Optimization of spatial structure designs of control rod using Monte Carlo code RMC  

作　　者：Hao LUO Mancang LI Shanfang HUANG Minyun LIU Kan WANG 

机构地区：[1]Department of Engineering Physics,Tsinghua University,Beijing 100084,China [2]Science and Technology on Reactor System Design Technology Laboratory,Nuclear Power Institute of China,Chengdu 610213,China [3]CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology,China National Nuclear Corporation Nuclear Power Institute of China,Chengdu 610213,China

出　　处：《Frontiers in Energy》2021年第4期974-983,共10页能源前沿（英文版）

基　　金：the National Key R&D Project(Grant No.2020YFB1901700);the National Natural Science Foundation of China(Grant No.11775127).

摘　　要：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 inefficient.Moreover,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 area.In 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 pins.The 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 stability.For the spatially mixed rod,rare-earth absorbers are combined with B4C in spatial structure.Compared with the homogenous B4C rod,mixed designs ensure more sufficient reactivity worth in the lifetime of the reactor.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 rods.The control rod with small-sized pins processes an enhanced safety performance and saves the investment in absorbers.The rod worth can be further enhanced by introducing small moderator pins,and the reactivity loss caused by the reduction of absorbers is sustainable.

关 键 词：control rod optimized spatial structure neutronic performance burnup stability 

分 类 号：O57[理学—粒子物理与原子核物理]