Explanation

Also known as neutron absorbing material, it is a materials that can significantly absorb neutrons and effectively control the reactivity of nuclear reactor. It is divided into three categories: control rod materials, chemical compensating agent and combustible poison. The control rod is a strong neutron absorber with fast movement speed, reliable operation, flexible use, and high control reactivity accuracy. The control rod is an indispensable component for emergency control and power regulation in the reactor core. Mainly controlling rapid changes in reactivity. The main requirements for control rod materials are: large neutron absorption cross section, such as hafnium, silver-indium-cadmium alloy; Anti radiation, anti corrosion and good mechanical properties. The requirements for chemical compensation agents include solubility in the coolant, stable chemical and physical properties, and a large absorption cross-section. It is non corrosive to the core structural components and does not adhere to the components. Boric acid can meet the above requirements. The main elements used as combustible toxins include boron and gadolinium. Boron glass is the most widely used in PWR. At the end of core life, boron is basically burned out. The left glass absorption section is relatively small, which has little impact on the core life.

Classification