National Report of The Slovak Republic , september 2001


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2.2.4 NPP V-2 units safety improvement programs


The objective of the operator is to not only maintain the present level of nuclear safety but also its improvement as suggested by new knowledge and experience from NPP operation. To meet this objective, „NPP V-2 Upgrading and Safety Improvement Programme“ was developed as described in more detail in chapter 5.4. In this section, measures implemented so far are summarized.

Selected actions relevant for NPP V-2 safety improvement which are in accordance with the Safety Concept have priority. The individual actions have been planned to become implemented during planned unit outages. So far, the following important safety and upgrading measures have been implemented:

  • upgrading of the upper distribution piping of SG feeding water and feeding heads,
  • installation of a pressurizer relief valve,
  • first phase of the seismic reinforcements of reactor coolant system loops,
  • replacement of category I uninterruptible supply accu-bateries,
  • implementation of a new redundant power source at system 4 of category I uninterruptible power supply,
  • introduction of symptom-oriented emergency operating procedures,
  • diagnostic systems for the monitoring of small leaks from primary circuit equipment meeting LBB criteria,
  • upgrading of the RC monitoring system (addition of a redundant environmental contact unit), and replacement of secondary computer system,
  • measure to prevent clogging of the emergency systems pump suction and of spray system nozzles,
  • installation of an automated fire extinguishing equipment for reactor coolant pump compartment,
  • replacement of all generator breakers,
  • replacement of electric protections of 6 kV drives,
  • installation of LFC terminals for remote control of electric parameters from dispatching center,
  • non-destructive tests:
    The following measures have been/are being implemented :
    having increased the sensitivity of the facility to reactor pressure vessel in-service inspections from the outside, integral test was performed during the outage of NPP V-2 unit 4 and subsequently control of unit 3 during 1999 EOH,
    staff qualification follows Slovak national standard STN EN 473 and is expected to be completed in 2002,
    the programme of operation defectoscopy of I&C lines (up to the first separating valve) connected to components and of primary circuit pipe systems is going on,
    operation testing of NPP V-2 equipment is going on according to the new guideline MN-14 that applies the most recent knowledge and experience in the field of non-destructive tests, and contains operation monitoring programs for all pipelines up to the first closing valve,
    appropriate samples with implanted material defects are being prepared in cooperation with VÚJE,
    qualification of a system of non-destructive testing according to IAEA guidelines is being prepared in cooperation with VÚJE,
  • fire prevention
    To improve fire safety and to resolve the safety-related problem, the following measures have been implemented or are being implemented:
    a systematic analysis of fire-related risk was conducted in 1998 based on which a fire project will be developed,
    to prevent spreading of smoke and fire, anti-fire flaps have been installed controlled by temperature in the corresponding air conditioning system and being independent from the other systems of the power plant,
    cable partitions and closures at MGU were coated with Dexaflamm, an fire resistant material. Wherever redundant cables cannot be separated, certified foaming materials will be used to cover them,
    fire resistant penetrations and barriers are subject of regular inspections,
    water guns to cool ceiling structures were installed at the machine room,
    semi-stable foam fire extinguishing equipment was installed to main oil tanks of turbo generators and to the oil systems of electric feed water pumps,
    floors of cable channels with a stable fire extinguishing equipment were insulated,
    electric fire detection was upgraded in electric buses and technological computer rooms,
    a new firewall was built between stand-by transformers AU01 and AU02, and the original firewalls between the unit and branch transformers were extended,
    junctions of 6 kV cables for diesel generator station were replaced,
    signaling of the fire doors positions in cable channels of the main production building and external cable channels was installed,
    firefighting cards were developed for the management of firefighting intervention by the plant fire brigade and operating staff.

A plant fire brigade is on duty around the hour at the Bohunice site and able to intervene at any place within minutes.

The following actions are planned to be implemented during 2001:

  • project documentation resulted from the Safety Concept,
  • modification of emergency low-pressure and spray pumps recirculation,
  • modification - relocation of emergency feed water lines from +14.7m.

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