Abstract
Korea Atomic Energy Research Institute (KAERI) established a multi-dimensional hydrogen analysis system to evaluate hydrogen release, distribution, and combustion in the containment of a Nuclear Power Plant (NPP), using MAAP, GASFLOW, and COM3D. In particular, KAERI developed an analysis methodology for a hydrogen flame acceleration, on the basis of the COM3D validation results against measured data of the hydrogen combustion tests in the ENACCEF and THAI facilities. The proposed analysis methodology accurately predicted the peak overpressure with an error range of approximately ±10%, using the Kawanabe model used for a turbulent flame speed in the COM3D. KAERI performed a hydrogen flame acceleration analysis using the multi-dimensional hydrogen analysis system for a severe accident initiated by a station blackout (SBO), under the assumption of 100% metal–water reaction in the Reactor Pressure Vessel (RPV), to evaluate an overpressure buildup in the containment of the Advanced Power Reactor 1400 MWe (APR1400). The magnitude of the overpressure buildup in the APR1400 containment might be used as a criterion to judge whether the containment integrity is maintained or not, when the hydrogen combustion occurs during a severe accident. The COM3D calculation results using the established analysis methodology showed that the calculated peak pressure in the containment was lower than the fracture pressure of the APR1400 containment. This calculation result might have resulted from a large air volume of the containment, a reduced hydrogen concentration owing to passive auto-catalytic recombiners installed in the containment during the hydrogen release from the RPV, and a lot of stem presence during the hydrogen combustion period in the containment. Therefore, we found that the current design of the APR1400 containment maintained its integrity when the flame acceleration occurred during the severe accident initiated by the SBO accident.
Highlights
There is extensive research on the possibility of a hydrogen explosion, and of a safety device to reduce the hydrogen concentration in the containment of a Nuclear Power Plant (NPP) in the Republic of Korea, since the hydrogen explosion accident of the NPP in Fukushima in 2011 [1,2]
The magnitude of the overpressure buildup in the Advanced Power Reactor 1400 MWe (APR1400) containment might be used as a criterion to judge whether the containment integrity is maintained or not, when the hydrogen combustion occurs during a severe accident
A 3-way valve located at the bottom of the pressurizer (PZR) in the safety depressurization system (SDS) changed the flow path of the discharge of the reactor coolant from the in-containment refueling water storage tank (IRWST) to the north SG compartment, when the severe accident occurred in the reactor pressure vessel (RPV) during the station blackout accident (SBO) accident, to prevent the hydrogen release to the IRWST, according to the severe accident management guideline (SMAG) [4]
Summary
There is extensive research on the possibility of a hydrogen explosion, and of a safety device to reduce the hydrogen concentration in the containment of a Nuclear Power Plant (NPP) in the Republic of Korea, since the hydrogen explosion accident of the NPP in Fukushima in 2011 [1,2]. Auto-catalytic Recombiners (PARs) were installed in all NPP containments, to reduce hydrogen concentration during a severe accident in the Republic of Korea [1]. Korea Atomic Energy Research Institute (KAERI) chose the COM3D [5] as the computational code for calculating the overpressure buildup, owing to the hydrogen flame acceleration, by evaluating its numerical methods, physical models, a solver algorithm, validation and application results, and its ability to connect an analysis code of a hydrogen distribution in the containment. It is necessary to evaluate an uncertainty of the COM3D code using experimental data, such as hydrogen combustion tests conducted in the ENACCEF and THAI facilities [9,10,11,12], before applying it to the hydrogen combustion during a severe accident in the APR1400 containment. A proper test data for the COM3D validation should be chosen by considering the hydrogen and steam concentrations predicted by the GASFLOW and the geometric characteristics of the APR1400 containment to increase the credibility of the COM3D code
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