CHARACTERIZATION OF ALTERNATE SOLVENT AND EVALUATION OF ITS ENERGETIC PROPERTIES DURING REPROCESSING OF SPENT NUCLEAR FUEL

Abstract

Spent nuclear Fuel reprocessing is an important step for closing up of the nuclear fuel cycle. The spent fuels from the PHWR reactors contain unreacted Uranium, newly formed Pu-239 from U-238 and fission products. These fission products are very dangerous and considered as nuclear waste. Reprocessing separates these three components form the spent fuel. Uranium goes for further fuel fabrication for the PHWR reactors, Plutonium goes for fuel fabrication for the fast breeder reactors and the fission products are disposed off safely. Reprocessing plants all over the world mainly follow PUREX process of solvent extraction. In the reprocessing plants, other than the chance of criticality, there is a significant potential of devastating `Red Oil' accidents which occur due to the interaction of the exrtactant tri-butyl phosphate and nitric acid at higher temperatures. The `red oil' is a highly energetic mixture of different components, generation of which follows a self accelerating exothermic runaway reaction with evolution of large quantity of detonable gases. The sudden release of these gases, if not vented with the rate it is produced, may lead to equipment rupture, cause explosion when mixed with air and release radioactive materials in the environment. This research work was aimed to evaluate an alternate solvent Tri iso-Amyl Phosphate which has more flexibility and advantages over the presently used Tri n-Butyl Phosphate. The contemporary and versatile extractant TBP and its properties with respect to red oil type reactions were surveyed from the literature. Physical properties like density, viscosity and refractive index values of the alternate solvent system in diluents were experimentally measured and empirical correlations were prescribed which has not been done earlier. Flash points of the extractant in different diluents were also experimentally measured. These values were correlated with the carbon number of the diluent itself. This would help in lab scale and plant scale solvent studies.