Evaluation of Local Accidents in LMFBR

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Kikuchi, Y.*; H.MIZUT*; H.YOSHI*; M.HIRO*

Kikuchi, Y.*; H.MIZUT*; H.YOSHI*; M.HIRO*

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This paper deals with the evaluation of local faults occurred in a fuel subassembly and a steam generator of a liquid metal cooled fast breeder reactor (LMFBR) system. Fuel pin integrity under various abnormal conditions is being confirmed by both out-of pile and in-pile tests. Out-of-pile experiments were conducted to evaluate the mechanical and thermal effects of fission gas ejection on adjacent pins and a wrapper tube. Out-of-pile experiments were conducted to measure local temperature rises due to fuel pin contact and local flow blockages, and the measured temperature rises agreed fairly with the predictions by computer codes. Extensive studies were conducted on local and bulk sodium boiling phenomena and the experimental results were in satisfactory agreement with the computer code predictions. Out-of-pile experiments are being conducted to measure the magnitude of pressure pulses generated in molten fuel-coolant interactions. The integrity of wrapper tubes to high pressure was examined by gunpowder explosive tests in water and the possibility of meltthrough to adjacent subassemblies were evaluated analytically. Various local anomaly detection methods are being studied along with the above experiments. Tests and analyses of sodium-water reaction also have been conducted to evaluate the integrity of a steam generator.