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EBO V-2 NPP consists of two units with WWER 440 improved type of V-213, which were commissioned in 1984 and 1985. The status of NPP in 1998 is characterized by stable operation, while in the first half of the year the units operated mainly in a automatic "primary control mode" according to the needs of the electric system within the range of nominal capacity (96+/-4%). Based on the request of the Slovak Energy Dispatch Center, both units of EBO V-2 NPP in the second half of the year operated in basic load mode, without regulation according to the needs of the electric system. On both units during, planned outages overhaulings were performed based on a long-term maintenance plan.

Assessment activity

In 1998 assessment activities of UJD focused on review of documentation of safety important systems and components of nuclear power units as these were prepared within the elaboration of a safety improvement programme on EBO V-2 NPP and submitted to UJD by the operator.

From those most demanding activities was the

assessment of mechanical strength of the bubble tower water tray system in case of large leakage of coolant from the primary circuit. Assessment of this issue required elaboration of 11 strength analyses. In their assessment UJD co-operated with the Material and Technology Faculty of Slovak Technical University in Trnava, which prepared control analyses for the bubble tower system of EBO V-2 NPP based on numerical methods.

When evaluating operational safety of EBO V-2 NPP, UJD focused on assessment of operational events. In 1998 there were 46 operational events recorded at EBO V-2 NPP (see Fig. 4). In two cases it was automatic scram of unit 3 and in one case of unit 4. In three cases it was spurious actuation of safety systems (see Fig. 5). In general it can be stated that the safety significance of these events was not high, and did not deviate from the long-term monitored average. During the whole year there was no uncontrolled leakage of radioactive substances into the working environment of NPP, or into environment in the vicinity of NPP. None of the operational events was assessed higher than 0 on the INES scale.



When assessing operational events of EBO V-2 NPP the most important reasons were the following:

  • aging of instrumentation and control equipment, the result of which was spurious actuation of safety system on the unit and subsequently also automatic reactor scram

  • incorrect setting of parameters of the primary circuit for testing safety valves on the pressurizer, discrepancy in the operational documentation and incompatibility of instrumentation and control devices, which resulted in actuation of two redundant safety system trains

  • incorrect activity of the operation personnel when testing safety valves of the steam generators, which resulted in change of parameters of the primary circuit, automatic actuation of safety systems and subsequently to manual shutdown of the reactor by the operation personnel.

In one case there was violation of limits and conditions of safe operation when the operation personnel found discrepancy between the required and actual quantity of borated water in the storage tank of the safety system for coolant injection into the primary circuit.


Statistical overview on the number of operational events on EBO V-2 NPP and their categorization in INES scale is also shown in Fig 4.

Inspection activity

Inspection activity at EBO V-2 NPP focused on planned inspections in compliance with the plan of inspections by UJD. Inspections were directed into areas of verification of adhering to limits and conditions during operation of units, physical protection of the nuclear installation, storage of fresh and spent nuclear fuel, following the program of quality assurance during operation and maintenance, qualification and training of personnel, in-service inspections of the equipment, on control of imposed measures from the previous resolutions and protocols from UJD inspections. Control of fulfillment of tasks, based on follow-up inspections, allows stating a continuous meeting of requirements of the regulatory authority within the set dates.

Based on an overall assessment of results from both assessment and inspection activities, and taking in regard evaluation of operational indicators (see Fig. 4, 5 and 6) UJD evaluated operation of EBO V-2 NPP in 1998 as safe and reliable .

Within the principle of transparency and openness in 1998 there were 2 international missions at EBO V-2 NPP. These missions were invited by the Slovak side and they made an independent review of nuclear safety:

  • The IAEA mission of OSART follow-up reviewing nuclear safety of operation of NPP came in March 1998. Particular goal of the mission in 1998 was to check implementation of recommendations of an analogy mission at EBO V-2 NPP performed in September 1996. In its conclusions in 98% of cases it states meeting or satisfactory meeting of recommendations of the OSART mission from 1996.

  • The IAEA mission, which was held in November 1998, focused on verification of site seismic characteristics of Jaslovské Bohunice (together also with EBO V-2 NPP). Conclusions of the mission will be available only in 1999.

© Nuclear Regulatory Authority of the Slovak Republic, 1999