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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

ANALYSIS OF PASSIVE DECAY POWER REMOVAL VIA TWO-PHASE BOILING-DRIVEN NATURAL CONVECTION IN THE NPR-HWR THIN RECTANGULAR FUEL CHANNELS

Get access (open in a dialog) DOI: 10.1615/IHTC10.2580
pages 203-208

要約

As part of an assessment of severe accident prevention and mitigation in the NPR-HWR advanced production reactor, in-core, boiling-driven natural convection was identified as an effective mechanism for long-term, passive decay power removal. Henry (1993) conducted experiments which showed that decay power levels (1-4% of nominal full power) could be removed via latent heat on a long-term basis. Incipient fuel dryout and overheat would ensue only when the two-phase level within the fuel assemblies was insufficient to cover the heated length. Henry (1993) then developed a thermal hydraulic model for predicting threshold conditions spawning incipient dryout in the thin rectangular subchannels that comprise the coolant annuli within the fuel assembly. Such a prediction is necessary for determining the duration of successful power removal provided by this mechanism. The model provides good agreement with the noted data and, more importantly, with data from independent tests on a full-scale assembly. The noted mechanism is gravity-dominant two-phase natural circulation. Thus, this work is distinct from the large body of research in high-power removal limits from completely submerged channels, entailing a friction-/acceleration-dominant two-phase natural circulation. Cheng (1991) and Mishima (1987) are two of numerous contributors in this related field.