The cross-sections of the 127I(n,2n)126I and 133Cs(n,2n)132Cs reactions at neutron energies of 13.83±0.05,14.33±0.10,and 14.79±0.10 MeV were measured relative to the 93Nb(n,2n)92mNb reaction using the a...The cross-sections of the 127I(n,2n)126I and 133Cs(n,2n)132Cs reactions at neutron energies of 13.83±0.05,14.33±0.10,and 14.79±0.10 MeV were measured relative to the 93Nb(n,2n)92mNb reaction using the activation technique in combination with off-lineγ-ray spectrometry.A neutron beam was generated from the T(d,n)4He reaction using the K-400 neutron generator at the China Academy of Engineering Physics.Considering the correlations between different attributes,detailed uncertainty propagation was performed using covariance analysis,and the cross-sections were reported with their uncertainties and correlation matrix.The uncertainty of the measurement cross-sections ranged from 4.84 to 5.90%,which is lower than previous experimental data.Furthermore,the theoretical excitation functions of the 127I(n,2n)126I and 133Cs(n,2n)132Cs reactions were calculated using the TALYS-1.95 and EMPIRE-3.2.3 codes.Then,the experimentally determined cross-sections were analyzed by comparing them with literature data available in the EXFOR database and evaluated nuclear data in the ENDF/B-VIII.0,JEFF-3.3,JENDL-5,BROND-3.1,CENDL-3.2,and TENDL-2021 databases.Compared with the values previously reported in the 13.8-14.8 MeV energy region,the precision of the results obtained in this study was greatly improved.The current experimental results with thorough uncertainties and covariance information are critical for verifying the reliability of the theoretical model and improving the quality of the nuclear database.展开更多
The fission yield data in the 14 MeV energy neutron induced fission of^(238)U play an important role in decay heat calculations and generation-Ⅳ reactor designs.In order to accurately measure fission product yields(F...The fission yield data in the 14 MeV energy neutron induced fission of^(238)U play an important role in decay heat calculations and generation-Ⅳ reactor designs.In order to accurately measure fission product yields(FPYs)of^(238)U induced by 14 MeV neutrons,the cumulative yields of fission products ranging from^(92)Sr to^(147)Nd in the^(239)U(n,f) reaction with a 14.7 MeV neutron were determined using an off-line γ-ray spectrometric technique.The14.7 MeV quasi-monoenergetic neutron beam was provided by the K-400 D-T neutron generator at China Academy of Engineering Physics(CAEP).Fission products were measured by a low background high purity germanium gamma spectrometer.The neutron flux was obtained from the^(93)Nb(n.2n)^(92m)Nb reaction,and the mean neutron energy was calculated using the cross-section ratios for the^(90)Zr(n,2n)^(89)Zr and^(93)Nb(n,2n)^(92m)Nb reactions.With a series of corrections,high precision cumulative yields of 20 fission products were obtained.Our FPYs for the^(238)U(n,f) reaction at 14.7 MeV were compared with the existing experimental nuclear reaction data and evaluated nuclear data,respectively.The results will be helpful in the design of a generation-Ⅳ reactor and the construction of evaluated fission yield databases.展开更多
The isomeric ratio of^(184m,g)Re and the half-life of^(184g)Re were measured in the ^(185)Re(n,2n)^(184)Re reaction at 14.8 MeV,and the uncertainty was discussed in detail.The measurements were performed using the act...The isomeric ratio of^(184m,g)Re and the half-life of^(184g)Re were measured in the ^(185)Re(n,2n)^(184)Re reaction at 14.8 MeV,and the uncertainty was discussed in detail.The measurements were performed using the activation method implemented for a rhenium sample using the K-400 neutron generator at the Chinese Academy of Engineering Physics(CAEP).Isomeric state and ground state nuclei of ^(184)Re were identified by their γ-ray spectra.To eliminate the effect of the γ-ray emitted from the isomer on the counting of the ground state characteristic peaks,the isomeric ratio of^(184m,g)Re was calculated to be 0.29±0.11 according to the neutron activation cross-section formula.This result is consistent with previous data within the uncertainty and can be used to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum.Through exponential function fitting and a detailed discussion of the uncertainty evaluation,the half-life of^(184g)Re was determined as 35.43±0.16 d,which is consistent with the currently recommended value;however,the uncertainty assessment of the latter was barely documented.In addition,this study indicates that the half-life of the ground state can be obtained by eliminating the contamination of γ-rays emitted from the isomer,which provides the possibility of determining the half-lives of nuclides containing isomers.展开更多
基金Supported by the Key Laboratory of Nuclear Data Foundation(JCKY2022201C151)the National Natural Science Foundation of China(11975113).
