BWRX-300’s Nominal Pressure and Temperature Testing (1): Analysis of Test Results from Various Large Diameter Chimney Tests at Elevated Pressure and Temperature

Abstract

The BWRX-300 is a water-cooled natural circulation small modular reactor developed by GE Hitachi Nuclear Energy in cooperation with Hitachi-GE Nuclear Energy. BWRX-300 is equipped with passive safety systems and leverages the design and licensing of USNRC-certified ESBWR. Like the ESBWR, the BWRX-300 uses a tall chimney above the core to provide natural circulation head to drive sufficient core flow and ensure fuel is operated within its thermal limits. The TRACG system code has been qualified for calculating thermal limits in BWRs including the natural circulation ESBWR. To support extending the TRACG qualification to the large-diameter simplified chimney of BWRX-300, test data have been obtained in Hitachi Utility Steam Test LEading facility (HUSTLE) using two down-scaled chimneys of 0.5 m and 0.35 m in diameter, at nominal BWR operating conditions of 7.17 MPa and 289 ℃ and flow rates scaled from BWRX-300 chimney operating conditions. Some previously published data for 0.5 m chimney were compared with additional test results for a smaller 0.35 m diameter chimney and with other similar tests. The test data were compared with some theoretical models. The study analyzed how the test data scale with various parameters including the chimney diameter and the results provide additional insight into the behavior of two-phase flow in large diameter vertical channels, especially in the high void-fraction range.