Experimental Study Of 70-100 MeV Proton Induced Reactions With ADS Key Materials Of Copper,Lead,Bismuth And Thorium

Accelerator Driven System（ADS）is regarded as an efficient way to solve those current difficulties,which are adequate supply of nuclear fuel,safety operation of nuclear reactor and security disposal of nuclear waste.Copper is an important structural material for Radio Frequency Quadrupole（RFQ）,accelerator high frequency cavity and magnet coil.Lead or lead–bismuth eutectic are widely used as target and coolant materials in ADS system.Thorium can be used for the proliferation of nuclear fuel.Copper and lead are also widely used for shielding neutrons and gamma rays in nuclear facilities.Except for nuclear energy,medical radioisotopes of ²¹³Bi,²²³Ra,²²⁵Ac and²²⁶Th,can be produced by the irradiation of thorium target with medium or low energy protons generated by accelerator.Those isotopes can be used to kill cancer cells with the monoclonal antibodies.Therefore,it is important to study the nuclear reaction data related to accelerator driven subcritical system and medical radioisotope production.The research and development of ADS and the production of medical isotopes require high accuracy of nuclear data with wide energy range.However,experimental measurements cannot be carried out in the full energy range.The evaluated nuclear data library or nuclear reaction model can be used to obtain those nuclear reaction data.It has great impact on the design,safety operation and radiation protection of nuclear facilities for the reliability of evaluated nuclear data and nuclear reaction model.As a result,the reliabilities needed to be verified and validated when using those evaluated nuclear data and nuclear reaction models.Based on the 100 Me V proton beam generated by the separated sector cyclotron of the Heavy Ion Research Facility in Lanzhou（HIRFL）,the aluminum,copper,lead,bismuth and thorium targets with stacked style were irradiated.After a period of cooling time,radioactivities of those samples were measured several times using a lead shielded,high energy resolution HPGe detector.Then,the experimental data were analyzed and processed with the ROOT program,and finally the production cross sections of radionuclides at multiple energies were obtained.Our experimental results show that the measurement data of this work are in good agreement with most of the previous experimental data.For nuclear reactions of ^natPb（p,x）²⁰²Bi and ^natPb（p,x）²⁰³Pb,our results fill the blank of experimental data in some energy regions.Besides,we also found that,the divergences among the existing experimental data may come from the difference of experimental measurement methods and the decay data of radionuclide.At the same time,the reliabilities of evaluated nuclear data from the ENDF/B-VIII.0,JENDL-4.0/HE and PADF-2007 as well as the calculation results of nuclear level density models with TALYS-1.96 code were verified by compared with experimental data.In terms of evaluated nuclear data,our results show that the JENDL-4.0/HE is better than ENDF/B-VIII.0 and PADF-2007 libraries for the production cross sections of radionuclides of proton induced reaction on copper.And the PADF-2007 is better than JENDL-4.0/HE and ENDF/B-VIII.0 libraries for proton induced reactions on lead or bismuth.In the cases of theoretical calculations:（a）calculated results of ^natCu（p,x）^61,64Cu reactions,with six nuclear level density models of the TALYS-1.96code,are in good agreement with experimental data.However,for the multinucleon emission reactions,such as ^natCu（p,x）^52,54Mn,poor agreement were found.（b）level density models 1/2/4 are better than 3/5/6 for lead and bismuth samples calculated with TALYS-1.96 code,in spite of the poor agreements in ^natPb（p,x）²⁰³Pb and ²⁰⁹Bi（p,x）²⁰⁴Po.For thorium samples,calculated results of the six nuclear level density models with the TALYS-1.96 code are in poor agreements with the experimental data.In addition,calculation results of TALYS-1.96 show that the production of residual nuclei mainly came from the compound process for nuclear reactions involving the multinucleon emission processes.In the cases of few nuclei emitting reactions,the residual nuclei mainly generated from the compound reactions for low incident energy,and as the increase of proton energy,contribution of the preequilibrium emission process increases,but the contribution of direct reaction is always small.Production yields of ^{55,56,57,58,60}Co,⁵⁷Ni,^{203,205,206,207}Bi,²²³Ra,²²⁵Ac,^226,227Th,²³⁰Pa and ²³⁰U were calculated.Calculation results show that shorter-lived nuclides,such as⁵⁷Ni,⁵⁵Co and ²⁰³Bi,contribute more to the total radioactivity of the sample during the irradiation time.After a period of cooling time,medium-lived nuclides contribute more to the total radioactivity.Radioactivities of some nuclides can continue to increase for some time after irradiation due to the presence of mother nucleus or radioactive decay chain.The production yields of ²²⁶Th,²²³Ra and ²¹³Bi could reach to 10.4 Ci,10.7 Ci and 4.1 Ci,for the proton energy of 100 Me V,intensity of 0.2 m A and irradiation time of 15 days.According to the estimated demand of about 0.1 m Ci for a single patient in the literature,the production yields of medical radioisotopes by proton irradiation on thorium target can meet the clinical needs of a certain scale.