Nuclear Techniques ›› 2014, Vol. 37 ›› Issue (03): 30602-030602.doi: 10.11889/j.0253-3219.2014.hjs.37.030602

• NUCLEAR ENERGY SCIENCE AND ENGINEERING • Previous Articles     Next Articles

Measurement of the generation ratio of 233U and the average radiation capture cross section of 232Th with 232ThO2 irradiated by fast neutrons

WANG Qiang ZENG Lina AI Zihui SONG Lingli XIE Qilin ZHENG Chun GONG Jian   

  1. (Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China)
  • Received:2013-07-19 Revised:2013-10-12 Online:2014-03-10 Published:2014-03-14

Abstract:

Background: Thorium-Uranium cycle plays an important role in the future’s power production technology. Nuclear data involved are urgently needed for engineering design and other purposes since there are obvious differences between the existing evaluated data. Macroscopic neutron integral experiment can be used as a good tool to survey the confusion. Purpose: Macroscopic neutron integral experiment based on radioactive method was carried out to measure the generation ratio of 233U nuclide and the average radiation capture cross section of 232Th while a ThO2 sample was irradiated by fast neutrons leakage from a fast critical facility. We expect that these data can be used as a reference for the research of Th-U cycle. Methods: Radiation capture reactions of 232Th nuclides occur when the nuclides are irradiated by neutrons. 233U nuclides will be generated after two cascade decays by emitting beta rays from the activation products, which are 233Th nuclides. The ThO2 sample was prepared as a slice of 20mm×10 mm from 0.74336-g ThO2 powders of 99.9% enriched. The neutron flux was measured by activation method which was 4.07×109 cm?2?s?1 at the sample’s irradiation position while the facility worked at the power level of 180 watts. The leakage neutrons’ energy distribution was calculated by MC method and it is very close to the fission spectrum with the averaged energy of 1.42 MeV. After irradiation and then a period of cooling time the gamma rays emitted from the sample were measured by an HPGe spectrometer which had been pre-calibrated. From these data the activity of 233Pa was calculated and then the generation ratio of 233U and the average radiation capture cross section of 232Th were calculated. The measured average radiation capture cross section was compared with the cross sections calculated based on the ENDFB-VII.1, CENDL-3.1, JENDL-4.0, BROND2.2 databases. Results: The measured generation ratio of 233U was 4.01×10?12 with an uncertainty of 6.1% while the neutron fluence at the irradiation place was 2.99×1013 cm?2 and the measured average radiation capture cross section of 232Th was 134.3 mb with an uncertainty of 12.4%. The average radiation capture cross section calculated based on CENDL-3.1 database was 18.5% smaller than the measured one. Conclusion: More experimental data are needed to evaluate the serviceability of the cross sections of 232Th (n,γ) reaction from different databases.

Key words: Th-U cycle, Nuclear fuel analysis, Critical facility, Activity, Average cross section