Abstract
The containment is an ultimate and important barrier to mitigate the consequences after the release of mass and energy during such scenarios as loss of coolant accident (LOCA) or main steam line break (MSLB). In this investigation, a passive containment cooling system (PCCS) concept is proposed for a large dry concrete containment. The system is composed of series of heat exchangers, long connecting pipes with relatively large diameter, valves, and a water tank, which is located at the top of the system and serves as the final heat sink. The performance of the system is numerically studied in detail under different conditions. In addition, the influences of condensation heat transfer conditions and containment environment temperature conditions are also studied on the behaviors of the system. The results reveal that four distinct operating stages could be experienced as follows: startup stage, single phase quasisteady stage, flashing speed-up transient stage, and flashing dominated quasisteady operating stage. Furthermore, the mechanisms of system behaviors are thus analyzed. Moreover, the feasibility of the system is also discussed to meet the design purpose for the containment integrity requirement. Considering the passive feature and the compactness of the system, the proposed PCCS is promising for the advanced integral type reactor.
Highlights
In order to prevent the radioactive species escaping to atmosphere, high integrity containment has been one of the most active design focuses in recent years
Enlightened by internal evaporator-only (IEO) design concept, we present an openloop passive containment cooling system (OLPCCS) concept, which is composed of heat exchangers located in the containment, long connecting pipes with relatively large diameter, valves, and one water tank located outside the containment
In order to ensure the integrity of the containment after typical accidents, the conceptual OLPCCS is proposed and the PCCSTS code is developed to simulate the behavior of OLPCCS
Summary
In order to prevent the radioactive species escaping to atmosphere, high integrity containment has been one of the most active design focuses in recent years. Most investigations on the behaviors of the natural circulation under low-pressure conditions were contributing to the studies of either start-up procedures to cross the instability region (Jiang et al [10], van der Hagen and Stekelenburg [11], Manera et al [12], and Kuran et al [13]) or two-phase flow instabilities (Aguirre et al [14], Aritomi et al [15], Van Bragt and van der Hagen [16], Guanghui et al [17], etc.) for the boiling water reactors (BWRs). The heat removal capabilities of the system are analyzed
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