Safety margins improvement by means of the passive second stage hydroaccumulators in a VVER-1000/V320 reactor

• Published in: Nuclear engineering and design 2023-12, Vol.414, p.112644, Article 112644
• Main Authors: Redondo-Valero, Elena, Queral, César, Fernandez-Cosials, Kevin, Sanchez-Espinoza, Víctor
• Format: Article
• Language: English
• Subjects: LOCA; Passive safety systems; SBO; Second Stage Hydroaccumulators (HA-2); VVER-1000
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2023.112644

•The impact of the HA-2 passive safety system in LOCA along with SBO sequences is verified.•HA-2 impact in the LPIS, HPIS and HA-1 success criteria for medium/large LOCA sequences is analyzed.•A review of the passive emergency core cooling systems is performed. Since the Fukushima accident, there has been a new surge in interest in passive safety systems that ensure the core integrity in accidental sequences involving a total loss of AC power. In this sense, the majority of the GEN-III reactors incorporate advanced passive safety systems. One such system is the Second Stage Hydroaccumulators (HA-2) system, which is a passive safety injection system included in some advanced VVER reactors. The goal of this paper is to analyse the impact of the HA-2 on the events of a LOCA sequence, with and without SBO. For this purpose, a VVER-1000/V320 thermal hydraulic model for TRACEV5P5 code has been modified to include the HA-2 system. By analysing the results, it is found that the single performance of this passive safety system along with the accumulators, without considering any other management action, is enough to avoid the core damage in medium/large LOCA along with SBO during 24 h, moreover this system allows also to relax the success criteria of the active High and Low Pressure Safety Injection Systems in medium/large LOCA sequences without SBO conditions.