文摘The cross-sections of the 127I(n,2n)126I and 133Cs(n,2n)132Cs reactions at neutron energies of 13.83±0.05,14.33±0.10,and 14.79±0.10 MeV were measured relative to the 93Nb(n,2n)92mNb reaction using the activation technique in combination with off-lineγ-ray spectrometry.A neutron beam was generated from the T(d,n)4He reaction using the K-400 neutron generator at the China Academy of Engineering Physics.Considering the correlations between different attributes,detailed uncertainty propagation was performed using covariance analysis,and the cross-sections were reported with their uncertainties and correlation matrix.The uncertainty of the measurement cross-sections ranged from 4.84 to 5.90%,which is lower than previous experimental data.Furthermore,the theoretical excitation functions of the 127I(n,2n)126I and 133Cs(n,2n)132Cs reactions were calculated using the TALYS-1.95 and EMPIRE-3.2.3 codes.Then,the experimentally determined cross-sections were analyzed by comparing them with literature data available in the EXFOR database and evaluated nuclear data in the ENDF/B-VIII.0,JEFF-3.3,JENDL-5,BROND-3.1,CENDL-3.2,and TENDL-2021 databases.Compared with the values previously reported in the 13.8-14.8 MeV energy region,the precision of the results obtained in this study was greatly improved.The current experimental results with thorough uncertainties and covariance information are critical for verifying the reliability of the theoretical model and improving the quality of the nuclear database.
基金Supported by the National Natural Science Foundation of China (11975113)。
文摘The fission yield data in the 14 MeV energy neutron induced fission of^(238)U play an important role in decay heat calculations and generation-Ⅳ reactor designs.In order to accurately measure fission product yields(FPYs)of^(238)U induced by 14 MeV neutrons,the cumulative yields of fission products ranging from^(92)Sr to^(147)Nd in the^(239)U(n,f) reaction with a 14.7 MeV neutron were determined using an off-line γ-ray spectrometric technique.The14.7 MeV quasi-monoenergetic neutron beam was provided by the K-400 D-T neutron generator at China Academy of Engineering Physics(CAEP).Fission products were measured by a low background high purity germanium gamma spectrometer.The neutron flux was obtained from the^(93)Nb(n.2n)^(92m)Nb reaction,and the mean neutron energy was calculated using the cross-section ratios for the^(90)Zr(n,2n)^(89)Zr and^(93)Nb(n,2n)^(92m)Nb reactions.With a series of corrections,high precision cumulative yields of 20 fission products were obtained.Our FPYs for the^(238)U(n,f) reaction at 14.7 MeV were compared with the existing experimental nuclear reaction data and evaluated nuclear data,respectively.The results will be helpful in the design of a generation-Ⅳ reactor and the construction of evaluated fission yield databases.
基金Supported by the National Natural Science Foundation of China(11975113)。
文摘The isomeric ratio of^(184m,g)Re and the half-life of^(184g)Re were measured in the ^(185)Re(n,2n)^(184)Re reaction at 14.8 MeV,and the uncertainty was discussed in detail.The measurements were performed using the activation method implemented for a rhenium sample using the K-400 neutron generator at the Chinese Academy of Engineering Physics(CAEP).Isomeric state and ground state nuclei of ^(184)Re were identified by their γ-ray spectra.To eliminate the effect of the γ-ray emitted from the isomer on the counting of the ground state characteristic peaks,the isomeric ratio of^(184m,g)Re was calculated to be 0.29±0.11 according to the neutron activation cross-section formula.This result is consistent with previous data within the uncertainty and can be used to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum.Through exponential function fitting and a detailed discussion of the uncertainty evaluation,the half-life of^(184g)Re was determined as 35.43±0.16 d,which is consistent with the currently recommended value;however,the uncertainty assessment of the latter was barely documented.In addition,this study indicates that the half-life of the ground state can be obtained by eliminating the contamination of γ-rays emitted from the isomer,which provides the possibility of determining the half-lives of nuclides containing isomers.
