Affiliation(s)
1. Department of Nuclear Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan
2. Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550, Japan
ABSTRACT
A burnup calculation has
been performed to evaluate heavy rare earth (terbium―Tb, dysprosium―Dy)
production in spent gadolinium oxide (Gd2O3) installed as
a BP (burnable poison). Each amount of Tb and Dy production derived from the BP
has been about 30-40 times larger than those created
in FP (fission products). Required cooling time to achieve exemption level on
radioactivity concentration produced Tb and Dy derived from the BP are much
shorter (BP-Tb: 7.9y, BP-Dy: < 0.1y) than those created in FP (FP-Tb: 3,616y, FP-Dy: 6.9y). However, the BP is mixed
homogeneously with UO2 pellet in current nuclear fuel system of LWRs
(light water reactors), and hence mixing of FP cannot be not avoided. In such a
mixture case, the required cooling time of recovered Tb will become 2,653y and that of recovered Dy be 4.8y. For this
reason, recovered Tb is unlikely to be resource for utilization, while
recovered Dy must be the resource provided the precise separation from the
other FP.
KEYWORDS
Burnable poison, heavy rare earth, Tb, Dy, fission products, Adv.-ORIENT
Cycle.
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