Akademik Veri Yönetim Sistemi
KERNTECHNIK, cilt.71, ss.247-257, 2006 (SCI-Expanded, Scopus)
Nuclear waste actinides can be used as a booster fissile fuel material in form of mixed fuel with thorium in a CANDU reactor in order to assure the initial criticality at startup. Two different fuel compositions have been found useful to provide sufficient reactor criticality over a long operation period: 1) 95% thoria (ThO) + 5% minor actinides MAO(2) and 2) 90% ThO2 + 5% MAO(2) + 5% UO2. The latter allows a higher degree of nuclear safeguarding through denaturing the new U-233 fuel with U-238. The temporal variation of the criticality k(infinity) and the burn-up values of the reactor have been calculated by full power operation for a period of 10 years. The criticality starts by k(infinity) > 1.3 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout in the actinide fuel. The criticality becomes quasi constant after the 2(nd) year and remains close to k(infinity) = similar to 1.06 for similar to 10 years. After the 2(nd) year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn up could be achieved with the same fuel material (up to 200 000 MW.D/MT), provided that the fuel rod claddings would be replaced periodically (after every 50 000 or 100 000 MW.D/MT). The reactor criticality can be maintained until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.