Map of Bohunice
New plant at Bohunice
The construction of a new NPP-plant is planned at the site of the existing NPP at Bohunice. The plan the Slowak cabinet approved in Dec. 2008 declares that the construction works will be finished in 2020.
The NPP is expected to cost 4 - 6 billion euros, the Czech power company CEZ will be the strategic partner of the project. CEZ was classified the most suitable of 10 potential investors by the Slowak government.
The remaining two units at Bohunice (after the shutdown of Bohunice V1-unit 2 by the end of 2008) are operated by Slovakia's dominant power maker, Slovenske Elektrarne.
Reactors permanently shutdown
Earlier, five reactor units and several auxiliary facilities for treatment and storage of waste were located at Bohunice.
One reactor unit (A1) has been closed after two severe accidents in 1979. A1 is the first reactor Slovakia that is being decommissioned.
- Bohunice V1 consists of 2 WWER 440 V230 units.
A safety upgrading of Bohunice V1 (units 1 and 2) was finalised in 2000.
- Bohunice V2 consists of 2 WWER 440 V213 units.
Disadvantages of Bohunice site
The site is unfavourable because of relatively high risk of earthquakes.
The reactors are constructed by AEE/Skoda.
An upgrade program on Bohunice V2 (units 3 and 4) is under way to improve seismic resistance, cooling systems, and instrument & control (I&C) systems with a view to extending operational life to 40 years (2025). Framatome ANP is replacing the I&C systems progressively to 2008.
Spent fuel storage facility at Bohunice
An interim spent fuel storage pool with a capacity of 1680 t is also located at Bohunice. A reconstruction aimed at seismic upgrade and enhancing the storage capacity to be sufficient for all spent fuel from the expected Bohunice V1 and V2 operation was completed in 1999.
The Bohunice Radwaste Conditioning Centre (BSC RAO) treats and conditions liquid and solid radioactive wastes generated from decommissioning of A1, from the operation of the NPPs V1 and V2, and also from hospitals, research institutes and industry. A licence was granted for permanent operation of BSC RAO in early 2001.
Facilities in Bohunice
|plant||reactor typ||construction start||operation start||shut down|
|Bohunice A1||GC-HW 144MW||1958||1972||1979|
CEZ will construct the new plant
Czech energy company CEZ together with Slovak Nuclear
Decomissioning Company JAVYS is going to construct the new reactor block in nuclear power plant Jaslovske Bohunice. The contract for the project will be signed on May 29 between CEZ and the Slowak government.
After a tender for suppliers of technology the amount of investment will be specified.
The Slowakian head of state announces that he plans to recommission the reactor two due to the stop of gas supply from Russia.
Shutdown of Bohunice-2
Bohunice 2 has been shutdown as promised in the membership treaty.
The Slowakian Government plans to build a new reactor at Bohunice
According to the annual report of the UJD, the nuclear regulatory of the Slovak Republic, in 2004 1 incident of Bohunice 2 was categorized as INES 1.
Jan Figel, Slovak´s EU-commissar, has annonced that Bohunice will be shutdown as agreed upon with the EU. Two weeks ago the Slovak minister for economy Pavel Rusko has caused irritation with his statement that the plans for Bohunice´s shutdown have to be reviewed.
In 2003 in Bohunice-1 and 2 25 events labelled with INES 0 occured according to the UJB annual report.
In 2003 in Bohunice-3 and 4 14 events labelled INES 0 occured according to the UJB annual report.
In 2002 in Bohunice-1 and 2 23 events labelled with INES 0 occured according to the UJB annual report.
In 2002 in Bohunice-3 and 4 13 events labelled INES 0 occured according to the UJB annual report.
In 2001 in Bohunice-1 and 2 19 events labelled with INES 0 occured according to the UJB annual report.
In 2001 in Bohunice-3 and 4 10 events labelled INES 0 occured according to the UJB annual report.
In 2000 in Bohunice-1 and 2 20 events labelled with INES 0 occured according to the UJB annual report.
In 2000 in Bohunice-3 and 4 19 events labelled INES 0 and one event labelled INES 1 occured according to the UJB annual report.
In 1999 in Bohunice-1 and 2 28 events labelled with INES 0 occured according to the UJB annual report.
In 1999 in Bohunice-3 and 4 13 events labelled INES 0 occured according to the UJB annual report.
In October the Commission secured commitments from Slovakia to close two reactors at its Bohunice plant by 2008..
In 1998 in Bohunice-1 and 2 23 events labelled with INES 0 and 2 events labelles with INES 1 occured according to the UJB annual report.
In 1998 in Bohunice-3 and 4 15 events labelled INES 0 occured according to the UJB annual report.
Engineering safety evaluation of Dukovany and Bohunice V2:
The engineering safety evaluation was performed by the European Nuclear Assistance Consortium (ENAC) for the Czech Republic's Dukovany and Slovakia's Bohunice V2 NPPs. This project was financed by the European Commission through the PHARE program. The project aims first to determine pragmatic, cost-effective changes to the design and operation of the plants to enable them to achieve adequate safety, and second to develop conditions for plant life extension.
The engineering safety evaluation was performed in three phases:
· Internal Audit of Dukovany NPP
· External Audit of Dukovany NPP
· safety review team led by Siemens with support from Ansaldo and Framatome
· systems review team led by NNC with support from EDF and Empresarios Agrupados
· components review team led by Empresarios Agrupados with support from the Dutch Nuclear Consortium and Siemens
· operations review team led by Belgatom with support from EDF
· Extension to Bohunice V2: This engineering safety evaluation of Bohunice V2 used the same approach as for Dukovany. Recognizing the very close similiraties between the two plants, the assessment of Bohunice V2 addressed only the differences between the two plants.
