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NPP V-1 Bohunice is equipped with two reactors of WWER 440 type V-230 and was put into operation in 1978 -1980 as one of the last nuclear power plants with this type of reactor. Both units of NPP V-1 Bohunice operated in 1999 according to the requirements of the energy dispatch at nominal output, or in a regime of tertiary regulation. Since 1990 there have been permanent improvements performed on NPP V-1 Bohunice, the aim of which is to improve nuclear safety of this NPP to the target level which in 1994 was set by UJD and which is in compliance with the recommendations of the IAEA. Planned activities within the safety improvement program were completed in 1999 on unit 2 of NPP V-1 Bohunice especially by realization of accident localization system, emergency core cooling system for the reactor core, automated protection devices for the reactor, completing partial works on the air system and completing the works of seismic resistance of the unit. Although 23 changes and improvements were implemented on Unit 1 during the overhaul in 1999, the program of reconstruction on this unit will be completely accomplished only during the planned outage of Unit 1 in the first half of 2000. In April and May 2000 the schedule of general overhaul considers also a parallel outage of both units of NPP V-1 Bohunice, to enable reconstruction works on common equipment of NPP. In 1999 there were general repairs performed on both units of NPP Bohunice related to the refueling. In October 1999 there was a mission of representatives of Western Nuclear Regulatory Authorities (WENRA). Ten mission members from England, Belgium, Finland, France, Germany and Italy, together with the UJD inspectors and experts of the operator assessed safety of operated units of WWER-440/V-230 of NPP V-1 Bohunice. Members of the mission prepared a report for the European Commission on the current status of safety of these units, which is a complement to the safety assessment performed in March 1999.

Assessment activity

Assessment activities of UJD in 1999 on NPP V-1 Bohunice focused mainly on projects related to preparation of documentation for reconstruction of unit 1 and completion of the gradual reconstruction on unit 2. Within the project preparation for completion of reconstruction works on Unit 1 (during the overhaul) the attention focused on the system of emergency core cooling, spray system for the hermetic zone, accident localization system and system of service water. In connection with this UJD performed:

  1. Assessment and approval of design changes.
  2. Assessment and approval of documentation for quality assurance in realization of design changes
  3. Assessment of program of complex testing of reconstructed systems that concentrated on demonstrating and documenting the functionality.
  4. Assessment of changes in the system of instrumentation and control.
  5. Control, verification and validation of nozzles strength calculation of the emergency cooling system.
  6. Monitoring and assessment of the test of digital system of automatic protection device, which is installed on unit 1 and so far works only in open loop without connection to the actuators of safety systems, and where during the overhaul on Unit 1 the existing protection and control systems were replaced.

On Unit 2 of NPP V-1 Bohunice, UJD monitored and assessed the activities related to the completion of reconstruction works, which were realized in 1999 during the outage for overhaul. Mostly these were the activities, which started, and were in progress already in 1998 and that is on the accident localization systems, emergency core cooling system, service water and system of instrumentation and control.

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