Process and device of thermal shielding of the vessel of a nuclear reactor

This invention relates to the thermal protection of the vessel of a liquid metal cooled integrated nuclear reactor. The process consists in circulating along the vessel part of the liquid metal injected at the bottom of the core. In a leak tight annular chamber above the flowing liquid metal, an inert gas (argon) is placed under pressure to regulate the gas-liquid metal interface in this chamber so as to obtain a distribution of temperatures along the vessel so that the range of stress changes is restricted. According to a first variant of the invention, the inert gas pressure is created by trapping in the chamber a mass of argon under an initial pressure so that the level of the gas-liquid metal interface in this chamber is kept appreciably constant during the power changes of the reactor. Accoding to a second variant of the invention, this pressure is achieved by trapping in the chamber a mass of argon, the pressure of which is adjusted, whilst the reactor is working, so that the power changes of the reactor generate movements of the gas-liquid metal interface that will maintain the thermal gradient, created along the vessel, at an appreciably constant and sufficiently low level