Based on the mass distribution data up to 200 MeV measured by Zoller with kinetic energy method (corrected), the systematics on dependence of chain yield on incident neutron energy for each mass number A with a linear...Based on the mass distribution data up to 200 MeV measured by Zoller with kinetic energy method (corrected), the systematics on dependence of chain yield on incident neutron energy for each mass number A with a linear and quadric function was studied. And also the systematics of mass distribution on mass A and incident neutron energy was investigated by using 5 (or 3 ) Gaussian model. A code of nonlinear squared least method was developed and the parameters were deduced by fitting the experimental data. The calculated results with the parameters obtained could reproduce the experimental data used well. But comparisons with the data measured by radiochemistry method show some systematical difference. It is shown that there is some systematical difference between the measured data with kinetic and radioactive nuclide methods, the reasons of which need to be investigate further.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
From both the fundamental and applied perspectives, fragment mass distributions are important observablesof fission. We apply the Bayesian neural network (BNN) approach to learn the existing neutron induced fissionyie...From both the fundamental and applied perspectives, fragment mass distributions are important observablesof fission. We apply the Bayesian neural network (BNN) approach to learn the existing neutron induced fissionyields and predict unknowns with uncertainty quantification. Comparing the predicted results with experimentaldata, the BNN evaluation results are found to be satisfactory for the distribution positions and energy dependenciesof fission yields. Predictions are made for the fragment mass distributions of several actinides, which may beuseful for future experiments.展开更多
Neutron-induced fission is an important research object in basic science.Moreover,its product yield data are an indispensable nuclear data basis in nuclear engineering and technology.The fission yield tensor decomposi...Neutron-induced fission is an important research object in basic science.Moreover,its product yield data are an indispensable nuclear data basis in nuclear engineering and technology.The fission yield tensor decomposition(FYTD)model has been developed and used to evaluate the independent fission product yield.In general,fission yield data are verified by the direct comparison of experimental and evaluated data.However,such direct comparison cannot reflect the impact of the evaluated data on application scenarios,such as reactor transport-burnup simulation.Therefore,this study applies the evaluated fission yield data in transport-burnup simulation to verify their accuracy and possibility of application.Herein,the evaluated yield data of235U and239Pu are applied in the transport-burnup simulation of a pressurized water reactor(PWR)and sodium-cooled fast reactor(SFR)for verification.During the reactor operation stage,the errors in pin-cell reactivity caused by the evaluated fission yield do not exceed 500 and 200 pcm for the PWR and SFR,respectively.The errors in decay heat and135Xe and149Sm concentrations during the short-term shutdown of the PWR are all less than 1%;the errors in decay heat and activity of the spent fuel of the PWR and SFR during the temporary storage stage are all less than 2%.For the PWR,the errors in important nuclide concentrations in spent fuel,such as90Sr,137Cs,85Kr,and99Tc,are all less than 6%,and a larger error of 37%is observed on129I.For the SFR,the concentration errors of ten important nuclides in spent fuel are all less than 16%.A comparison of various aspects reveals that the transport-burnup simulation results using the FYTD model evaluation have little difference compared with the reference results using ENDF/B-Ⅷ.0 data.This proves that the evaluation of the FYTD model may have application value in reactor physical analysis.展开更多
Photofission fragments mass yield for^(232)Th,^(234;238) U,^(237) Np, and^(239;240;242) Pu isotopes are investigated.The calculations are done using a developed approach based on Gorodisskiy's phenomenological for...Photofission fragments mass yield for^(232)Th,^(234;238) U,^(237) Np, and^(239;240;242) Pu isotopes are investigated.The calculations are done using a developed approach based on Gorodisskiy's phenomenological formalism. The Gorodisskiy's method is developed to be applied for the neutron-induced fission. Here we revised it for application to photofission. The effect of emitted neutron prior to fission on the fission fragment mass yields has also been studied. The peak-to-valley ratio is extracted for the240 Pu isotope as a function of energy. Obtained results of the present formalism are compared with the available experimental data. Satisfactory agreement is achieved between the results of present approach and the experimental data.展开更多
