Reducing the Long-term Hazard of Reactor Waste through Actinide Removal and Destruction in LWR's

Artikel i vetenskaplig tidskrift, 1980

Public opposition to nuclear power has focused on the long-term risks from reactor waste. In the Purex process used in Europe, this waste is a concentrated nitric acid solution containing all nonvolatile fission products and the actinides Np, Am, and Cm, plus smaller amounts of U and Pu. Techniques have recently been described which guarantee an absolutely safe containment of this high-active waste (HAW) for about 1000 years. At longer times, the risk to the biosphere is dominated by the actinides. If these actinides are isolated from the rest of the HAW and destroyed through nuclear incineration, the long-term risks of the HAW will be dramatically reduced. This paper presents a detailed scheme for removing the actinides from the Purex-HAW solution. In principle, the process consists of three different solvent extraction cycles, using HDEHP and TBP in three successive steps. The scheme has been tested on a synthetic HAW solution containing all fission products and actinides (except Z 96, Cm) using laboratory-scale mixer-settler batteries. Results from runs on old Purex waste are also presented. If applied to fresh Purex waste, the process will encounter problems due to radiation damage to the reagents. In practice, this difficulty can be circumvented by using short contact times in the solvent extraction process. Extremely rapid multistage solvent extraction separations can be carried out by the SISAK technique (i.e., batteries of static mixers and special centrifugal separators). This technique is also described.