Patent ID: 8553829
Filing Date: 2013-10-08
Classification: G21C,G21D,Y02E

Abstract:
1. A method for prediction of a plurality of variables characterizing fuel performance, utilizing a reduced order model computer program, applied to nuclear reactor operations, and comprising: a. loading a computer program into a computer; inputting, into the computer, reactor core instrumentation measurements; using said measurements to provide input to core monitoring software; accessing the monitoring software generated operational data of linear heat generation rate, neutron flux, burnup, fast neutron fluence, for all or the majority of fuel rods at several axial locations; and, b. calculating an evolution of clad hoop stress with time upon gap size reaching zero by where t is time, δ is pellet-clad gap size relative to clad inner radius, σ is clad hoop stress, E is clad material Young's modulus, the function ƒ is clad inelastic strain rate as function of hoop stress while being irradiated with a given fast neutron flux level and having accumulated a fast neutron fluence, specific for a given clad material and heat treatment, P is linear heat generation rate in pellets of a fuel rod as provided by reactor instrumentation and monitoring software, a 0 is pellet strain rate per unit linear power, and a 1 is pellet strain per unit linear power and, c. the parameter a where B is the burnup in MWd/kgU, P is linear power in kW/m, p u is fraction of unstable pores in the ceramic pellet material, and p s is a fraction of stable pores in the same material; d. the parameter a e. a clad creep rate function ƒ(σ), being generally dependent on stress and fast neutron flux, Φ, is determined by where a coefficient set c T , s, c IRR , v, w is specific to clad material and heat treatment; f. displaying the calculated parameters, σ and/or δ, and g. said displayed calculated parameters prompting nuclear reactor operators in taking operational steps for nuclear reactor operations.