Evaluation Of Photon Induced Nuclear Reaction Data Of ^50,51V And ²⁰⁹Bi In The Energy Range Of 200MeV

Photonuclear Data?PD?are the important data in the particle transport calculation for nuclear device.At the same time,they are also important in many other fields such as nuclear waste transmutation,radiological medicine,radiation damage,explosive detection and the fundamental nuclear astrophysics.Since 1950s,from the bremsstrahlung photon spectrum,the quasimonochromatic positron annihilation?beams to the laser Compton-scattering?-ray beams?LCS?,many experimental facilities and techniques have been established and improved to obtain better PD values.Several international cooperation were also initiated by the United States and the International Atomic Energy Agency?IAEA?to specially evaluate PD,as a result,the first PD library,namely IAEA/PD-1999,was built and released to public.However,limited by the previous experiment and evaluation conditions,the data quality and total amount of IAEA/PD-1999 are needed to improve to support the current nuclear data application.In recent years,with the fast development of LCS and the ring ratio neutron detection in Japan,Romania and China,many new experimental photonuclear data have been reported with high quality.Consequently,IAEA initiated the new international cooperation to update IAEA/PD lib since 2016.China Nuclear Data Center participated in this project,and developed a new photonuclear reaction code system MEND-G in cooperation with Nankai University and MEND-G is suitable to apply to calculate the nuclear reaction for medium-heavy nuclei below 200MeV.Based on the researches above,the new evaluations of PD are carried out for the isotopes of vanadium(^50,51V)and bismuth(²⁰⁹Bi)within the energy range of 200MeV:Firstly,the experimental photonuclear data of ^50,51V,²⁰⁹Bi available are collected as much as possible.Through the systematical comparison and evaluation for the photon-absorption cross sections,the total and partial photoneutron cross sections,the photon neutron yield cross sections and the charged particle emission cross sections,the experimental database is estabilied to support the future model calculations.In particular,the well-known deviations between the reported experimental data from Saclay?France?and the Lawrence Livemore?the United States?,and the latest measurements from Konan?Japan?are specially concentrated in our work.Secondly,the photon absorption cross sections are theoretically determined through combining the simplified modified Lorentz model?SMLO?in the nuclear giant dipole resonance?GDR?and the quasi deuteron model,and the photon strength function for GDR is also generated at the same time to support the cross section calculation.Thirdly,the latest MEND-G code is used to calculate the photonuclear reactions of ^50,51V,²⁰⁹Bi.Under the constraint of the recommended experimental data,the competitive reactions of the neutron and charged particle emission reactions were calculated via optimizing the model parameters for the equilibrium and pre-equilibrium particle emission processes in the compound nuclei.After the comparisons of the evaluated data in Japanese and Europen libraries,experimental data and our new evaluated results,it is shown that the current work is satisfactory to describe the measurements,and the model parameters are all within the reasonable range in physics.Finally,starting from the least square method,the uncertainties of the theoretical photonuclear reaction cross sections of ²⁰⁹Bi are explored preliminarily.By calculating the sensitivity of important physical parameters and estimating the uncertainty of model parameters,the uncertainties of photonuclear reaction cross sections are derived and compared with the experimental uncertainty range.The photonuclear reaction data obtained in this work have been output in the standard international ENDF/B-6 format,and the data files are also accepted in the upcoming Chinese CENDL-3.2 library?PD sublibrary?.