Published: 1978
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The principal objectives of the fission product release program are to determine the quantity of radiologically significant fission products released from defected LWR fuel rods under accident conditions, identify their chemical and physical forms, and interpret the results for use as input to computer models of postulated transportation and loss-of-coolant accidents. Experimental work with flowing steam in the temperature range 500 to 1200°C and with dry air at 500°C and 700°C has been completed. One series of tests, the Implant Test Series, employed simulated fission products which were coated on unirradiated UO2 fuel pellets; a second series, the Low Burnup Fuel Test Series, used fuel capsules irradiated to 1000 MWd/MT at high heat rating (560 to 660 W/cm), and a third series of experiments, the High Burnup Test Series, used fuel irradiated to 30,000 MWd/MT in the H.B. Robinson reactor at low heat rating (175 to 320 W/cm). Sufficient analytical results have been obtained to permit the formulation of a preliminary empirical model for cesium release in steam. The model assumes that cesium release is the sum of two components: burst release (that carried out with escaping plenum gas when the rod ruptures) and diffusion release (that diffusing from the gap space after the plenum gas has vented).