Accelerator-driven subcritical systems (ADS) are among the most promising options for next-generation nuclear power systems. Various radionuclides are produced during the process of protons bombarding the target in the ADS, and the cross-sections of various long-lived radionuclides have not been accurately measured. These long-lived nuclides are related to ADS radioactive waste treatment, therefore, accurate evaluation of long-lived radionuclides generated in ADS spallation targets is a key topic in applied research.
This study aims to determinate production cross-sections of natPb(p,x)207Bi and natPb(p,x)194Hg reactions according to measurement data, and compare them with existing experimental and theoretical results.
The proton activation method was employed to effectively estimate the cross section of long-lived nuclides produced by the interaction between protons and spallation target materials. Four proton-irradiated natural lead samples were irradiated with protons at energies of 40 MeV, 70 MeV, 100 MeV, and 400 MeV for 90 min, 75 min, 40 min, and 25 min, respectively. After cooling for approximately 20 a, the samples were measured using an ultralow background gamma spectrometer GeTHU in the China Jinping Underground Laboratory (CJPL), and the GeTHU detection efficiency was calculated using the Simulation and Analysis for Germanium Experiments (SAGE) simulation framework. Combined with the irradiation parameters of the samples, the total production cross-sections of the two nuclides were calculated using a cross-section calculation formula. Experimental results are evaluated and compared with those of existing studies.
The production cross-sections of natPb(p,x)207Bi reaction in the natural lead samples irradiated by protons with four different energies (40 MeV, 70 MeV, 100 MeV and 400 MeV) are calculated as (40.70±3.59) mb, (19.31±1.43) mb, (13.15±0.96) mb, and (2.90±0.22) mb, respectively. The calculated production cross-section of natPb(p,x)194Hg reaction in the natural lead sample irradiated by protons with an energy of 400 MeV is (57.07±7.83) mb. Based on the same samples, the measurement results of cross-section remain consistent within the error range. The cross-sections of natPb(p, x)207Bi are closer to TENDL's evaluated cross-sections. The cross-section of natPb(p, x)194Hg is consistent with the theoretical expectation of INCL++/ABLA. In addition, different sources that contribute to the total uncertainty of both reactions are explained in detail.
The production cross-sections of natPb(p,x)207Bi and natPb(p,x)194Hg reactions measured herein were calculated independently and showed good agreement with existing results. These results demonstrate that GeTHU is capable of measuring low-activity and long-lived radionuclides in the CJPL. Finally, the results of this study also provide the latest experimental evidence for the evaluation of radioactive waste in ADS.
