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Preliminary control rod lifetime assessment for the versatile test reactor

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4 Scopus citations

Abstract

Preliminary control rod performance and depletion analyses were carried out for the VTR, using the reference VTR core layout and design characteristics. For the basic control rods design assumed, using natural boron, the reactivity worth is about 6000 pcm for the primary rods when the absorber is fresh. The loss of reactivity worth due to the depletion of B4C is about 60 pcm per irradiation cycle. It is observed that both the concentration of B-10 and the CR reactivity worth are roughly linear with the irradiation time. Several alternate design options were analyzed to understand the tradeoffs resulting from using a enriched boron when trying to increase the control rods reactivity worth. It was shown that using the same geometry with enriched B-10 could increase the CR reactivity worth but that the CR reactivity worth is not linear with B-10 enrichment due to the self-shielding effect. It also has several drawbacks, such as reduced core excess reactivity, and shorter control rod lifetime. A mitigation strategy to these drawbacks is to use both natural and enriched boron in the control rod, with the natural boron in the lower region of the pins and the enriched boron in the upper region. This design option can allow increasing the CR reactivity worth significantly, while maintaining all the advantages of natural boron.

Original languageEnglish
Pages (from-to)809-811
Number of pages3
JournalTransactions of the American Nuclear Society
Volume120
StatePublished - Jun 2019
Event2019 Transactions of the American Nuclear Society, ANS 2019 - Minneapolis, United States
Duration: Jun 9 2019Jun 13 2019

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