Status report on the IAEA's WREBUS study

In late 1987, the International Atomic Energy Agency initiated a multinational study called Water Reactor Extended Burn-Up Study, or WREBUS. The principal purpose of the study is to determine whether economic incentives may exist to extend the burnup of water reactor fuel beyond the range which has previously been accepted as economically justified for utility implementation; i.e., beyond discharge batch average values of about 45 MWd/kgU for BWRs and 50 MWd/kgU for PWRs. This study has been initiated by assuming that significantly higher burnups would not introduce serious new technical problems which would substantially increase costs, by determining required enrichments for the higher burnups for a variety of reactors and cycle lengths, and by computing corresponding fuel cycle costs first for an agreed-upon set of economic parameters and second (optionally) for any country's own set of economic parameters. Sensitivity studies were done to determine the importance of each of the principal economic parameters. A benchmark exercise was also conducted in which each country (or country team) used the same enrichments and reactor characteristics; this exercise showed that within round-off error each of the fuel cycle cost codes used by the various participants gave essentially the same results for the same inputs. Following the economic studies, the technical issues foreseen for burnup extension beyond the present ranges are reviewed, together with potential licensing, safety, and environmental effects. This review provides an indication of the extent to which the previous assumption of no serious new technical issues may be valid and indicates the scope and nature of research and development efforts that would be needed to proceed to the higher discharge burnups studied. The WREBUS study is till under way; it is the intent of this paper to provide a status report on its results. 6 figs, 2 tabs