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A STUDY ON BURNABLE ABSORBER FOR A FAST SUB-CRITICAL REACTOR HYPER<br />

Yong Hee Kim, Won Seok Park<br />

Korea Atomic <strong>Energy</strong> Research Institute<br />

P.O. Box 105, Yusong, Taejon, 305-600, Korea<br />

Jong Seong Jeong<br />

Department of <strong>Nuclear</strong> Engineering, Seoul National University<br />

Shinrim-dong Kwanak-ku Seoul 151-742, Korea<br />

Abstract<br />

This paper is concerned with development of burnable absorber technologies for an accelerator driven<br />

system (ADS) with fast neutron spectrum, HYPER (Hybrid Power Extraction Reactor). Concerning<br />

the ADS loaded with TRUs (Transuranic Elements), one of the major problems is a large burn-up<br />

reactivity swing and the consequent unfavourable slanting of the radial power distribution over a<br />

depletion period. In order to reduce the reactivity drop during core burn-up, B 4 C is introduced as a<br />

burnable absorber and its efficacy is evaluated for the HYPER system. Taking into account the<br />

radioactive TRU fuel, the inner surface of the fuel clad is coated with a thin B 4 C layer. Two concepts<br />

of the burnable absorber application are considered, homogeneous and heterogeneous loading of B 4 C.<br />

In the homogeneous application, B 4 C is used in all fuel rods, while the burnable absorber is utilised<br />

only in the outer zone of the core in the heterogeneous loading. The burn-up characteristics of the<br />

HYPER cores with and without the B 4 C burnable absorber are analysed with a Monte Carlo code,<br />

called MCNAP.<br />

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