Cooling water injection pipelines in the pressure vessel of reactor

Purpose: To prevent the generation of a great thermal fatigue in the joint between the vessel and the cooling water injection pipeline of a nuclear power plant to thereby improve the safetiness of a reactor core. Constitution: The thermal sleeve for cooling water supply feed to the cooling water injection nozzle of a reactor pressure vessel is bent in its midway within the pressure vessel and extended upward. While cooling water flows from the nozzle and passes through the horizontal pipe and the vertical pipe of a thermal sleeve into the pressure vessel, no convection is resulted within the sleeve due to the temperature difference, that is, the specific gravity difference in which the temperature in the upper portion of the vertical pipe of the sleeve is higher than that in the lower portion thereof. Accordingly, no thermal stress due to temperature changes repeated in a high frequency is generated in this portion. (Horiuchi, T.)