Technical Aspects and Benefits of the use of RU in CANDU Reactors

Abstract

The use of recovered uranium (RU) in CANDUs is an excellent example of the environmental 3R's (Reduce, Reuse, Recycle) as applied to global nuclear energy use. RU fuel offers a very attractive alternative to the use of natural uranium (NU) and slightly enriched uranium (SEU) in CANDU reactors because fuel economy is expected to improve even more through the use of RU. RU, with a about 0.9 % ²³⁵U enrichment results in an average discharge burnup of about twice that of NU in a CANDU reactor thereby increasing resource utilization and reducing fuel requirements. Spent fuel volumes and fuelling costs are reduced. Therefore, the use of RU in CANDU reactors potentially offers economic, environmental and public acceptance benefits on both the front-end and back-end. These benefits all fit well with the PWR-CANDU fuel cycle synergy. RU also offers greater flexibility in reactor and bundle designs and a power uprating capability RU fuel can be packaged in the CANFLEX fuel bundle, since the full benefits of the use of RU in CANDU reactors are achieved through the provision of enhanced margins in the bundle design.

RU, like NU and SEU, is a nuclear fuel commodity available from several sources. The cumulative quantity of RU projected to arise by the year 2000 from the reprocessing of spent oxide fuel in Europe and Japan is approaching 25,000 te. This quantity would provide sufficient fuel for 500 CANDU-6 reactor years of operation. Security of supply is, therefore, not an issue, and in addition, SEU of equivalent enrichment can be always be substituted for RU. It is anticipated that using RU in CA NDU reactors will provide improvements in fuel cycle economics.

The suitability of RU as a reactor fuel for CANDU has been studied in KAERI and AECL: CANDU fuel fabricated from RU meets CANDU specifications; utilizing RU does not introduce serious radiological difficulties, and no special precautions or technologies are required for handling of RU fuel bundles; hence new fuel receipt and management at reactor is particularly simple. Under current legislation and practice, it is also recognized that there are no obstacles to international or domestic transport of commercial quantities of RUO₂ powder.