VISA-II - A Computer Code for Predicting the Probability of Reactor Pressure Vessel Failure.

摘要

The VISA-II (Vessel Integrity Simulation Analysis) code was originally developed as part of the NRC staff evaluation of pressurized thermal shock. VISA-II uses Monte Carlo simulation to evaluate the failure probability of a pressurized water reactor (PWR) vessel subjected to a pressure and thermal transient specified by the user. Linear elastic fracture mechanics is used to model crack initiation and growth. Parameters for crack size and location, copper content, initial reference temperature of the nill-ductility transition, fluence, crack-initiation fracture toughness, and arrest fracture toughness are treated as random variables. The report documents an upgraded version of the original VISA code as described in NUREG/CR-3384. Improvements include a treatment of cladding effects, simulation of flaw size, shape and location, a simulation of inservice inspection, an updated simulation of the reference temperature of the nill-ductility transition, and treatment of vessels with multiple welds and initial flaws. The code has been extensively tested and verified and is written in FORTRAN for ease of installation on different computers.