COOLABILITY OF COARSE CORIUM DEBRIS BEDS (REACTOR SAFETY, POST ACCIDENT REMOVAL, VOLUMETRICALLY HEAT BED, NATURAL BOILING POROUS MEDIA)
Abstract
Because of a corium-coolant interaction, a bed of volumetrically heated particles submerged in the coolant will be formed either in the vessel or in the cavity under a hypothetic reactor core melt down accident. Hence, coolability of the debris bed is essential to the reactor safety. A large scale test facility with extensive instrumentation was constructed to simulate the coarse corium debris bed. The facility which employed a variable 100 kw DC power generator had a cylindrical test bed 101.6 cm in height and 21.6 cm in diameter. The bed was assembled by packing alternating layers of heaters and stone gravel. The effects of power distribution, bed depth, submergence, particle shape, and pressure on coolability of debris beds have been investigated. Also, the dryout transient phenomena such as dryout inception behavior, dryout inception position, and dryout propagation in three dimensions have been studied. The results indicate that the dryout delay time is simply related to the applied power. The relationship, called the constant energy line, is useful to uniquely define the incipient dryout heat flux. It also provides a convenient and highly accurate means for the experimental measurement of the incipient dryout heat flux. A model based on the flooding phenomenon was developed to predict the dryout inception position. The results are encouraging. New functions based on the present data for relative permeabilities of turbulent flow were suggested. With these functions, the theoretical model not only predicts the present dryout data but also successfully predicts the void-fraction data obtained from the cocurrent flow experiment and the sparging experiment.
Degree
Ph.D.
Subject Area
Nuclear physics
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