Development of Measurement System for Sealing Performance

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(1) Gas leakage rates of 10^<-4> to 0.1cm^3/s from very narrow orifices and capillaries were investigated. It can be seen from the results that choked and free expansion jet flow rates from a very narrow orifice can be evaluated by the correlations used for a narmally sized orifice, and that for gas leakage rates of 10^<-4> to 0.1cm^3/s which is closely related to the sealing performance of transport casks of radioactive materials, both choked and molecular flows can be ignored but friction loss of laminar flows considering gas expansion effect governs the flow.(2) Gas leakage rates were investigated from leak paths simulated dy scratches on an O-ring surface. It is clarified from the results that their simulated leak paths including multiple leak paths can be approximated by a circular channel and by introducing the eigenvalue of leak paths (D^4/a).(3) A measurement system of gas leakage rates, which measures directly gas flow rates using a capillary as a sensor, was developed. This system can be measure the leakage flow rates of 10^<-4> to 10^<-2>cm^3/s required for the preshipment test to transport casks of radioactive materials for a short period.(4) Another measurement system of gas leakage rates, which measures pressure decreasing rates, was developed. This system can measure them simultaneously at multiple points with high accuracy,(5) The other measurement system of very small gas leakage rates less than 10^<-4>cm^3/s was developed, which exhaust gas inflowing through a narrow tube only on low temperature surface for a short period.