Solid absorbant safety device for a nuclear reactor

In combination, a water cooled reactor and a safety device, said reactor comprising:

• water maintained under pressure within said reactor,
• a core immersed in said water and comprising several elongated vertical guide tubes open to said water,
• said safety device comprising:
• a vertical cylindrical tank mounted above said core and immersed in said water,
• conduit means connecting the bottom of said tank to said tubes,
• means forming within said cylindrical tank, fluid connected, upper, lower and intermediate compartments,
• absorbant in particulate form within said intermediate compartment,
• an opening within said lower compartment providing fluid communication between said conduit means and said lower compartment,
• fluid under pressure within said tank upper compartment,
• a closing element closing off said opening at the bottom of said lower compartment, said closing element comprising a uranium plug brazed at its periphery by means of a fusible metal to the tank wall defining said opening;
• whereby, in response to depressurization of the water within which said core and said tank are immersed, said plug is ejected by a pressure differential existing between said tank interior and exterior upon overheating of the brazed metal to initiate a rapid flow of pressurized fluid from said tank to said elongated guide tubes with fluid flow through said intermediate compartment fluidizing said particulate absorbant and forcing it to flow with said pressurized fluid through said conduit means and into said elongated guide tubes.