1999 Fiscal Year Final Research Report Summary
RESEARCH ON THE GENERATION MECHANISM OF BURNOUT JUST UPSTREAM OF THE SPACER SUPPORTING BWR-NUCLEAR ROD BUNDLE
| Project/Area Number |
10450087
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
FUKANO Tohru Kyushu University, Department of Mechanical Engineering Science, Professor, 大学院・工学研究科, 教授 (60037968)
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| Co-Investigator(Kenkyū-buntansha) |
渡部 正夫 九州大学, 大学院・工学研究科, 助教授 (30274484)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Nuclear Reactor / Nuclear Fuel Rods / Spacer / Critical Heat Flux / Flow Pattern / Temperature Fluctuation / 過渡変動 |
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| Research Abstract |
A cylindrical flow obstruction which simulates a spacer supporting nuclear fuel rods in BWR was installed in the vertical annular channel. Flow patters, especially the generation of drypatch and burnout, were carefully observed by a high speed video camera. The time variations of temperature on the heating tube surface were simultaneously measured near the spacer at six axially different locations. The results are summarized as follows.
(1) Large amplitude temperature change is caused by rapid increase in heat transfer through quite thin liquid film prior to the generation of drypatch which causes the rapid temperature increase due to deterioration of heat transfer.
(2) In the case that the liquid was sub cooled at the inlet of the heating test section the temperature difference caused by the occurrence of drypatch was the largest, at most 5℃, when the superficial vapor velocity jG is around 15〜20m/s. Under the condition of jG > 20 m/sit decreased even though the heat flux increased because the annular flow pattern became more fully developed and steady. The generation of drypatch is caused by the drainage in the former case and vaporization of base film liquid.
(3) In the case that the void ratio was positive, the flow pattern was slug flow at the inlet and the liquid flow rate was low (jL = 0.1 m/s), the overall flow structure becomes unstable and the maximum temperature attains 140℃ when the drypatch occurred. The area map of the dtypatch generation was proposed.
(4) The temperature gradually approached to the final state in the case of sudden change in the heat flux in both cases of increasing and decreasing.
(5) In the case of sudden increase in inlet quality temperature gradually changed also, while in its sudden decrease the large and sudden increase in the heating surface temperature. The larger the temperature decrease the easier the occurrence of the burnout.
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