Leak rate analysis of the Westinghouse Reactor Coolant Pump

Boardman, T.J.; Jeanmougin, N.; Lofaro, R.; Prevost, Jeff

doi:10.2172/5496369

Cited by 9 publications

(8 citation statements)

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“…6. Surge line failure probabilities as a function of time given the occdrrence of TMLB' sequences with seal leaks of 250 gpm per RCP in the Surry NPP.…”

mentioning

confidence: 99%

Assessment of the potential for high-pressure melt ejection resulting from a Surry station blackout transient

Knudson¹,

Dobbe²

1993

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Containment integrity could be challenged by direct heating associated with a high pressure melt ejection (HPME) of core materials following reactor vessel breach during certain severe accidents. Intentional reactor coolant system (RCS) depressurization, where operators latch pressurizer relief valves open, has been proposed as an accident management strategy to reduce risks by mitigating the severity of HPME. However; decay heat levels, valve capacities, and other plant-specific characteristics determine whether the required operator action will be effective. Without operator action, natural circulation flows could heat ex-vessel RCS pressure boundaries (surge line and hot leg piping, steam generator tubes, etc.) to the point of failure before vessel breach, providing an alternate mechanism for RCS depressurization and HPME mitigation. This report contains an assessment of the potential for HI'ME during a Surry station blackout transient without operator action and without recovery. The assessment included a detailed transient analysis using the SCDAP/RELAP5/MOD3 computer code to calculate the plant response with and without hot leg countercurrent natural circulation, with and without reactor coolant pump seal leakage, and with variations on selected core damage progression parameters. RCS depressurizativn-related probabilities were also evaluated. primarily based on the code results.

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“…6. Surge line failure probabilities as a function of time given the occdrrence of TMLB' sequences with seal leaks of 250 gpm per RCP in the Surry NPP.…”

mentioning

confidence: 99%

Assessment of the potential for high-pressure melt ejection resulting from a Surry station blackout transient

Knudson¹,

Dobbe²

1993

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“…The short term station blackout sequence described considers that, with the loss of AC power, the RCS pump seals leak due to loss of fluid backpressure and cooling of the seals [9]. Leaks are modeled at each of the four reactor coolant pumps that allow the liquid RCS coolant to escape at the pump locations.…”

Section: Description Of Short Term Station Blackout With Leaking Pumpmentioning

confidence: 99%

An uncertainty analysis of the hydrogen source term for a station blackout accident in Sequoyah using MELCOR 1.8.5

Gauntt

Bixler

Wagner

2014

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A methodology for using the MELCOR code with the Latin Hypercube Sampling method was developed to estimate uncertainty in various predicted quantities such as hydrogen generation or release of fission products under severe accident conditions. In this case, the emphasis was on estimating the range of hydrogen sources in station blackout conditions in the Sequoyah Ice Condenser plant, taking into account uncertainties in the modeled physics known to affect hydrogen generation. The method uses user-specified likelihood distributions for uncertain model parameters, which may include uncertainties of a stochastic nature, to produce a collection of code calculations, or realizations, characterizing the range of possible outcomes. Forty MELCOR code realizations of Sequoyah were conducted that included 10 uncertain parameters, producing a range of in-vessel hydrogen quantities. The range of total hydrogen produced was approximately 583kg  131kg. Sensitivity analyses revealed expected trends with respected to the parameters of greatest importance, however, considerable scatter in results when plotted against any of the uncertain parameters was observed, with no parameter manifesting dominant effects on hydrogen generation. It is concluded that, with respect to the physics parameters investigated, in order to further reduce predicted hydrogen uncertainty, it would be necessary to reduce all physics parameter uncertainties similarly, bearing in mind that some parameters are inherently uncertain within a range. It is suspected that some residual uncertainty associated with modeling complex, coupled and synergistic phenomena, is an inherent aspect of complex systems and cannot be reduced to point value estimates. The probabilistic analyses such as the one demonstrated in this work are important to properly characterize response of complex systems such as severe accident progression in nuclear power plants.

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“…25 Specifically, Westinghouse seals are expected to leak 21 gpm of subcooled water per RCP at nominal operating conditions if seal cooling water is lost. 26 Subsequent seal degradation and failure is expected as a TMLB' accident progresses because the seals are not designed for exposure to high temperature steam. The seals are particularly vulnerable to failure when fluid in the RCP reaches a saturated condition because seal faces tend to pop open as a result of two-phase flow instabilities.…”

Section: Surry Analyses With Rcp Seal Leaksmentioning

confidence: 99%

“…1 seal cooling water is lost. 26 Since seal cooling water is lost when AC power is lost, a seal leak area equivalent to 21 gpm per RCP was introduced in all Surry and Zion analyses with RCP leaks at TMLB' accident initiation. Subsequent seal degradation and failure is expected as a TMLB' accident progresses because the seals are not designed for exposure to high temperature steam.…”

Section: Rcs Depressurization With Rcp Seal Leaksmentioning

confidence: 99%

SCDAP/RELAP5 Evaluation of the Potential for Steam Generator Tube Ruptures as a Result of Severe Accidents in Operating PWRs

Knudson¹,

Ghan²,

Dobbe³

1998

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Leak rate analysis of the Westinghouse Reactor Coolant Pump

Cited by 9 publications

References 0 publications

Assessment of the potential for high-pressure melt ejection resulting from a Surry station blackout transient

Assessment of the potential for high-pressure melt ejection resulting from a Surry station blackout transient

An uncertainty analysis of the hydrogen source term for a station blackout accident in Sequoyah using MELCOR 1.8.5

SCDAP/RELAP5 Evaluation of the Potential for Steam Generator Tube Ruptures as a Result of Severe Accidents in Operating PWRs

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