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NUCLEAR POWER PLANT V-2 BOHUNICE

Nuclear Power Plant V-2 Bohunice consists of two units with WWER 440 type reactor of improved V-213 type, which were put into operation between 1984 and 1985.
Both units operated in 1999 according to the needs of the energy dispatch center in base load, or also in the regime of "tertiary regulation ". From both units of NPP V-2 Bohunice also the non-electric production -heat -was used by off take from the turbine, which served, as needed, as a heat source for heating Trnava, Hlohovec and Leopoldov towns. In 1999 both units underwent planned overhaul connected with refueling, while on unit 3 an extended overhaul was performed. The most important activity during the planned extended overhaul on unit 3 was in-service inspection of equipment both in primary and secondary circuit, including the inspection of the pressure vessel body of the reactor.


Assessment activity

During the planned outages on units 3 and 4 of NPP V-2 Bohunice in 1999, the assessment activity of UJD focused on review of design changes on systems important from the safety aspect, which were presented by the operator with the aim to improve the safety level and the reliability of the unit. The following design changes were reviewed as the most important:

  1. Additional fire extinguishing equipment on the floor of main circulating pumps on both units (in 1999 the monitoring camera was installed)
  2. Protective constructions of suction sieves in the suction pump system of the emergency core cooling on the steam generator floor. (In Unit 3 these were realized on all 3 systems, Unit 4 only on one system.)
  3. Harmonization of the electric power supply and high-pressure air on fast-acting valves

Assessment activities of UJD at NPP V-2 Bohunice in 1999 focused also on operational inspection on equipment of both units. In 1999 certain changes were introduced with respect to applied technique of nondestructive inspections.

On unit 3 within the expanded overhaul the original program of operational controls was performed, including inspection of the pressure reactor vessel from inside.
Based on the request of UJD in 1999 also an inspection on the reactor pressure vessel from outside was performed, using innovated equipment for non-destructive inspection. In-service inspections on Unit 4 were realized during the overhaul of Unit 4. It can be stated that during the in-service inspections at NPP V-2 Bohunice no new indications were found and the condition of components of both units can be evaluated as good.
Assessment activities of UJD also focused on realization of measures to increase tightness of the hermetic zone (requested by UJD). In 1999 the achieved leakage from the hermetic zone on Unit 3 was decreased to the level of 10, 34 % per day. Analogical value on Unit 4 achieved 11, 98 % per day. In both cases it is lower than the prescribed limits and conditions of safe operation.
An important part in the assessment of operational safety of NPP V-2 Bohunice for 1999 from the side of UJD was the assessment of operational events. In 1999 there were 54 events in total on both units of NPP V-2 Bohunice, 13 of which were assessed as INES 0 events. Reactor of Unit 3 was shutdown once during 1999 by automatic protection system, there was no automatic scram on the reactor of Unit 4. None of the events was categorized as level 1 on the INES scale or higher.

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