Author: Peter Brent Chadly

Publisher:

Published: 1983

Total Pages: 122

ISBN-13:

A vital safety concern in the analysis of nuclear power reactors is the thermal hydraulic behavior of the reactor coolant system under steady state and transient conditions. The goal of this study has been to develop an appropriate model for the U-tube type steam generators in a typical pressurized water reactor. To perform this modeling, the RETRAN computer code package was utilized. RETRAN is designed to provide a best-estimate thermal hydraulic analysis of complex fluid flow systems such as are associated with light water reactors. The code solves both steady state and time dependent problems. The Trojan nuclear plant in Prescott, Oregon, owned and operated by the Portland General Electric Company (PGE) served as the basis for this computer model. A crude primary loop RETRAN model was provided by PGE for use as a starting point. In this study, a detailed steam generator model was developed and merged with the primary loop model to create an expanded RETRAN system model. The principal objective was to demonstrate the capability of the model to calculate steam generator fluid properties for a steady state case at rated conditions. This was done by prescribing known boundary conditions for the nominal case and then comparing calculated fluid properties with measured data. After a nominal steady state solution was obtained, another objective was the demonstration of the modeling capability for steady states at partial power levels. These steady state cases were obtained by varying input boundary conditions to correspond to the partial power levels. Again, the consistency of the resulting steady state calculations was verified by comparison of calculated fluid properties with measured data. The final objective of this study was to model the response of the system under hypothetical transient conditions. A step load decrease of 10% was selected since it is within the normal operating design capabilities of the steam generator. Perturbations were input to the nominal steady state case as step changes in fluid boundary conditions, both for reasons of simplicity in modeling and to provide a conservative test of the model's stability under fluctuations which are severe compared with normal operational transients. This transient calculation approached an asymptotic set of steady state conditions which yielded good agreement with those predicted by linear interpolation of steady state quantities calculated for power levels bracketing the target power level.