Implementation of the Gradual Upgrading Project
implementation of the gradual upgrading of NPP V-1 was organized by the REKON Consortium
under a general delivery contract. The scope of the general delivery included:
||development of projects for
construction permits for the individual systems,
||development of executive
projects for the individual systems,
||drafting of the safety analysis
report and conduction of analyses,
||development of programs of
||drafting of operating
||delivery of equipment, systems
and components, including delivery of technical documentation, equipment maintenance
schedules, and staff training plans,
||assembly of the systems,
including pre-operational testing, commissioning and handing over to the client.
The gradual upgrading programme was partly
implemented during normal operation of V-1 units, but mainly during planed unit refueling
outages and overhauls (OH). The outages were extended depending on the extent of the
upgrading works to be performed. The gradual upgrading commenced during unit 2 OH in 1996
and was completed during unit 1 OH in 2000.
The implementation works were divided among the following 15 functional technological
- Upgrading of pressurizer safety valves and the relief line
from pressurizer to the relieve tank, that cover the “BLEED” function for “Primary
Side Bleed and Feed”.
- Upgrading of the emergency feed water system, to cover the
„FEED” function for “Secondary Side Bleed and Feed”. The system is currently
designed for 72 hours of operation without the need of being supplied by feed water.
- Upgrading of the steam generators relieve valves, to cover
the “ BLEED” function for “Secondary Side Bleed and Feed”.
- Grid III Madunice - off-site emergency power supply from the
near-by hydroelectric power station, to improve black-out management.
- Upgrading of the emergency core cooling system to provide
for two separate and independent redundancies, to cover the function of core cooling for
extended LOCA accidents and the “FEED” function for „Primary Side Bleed and Feed“.
Every redundancy comprises two high-pressure pumps and one low-pressure pump. The system
has been designed to be able to cope with the LOCA range and to ensure core subcriticality
upon secondary system breaks and upon seismic events (a new 80 m3 boric acid
concentrate tank). The system is designed ensure core residual heat removal.
- Improved fire resistance - 14 measures.
- Upgrading of the electro system to provide two independent
and separate redundancies. The capacity of the emergency supplies (from DG) has been
doubled to provide power supply for newly installed emergency systems. The capacity of the
batteries was raised from 30 minutes to 2 hours.
||Replacement of outdated motor
||Upgrading of the DG control and
||Upgrading of 6 kV, 0.4 kV, 220V
DC/AC distribution switchboards
- Upgrading of the instrumentation and control system
||Replacement of reactor
protection system (RTS+ESFAS) for a new digital system TELEPERM XS from Siemens,
||Replacement of the reactor power
||Replacement of the external
neutron flux measurement system,
||Replacement of the in-core
||Installation of a reactor power
||Improvement of PAMS (higher
||Improvement of radiation
- Upgrading of the containment spray system to provide two
separate and independent redundancies.
- Installation of an accidents localization system within the
confinement after LOCA.
- Improvement of the confinement integrity, through adding of
fast-acting flaps to the air conditioning piping at the confinement border. The tightness
improvement of units 1 and 2 confinement is illustrated in Fig. 2.1.2.
Fig.2.1.2 Results of
the NPP V-1 units confinement leak tightness improvement
- Confinement reinforcement, to provide
for confinement resistance against overpressure and negative pressure. For overpressure
the resistance is 60kPa for DBA, i.e. break of O200mm, and 120 kPa for BDBA, i.e. break of
O500mm. Resistance for negative pressure is 15 kPa.
- Installation of the essential service water
system for cooling of safety systems and its separation from old service water system (non
safety related). The new system of essential service water was designed to ensure 72 hours
of operation without the need of other external water source.
- Upgrading of air conditioning systems
for cooling the new electric and I&C systems compartments.
- Improvement of the seismic resistance
of equipment that may negatively effect safety systems.
A simplified draft of safety systems of the
NPP V-1 primary circuit following the gradual upgrading is on Fig. 2.1.3.(a new 80 m3
boric acid concentrate tank not included).
Fig. 2.1.3 Safety systems of NPP V-1 units
following the gradual upgrading
2. Steam generator
3. Main circulation pump
4. Main isolation valve – hot leg
5. Main isolation valve – cold leg
7. Pressurizer relieve tank
8.HP emergency core cooling pump
Low-pressure emergency core cooling pump
10. Spray system pump
boric acid storage tank
12. Heat exchangers
Spray system nozzles
Fig. 2.1.4 illustrates time schedule of the whole gradual upgrading of NPP V-1.
Fig. 2.1.4 Implementation time schedule of NPP V-1 gradual
Having implemented the NPP V-1 gradual
upgrading programme, the objectives set by ÚJD Decision No.1/94 were met, representing a
precondition for granting approval for further operation of the NPP. The completion of the
reconstruction works resulted in a marked improvement of NPP V-1´s nuclear safety
standard, thus achieving the internationally acceptable standards of safety and operating
reliability. At the same time, preconditions were created for a safe, reliable, economical
and environmentally-friendly operation of NPP Bohunice V-1 to be continued at least
through the end of its designed service life.
Previously, ÚJD approved further operation of NPP V-1 units conditional upon meeting the
above criteria connected with the progress of works on safety improvement. The approval
remained valid for always one fuel cycle. Based on a review of the safety report following
the gradual upgrading of the units, ÚJD is about to issue a decision on the approval of
continued operation of NPP V-1 unit I, stating conditions listed in the annex of the