Validation Results of TRACG05 Against BWR and ABWR Start-Up Test Data

Abstract

Studies have been made on application of TRACG05, which is the latest version of TRACG code, to Best Estimate Plus Uncertainty (BEPU) approach for Anticipated Operational Occurrences (AOO) in BWR and ABWR. This paper presents validation results of TRACG05 against BWR and ABWR start-up test data. TRACG05 analyses of BWR and ABWR start-up tests, such as generator load rejection (pressurization event) and recirculation pump trip (core flow decrease event), were performed using standard plant nodalization and nominal inputs. In addition to the nominal cases, sensitivity studies and statistical analyses were conducted. The sensitivity studies include the sensitivities to TRACG05 model uncertainties, which have relatively high importance being tabulated in a Phenomena Identification and Ranking Table (PIRT), and nodalizaton. The sensitivity analyses include the random variation of TRACG05 model uncertainties, which have High ranking in PIRT, and initial core power. These uncertainties were preliminarily evaluated from comparisons of calculated results to separate effects test data, integral test data and component test data. TRACG05 calculated results of the nominal cases agree to the start-up test data with reasonable accuracy. For statistical analyses, the standard deviations of the key parameters related to the safety parameters (critical power ratio, etc) for AOO were calculated at each time step. The test data basically fall inside the 2 sigma bands. It indicates that the differences between calculated results and test data are within the uncertainties of TRACG05 model and initial core power that are taken into account for safety analyses in BEPU process. It is concluded that the TRACG05 code using the standard nodalization, inputs and model uncertainties is validated against the full-scale plant data and is capable of predicting the AOO transients.