Calculation of the decay heat from the decay/buildup of radionuclides generated after nuclear fission is one of the highest priorities in the nuclear industry. These calculations become more important if they are made...Calculation of the decay heat from the decay/buildup of radionuclides generated after nuclear fission is one of the highest priorities in the nuclear industry. These calculations become more important if they are made together with the analysis of the most important isotopes affecting the decay heat. They are useful in designing the necessary nuclear safety for spent fuels, and their importance cannot be overlooked in the designs of transporting fuel storage containers as well as in the management of the radioactive waste generated. In this paper, by using MATLAB, the decay heat after the thermal fission of a U-235 nucleus was numerically calculated by solving linear differential equations for all the buildups/decays of the fission products. Also, the most contribution of radioactive isotopes to the decay heat was analyzed by using Microsoft Excel. The most influential isotopes were deduced in two ways;either by calculating the most influential isotopes at specific times, or by determining the largest influences in a cumulative manner. All required nuclear data such as decay constants their branching ratios, independent fission yield, and average α-, β-, and γ-energies released per disintegration of any nuclide, have been extracted from the latest version of the Evaluated Nuclear Data Files (ENDF) database ENDF/B-VIII.0. The two different methods used showed a difference in the contributing isotopes, which is logical for the difference in the method of calculation. The first method is suitable for instantaneous data while the second method is more suitable when there is a need to know the cumulative calculations. In sum, we can say that both methods complement each other, and neither of them can be dispensed with in the accurate calculations related to transportation and storage of spent fuel.展开更多
A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields...A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields of nucleons are determined from the equilibrium conditions of the nuclear fragments post-fission ensemble. Here we consider protons and neutrons of different fragments as statistically non-equivalent. The abilities of the proposed statistical method for explanation of the U, Pa, Th, Ac and Ra post-fission fragments ordering and neutron emission function calculation have been demonstrated.展开更多
In this study,Langevin approach incorporated with the statistical model is adopted to investigate independent fission yields for a large quantity of fission products and the dependence of prompt fission observables on...In this study,Langevin approach incorporated with the statistical model is adopted to investigate independent fission yields for a large quantity of fission products and the dependence of prompt fission observables on the incident neutron energy in^(235)U(n,f).The neutron evaporation from the fission process is considered by coupling the Weisskopf statistical model to Langevin dynamical simulation,where the potential energy surface of the respective fissioning nucleus from each fission chance is calculated using the macroscopic-microscopic model within the two-center shell model.The partitions of the charge and total excitation energy between the two complementary fragments are evaluated such that the prompt neutron emissions from fission fragments can be described based on the characteristics of primary fragments.With the present model,the calculated independent fission yields of the isotopes from Z=30-61 in 14 MeV n+^(235)U fission are in good agreement with the evaluated data from ENDF/BVⅢ.0.Moreover,the evolution of the independent mass yields and the cumulative yields for select isotopes with the incident neutron energy,as well as the tendency of both the average TKE and prompt neutron multiplicity with the increase in the incident neutron energy,are consistent with the experimental data.The present model can aid in reproducing prompt fission observables across a range of incident neutron energies for major actinides.展开更多
文摘Based on the mass distribution data up to 200 MeV measured by Zoller with kinetic energy method (corrected), the systematics on dependence of chain yield on incident neutron energy for each mass number A with a linear and quadric function was studied. And also the systematics of mass distribution on mass A and incident neutron energy was investigated by using 5 (or 3 ) Gaussian model. A code of nonlinear squared least method was developed and the parameters were deduced by fitting the experimental data. The calculated results with the parameters obtained could reproduce the experimental data used well. But comparisons with the data measured by radiochemistry method show some systematical difference. It is shown that there is some systematical difference between the measured data with kinetic and radioactive nuclide methods, the reasons of which need to be investigate further.
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the National Natural Science Foundation of China(12175064,U2167203)the Outstanding Youth Science Foundation of Hunan Province,China(2022JJ10031)。
文摘From both the fundamental and applied perspectives, fragment mass distributions are important observablesof fission. We apply the Bayesian neural network (BNN) approach to learn the existing neutron induced fissionyields and predict unknowns with uncertainty quantification. Comparing the predicted results with experimentaldata, the BNN evaluation results are found to be satisfactory for the distribution positions and energy dependenciesof fission yields. Predictions are made for the fragment mass distributions of several actinides, which may beuseful for future experiments.
基金the National Natural Science Foundation of China(Nos.11875328,12075327 and 12105170)the Key Laboratory of Nuclear Data foundation(No.JCKY2022201C157)+1 种基金the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.22lgqb39)the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(No.NLK2020-02).
