Innovative two-phase thermosyphon-based PRHR system for prolonged passive heat removal in light water reactors

Abstract

This research aims to develop a passive residual heat removal system (PRHR) for 300 MW thermal power light water reactors (LWRs) utilizing a novel two-phase thermosyphon configuration. The proposed PRHR design includes an evaporator section immersed in the steam path of the PRHR, enabling efficient heat transfer directly from the steam source. The primary objectives are to investigate the thermal performance characteristics of the two-phase thermosyphon when operating in the steam environment of the PRHR, and to assess the effectiveness of direct heat extraction from the PRHR steam in reducing the size of heat exchange equipment required for long-term heat removal. The novelty of this research lies in the development of a conceptual PRHR design that extends passive heat removal capabilities beyond the conventional 72-h operational window. While existing PRHR systems necessitate operator intervention to prolong functionality, the proposed configuration leverages the inherent advantages of two-phase thermosyphons, offering sustained passive heat removal with enhanced thermal conductivity and efficiency. To support this novel concept, the research involves experimental evaluations of the two-phase thermosyphon's thermal performance when subjected to steam heat sources ranging from 1 to 3 bar. Experimental data will validate numerical models, enabling the determination of design parameters for the PRHR configuration specified for 300 MW thermal power LWRs. This comprehensive research initiative represents a significant step toward enhancing the safety and reliability of PRHR systems for advanced nuclear reactors.