Integral Experiment on Induced Radioactivity and Decay-Heat of Mercury with 14 MeV Neutrons

Abstract

For spallation neuron target design, an accurate estimation of induced activity is strongly requested. Mercury is the most promising material for the high-power spallation target. An integral experiment on induced radioactivity and decay-heat was carried out using a small mercury assembly and a D-T neutron source (Fusion Neutronics Source) at Japan Atomic Energy Research Institute (JAERI). Mercury-oxide (HgO) powder wrapped with a plastic sheet was irradiated in the mercury assembly for 6.7 hours. After the irradiation, the induced activities were measured with HPGe detectors. The radioactive products of ^{197m, g}Hg, ^199mHg, ²⁰³Hg, ^198gAu and ¹⁹⁹Au were identified in the measured gamma-ray spectra. For the decay-heat measurement, a whole-energy absorption detector, which consisted with a pair of BGO scintillators, was used. The measurements were performed at various cooling times from 2.5 hours to 110 days. Experimental results of the radioactivity and the decay heat were compared with the calculation with DCHAIN-SP 2001. It was shown that the calculation reproduced the experiment within the accuracy of 20% by using the activation cross section curves evaluated on the basis of our experimental cross section data.

Keywords:

• Mercury
• Radioactivity
• Decay-heat
• Neutron
• 14 MeV
• FNS
• MCNP-4B
• DCHAIN-SP 2001
• FENDL Activation File
• JENDL-3