Evaluation of the RCS depressurization strategy for the high pressure sequences by using SCDAP/RELAP5

Park, Rae-Joon; Kim, Sang-Baik; Kim, Hee‐Dong

doi:10.1016/j.anucene.2007.07.004

Cited by 13 publications

(6 citation statements)

References 2 publications

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“…During the candling process, the molten core materials can be refrozen by the candling heat transfer and form the blockage. Because the lower value of SC1141(2) indicates the slower downward flow of molten core materials, the possibility of blockage formation increased with the lower value of SC1141 (2). Therefore, the increment of blockage could delay the relocation time.…”

Section: Regression Analysis Of Uncertainty Parameters On Accidentmentioning

confidence: 99%

“…However, due to the large scale of nuclear power plants, not many experimental studies were conducted for the accident sequence. Therefore the researches about the SA progress were conducted mostly by the numerical analysis [1][2][3][4][5]. As far as the numerical analysis of SA progress is concerned, lumped parameter SA codes such as MELCOR [6], MAAP [7], and SCDAP/RELAP [8] have been utilized in general.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress

Choi

Kim

Jeon

et al. 2018

Science and Technology of Nuclear Installations

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Uncertainty of a severe accident code output needs to be handled reliably considering its use in safety regulation of nuclear industry. In particular, severe accident codes are utilized for probabilistic safety assessment (PSA), where the uncertainty of severe accident progress should be considered carefully due to its influence on human reliability analysis. Therefore, in this study, the uncertainty analysis of severe accident progress was performed using MELCOR code, and a total of 200 data sets of in-vessel uncertainty parameters were generated by Latin hypercube sampling method. The rank regression analysis was also performed to investigate the effect of uncertainty parameters on the severe accident progress. Sensitivity coefficients (SCs) in MELCOR such as molten clad drainage rate and zircaloy melt breakout temperature showed significant influence on relocation time and dryout time of lower plenum. However, the influence of uncertainty parameter diminished as the accident progressed.

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Section: Regression Analysis Of Uncertainty Parameters On Accidentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress

Choi

Kim

Jeon

et al. 2018

Science and Technology of Nuclear Installations

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“…Birchley et al analyzed the loss of RHR for a Westinghouse two-loop PWR [14]. Park et al evaluated the effectiveness of the RCS depressurization strategy of the SBLOCA and TLOFW for OPR1000 [15,16] and APR1400 [17]. Huh et al studied the optimum area of the flow path of RCS depressurization for severe accident mitigation with the MELCOR for the Ulchin unit 1 PWR [18].…”

Section: Introductionmentioning

confidence: 99%

Effectiveness and adverse effects of reactor coolant system depressurization strategy with various severe accident management guidance entry conditions for OPR1000

Seo

Lee

et al. 2014

Journal of Nuclear Science and Technology

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Severe accident analysis for Korean OPR1000 with MELCOR 1.8.6 was performed by adapting a mitigation strategy under different entry conditions of Severe Accident Management Guidance (SAMG). The analysis was focused on the effectiveness of the mitigation strategy and its adverse effects. Four core exit temperatures (CETs) were selected as SAMG entry conditions, and Small Break Loss of Coolant Accident (SBLOCA), Station Blackout (SBO), and Total Loss of Feed Water (TLOFW) were selected as postulated scenarios that may propagate into severe accidents. In order to delay reactor pressure vessel (RPV) failure, entering the SAMG when the CET reached 923 K, 923 K, and 753 K resulted in the best results for SBLOCA, SBO, and TLOFW scenarios, respectively. This implies that using event-based diagnosis for severe accidents may be more beneficial than using symptom-based diagnosis. There is no significant difference among selected SAMG entry conditions in light of the operator's available action time before the RPV failure. Potential vulnerability of the RPV due to hydrogen generation was analyzed to investigate the foreseeable adverse effects that act against the accident mitigation strategies. For the SBLOCA cases, mitigation cases generated more hydrogen than the base case. However, the amount of hydrogen generated was similar between the base and mitigation cases for SBO and TLOFW. Hydrogen concentrations of containment were less than 5% before RPV failure for most cases.

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“…In addition, SC-DAP/RELAP5 code was introduced to evaluate suitability of SAMG entry condition (CET = 922 K) set for the Optimized Power Reactor (OPR1000) by assuming the high pressure sequences accidents having high probability of transition to severe accident [6]. Using the same code, Reactor Coolant System (RCS) depressurization and coolant injection strategies of SAMG were evaluated for Small Break LOCA (SBLOCA) and TLOFW scenarios [7,8]. Using MELCOR 1.8.5, bleed and feed strategy of SAMG was simulated for Kuosheng BWR [9].…”

Section: Introductionmentioning

confidence: 99%

“…To fulfill this, severe accident simulations of Korean OPR1000 were performed with SAMG strategy developed in 1998 [12]. According to PSA results for OPR1000, it is evaluated that SB/MB/LBLOCA without Safety Injection (SI), SBO, and TLOFW scenarios bear high possibility of proceeding to a severe accident [7]. Therefore, these scenarios are assessed using MELCOR 1.8.6.…”

Section: Introductionmentioning

confidence: 99%

Validation of RCS depressurization strategy and core coolability map for independent scenarios of SBLOCA, SBO, and TLOFW

Lee

Kim

et al. 2013

Journal of Nuclear Science and Technology

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Severe accident analysis for Small Break (SB), Middle Break (MB), and Large Break (LB) Loss-Of-Coolant Accident (LOCA), Station Black Out (SBO), Total Loss-Of-Feed-Water (TLOFW) was performed and effectiveness of Reactor Coolant System (RCS) depressurization strategies of OPR1000 was analyzed using MELCOR 1.8.6 code. Required injection flow rate has been derived using Core Exit Temperature (CET) information obtained from MELCOR calculation and a simple model and corresponding coolability map have been suggested to assist effective operator action. The depressurization strategies using secondary Atmospheric Dump Valve (ADV) for SBLOCA, pressurizer Safety Depressurization System (SDS) for SBO and TLOFW were introduced in 5 min since the initiation of Severe Accident Management Guidance (SAMG). Respective mitigation strategy employed leads to significant delay of the reactor pressure vessel failure and RCS pressure at Reactor Pressure Vessel (RPV) failure was lower than the SAMG target pressure of 2.86 MPa. Thus, possibility of High Pressure Melt Ejection (HPME) and impair of containment building is expected to avoid effectively. Using CET information obtained from MELCOR calculation, a simple model and a coolability map for the required injection flow rate were developed for recovery of core coolability. It is suggested that the coolability map based on MELCOR calculation results may provide decisive and intuitive information to operators for more effective safety management.

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Evaluation of the RCS depressurization strategy for the high pressure sequences by using SCDAP/RELAP5

Cited by 13 publications

References 2 publications

Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress

Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress

Effectiveness and adverse effects of reactor coolant system depressurization strategy with various severe accident management guidance entry conditions for OPR1000

Validation of RCS depressurization strategy and core coolability map for independent scenarios of SBLOCA, SBO, and TLOFW

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