A study of large break LOCA in the AP1000 reactor containment

Invariant methods for an ensemble-based sensitivity analysis of a passive containment cooling system of an AP1000 nuclear power plant

“…Figure 2 shows the PCCS of the AP1000 (Westinghouse Electric Company). For the quantification of the functional failure of the PCCS of the AP1000 following a LOCA, a TH model for stratified heat transfer with non-condensed gas has been developed, that consists in four phases (Rahim et al 2012): 1) blowdown, from the accident initiation (by a doubleended guillotine pipe break in a primary coolant line affecting the normal operation of the reactor at steady-state full power) to the time at which the primary circuit pressure reaches the containment pressure; 2) refill, from the end of the blowdown to the time when the Emergency Core Cooling System (ECCS) refills the vessel lower plenum; 3) reflood, which begins when water starts flooding the core and ends when this is completely quenched; 4) post-reflood, which starts after the core quenching and during which energy is released to the Reactor Coolant System (RCS).…”

Finite mixture models for sensitivity analysis of thermal hydraulic codes for passive safety systems analysis

“…A TH code for simulating a LOCA follows the phenomena evolution typically in four phases [Rahim et al 2011]: 1) blowdown, from the accident initiation (by a double-ended guillotine pipe break in a primary coolant line affecting the normal operation of the reactor at steady-state full power) to the time at which the primary circuit pressure reaches the containment pressure; 2) refill, from the end of the blowdown to the time when the Emergency Core Cooling System (ECCS) refills the vessel lower plenum; 3) reflood, which begins when water starts flooding the core and ends when this is completely quenched; 4) post-reflood, which starts after the core quenching and during which energy is released to the Reactor Coolant System (RCS).…”

“…Among the SA techniques, it is possible to identify three families: Local, Regional and Global [Saltelli et al 2000]. The local approach to SA consists in evaluating the effect on the output of small variations around fixed values in the input parameters.…”

Reliability Study of the AP1000 Passive Safety System by Fuzzy Approach

“…AP1000, which is designed based on the Westinghouse proven pressurized water reactors [22,23], has implemented the concept of passive system into its safety injection system, residual heat removal system and containment cooling system. The major advantage of these passive safety systems is that the long-term accident mitigation can be maintained without the involvement of the operators and reliance on the AC power sources from offsite or onsite [3,9]. AP1000 reactors provide three passive safety systems to mitigate the large break LOCA, namely: injection system by accumulator (AI), low pressure injection system (LPI) which injects water from in-containment refueling water storage tank (IRWST) and long term cooling system (LTC) which injects water from passive containment cooling water storage tank (PCCWST) [16].…”

“…In line with this, the concepts of passive systems have been the focus of recent innovations to the designs of nuclear power plant safety systems. The Westinghouse AP1000 is a two-loop advanced light water reactor which implements passive concept to its safety systems based on gravity, convection, condensation and heat circulation [1][2][3][4][5]. AP1000 has been certified as a generation III+ reactor by the United States Nuclear Energy Commission (US-NRC) and the European Utility Requirements [6,7].…”