chapter  2
Waste characteristics
Pages 1

The waste was generated during the chemical separation processes that were used for recovery of plutonium from nuclear fuels irradiated in reactors. Many types of separation processes were used over the years especially as experience was progressively gained in separating them better and in generating lesser volume of wastes. In all chemical processes, the separation was achieved in acidic environments. In most cases, the waste stream was first converted to an alkaline state by adding chemicals and then stored in carbon steel containments. In other cases, although few, the waste remained highly acidic and was stored in stainless steel containments. Subsequently, with the rapid generation of the waste compared to the available storage space, further treatments became necessary. In some cases, the fission products were separated from the waste by differential settlement (e.g., for strontium 90) or by scavenging with other chemicals (e.g., for cesium 137). The waste volume was reduced and concentrated using evaporators. For control of the waste chemistry and maintaining a desirable pH level that would minimize metallic corrosion, chemicals were periodically added in some instances. As a result of all these chemical treatments and the diverse composition of the fission products, a large number of chemical species, probably composed of half the elements in the Periodic Table, are present in the waste. Chemical reactions also occurred over the years in the radioactive environment. Thus, although there is a historical track record of chemical streams that went into the containments, in many instances, an adequate knowledge of the present waste characteristics does not exist. Despite this deficiency of precise characterization, the following general physical and chemical characteristics of the waste can be postulated for structural engineering needs.