The influence of radiation on the stability of CsI in flowing steam

In the recent past, concern was raised regarding the potential of ionizing radiation to affect the stability of CsI in a reactor coolant system following the release of fission products during a severe accident. We have conducted a series of experiments to specifically address the issue of CsI stability and its potential for reaction, in steam, with Type 304 stainless steel while exposed to a radiation field. The experiments were conducted in a 2.5-cm stainless steel flow pipe at temperatures between 900 and 950 degrees Celsius, and at 100 kPa. Molecular CsI, at concentrations ranging from 60 to 240 ppm, was passed through the flow pipe in steam and collected in that water condensed at the end of the pipe. The condensate was analyzed for Cs+ and I- concentrations. The ratio of these ions is an indicator of the fraction of CsI that dissociated during the transit of the pipe. A specially constructed flask containing 12 kCi (444 TBq) of cobalt-60 provided a radiation field of 0.3 to 9 krad/min (3 to 90 Gy/min). The results of the tests showed no correlation between CsI stability and the applied radiation field. The fraction of CsI dissociated, as measured by a deficiency of Cs+ in the condensate, varied between 0 and 35% with a weak correlation for increasing dissociation with decreasing CsI concentration. It is assumed that the cesium not found in the condensate formed CsOH in the pipe during transit, and then reacted with the stainless steel