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Science and Technology of Nuclear Installations
Volume 2013 (2013), Article ID 879634, 7 pages
Research Article

Improvement of Core Performance by Introduction of Moderators in a Blanket Region of Fast Reactors

Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2 Aramaki Aoba, Aoba-ku, Sendai 980-8579, Japan

Received 4 September 2012; Accepted 4 February 2013

Academic Editor: Wei Shen

Copyright © 2013 Toshio Wakabayashi. 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.


An application of deuteride moderator for fast reactor cores is proposed for power flattening that can mitigate thermal spikes and alleviate the decrease in breeding ratio, which sometimes occurs when hydrogen moderator is applied as a moderator. Zirconium deuteride is employed in a form of pin arrays at the inner most rows of radial blanket fuel assemblies, which works as a reflector in order to flatten the radial power distribution in the outer core region of MONJU. The power flattening can be utilized to increase core average burn-up by increasing operational time. The core characteristics have been evaluated with a continuous-energy model Monte Carlo code MVP and the JENDL-3.3 cross-section library. The result indicates that the discharged fuel burn-up can be increased by about 7% relative to that of no moderator in the blanket region due to the power flattening when the number of deuteride moderator pins is 61. The core characteristics and core safety such as void reactivity, Doppler coefficient, and reactivity insertion that occurred at dissolution of deuteron were evaluated. It was clear that the serious drawback did not appear from the viewpoints of the core characteristics and core safety.