| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
A number of researches have been so far reported on the chemical effects of nuclear transformations, i.e., hot-atom chemistry abbreviated by HAC. Hot atoms are in highly excited states because of nuclear recoil. It is a research goal of solid-phase HAC to make clear as to what happens in solid immediately after the nuclear event. However, it has been expected that the distribution of radiochemical products measured in conventional solid-phaseHAC should be seriously affected in solid during dissolution and chemical analysis. By emission Mossbauer spectroscopy we could obtain information non-destructively on the chemical effects associated with a nuclear decay of Mossbauer transition. If the emission Mossbauer spectrum is measured for the source system fed through a nuclear reaction, that is, in an in-beam Mossbauer spectroscopic work, the chemical effects of the combination of the nuclear reaction and the subsequent prompt decays to Mossbauerr level should appear in the spectrum. The co
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ntribution to HAC effects is assumed to be much greater from the nuclear reaction than from the following Mossbauer decay because of their recoil energies.
In the present project, we did the neutron in-beam ^<57>Fe Mossbauer spectroscopic investigations for iron compounds such as iron sulfide, allowing us to obtain non-destructively the information with the time scale of 100 ns, which much shorter than that in the conventional HAC techniques. Our research attention and interest were paid to the chemical effects associated with the ^<56>Fe(n, γ)^<57>Fe reaction, such as chemical-bond rupture and change of iron oxidation-state as the hot-atom effects. Another important aim of our study was to establish the in-beam Mossbauer spectroscopy in neutron facilities, by which we present the experimental results on the chemical behaviors of neutron-induced hot-atoms in solid. Mossbauer measurements were carried out using a parallel plate avalanche counter (PPAC) at the prompt γ-ray analysis setup at the neutron beam hall of the JRR-3M reactor of Japan Atomic Energy Research Institute. The PPACs were fabricated and improved in the present work. The in-beam emission Mossbauer spectrum of pyrite showed two doublets. One component corresponding to pyrite occupied 1/3 of the total peak area, and the other major component was tentatively assumed as Fe^<3+> at the interstitial site of pyrite. The emission spectrum of marcasite was also composed of two doublets : one corresponding to marcasite, and the other doublet. In both iron disulfides, it was revealed that recoil of the cascade γ-ray emission promptly after the neutron capture reaction produced one new species distinguishable from the original target compound by in-beam ^<57>Fe Mossbauer spectroscopy. Less
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