Control rod is the most important approach to control reactivity in reactors,which is currently a cluster of pins filled with boron carbide(B4C).In this case,neutrons are captured in the outer region,and thus the inne...
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Control rod is the most important approach to control reactivity in reactors,which is currently a cluster of pins filled with boron carbide(B4C).In this case,neutrons are captured in the outer region,and thus the inner absorber is ***,the lifetime of the control rod is challenged due to the high reactivity worth loss resulted from the excessive degradation of B4C in the high flux *** this work,some control rod designs are proposed with optimized spatial structures including the spatially mixed rod,radially moderated rod,and composite control rod with small-sized *** control rod worth and effective absorption cross section of these designs are computed using the Monte Carlo code RMC.A long-time depletion calculation is conducted to evaluate their burnup *** the spatially mixed rod,rare-earth absorbers are combined with B4C in spatial *** with the homogenous B4C rod,mixed designs ensure more sufficient reactivity worth in the lifetime of the *** minimum reactivity loss at the end of the cycle is only 1.8%from the dysprosium titanate rod,while the loss for pure B4C rod is nearly 12%.For the radially moderated design,a doubled neutronic efficiency is achieved when the volume ratio of moderator equals approximately 0.3,while excessive moderating may lead to the failure of control *** control rod with small-sized pins processes an enhanced safety performance and saves the investment in *** rod worth can be further enhanced by introducing small moderator pins,and the reactivity loss caused by the reduction of absorbers is sustainable.
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