• Title/Summary/Keyword: LBLOCA Reflood

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CORE THERMAL HYDRAULIC BEHAVIOR DURING THE REFLOOD PHASE OF COLD-LEG LBLOCA EXPERIMENTS USING THE ATLAS TEST FACILITY

  • Cho, Seok;Park, Hyun-Sik;Choi, Ki-Yong;Kang, Kyoung-Ho;Baek, Won-Pil;Kim, Yeon-Sik
    • Nuclear Engineering and Technology
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    • v.41 no.10
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    • pp.1263-1274
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    • 2009

  • Several experimental tests to simulate a reflood phase of a cold-leg LBLOCA of the APR1400 have been performed using the ATLAS facility. This paper describes the related experimental results with respect to the thermal-hydraulic behavior in the core and the system-core interactions during the reflood phase of the cold-leg LBLOCA conditions. The present descriptions will be focused on the LB-CL-09, LB-CL-11, LB-CL-14, and LB-CL-15 tests performed using the ATLAS. The LB-CL-09 is an integral effect test with conservative boundary condition; the LB-CL-11 and -14 are integral effect tests with realistic boundary conditions, and the LB-CL-15 is a separated effect test. The objectives of these tests are to investigate the thermal-hydraulic behavior during an entire reflood phase and to provide reliable experimental data for validating the LBLOCA analysis methodology for the APR1400. The initial and boundary conditions were obtained by applying scaling ratios to the MARS simulation results for the LBLOCA scenario of the APR1400. The ECC water flow rate from the safety injection tanks and the decay heat were simulated from the start of the reflood phase. The simulated core power was controlled to be 1.2 times that of the ANS-73 decay heat curve for LB-CL-09 and 1.02 times that of the ANS-79 decay curve for LB-CL-11, -14, and -15. The simulated ECC water flow rate from the high pressure safety injection pump was 0.32 kg/s. The present experimental data showed that the cladding temperature behavior is closely related to the collapsed water level in the core and the downcomer.

  • https://doi.org/10.5516/NET.2009.41.10.1263 인용 PDF KSCI

MAJOR THERMAL-HYDRAULIC PHENOMENA FOUND DURING ATLAS LBLOCA REFLOOD TESTS FOR AN ADVANCED PRESSURIZED WATER REACTOR APR1400

  • Park, Hyun-Sik;Choi, Ki-Yong;Cho, Seok;Kang, Kyoung-Ho;Kim, Yeon-Sik
    • Nuclear Engineering and Technology
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    • v.43 no.3
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    • pp.257-270
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    • 2011

  • A set of reflood tests has been performed using ATLAS, which is a thermal-hydraulic integral effect test facility for the pressurized water reactors of APR1400 and OPR1000. Several important phenomena were observed during the ATLAS LBLOCA reflood tests, including core quenching, down-comer boiling, ECC bypass, and steam binding. The present paper discusses those four topics based on the LB-CL-11 test, which is a best-estimate simulation of the LBLOCA reflood phase for APR1400 using ATLAS. Both homogeneous bottom quenching and inhomogeneous top quenching were observed for a uniform radial power profile during the LB-CL-11 test. From the observation of the down-comer boiling phenomena during the LB-CL-11 test, it was found that the measured void fraction in the lower down-comer region was relatively smaller than that estimated from the RELAP5 code, which predicted an unrealistically higher void generation and magnified the downcomer boiling effect for APR1400. The direct ECC bypass was the dominant ECC bypass mechanism throughout the test even though sweep-out occurred during the earlier period. The ECC bypass fractions were between 0.2 and 0.6 during the later test period. The steam binding phenomena was observed, and its effect on the collapsed water levels of the core and down-comer was discussed.

  • https://doi.org/10.5516/NET.2011.43.3.257 인용 PDF KSCI

Air-Water Test on the Direct ECC Bypass During LBLOCA Reflood Phase with DVI : UPTF Test 21-D Counterpart Test

  • Yun, Byong-Jo;Kwon, Tae-Soon;Song, Chul-Hwa;Euh, Dong-Jin;Park, Jong-Kyun;Cho, Hyoung-Kyu;Park, Goon-Cherl
    • Nuclear Engineering and Technology
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    • v.33 no.3
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    • pp.315-326
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    • 2001

  • Direct ECC bypass phenomena that occur in a reactor vessel downcomer with a Direct Vessel Injection (DVI) system during the reflood phase of a Large Break Loss-of-Coolant Accident (LBLOCA) are experimentally investigated using a transparent l/7.5 scaled down test facility of the Upper Plenum Test Facility (UPTF). A series of separate effect tests are peformed in order to investigate the mechanisms of direct ECC bypass and to find out its scaling parameters. Various flow regimes and phasic distribution in downcomer are identified and mapped, and the fraction of direct ECC bypass is measured under a wide range of air and water injection conditions. From the counterpart test of the UPTF Test 21-D, the dimensionless gas velocity ( $j^{*}$$_{g,eff}$) is derived experimentally, which is believed to be a major scaling parameter for the fraction of direct ECC bypass. And it is found out that the direct ECC bypass is greatly affected by the spreading width of ECC water film and the geometric configuration of the downcomer.r.

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Improvements to the RELAP5/MOD3 Reflood Model and Assessment (RELAP5 /MOD3 재관수 모델의 개선 및 평가)

  • Chung, B.D.;Lee, Y.J.;Park, C.E.;Choi, C.J.;Hwang, T.S.
    • Nuclear Engineering and Technology
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    • v.26 no.2
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    • pp.265-276
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    • 1994

  • Several improvements to the RELAP5/MOD3 reflood model hate been made. These improvement were made to correct deficiencies in the reflood model identified by the assessment of the RELAP5/MOD3 code against FLECHT-SEASET experiments. The improvements consist of modification of reflood wall heat transfer package and adjusting the droplet size in dispersed flow regime. The time smoothing of wall vaporization and level tracking of transition flow are also added to eliminate the pressure spikes and level oscillation during reflood process. Assessment of the improved model against FLECHT-SEASET experimental data and application of LBLOCA analysis for plant shows that the deficiencies have been corrected.

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