Basic Boiling Experiments with An Inclined Narrow Gap Associated With In-Vessel Retention

Conference · Mon Jul 01 04:00:00 EDT 2002

OSTI ID:21167845

Terazu, Kuninobu; Watanabe, Fukashi ^[1]; Iwaki, Chikako; Yokobori, Seiichi; Akinaga, Makoto ^[2]; Hamazaki, Ryoichi ^[3]; SATO, Ken-ichi ^[4]

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1. Nuclear Power Engineering Department, Tokyo Electric Power Company, 1-3 Uchisaiwai-cho 1-chome, Chiyoda-ku, Tokyo 100-0011 (Japan)
2. Power and Industrial Systems R and D Center, Toshiba Corporation, 4-1 Ukishima-cho, Kawasaki-ku, Kawasaki, 210-0862 (Japan)
3. Isogo Nuclear Engineering Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama, 235-8523 (Japan)
4. Nuclear Power Division, Power and Industrial Systems, Hitachi, Ltd., 1-1, Saiwai-cho 3-chome, Hitachi, 317-8511 (Japan)

In the case of a severe accident with relocation of the molten corium into the lower plenum of reactor pressure vessel (RPV), the successful in-vessel corium retention (IVR) can prevent the progress to ex-vessel events with uncertainties and avoid the containment failure. One of the key phenomena governing the possibility of IVR would be the gap formation and cooling between a corium crust and the RPV wall, and for the achievement of IVR, it would be necessary to supply cooling water to RPV as early as possible. The BWR features relative to IVR behavior are a deep and massive water pool in the lower plenum, and many of control rod drive guide tubes (CRDGT) installed in the lower head of RPV, in which water is injected continuously except in the case of station blackout scenario. The present paper describes the basic boiling experiment conducted in order to investigate the boiling characteristics in an inclined narrow gap simulating a part of the lower head curvature. The boiling experiments were composed of visualization tests and heat transfer tests. In the visualization tests, two types of inclined gap were constructed using the parallel plate and the V-shaped parallel plate with heating from the top plate, and the boiling flow pattern was observed with various gap width and heat flux. These observation results showed that water was easily supplied from the gap bottom of parallel plate even in a very narrow gap with smaller width than 1 mm, and water could flow continuously in the narrow gap by the geometric and thermal imbalance from the experiment results using the V-shaped parallel plate. In the heat transfer tests, the critical heat flux (CHF) data in an inclined narrow channel formed by the parallel plates were measured in terms of the parameters of gap width, heated length and inclined angle of a channel, and the effect of inclination was incorporated into the existing CHF correlation for a narrow gap. The CHF correlation modified for an inclined narrow gap was applied to analysis of the IVR transient for typical BWR conditions. The analysis code is based on the existing correlations and models for various phenomena supposed to occur during IVR, such as a melt jet breakup and quenching in a water pool, thermal interaction between corium and CRDGT, heat transfer from accumulated corium and gap cooling of lower head. Results of sensitivity analysis demonstrated that the early recovery of water injection to RPV using CRD system would lead to successful IVR. (authors)

• Research Organization: American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 21167845
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
BOILING
BWR TYPE REACTORS
CONTROL ROD DRIVES
COOLING
CORIUM
CRITICAL HEAT FLUX
GUIDE TUBES
HEAT TRANSFER
PLATES
PRESSURE VESSELS
REACTOR ACCIDENTS
RETENTION
SENSITIVITY ANALYSIS
WATER
WIDTH