Computer analysis of the system during generation ceramic covering on a cladding of a fuel element simulator with sublayer lead – magnesium - zirconium

The method of computer analysis of system parameters at formation of protective coating on the shell of fuel element of fast reactors is presented, which can serve as a prerequisite for development of cognitive architecture of control of nuclear power engineering processes by control of composition of gas phase in reactor core, containment, other tanks and making decisions on results of process parameters deviation from stationary function. The work was carried out to justify the prospects of using a liquid metal sublayer (LMS) instead of a gas sublayer in fuel elements, which allows, due to the high thermal conductivity of the liquid metal, to increase the width of the gap between the fuel and the shell and, therefore, to increase the fuel element life limited by the contact of the fuel with the shell. At the same time, safety in case of UTOP (uncontrolled increase of power), ULOF (termination of coolant flow through the reactor) accidents is increased due to significant decrease of temperature in the fuel center. However, the possibility of using LMS is limited by the substantial mass transfer - corrosion dissolution in the lead of the components of the fuel element shell in the hot zone and precipitation in the cold zone. In this article, the basis for computer analysis was studies on the absorption of gas (nitrogen) when forming a protective ceramic coating of zirconium nitride on the surface of the shell of a pipe-in-pipe type fuel element simulator to suppress the corrosion process from eutectic alloy lead-magnesium-zirconium. Abnormal intense decrease of nitrogen pressure (p, kPa) in expansion tank with Pb-Mg-Zr alloy at increased temperature (about 950 K) according to linear kinetic law (t, c), connected with its interaction with system components, was revealed: p, kPa=−0.0002⋅t−77.867 R2=0.942. Method of diagnostics of system parameters at formation of anticorrosive coating by nitrogen absorption is developed, empirical dependencies of process flow in wide range of temperature are built.