Investigation of core meltdown phenomena and radioactive materials release in VVER‐1000/V446 nuclear reactor at severe accident condition due to LBLOCA along SBO. (18th December 2019)

• Record Type: Journal Article
• Authors: Ghasemi, A.; Pirouzmand, A.; Kamyab, S.
• Other Names: Park Moon‐Ghu guestEditor.
• Is Part Of: International journal of energy research. Volume 44:Number 10(2020)
• Page Start: 8113
• Page End: 8124
• Publication Date: 2019-12-18
• Subjects: VVER‐1000 -- Severe Accident -- LBLOCA -- SBO -- Radioactive material release -- Core meltdown -- Creep rupture; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.5056
• Languages: English
• ISSNs: 0363-907X

Abstract

Abstract: In this study, VVER‐1000/V446 nuclear reactor modeling using RELAP5/SCDAP3.4 code to investigate the reactor core behavior during severe accident conditions in a LBLOCA scenario along with station‐black‐out (SBO) is carried out. The analyses are performed in two stages, before and after the core heat up, without considering operator's action on the accident management. Fuel assemblies in the core are grouped into five based on average power peaking factors and are modeled in SCDAP code. For each group a corresponding channel is modeled in RELAP5 code plus a bypass channel. In the first stage, the study of ECCS and KWU tanks efficiency to keep the reactor core in the safe condition, the calculation of the elapsed time before the reactor core heat up and the estimation of available time for operator's action to avoid core degradation, are investigated. In the second part the results of Hydrogen production rate, cladding oxide thickness, cladding damage level, release of fission products into the coolant are studied. Analysis of the scenario by the code shows the production of around 350kg Hydrogen with the maximum rate of about 1kg/s and releasing a large amount of FPs in the order of 10kg. The results also demonstrate that the operators have ∼3 h before the fuel rod cladding rupture and ∼2.5 h before the inception of exothermic steam‐zirconium reaction. Finally, using a geometric mesh for the lower plenum and applying the COUPLE code, the results show that the core slumping into the lower plenum and the lower plenum rupture occur at 17561 and 18370 seconds after the onset of accident, respectively. Abstract : VVER‐1000/V446 nuclear reactor is modelled using RELAP5/SCDAP3.4 code for analysis of the reactor core behavior during severe accident conditions in a LBLOCA+SBO scenario. The results show the production of around 350kg Hydrogen with the maximum rate of 1kg/s and releasing a large amount of FPs in the order of 10kg. Based on the code results, the operators have ∼2.5 h before the fuel cladding to erode and breach, ∼3 h before the onset of steam‐zirconium reaction, and 5.1 h before the lower plenum rupture.