文摘Neutron-induced fission is an important research object in basic science.Moreover,its product yield data are an indispensable nuclear data basis in nuclear engineering and technology.The fission yield tensor decomposition(FYTD)model has been developed and used to evaluate the independent fission product yield.In general,fission yield data are verified by the direct comparison of experimental and evaluated data.However,such direct comparison cannot reflect the impact of the evaluated data on application scenarios,such as reactor transport-burnup simulation.Therefore,this study applies the evaluated fission yield data in transport-burnup simulation to verify their accuracy and possibility of application.Herein,the evaluated yield data of235U and239Pu are applied in the transport-burnup simulation of a pressurized water reactor(PWR)and sodium-cooled fast reactor(SFR)for verification.During the reactor operation stage,the errors in pin-cell reactivity caused by the evaluated fission yield do not exceed 500 and 200 pcm for the PWR and SFR,respectively.The errors in decay heat and135Xe and149Sm concentrations during the short-term shutdown of the PWR are all less than 1%;the errors in decay heat and activity of the spent fuel of the PWR and SFR during the temporary storage stage are all less than 2%.For the PWR,the errors in important nuclide concentrations in spent fuel,such as90Sr,137Cs,85Kr,and99Tc,are all less than 6%,and a larger error of 37%is observed on129I.For the SFR,the concentration errors of ten important nuclides in spent fuel are all less than 16%.A comparison of various aspects reveals that the transport-burnup simulation results using the FYTD model evaluation have little difference compared with the reference results using ENDF/B-Ⅷ.0 data.This proves that the evaluation of the FYTD model may have application value in reactor physical analysis.
文摘Photofission fragments mass yield for^(232)Th,^(234;238) U,^(237) Np, and^(239;240;242) Pu isotopes are investigated.The calculations are done using a developed approach based on Gorodisskiy's phenomenological formalism. The Gorodisskiy's method is developed to be applied for the neutron-induced fission. Here we revised it for application to photofission. The effect of emitted neutron prior to fission on the fission fragment mass yields has also been studied. The peak-to-valley ratio is extracted for the240 Pu isotope as a function of energy. Obtained results of the present formalism are compared with the available experimental data. Satisfactory agreement is achieved between the results of present approach and the experimental data.
文摘Calculation of the decay heat from the decay/buildup of radionuclides generated after nuclear fission is one of the highest priorities in the nuclear industry. These calculations become more important if they are made together with the analysis of the most important isotopes affecting the decay heat. They are useful in designing the necessary nuclear safety for spent fuels, and their importance cannot be overlooked in the designs of transporting fuel storage containers as well as in the management of the radioactive waste generated. In this paper, by using MATLAB, the decay heat after the thermal fission of a U-235 nucleus was numerically calculated by solving linear differential equations for all the buildups/decays of the fission products. Also, the most contribution of radioactive isotopes to the decay heat was analyzed by using Microsoft Excel. The most influential isotopes were deduced in two ways;either by calculating the most influential isotopes at specific times, or by determining the largest influences in a cumulative manner. All required nuclear data such as decay constants their branching ratios, independent fission yield, and average α-, β-, and γ-energies released per disintegration of any nuclide, have been extracted from the latest version of the Evaluated Nuclear Data Files (ENDF) database ENDF/B-VIII.0. The two different methods used showed a difference in the contributing isotopes, which is logical for the difference in the method of calculation. The first method is suitable for instantaneous data while the second method is more suitable when there is a need to know the cumulative calculations. In sum, we can say that both methods complement each other, and neither of them can be dispensed with in the accurate calculations related to transportation and storage of spent fuel.
文摘A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields of nucleons are determined from the equilibrium conditions of the nuclear fragments post-fission ensemble. Here we consider protons and neutrons of different fragments as statistically non-equivalent. The abilities of the proposed statistical method for explanation of the U, Pa, Th, Ac and Ra post-fission fragments ordering and neutron emission function calculation have been demonstrated.
基金Supported by the National Natural Science Foundation of China(12105369,12375129)the Continuous-Support Basic Scientific Research Project(BJ010261223282)。
文摘In this study,Langevin approach incorporated with the statistical model is adopted to investigate independent fission yields for a large quantity of fission products and the dependence of prompt fission observables on the incident neutron energy in^(235)U(n,f).The neutron evaporation from the fission process is considered by coupling the Weisskopf statistical model to Langevin dynamical simulation,where the potential energy surface of the respective fissioning nucleus from each fission chance is calculated using the macroscopic-microscopic model within the two-center shell model.The partitions of the charge and total excitation energy between the two complementary fragments are evaluated such that the prompt neutron emissions from fission fragments can be described based on the characteristics of primary fragments.With the present model,the calculated independent fission yields of the isotopes from Z=30-61 in 14 MeV n+^(235)U fission are in good agreement with the evaluated data from ENDF/BVⅢ.0.Moreover,the evolution of the independent mass yields and the cumulative yields for select isotopes with the incident neutron energy,as well as the tendency of both the average TKE and prompt neutron multiplicity with the increase in the incident neutron energy,are consistent with the experimental data.The present model can aid in reproducing prompt fission observables across a range of incident neutron energies for major actinides.
