEVD HERMSOORFSODIUM tWT II56 _J—e0 2-00 4-00 6.00 8.00 10.0 12-0 M'QOutgoing Neutron Energy (MeV)0 2.00 4.00 6.00 8.00 10.0 12.0 14.0Outgoing Neutron Energyw1i—i—i i i r~EN = M-6 MEV•HERMSDORFK. H-Q MEV13130 2.00 4.00 6.CO 8.00 10.0 12.0 14.0Outgoing Neutron Energy fMeV2oCOCO0100 2.00 4.00 S.00 8-00 !0.0 12-0 MOutgomg Neutron Energy ( MeV ]o0)COo)inot.EN = 1 4 . e NEVQ HERHSOORFA (XRYEUX. 14 -0 HEVCfiLCIUM MqT 3202-00 4.00 6.00 8.00 10.0 12.0 H-0; ; Outgoing Neutron Energy (MeV)Fig. 1. Partial and Total Neutron Emission Spectra from the ENDF/B-V Files Compared with the ExperimentalData of Hemisdorf et al. 'and Clayeux *nd Voigriier for the Elements Sodium, Magnesium, Aluminum, Silicon, andCalcium.'AGE£Oin>0)I I I T Iii EN = 14.6 J1EV• HERMSOO'RFTITflMUM "FIT 322EOHIinI I Io z.oa «-oo s.oa s.oo io-o 12.0 14.0Outgoing Neutron Energy (MeV0"52e520'521 1j ^^\^-\'N.Nfil \V̂ 1 \1 1EN = 14.6 MEV• HERMSDORFVflNflOlUn HRT1 1i 1323——-o « c r e ^ _- .1 10 2.00 4.00 6.00 8.00 10.0 1Z.0 14.0Outgoing Neutron Energy (MeV)IO1.norm E N - M . 6 . n E V• HERMSOORFCHROMIUM HAT 324a J.oo <.oo s.oo a.oo 10.0 12.0 14.0Outgoing Neutron Energy (MeV)EOOCOoLoEN = 14.S HEV• HERMSDURFACLRTEUX, 14 .0 I1EVIRON HUT 119210s525 5E— 2 Li"-'C° io" -oCO2.00 4.00 5.0C 3.00 10.0 12.0 H.OOutgoing Neutron Energy (MeVoLo2 _16'EN ; 14 .6 (1EVQHERHSDORFA ClflYEUX. 1 4 . 0 MEVNICKEL (TOT 328s _0 2-00 4.00 6.00 3.00 10.0 12-0 14.0Outgcng Neutron Energy fMeVJOaCO1052Itf5210=52520°5. 2_ 1IlUM 1 MOTIN1 1 1 1 1 1EN = 14.6 MEV —dHERMSDORF^CLHTEUX. 14-0 MEV —COPPER MPIT IZ95 i_\ \ \ ~ ~v \ \\ \ No 2.00 4.oo s.oo s.oa 10.0 u.o 14.0Outgo ing Neu t ron Energy (MeVli Fig. 2. Partial and Total Neutron Emission Spectra from the ENDF/B-V Files Compared with the Experimentali Data of Hermsdorf et al: and Clayeux and Voignier for the Elements Titanium, Vanadium, Chromium, Iron, Nickel,[and Copper. : ieotOEN = 14-6 1EVQ HERrtSDORFN!08IU« MflT 11891 1 1 I I0 2.00 4.00 6-00 8.00 10.0 12.0 H.OOutgong Neutron Energy ( MeV I1 I I l i l iEN = 14.6 MEV0 HERMSOORfW-182 MRT 112B0 2.00 4.00 6.00 6.GO 10.0 12.0 H.OOutgoing Neutron Energy (MeV)ooto0 2.00 «-00 6.00 a.00 10.0 12.0 U.OOutgoing Neutron Energy (MeV)Outgcng Neutron Energy t MeVO01inmCDOL105219s52ID*5210'5210°520'521 1 1 1 1 1i r e im E N = 1 4 - 6 " E vJ S ^ X DHERfiSDORF _r \ H-186 HUT 113!" ^ , ~ ^ V IN.T> D1SCRETI\ 1= \\~ \ 1 1 1 \ 11—-IT0 2.0D t.OD 6.CO 8.00 10.0 12.0 M.OOutgcng Neutron Energy (MeV)o(0to105ZIt?52id"• 5210'53I t f52n'1EN = 1 4 . B t• y D HERHSDORF« / \ , „ * CLRYEUX.F %•- V -EV14.0 MEV —HBT 382\ ^ <».»' 1 OISC»E!£- /I- \I N . N ' l CQNTINJLJR1" L1 1h—i -t-- -0 2.00 «-00 5.00 3.QO 10.0 1Z.0Outgoing Neutron Energy tMeV)Fig. 3. Partial and Total Neutron Emission Spectra from the ENDF/B-V Files Compared with the ExperimentalData of Hermsdorf et at. and Clayeux and Voignier for the Elements Niobium, Tungsten, and Lead.•P\-

Neutron emission spectra induced by 14-MeV neutrons from the Evaluated Nuclear Data File (ENDF/B-V): a critical review

https://digital.library.unt.edu/ark:/67531/metadc1097430/m2/1/high_res_d/5907419.pdf

Neutron emission spectra induced by 14-MeV neutrons from the Evaluated Nuclear Data File (ENDF/B-V): a critical review

Abstract

Similar works

Full text

Available Versions

UNT Digital Library