Qualification of RELAP5 Input for VVER-1200 NPP and LBLOCA
Loading...
Date
2025-06-21
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Nuclear Technology ANS
Abstract
The construction of the Akkuyu Nuclear Power Plant (NPP), consisting of four VVER-1200
units with a total capacity of 4800 MWe, is currently underway at the Akkuyu site in Mersin, Türkiye. As
part of the “Thermal-hydraulics Analyses of Akkuyu Nuclear Power Plant” project, undertaken at the
Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), an input model for the Akkuyu NPP has
been developed for the RELAP5/mod3.3 code. This model comprises 939 control volumes, 1110 junctions,
and 862 heat structures utilizing technical data from the Preliminary Safety Analysis Report (PSAR)
submitted to the Nuclear Regulatory Authority.
The project aims to develop an input model for steady-state and transient analyses of the Akkuyu NPP,
ensuring its qualification through comparative assessment with PSAR data and related technical documents.
The qualification process, designed to achieve a realistic representation of the NPP, includes (1)
a geometrical data consistency check, (2) a steady-state consistency check, and (3) a transient consistency
check. The NPP data serve as the primary reference for the entire qualification process. Additionally, the
RELAP5 capability to simulate the passive heat removal system (PHRS) is also evaluated under a steadystate
condition, based on the GAMBIT-06 data given by the designer, since this system is essential for
passive cooldown of the steam generator secondary side. The transient check includes the large break loss
of coolant accident (LBLOCA) scenario, as it represents the most safety-critical design basis accident.
RELAP5 results are in agreement with the results given in the PSAR. The 100 000-second RELAP5
simulation confirmed that long-term core cooling is maintained and fuel cladding temperatures remain
below 1200°C, meeting licensing acceptance criteria for this accident scenario. Given the significance of
decay power in this analysis, it was determined that the ANS79-1 option in RELAP5, with a fission product
yield factor of 1.0, aligns with the Chapter 15 (Accident Analysis) results of PSAR.
Description
Keywords
Accident analysis, Akkuyu NPP, LOCA, thermal-hydraulics, VVER.