Multiscale Thermal Hydraulic Study under the Inadvertent Safety Injection System Operation Scenario of Typical Pressurized Water Reactor

Abstract

The Reactor Pressure Vessel (RPV) inlet nozzles and downcomer wall in Pressurized Water Reactors (PWR) may suffer serious thermal shock caused by cold water from reactor Safety Injection System (SIS) in some unexpected accident scenarios. It implies the formation of great temperature gradient on the inlet nozzles and RPV wall, leading to the localized stresses and propagation of possible flaws that appeared in the material. In this paper, the multiscale thermal hydraulic analysis was performed for Chashma Nuclear Power Plant (NPP) under the inadvertent SIS operation scenario. The primary loop and SIS were modeled using onedimensional method, while the three-dimensional models of reactor cold leg, RPV inlet nozzles, and downcomer were established. Then, the inadvertent Safety Injection System operation scenario was simulated using RELAP5 code, providing the boundary conditions for three-dimensional Computational Fluid Dynamics (CFD) analysis. The fluid and solid coupling heat transfer simulation method was employed. Results show that the maximum temperature difference was about 80 K in the most conservative condition and the RPV inlet nozzle region was the most critical region during the accident. This work could provide in-depth understanding on the effect of cold coolant injection along the main pipes and RPV wall during the accident scenario.

Thermomechanical Analysis of a Reactor Pressure Vessel under Pressurized Thermal Shock Caused by Inadvertent Actuation of the Safety Injection System

“…ese pump outlets are linked to a pipe header with discharge channels connected to the cold or hot legs of the coolant system. Following the operation of the injection system, the high-pressure pumps cause the cooling water from the RWST to be released into the core of the reactor [18]. Transient incidents that cause the unintentional injection of cooling water directly into the RPV's downcomer give rise to high pressurizer levels.…”

“…e inadvertent actuation of the SIS PTS transient loads used in this paper was determined by Wang et al [18].…”

Integrity Evaluation of a Reactor Pressure Vessel Based on a Sequential Abaqus-FRANC3D Simulation Method

“…e outlets of the pumps are connected to a common pipe header with four discharge pipelines connected to the hot legs or cold legs of the RCS. Under the condition of the safety injection, the HPSI pumps enable cold water from the RWST to be pumped into the reactor core [19]. Events leading to the inadvertent injection of colder water directly into the downcomer result in the increase of the core power and pressurizer level.…”

“…e AOO PTS event initiated by an inadvertent SIS operation selected for this study was investigated by Wang et al [19]. is type of event frequently occurred in the lifetime of PWR NPPs as reported in IAEA operational experience feedback reports [14,26].…”