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Science and Technology of Nuclear Installations
Volume 2013 (2013), Article ID 867561, 8 pages
http://dx.doi.org/10.1155/2013/867561
Research Article

Study of Thorium-Plutonium Fuel for Possible Operating Cycle Extension in PWRs

1Thor Energy AS, Sommerrogaten 13-15, 0255 Oslo, Norway
2Division of Nuclear Engineering, Department of Applied Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
3Ringhals AB, 432 85 Väröbacka, Sweden

Received 14 October 2012; Accepted 11 January 2013

Academic Editor: Hangbok Choi

Copyright © 2013 Klara Insulander Björk et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Computer simulations have been carried out to investigate the possibility of extending operating cycle length in the Pressurised Water Reactor Ringhals 3 by the use of thorium-plutonium oxide fuel. The calculations have been carried out using tools and methods that are normally employed for reload design and safety evaluation in Ringhals 3. The 3-batch reload scheme and the power level have been kept unchanged, and a normal uranium oxide fuel assembly designed for a 12-month operating cycle in this reactor is used as a reference. The use of plutonium as the fissile component reduces the worth of control rods and soluble boron, which makes it necessary to modify the control systems. The delayed neutron fraction is low compared with the reference, but simulations and qualitative assessments of relevant transients indicate that the reactor could still be operated safely. Differences in reactivity coefficients are mainly beneficial for the outcome of transient simulations for the thorium based fuel. A 50% extension of the current 12-month operating cycle length should be possible with thorium-plutonium mixed oxide fuel, given an upgrade of the control systems. More detailed simulations have to be carried out for some transients in order to confirm the qualitative reasoning presented.