In the years 2018 to 2020, the company VUJE, a.s., supplied the system for monitoring the concentration of hydrogen in the containment for beyond design basis accidents for Rivne Nuclear Power Plant (RNPP)  Units 3 and 4. The system was delivered to RNPP as part of the implementation of measures within the Complex Consolidated Safety Upgrade Program for the Ukraine Nuclear Power Plants.

At Unit 3 of RNPP, the system was put into commercial operation on January 2, 2020. At Unit 4, the system is on trial run. As soon as the trial run is finished and the final acceptance tests implemented, the system will have been put into commercial operation after Unit 4 shutdown, expectadly by the beginning of 2021.

The hydrogen concentration monitoring system (HCMS) enables continuous monitoring of the   volume of hydrogen in the containment during normal operation, and as well during design and beyond design basis accidents; and based on this, deciding on appropriate measures by the unit management in order to prevent hazardous hydrogen accumulation and combustion or explosion.

HCMS system includes twelve KAMOS measuring probes and a software and hardware complex (SHC) that consists of two cabinets. Each cabinet receives the signals from six KAMOS probes and one external Safir-type pressure transducer.

SHC provides the following:

• Measurement, processing and calculation of the ambient parameters in the containment, i.e. hydrogen, oxygen and water steam concentration, pressure, and temperature;
• Data relevant to a particular parameter displayed on the personnel monitors in the form of  hydrogen safety diagram Shapiro - Moffette;
• Data storage - on the actual state of hydrogen safety in the containment;
• Delivery of computerized data to CIS, PAMS, and “Black box”, and I&C; 
• Notifications generated in MCR and ECR as signals of reaching the warning (2 % vol.) and emergency (4 % vol.) limits, and other relevant signals in the technological alarm lines;
• Continuous diagnostics of operability and functionality of the system.

HCMS system developed by VUJE, a.s. was originally designed for VVER type NPP with power of 440 MW. This version of the system was successfully installed in Paks NPP (Hungary), Mochovce NPP and Bohunice NPP (Slovakia).

Purposed by gradually increased nominal power of NPP units (from 440 MW up to 1000 ÷ 1300 MW), VUJE, a. s. developed a new version of HCMS system. KAMOS probes including installed combined sensors have been qualified for conditions of increased ambient parameters relevant to the values of beyond design basis accidents in the units VVER1000 MW. The overall system has been tested for seismic resistance and electromagnetic compatibility. As soon as the acceptance criteria were satisfied, the system was certified for the use in  RNPP  units 3,4.
The system has been modified according to the customer`s request, so it is possible to calibrate individual sensors of KAMOS probe periodically with no need to dismantle it and transfer to the measuring laboratories. This modification reduced the time for calibration as well as the time for the operation personnel attending the containment area.

Original version of the system can be partially modified according to the conditions of particular NPP in case the Kamos probe needs to be equipped with the combination sensors for hydrogen, temperature and pressure measurement. SHC cabinets can also be variably assembled and the data to be transferred to the particular NPP systems variably arranged.

HCMS system implemented in the NPP is another safety measure "after Fukushima" aimed at continuous checking the value of hydrogen concentration in the containment. This measure anyway will increase safety operation of NPP, and will improve the actual state monitoring and potential emergency states management.