EBULLITION WATER TYPE LIGHT WATER NUCLEAR REACTOR AND CONTROL ROD FOR USE IN THE EBULLITION WATER TYPE LIGHT WATER NUCLEAR REACTOR

摘要

To make compatible both the simplification of a structure of a periphery of a pressure vessel and the vicinity of a reactor core by eliminating a pump for controlling a reactor core flow rate, and a favorable spectrum shift operation.SOLUTION: An ebullition water type light water nuclear reactor 100 has: a reactor core 2 attached with a fuel rod which is filled with fuel; a control rod 5 for controlling the reactivity of a neutron and the fuel; and a control rod drive mechanism 7 arranged above the reactor core, and inserting and withdrawing the control rod to/from the reactor core from above the reactor core. The control rod comprises a reactivity control part 5A which is filled with a neutron absorber, and a follower part 5B filled with a material of lower neutron absorption performance than the neutron absorber. Lengths of the reactivity control part and the follower part are formed substantially the same as a height of the reactor core. The follower part is arranged below the reactivity control part.SELECTED DRAWING: Figure 1