Evaluation of reflooding effects on an overheated boiling water reactor core in a small steam-line break accident using MAAP, MELCOR, and SCDAP/RELAP5 computer codes

Journal Article · Sun Oct 01 00:00:00 EDT 1995 · Nuclear Technology

OSTI ID:131655

Lindholm, I; Pekkarinen, E ^[1]; Sjoevall, H ^[2]

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1. Technical Research Centre of Finland, Espoo (Finland)
2. Teollisuuden Voima Oy, Olkiluoto (Finland)

Selected core reflooding situations were investigated in the case of a Finnish boiling water reactor with three severe accident analysis computer codes (MAAP, MELCOR, and SCDAP/RELAP5). The unmitigated base case accident scenario was a 10% steam-line break without water makeup to the reactor pressure vessel initially. The pumping of water to the core was started with the auxiliary feed water system when the maximum fuel cladding temperature reached 1,500 K. The auxiliary feedwater system pumps water (temperature 303 K) through the core spray spargers (core spray) on the top of the core and through feedwater nozzles to the downcomer (downcomer injection). The scope of the study was restricted to cases where the overheated core was still geometrically intact at the start of the reflooding. The following different core reflooding situations were investigated: (1) auxiliary feedwater injection to core spray (45 kg/s); (2) auxiliary feedwater injection to downcomer (45 kg/s); (3) auxiliary feedwater injection to downcomer (45 kg/s) and to core spray (45 kg/s); (4) no reflooding of the core. All the three codes predicted debris formation after the water addition, and in all MAAP and MELCOR reflooding results the core was quenched. The major difference between the code predictions was in the amount of H{sub 2} produced, though the trends in H{sub 2} production were similar. Additional steam production during the quenching process accelerated the oxidation in the unquenched parts of the core. This result is in accordance with several experimental observations.

• OSTI ID: 131655
• Journal Information: Nuclear Technology, Vol. 112, Issue 1; Other Information: PBD: Oct 1995
• Country of Publication: United States
• Language: English

Related Subjects

22 NUCLEAR REACTOR TECHNOLOGY
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS
BWR TYPE REACTORS
REACTOR ACCIDENTS
REACTOR CORES
COMPUTERIZED SIMULATION
COOLING
REACTOR SAFETY
M CODES
S CODES
CORE SPRAY SYSTEMS
AUXILIARY SYSTEMS
QUENCHING
HYDROGEN PRODUCTION
FLUID-STRUCTURE INTERACTIONS
FLUID INJECTION