System Integral Test by BWR Drywell Cooler Applied as Accident Management

Nakamura, Hideo; Tobimatsu, Toshimi; Tahara, Mika; Yokobori, Seiichi; Akinaga, Makoto

doi:10.3327/taesj2002.2.240

Cited by 2 publications

(1 citation statement)

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“…Nagasaka et al conducted the system integral tests simulating BWR pressure vessel failure using the test facility with volumetric scaling ratio of 1/600 (Nagasaka et al, 2003). They also carried out severe accident analysis using MELCOR code with their original heat transfer correlations for the existing DWC that was validated by the system integral test data.…”

Section: Introductionmentioning

confidence: 99%

Effect of new drywell cooler application for venting start time during severe accidents

Ishida

Nagata

Kimura

et al. 2020

Mechanical Engineering Journal

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Nuclear power plants are equipped with a hardened containment venting system and a filtered containment venting system to avoid a primary containment vessel (PCV) break by over-pressurization. Considering the gas release from these venting systems, it is desirable to delay venting start time or to avoid operation of the systems by ensuring sufficient PCV cooling in view of the time needed to evacuate residents and the half-life of the radioactive materials.We have been developing a new drywell cooler specialized for severe accidents (DWC_SA) as one additional PCV cooling method. The DWC_SA can cool the PCV by continuous steam condensation using downward flow induced by natural force without any electrical devices in the PCV. We have already conducted element tests using a small tube bundle to confirm the occurrence of continuous downward flow with the DWC_SA configuration and to measure heat transfer rate of condensation with non-condensable gas (NCG). The heat transfer model was validated using the element test data. Here, to estimate plant performance of a representative advanced boiling water reactor (ABWR) applying the DWC_SA, we carried out a severe accident analysis using the MAAP code. We originally installed the heat transfer rate map of the DWC_SA as a function of pressure and NCG ratio in the code. The velocities using in the heat transfer model were estimated from CFD analysis. According to the severe accident analysis results, the DWC_SA can extend venting start time sufficiently to allow evacuation of residents in the accident scenario (LOCA with large pipe failure + ECCS failure + SBO) with the external water injection into the PCV and it can avoid operation of the containment venting systems in the case of internal water circulation in the PCV.

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Section: Introductionmentioning

confidence: 99%

Effect of new drywell cooler application for venting start time during severe accidents

Ishida

Nagata

Kimura

et al. 2020

Mechanical Engineering Journal

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Large-Scale Containment Cooler Performance Experiments under Accident Conditions

Kapulla

Mignot

Paladino

2012

Science and Technology of Nuclear Installations

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Computational Fluid Dynamics codes are increasingly used to simulate containment conditions after various transient accident scenarios. This paper presents validation experiments, conducted in the frame of the OECD/SETH-2 project. These experiments address the combined effects of mass sources and heat sinks related to gas mixing and hydrogen transport within containment compartments. A wall jet interacts with an operating containment cooler located in the middle (M-configuration) and the top (T-configuration) of the containment vessel. The experiments are characterized by a 3-phase injection scenario. In Phase I, pure steam is injected, while in Phase II, a helium-steam mixture is injected. Finally, in Phase III, pure steam is injected again. Results for the M-configuration show helium stratification build up during Phase II. During Phase III, a positively buoyant plume emerging from the cooler housing becomes negatively buoyant once it reaches the helium-steam layer and continuously erodes the layer. For the M-configuration, a strong degradation of the cooler performance was observed during the injection of the helium/steam mixture (Phase II). For the T-configuration, we observe a mainly downwards acting cooler resulting in a combination of forced and natural convection flow patterns. The cooler performance degradation was much weaker compared with the M-configuration and a good mixing was ensured by the operation of the cooler.

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System Integral Test by BWR Drywell Cooler Applied as Accident Management

Cited by 2 publications

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Effect of new drywell cooler application for venting start time during severe accidents

Effect of new drywell cooler application for venting start time during severe accidents

Large-Scale Containment Cooler Performance Experiments under Accident Conditions

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