Improvements relating to liquid metal cooled nuclear reactors

A method is described for detecting leaks in fuel elements in a liquid metal cooled reactor having a core comprised of fuel element stacks. Conventional methods employ a sampler with intricate piping arranged inside the reactor, but this complicates recharging of the stacks, involving dismantling of the whole installation. The method described provides for the consecutive checking of all fuel element stacks for leakage in a more convenient manner. The upper portion of a stack to be tested is located within a downwardly open tube of the recharging mechanism, with a sample of coolant surrounding it, and an inert gas is introduced into the coolant sample through an inlet in the recharging mechanism. This gas is collected, after bubbling through the sample into a space above the sample, and passed through an outlet in the recharging mechanism into a device for measuring the level of radioactivity. The method permits a consecutive check, on stopping the reactor, of all stacks without removing them from the reactor core, and facilitates removing faulty stacks from the reactor. If required the stacks may be checked during recharging operations, both when the coolant is stationary or is circulating, and the reactor shut down time is considerably reduced. Alternative forms of the required apparatus are described. (U.K.)