Fast spectrum control rod materials

Nagata, Takako; Maeda, Koji  

This article is a review of fast reactor control rod materials and is part of the Elsevier Comprehensive Nuclear Materials Series. Control rods have three primary functions; reactivity compensation during the operating cycle, start-and-stop control for normal operation, and rapid shutdown during abnormal conditions. As an absorber material, boron carbide (BC) is mainly used in fast reactor systems, such as the Japanese experimental reactor JOYO. The current core configuration of JOYO is Mark-3 (MK-3). The control rods are inserted automatically when abnormal conditions occur. In both the MK-2 and MK-3 cores, all control rods have the same structure and functions. Every control rod assembly has seven control rod elements, and BC pellets are used as absorbers. The boron in BC includes B and B. Control rods function as safety (shutdown) rods, regulating rods, rapid shutdown rods, additional shutdown rods, absorber pins, worth of controlled rods, vertical travel of control rods, rod-drop time, and features of the drive mechanism.