Gaseous fission products removal from an interior cavity of a fuel element in a multielement EGC

The results of optimization calculations of a gas-removal apparatus in the form of a tube with a capillary tip are presented. Specifically, a criterion for choosing the length of a gas-removal tube for securing serviceability during a period of formation of an isothermal cavity in a uranium dioxide kernel is developed, the requirements for the geometric characteristics of a perforated protective screen are presented, and a mechanism for restoring the serviceability of the gas-removal system during a malfunction owing to mass transfer in irregular operating regimes of the EGC is described and substantiated. It is shown that uranium dioxide with sub-stoichiometric composition and single-crystal tungsten must be used for the gas-removal tube in order for the tube to be chemically stable and stable under thermal cycling. The results of reactor tests of an EGC are presented, and qualitatively confirm the computational results.