Investigation of CANDU reactors as a thorium burner

• Published in: Energy conversion and management Vol. 47; no. 13; pp. 1661 - 1675
• Main Authors: SAHIN, Sümer, YILDIZ, Kadir, SAHIN, Haci Mehmet, ACIR, Adem
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2006; Elsevier
• Subjects: Applied sciences; CANDU reactors; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; High burn-up; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; Plutonium; Preparation and processing of nuclear fuels; Thorium; CANDU reactors; Plutonium; High burn-up; Thorium; Booster; Burnup; Nuclear reactor; CANDU type reactors; High bum-up; Fuel; Fuel rod; Burner; Manufacturing cost; Cost lowering; Irradiated nuclear fuel; Criticality
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2005.10.013

Large quantities of plutonium have been accumulated in the nuclear waste of civilian LWRs and CANDU reactors. Reactor grade plutonium can be used as a booster fissile fuel material in the form of mixed ThO 2/PuO 2 fuel in a CANDU fuel bundle in order to assure reactor criticality. The paper investigates the prospects of exploiting the rich world thorium reserves in CANDU reactors. Two different fuel compositions have been selected for investigations: (1) 96% thoria (ThO 2) + 4% PuO 2 and (2) 91% ThO 2 + 5% UO 2 + 4% PuO 2. The latter is used for the purpose of denaturing the new 233U fuel with 238U. The behavior of the reactor criticality k ∞ and the burn-up values of the reactor have been pursued by full power operation for >∼8 years. The reactor starts with k ∞ = ∼1.39 and decreases asymptotically to values of k ∞ > 1.06, which is still tolerable and useable in a CANDU reactor. The reactor criticality k ∞ remains nearly constant between the 4th year and the 7th year of plant operation, and then, a slight increase is observed thereafter, along with a continuous depletion of the thorium fuel. After the 2nd year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn-up can be achieved with the same fuel (>160,000 MW D/MT). The reactor criticality would be sufficient until a great fraction of the thorium fuel is burned up, provided that the fuel rods could be fabricated to withstand such high burn-up levels. Fuel fabrication costs and nuclear waste mass for final disposal per unit energy could be reduced drastically.