Volatilization of Cesium-137 from Soil with Chloride Amendments during Heating and Vitrification

In situ vitrification demonstration at Pit 1, Oak Ridge National Laboratory. Volume 2: Site characterization report of the Pit 1 area

“…41. As observed previously with other 137Cs contaminated soils (Spalding 1994), no volatilization of '37Cs was observed until treatment to temperatures above 1000°C where increasing temperature led to SO increased volatilization of 137Cs. Most importantly, the degree of i37Cs volatilization observed in these pit 1 soil samples was not unusual compared with other soils investigated previously, such as the 1987 soils where only minimal volatilization was observed in the field.…”

“…The sampling of perched groundwater from pit 1 on August 22,1994, was carried out under the proscriptions of the phase I1 quality assurance project plan (Spalding 1994). Because of the quality control samples included in this sampling effort, a high degree of confidence is warranted in the findings with actual water samples.…”

“…The previous 1987 pilot-scale ISV test at ORNL had found only 0.12% of the buried Cs inventory had volatilized during its vitrification . Subsequent research has identified that unusual sources and amounts of chlorine, such as the polyvinyl chloride (PVC) pipe used to enclose the radioactive sludge sample during the 1991 demonstration, as the probable cause of enhanced volatilization of 137Cs (Spalding 1994); this later investigation identified several factors, in addition to chloride sources, such as limestone content, heating rate, processing temperature, and presence of other chemicals such as borate which can enhance or diminish the volatility of 137Cs during vitrification of soil.…”

“…In particular, the effects of limestone amendment to ISV melts on volatilization of 137Cs needed to be examined for pit 1 soil and melt materials because of the potential for limestone for adjusting ISV processing temperature Spalding 1994).…”

“…40 were prepared in small alumina crucibles as described in Spalding (1994). These crucibles were assayed nondestructively via gamma spectroscopy for I3' Cs activity before and after sequential treatments of 2 hours at final temperatures of 100, 550, 800, 1000, 1200, 1300, 1400, 1500,1600, and 1700°C in a box furnace with an average heating rate of 23"C/min.…”