Core Monitoring and Surveillance of the VVER-440 Type of Reactors in Czech Republic and Slovak Republic

Molnar, Jozef ; UJV Rez

25th Symposium of AER on VVER Reactor Physics and Reactor Safety (2015, Balatongyörök, Hungary)
Core surveillance and monitoring


During the 70? of the last century 12 units of Russian VVER-440 type of reactors were
started to build on the territory of Czechoslovakia (now on the territory of the Czech and
Slovak Republic). Nowadays 2 units were already shutdown in Slovakia, 4+4 units are
operates in both countries and 2 units are still under finalizing in Slovakia. During these units
operation period, wide range of modifications and upgrades were performed to strengthen the
nuclear safety and reactors operability.
In scope of strengthening the reactor?s core monitoring and surveillance, the original VK3
system was completely replaced with advanced computer based core monitoring and
surveillance system SCORPIO-VVER. Since 1999 up to today the SCORPIO-VVER system
were installed on four units of Dukovany NPP (Czech Republic), on two units of Bohunice
NPP (Slovak Republic) and on the full scale plant training simulator for EBO V2 plant. The
system is a valuable tool for the reactor operators and reactor physicists and was licensed by
both Czech and Slovak Nuclear Regulatory Bodies as a Plant Technical Specification
Surveillance Tool.
The development of SCORPIO-VVER core monitoring system continues along with the
changes in VVER reactors operation. Within the planned upgrades the system is being
adapted according the utility needs. Between the most significant upgrades belongs the
modifications in connection with implementation of a new digital I&C system, adaptation of
the system to up-rated unit conditions, loading of the Gd2M+ fuel assemblies, improvements
in the area of core design (neutron physics, core thermal hydraulics and fuel thermal
mechanics), in design and methodology of the limit and technical specifications checking (online shutdown margin calculation) and improvements in the predictive part of the system
(Strategy Generator).
Since the first installation the SCORPIO-VVER system has a remarkable operating history and
experience. More than 16 years of experiences in 6 units of VVER-440 type of reactors, from
two different NPPs, in two different countries helps the SCORPIO-VVER Developer?s Team
to put the system to a very high level of quality and reliability.

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