Plant designing of ion exchange chemical uranium enrichment and its non-proliferation aspects

Abstract

The chemical uranium enrichment using ion exchanger had been developed mainly in Japan, but now only the academic studies have been continued at Tokyo Tech. For the purpose of revaluation as the alternative production process of the low enriched uranium for nuclear power plants, the plant design and the non-proliferation aspects of redox ion exchange chemical uranium enrichment (Redox Ion Exchange Method) were studied. The conceptual design of a commercial enrichment plant with a scale of 1400 tSWU/Y was newly performed based on data reported. It is composed of seven enrichment units with two enrichment columns with an inner diameter of 6.5 m and a height of 11 m and redox systems. It is evaluated as having the site area of 97,200 m 2 including the vacancy to double the production with subsidiary sections of pre-treatment and post-treatment of uranium or the like, a construction cost is 218 billion Japanese yen(JPY), and a cost per enrichment work is 18,000 JPY/kgSWU. As for the nuclear proliferation resistance of this process, it is suggested that the production of highly enriched uranium for weapon use is difficult from the view point of nuclear fission criticality and the lengthy equilibrium time mentioned as following. It is difficult to operate the enrichment plant for the production of highly enriched uranium of 50 wt% of 235U or higher, because the effective neutron multiplication factor ( k eff) in the enrichment columns becomes 1 or above depending on the enrichment conditions. And the required time for the production of highly enriched uranium of 90 wt% of 235U is estimated 10 thousands days or more, this means substantially impossible to get highly enriched uranium under the safeguard of IAEA by the Redox Ion Exchange Method. The Redox Ion Exchange Method is suggested to be a promising candidate for an alternative enrichment process to obtain low enriched uranium in the range 3–5 wt% 235U for nuclear power plant in the world. Furthermore, for the future prospective fuel cycle without UF 6, new front-end system coupled with uranium from seawater and chemical enrichment is proposed.