Crack detection cell for checking the leakproofness of fuel element units

A crack detection cell for checking the leakproofness of a fuel element in the deactivation swimming pool of a nuclear reactor, by measuring the gamma activity of fluids in contact with the fuel unit, said cell comprising:

• a double-walled chamber for resting vertically on the bottom of the deactivation swimming pool, the external wall of said chamber defining orifices which connect the gap between said walls of said chamber with the swimming pool;
• means for connecting said gap to a source of inert gas under pressure for creating a heat barrier between the interior of said chamber and the deactivation swimming pool;
• a leakproof pocket for receiving a fuel unit in a vertical position, said pocket being located inside said chamber and comprising an upper part for serving as a zone for introducing said unit and a leakproof cover for closing said pocket;
• means for introducing water into, and for removing water from, said pocket;
• heating means mounted on the lower part of said pocket and for heating water contained in said pocket by direct contact to cause a rise in temperature of a fuel element in said pocket;
• means for circulating said inert gas in said pocket;
• and
• means for continuously measuring the activity of the gas which has passed through the water contained in said pocket and in which the fuel element is immersed.