Atmospheric dispersion study with 85Kr and SF6 gas

85Kr concentration in air around the reprocessing plant was measured when it was released from the plant stack during the hot-test operation treating PWR spent fuels. A charcoal absorption method was devised for this experiment as a rapid, simple and inexpensive technique for the measurement of 85Kr concentration at about 10-9μCi/cm3. Special air samplers were located a few kilometers from the stack and the air was collected for an hour at a flow-rate of 1.5 liters per minute. About thirty air samples were taken and analyzed for 85Kr concentration successfully. The performance of the sampling and analytical methods employed was good, although some improvements were found to be necessary. An example is that an air-collection bag should be made of ''saran'' to minim+ze leakage. Usually sulfur hexafluoride gas is used as an air-tracer in an atmospheric diffusion study: analytical procedure for determining the gas concentration down to 10-3 ppb is well established. In this experiment SF6 gas was injected into the stack during the discharge of 85Kr and the concentration in sampled air was also determined. The results show a good correlation between 85Kr and SF6 concentration in sampled air. (author)