Analysis of critical pipe break sizes leading to reactor pressure vessel liquid level collapse and core uncovery with APROS. (December 2021)

• Record Type: Journal Article
• Authors: Wu, Qingyang; Li, Gen; Yan, Junjie; Deguchi, Yoshihiro
• Is Part Of: Progress in nuclear energy. Volume 142(2021)
• Publication Date: 2021-12
• Subjects: Liquid level collapse -- Core uncover -- Steam generator tube rupture -- Main steam line break -- Loss of coolant accident; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 333.7924
• DOI: 10.1016/j.pnucene.2021.104016
• Languages: English
• ISSNs: 0149-1970

Abstract

Abstract: Collapse of liquid level in reactor pressure vessel (RPV) and uncovery of core in typical pipeline rupture accidents, such as steam generator tube rupture (SGTR), main steam line break (MSLB), and loss of coolant accident (LOCA) for pressurized water reactor (PWR), may occur. This study used APROS to establish a full-scale simulation model of VVER440 reactor and evaluated different break sizes that can lead to RPV liquid level collapse and core uncovery during these accident processes. It is demonstrated that in SGTR accident, the liquid level in RPV collapsed under the condition of four or more heat transfer tube ruptures without the risk of core uncovery in all analyzed cases. In the MSLB accident, RPV liquid level collapse and core uncovery were absent due to the integrity of the primary circuit. In the LOCA accident, the RPV liquid level collapsed under a break size of 0.5% of pipe area (PA) of cold and hot leg. Notably, core uncovery occurred when the break area was 1.8% of PA in the cold leg and 65% of PA in the hot leg. The time required until core uncovery was earlier in the cold leg than that in the hot leg. Highlights: Full-scale modeling of the VVER440 pressurized water reactor was conducted using the APROS software. Critical break sizes that cause core uncovery in pipe rupture accidents is found. Effect of break sizes on the liquid level of pressure vessel in the pipe rupture accidents is evaluated.