| 摘要 |
PROBLEM TO BE SOLVED: To provide a neutron absorption element increased in Na inflow property without increasing a distance between vent holes. SOLUTION: This neutron absorption element comprises a coated tube immersed in a coolant formed of sodium, a pellet chamber formed by charging the coated tube with B<SB>4</SB>C pellets, an intermediate end plug fitted at the upper part of the pellet chamber, an upper chamber formed on the upper side of the intermediate end plug, vent tubes communicating the pellet chamber with the upper chamber through the intermediate end plug, vent holes passed through two upper and lower stages of the coated tubes in the upper chamber, and an Na inlet tube having an Na inflow hole opened in the upper surface of the intermediate end plug and extending from the Na inflow hole to the lower position of the lower end faces of the vent tubes through the intermediate end plug. Since helium gas of 0.05 MPa or below is sealed in the element, when the element is immersed in Na and solder seal is melt, the sodium flows into the element until pressures inside and outside the element come in an equilibrium state due to a difference in the pressures inside and outside the element. COPYRIGHT: (C)2004,JPO&NCIPI
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