Analysis of LSC phenomena of ATLAS cold leg SBLOCA tests using MARS-KS code

• Published in: Journal of nuclear science and technology Vol. 55; no. 11; pp. 1336 - 1354
• Main Authors: Hossen, Muhammed Mufazzal, Kang, Jun-young, Bae, Byoung-Uhn, Kim, Yeon-Sik, Kang, Kyoung-Ho
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis 02.11.2018; Taylor & Francis Ltd
• Subjects: Blowdown; Boilers; CCFL; Computational fluid dynamics; Computer simulation; Crossovers; Dimensional analysis; Flow velocity; Fluid flow; Food processing industry; Hydraulic tests; Hydraulics; loop seal clearing; MARS-KS; Mathematical analysis; Nuclear engineering; Nuclear safety; Pressure dependence; Pressurized water; Pressurized water reactors; Reactor safety; Refilling; SBLOCA; Sensitivity analysis; Steam flow; thermal hydraulics; Time dependence; Tubes
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/00223131.2018.1505568

Loop seal clearing (LSC) is an important phenomenon for the safety of a pressurized water reactor (PWR) during a small-break loss-of-coolant accident (SBLOCA). The investigation on an LSC phenomenon of 4″, 6″, and 8.5″ break cold leg SBLOCAs simulated by Advanced thermal-hydraulic Test Loop for Accident Simulation (ATLAS) is performed using a Multi-dimensional Analysis of Reactor Safety-KINS Standard (MARS-KS) code. The LSC triggers earlier for larger break sizes during tests and calculations. LSCs occur during the simultaneous sudden decrease of steam condensation rate and the sudden increase of the break volumetric flow rate while the core volumetric flow rate increases slowly in calculation. The five phases of an SBLOCA transient are blowdown, pressure plateau, LSC, boil-off, and core-recovery phase, which can be identified by observing the volumetric flow rate and the time-dependent pressure variation. Loop seal refilling (LSR) occurs due to the trivial steam flow rate to the crossover leg inlet in calculation. The sensitivity analysis shows that the combination of countercurrent flow limitation (CCFL) model option for hot leg and steam generator (SG) inlet (Kutateladze, c = 1.36, m = 1), crossover legs (Kutateladze, c = 1, m = 1), and SG U-tubes (Wallis, c = 1, m = 1) provide good prediction of the LSC phenomenon and thermal-hydraulics behaviors in an SBLOCA transient by MARS-KS code calculation.