Evaluation of Control Rod Designs for a Potential Configuration of the Versatile Test Reactor

摘要

Different control rod layouts were investigated for a conceptual configuration of the Versatile Test Reactor (VTR). Reducing the number of rods per assembly increases the B_4C volume fraction, thus increasing reactivity worth. Doing so also reduces the melting margin inside the pellets and the reactivity loss at EOL. As a result, the two most extreme cases, CR61 and CR7, were deemed less favorable. Overall, CR19 was found to have sufficient safety margins with the second best reactivity worth. The design only required a 44% I0B enrichment to reach the conservative margins put forward. The arrangement is recommended for both the control and safety rods of the VTR.