Unprocessed reactor fuel elements as a source for radiation processing

Spent fuel elements discharged from the DIDO-type research reactor, HIFAR, are allowed to cool for a few weeks and then cropped to remove excess metal. The elements are placed in a non-critical assembly in the bottom of an irradiated pond. Such a fuel element facility has been used for 15 years at the Australian Atomic Energy Commission's Research Establishment, Lucas Heights, in parallel with cobalt-60 facilities to carry out a range of irradiations involving such things as the sterilization of pharmaceuticals and medical products and of soils, polymerization and crosslinking of polymers and a wide range of radiation processing, radiation biology and radiation chemistry studies. In the years to come there will be an enormous supply of unprocessed fuel elements from power reactors. The technical feasibility of using these as a source for large scale radiation processes such as sewage treatment is assessed. Over the first few months during which the activity decays rapidly there is a need for frequent dosimetry and adjustments to dose delivered or to material flow rate. Possible ways of mitigating the effects of this major drawback are discussed. It is concluded that unprocessed fuel elements will not become a major source of radiation for processing and that electron accelerators appear to be the most satisfactory sources for large throughputs. (author)