| Project/Area Number |
61470162
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Nuclear engineering
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| Research Institution | Nagoya University |
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Principal Investigator |
NAITO Keiji Faculty of Engineering, Nagoya University, 工学部, 教授 (70022994)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUI Tsuneo Faculty of Engineering, Nagoya University, 工学部, 助手 (90135319)
INABA Hideaki Faculty of Engineering, Nagoya University, 工学部, 助教授 (70023306)
TSUJI Toshihide Faculty of Engineering, Nagoya University, 工学部, 助教授 (60023305)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Keywords | Advanced Nuclear Fuel / High Temperature Heat Capacity / Oxygen Potential / Electrical Conductivity / 直接加熱パルス型熱量計 / 電気伝導率 / 添加二酸化ウラン |
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| Research Abstract |
The oxygen partial pressure dependences of the daparture from stoichiometric composition and the electrical conductivity were measured for UO_<2+X> doped with chromium, lanthanum, gadolinium and titanium ions. (1) The electrical conductivity and the oxygen potentials of UO_<2+X> are increased( or decreased) by diping with lower( or higher) valent cations, since lower( higher) valent dopants substituted for uranium ions can act effectively as hole( or electron) donors and can also increase( or decrease) the oxidation state of the remaining uranium ions. (2) The lower electrical conductivity and the oxygen potentials of UO_<2+X> doped with titanium ions than that of UO_<2+X> can not be interpreted by the substitutional model, but may be explained by assuming the Ti^<4+> interstitials as the predominant defect. (3) From the oxygen partial pressure dependences of the compositional deviation from stoichiometry and the electrical conductivity, the defect structures of doped UO_<2+X> are prop
… More
osed on the basis of the frenkel pairs of oxygen.
2. Heat capacity measurement of UO_<2.004>, U_<0.956>Gd_<0.044>O_<2.000>, U_<0.927>Gd_<0.073>O_<1.998>, U_<0.899>Gd_<0.101>O_<2.001> and U_<0.858>Gd_<0.142>O_<1.998> was conducted from 310 to 1500K by means of direct heating pulse calorimetry. (1) An abrupt increase in the heat capacity of each sample was observed at high temperatures, and the onset temperature of the heat capacity anomaly was decreased as the gadolinium content of U_<1-y>Gd_yO_2 was increased. (2) The enthalpy and entropy of activation of the thermally activated process which causes the excess heat capacity were determined for each sample. (3) The enthalpy of activation for pure UO_2 was estimated by extrapolating that for doped UO_2 to zero-doped UO_2. This value is lower than that for the formation of Frenkel pairs of oxygen, but higher than that of the thermally activated process for the formation of an electron-hole pair obtained from theoretical calculation. (4) The electrical condictivity for UO_2 doped with 7.3 mol% GdO_<1.5> showed no anomaly in the electrical conductivity curve around the transition temperature found in the heat capacity curve. It is conluded that the predominant contribution to the heat capacity anomaly for U_<1-y>Gd_yO_2 at high temperature is due to the formation of Frenkel pairs and the contribution of an electron-hole pair is small. Less
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