Study on Accident Mitigation and Cooling of Damaged Core during Severe Accident of Right Water Nuclear Reactor

Quenching of a thin gap annular flow passage by gravitational liquid penetration was examined experimentally by using R-113。The outer wall was made of copper.The inner wall was made of copper or glass.The inner diameters of the outer wall of the annular flow passages were 40 and 41毫米and the outer diameters of the inner wall were 38，36 and 30毫米。By combining these，the annular gap spacings tested were 0.3，0.5，1.0，2.0 and 5.0 mmTwo-types of experiments were performed；1bottom-closed experiments where vapor generated flowed upward counter-currently，and2bottom-open experiments where liquid drained from the bottom and vapor generated flowed upward counter-currently，and2bottom-open experiments where liquid drained from the bottom and vapor generated flowed upward。The wall was heated up to 250℃initially，and then liquid was directed to the test section top to flow down into the test sectionResults obtained were(1)Quenching was observed for the gap spacing°≥1.0 mm。When the spacingó&lt；1.0 mm，the wall was gradually and monotonously cooled down without any quenching。When the bottom of th…More e flow channel was closed and the gap spacingó≥2.0 mm，liquid fell down into the flow passage without quenching the hot wall and accumulated in the flow channel.Then，the hot wall quenching proceeded upward from the bottom with the accumulation of liquid.Whenó=1.0 mm，the quenching propagated downward from the top(2)Overall trend observed in unheated glass inner-wall experiments and heated inner-wall experiments were fundamentally same(3)The relation between the wall super heat and the wall heat flux was quite similar to the boiling curve of the usual pool boiling。The heat flux during the film and the transition boiling period and the peak heat flux decreased as the gap spacing became narrow(4)Quenching simulation was performed by solving the two-dimensional and unsteady heat conduction@equation imposing the boiling curve on the inner heat transfer surface·If the relation between the surface temperature and the heat flux is properly given，the quenching propagation is adequenching vely reduced·The quenching velocity rougrough withly and Bi

Quenching of a thin gap annular flow passage by gravitational liquid penetration was examined experimentally by using R-113. The outer wall was made of copper. The inner wall was made of copper or glass. The inner diameters of the outer wall of the annular flow passages were 40 and 41 mm and the outer diameters of the inner wall were 38, 36 and 30 mm. By combining these, the annular gap spacings tested were 0.3, 0.5, 1.0, 2.0 and 5.0 mmTwo-types of experiments were performed; 1 bottom-closed experiments where vapor generated flowed upward counter-currently, and 2 bottom-open experiments where liquid drained from the bottom and vapor generated flowed upward. The wall was heated up to 250℃ initially, and then liquid was directed to the test section top to flow down into the test sectionResults obtained were(1) Quenching was observed for the gap spacing б ≧ 1.0 mm. When the spacing б < 1.0 mm, the wall was gradually and monotonously cooled down without any quenching. When the bottom of th … More e flow channel was closed and the gap spacing б ≧ 2.0 mm, liquid fell down into the flow passage without quenching the hot wall and accumulated in the flow channel. Then, the hot wall quenching proceeded upward from the bottom with the accumulation of liquid. When б = 1.0 mm, the quenching propagated downward from the top(2) Overall trend observed in unheated glass inner-wall experiments and heated inner-wall experiments were fundamentally same(3) The relation between the wall super heat and the wall heat flux was quite similar to the boiling curve of the usual pool boiling. The heat flux during the film and the transition boiling period and the peak heat flux decreased as the gap spacing became narrow(4) Quenching simulation was performed by solving the two-dimensional and unsteady heat conduction equation imposing the boiling curve on the inner heat transfer surface・If the relation between the surface temperature and the heat flux is properly given, the quenching propagation is adequately reproduced・The quenching velocity is roughly correlated with Pe and Bi numbers Less