Preventing water inflow to fuel element during vault flooding - by fission gas pressure rise produced by submerged bell

摘要

A fuel element for gas-cooled, fast reactors comprises an intended leadage point at which fission gas can pass out of the fuel element (including its separate fuel rods) into the extract system. When the fuel element is upright inside a flooded reactor vault or other flooded chamber, water entering at the point of intended leakage (III) ends a submerged bell, where it compresses the fission gas inside the fuel rod, thus preventing the water from entering the fuel rods. Pref. where the fuel elements are suspended from a top support plate and the intended point of leakage (III) is at the junction between element and plate, a line leads down from this point to a buffer vessel beneath the fuel rods, entering this buffer vessel from the bottom. The upper, gas-contg. part of the buffer vessel is connected by a pipe to the fission gas discharge duct located in the fuel rod support plate. An activated carbon cartridge may be incorporated in this line. Used esp. for gas-cooled, fast reactors where the fuel elements are connected by a point of intended leakage to a fission gas extract system and the reactor vault can be flooded during shutdown. The arrangement prevents water from penetrating into the fuel elements during this period.