الفهرس 
Introduction; Safety and Accidents in VVER-1000Only 14 pages are availabe for public view
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Abstract
The safety performance of nuclear power plants (NPPs) is a very important factor in evaluating nuclear energy sustainability. Safety analysis of passive and active safety systems have a positive influence on reactor transient mitigation. One of the common transients is primary coolant tube rupture (PCTR). This study focused on guillotine large break loss of coolant accident (LBLOCA) of ID=850-mm in one of reactor vessel cold leg. This occurred after establishment of a steady-state condition for the VVER-1000. Reactor safety analysis due to Station Black-out (SBO) transient was also investigated. The reactor responses and performance of passive accumulators (ACCs), low-pressure injection system (LPIS) and high-pressure injection system (HPIS) were investigated. The main safety margin considered during this research was to check the maximum value of the clad surface temperature and then compared with the design licensing limit of 1474 0K. Calculated events progression used the engineering-level RELAP5/SCDAPSIM MOD3.5 thermal-hydraulic program, which also provide a more detailed treatment of coolant system thermal hydraulics and core behaviour. The obtained results showed that actuation of emergency core cooling systems (ECCSs) at their actuation set-points provided core cooling by injecting water into reactor pressure vessel as expected. The peak cladding temperature did not overpass the licensing limit during this LB-LOCA transient. The primary pressure above the core decreases rapidly from 15.7 MPa to 1 MPa in „t‟ less than 10 sec, then stabilizes up to the end of transient. The fuel temperature decreased from 847 0K to 378 0K during the first 30 sec of the transient time. The coolant leakage reduces from 9945 kg/sec to approximately 461 kg/sec during the first 190 sec in the transient. During LB-LOCA accompanied with SBO transient, fuel temperature exceeded design licensing limit. The results revealed that the fuel damage decreases after the introduction of ACCs. Obtained results in the research were compared with MELCOR 2.1 and ASTEC V1.3 and a cohesive agreement was obtained. Overall, the study showed that within the design of the VVER-1000, safety systems of VVER-1000 have inherent robustness of containing guillotine LB-LOCA and SBO. Therefore, RELAP5/SCDAPSIM is capable of modelling a LB-LOCA and SBO in an VVER-1000 and it provides a significant analytical capability of safety systems for specialists in the field in NPP safety.