During the recent scheduled outage of unit 3 at Russia’s Kalinin NPP, specialists began to modernise the containment monitoring system (CMS) of the reactor compartment, the plant said on 18 May. This is the first time such work has been undertaken at a Russian NPP. Alexander Dorofeev, chief engineer of Kalinin NPP, explained that the shell (containment) is designed to protect the reactor plant from external natural and man-made influences, and prevents the release of radioactive substances into the environment in the event of an emergency.
The containment consists of metre-thick cylindrical reinforced concrete wall and domes, which ensure the tightness of the internal volume. The strength of the structure is assured by high-strength armoured ropes located in special channels inside the wall. They are tensioned with jacks, squeezing the shell, which prevents the appearance of cracks in the concrete.
“Earlier, the control of the tension of the ropes, the state of the protective shell and its tightness was carried out by three different systems. After modernisation, they will be replaced by the latest unified system, which will significantly increase the safety of operation, Dorofeev said.
Currently replacement of workstations is underway in the reactor department, as well as of basic and applied software, controllers of information exchange, switches and signal processing devices. In addition, an expert system based on the domestic software complex "CONT" is being introduced. It is necessary to analyse the state of the containment and assess its strength. To cover the entire volume of the containment, the system virtually divides it into 15,000 controlled zones, creates a detailed three-dimensional model and calculates in each zone.
Introduction of the expert system will make it possible to assess reliability of the containment during operation of the power unit. The data obtained will help to significantly optimise work to adjust tension in the reinforcing ropes during repair. “The implementation this large-scale project will significantly simplify the maintenance of the system, shorten the training time for personnel, and also reduce the likelihood of disruptions in operation of the unit due to the human error,” the plant noted.