| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The facility used was a R-113 closed-loop. The test section was a thick wall copper pipe of 240mm in length. 100mm in OD and 34 or 36mm in ID.A glass pipe was inserted into the test pipe to from a vertical-narrow-annular flow passage of 0.5,1,2 or 5mm gap. Following the Bond number scaling, the gap size was determined from the gap width between the reactor pressure vessel and the piled-up debris of the damaged core estimated in the TMI-2 accident. Experiments performed were the critical heat flux experiments of (1) bottom-closed counter-current flow and (2) bottom drainage counter-current flow. The flow state was recorded on a VTR with a CCD camera and a fiber scope.
The mode of heat transfer was nucleate boiling. As the heat flux was increased, the critical heat flux (CHF) condition was eventually reached. However, no abrupt wall temperature increase was observed then. After the heat flux was increased more, the sharp increase in the wall temperature was perceived. In both (1) and (2) experiments, after the counter-current flow limiting (CCFL) was initiated to restrict the liquid penetration into the flow passage, unstable-intermittent dray patches were formed partially on the heated surface and the CHF point was reached. At this stage, there is no sharp wall temperature increase. After the heat flux (i.e.the upward vapor flow) was elevated more, that liquid penetration was testricted more and the liquid penetrating rate becomes less than the evaporation rate, large-stable dry-patches were created and the wall temperature excursion started. No.difference was observed between the (1) and (2) experiments in the CHF heat flux q_<CHF> and the temperature excursion initiation heat flux q_<EXC>. The values of q_<CHF> in the present experiments were much lower, approximately one order, than values predicted with existing correlations.
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