The evaluation recognized that both Dukovany and Bohunice V2 utilize a well-proven design for which extensive operating experience is available. The operating experience is available. The basic design incorporates a number of features beneficial to safety (e.g. the relatively soft response to transients) and both plants are considered to be well operated.
The principal findings and concerns are:
· the vulnerability of the steam and feedwater pipework area on the +14,7 m level of the reactor and intermediate buildings to internal hazards is a concern repeatedly identified by this evaluation (and elsewhere);
· dependent failure of the ECCS due to sump screen blockage is a concern for which an acceptable resolution strategy has been identified and is to be implemented;
· the physical and functional separation of the unit main and emergency control rooms is another acknowledged area of concern;
· the capability of the bubble condenser to actually fulfill its safety function is the subject of a number of international projects in which both Dukovany and Bohunice are involved;
· the adequacy of the I&C systems in general (including the control facilities) is another area of concern for which a number of recommendations were identified for both plants;
· the adequacy of the hazard protection provisions remains a concern even though a large volume of work has been done and continues to be done, particularly on fire hazard;
· the adequacy of the safety and accident analysis performed remains a concern even though, as with hazards, a great deal of work has been, and is being done.
Upgrade the two early-design VVERs at Jaslovske Bohunice and complete basic engineering in mid-1996, paving the way for the units to operate through 2010.
Since 1990, Skoda Nuclear Construction (Plzen) has annealed both pressure vessels. Slovenske Elektrarne (SE) and its consultants will conclude contracts in a few weeks to install diagnostic systems, a symptom-oriented emergency procedure was developed with Westinghouse, and a probabilistic safety assessment (PSA) was made by consultant Electrowatt´s British office.
In 1994, the freshly formed Nuclear Regulatory Authority of the Slovak Republic called for 59 further measures. The basic design contracts for the backfits have been signed with Siemens and with industry in Slovakia and Czechia.
The backfitting should be finished at the latest by 1999, at a cost of about $180-million.
Among the measures called for are: Integrity improvements in the reactor coolant system; Reconstruction of the ECCS, to result in two fully independent trains, capable of removing decay heat after an earthquake; Equipping of the coolant system for both primary and secondary side bleed-and-feed accident management regimes; Improvement of confinement strength, integrity, and installation of isolation valves at the confinement boundary; Installation of hydrogen monitoring and recombining equipment; Reconstruction of the sprinkler system to two fully independent trains; Major improvements in electrical systems; Reinforcement of equipment for seismic protection; Improvements in the plant ventilation system and improvements in fire protection.
The measures will be gradually implemented during routine annual outages over 1996 to 1999.
SE said it must be demonstrated that V1 can withstand an earthquake of an intensity of 8 on the MSK scale, that safety systems have failure probabilities of 10 E-3 or less, that the reliability of the reactor scram system is at least 10 E-5, and that the annual core damage frequency "must be 10E-4 or better" when the backfitting program is completed in 1999.
The "small reconstruction" program has already borne fruit, SE officials said, with annual core damage frequency reduced from about 1,7 E-3 to about 8,89 E-4.
Leak-tightness improvements carried out had reduced leakage from 5,000% of volume over a 24-hour period to 132% (unit 1) and 125% (unit 2).
Annealing of both pressure vessels in 1993 was successful. While during 1985-93 the critical temperature of the two vessels was above 150 °C, annealing has reduced the temperature to about 110° and 60 °C, respectively.
Slovakia's chief nuclear regulator said Bohunice- V1 can be safely operated until the scheduled technical end of its lifetime in 2005. Bohunice V1 underwent more than 80 backfits required by the AEC in 1991 ( small reconstruction). Thanks to this program the plant's core damage frequency dropped from 17 in 10 000 reactor years to 0,9.
With almost US$ 200 million sunk into the plant shutdown before the end of its lifetime is unlikely.
French company SGN proposed vitrification as the most appropriate conditioning method for spent fuel damaged in the 1977 accident. SGN's feasibility study was performed under a contract from June 1994 and suggests dissolution and vitrification would provide highest integrity of the package. SNF said a centralized facility for vitrification and storage could be ready to start up at the end of 1999. The plant could also vitrify other liquid waste stored at the site, including 40 m³. of potassium chromate solution used as a medium to store the A-1 fuel.
Shutdown of unit-2 because of an electrical fault in the monitoring system, which triggered an alarm and initiated the reactor trip signal.
RPV vessel annealing
RPV vessel annealing.
Following a start of the unit a large replacement of reactor coolant was carried out to decrease boron concentration. Due to increase in coolant letdown into the sump,and to a low drain capacity the water flooded the floor of two rooms in auxiliary building.
Slow Scram HO-2 lost power due to a relay fault. Shutdown, because of subsequent rod drops. A number of occurences indicated a lack of safety provisions concerning signals of both HPCI pumps and reactor scram from LOCA.
At the beginning of refueling outage reactor loops were drained, when water expulsion from a siphon at the tank of organized leaks caused a gas activity of 900 kBq/m³ in the rooms with this tanks.
Ground short circuit at 6 kV MCP cable joint, caused by increased temperatur in cable corridor ( recurrent problem of isolation of cables!)
Short in a 6 kV cable joint feeding a FW pump motor
caused a fire. Fire was suppressed by manual extinguishers.- Manual scram; The fire showed a number of deficiencies in fire protection.
At low power during a test of SG relief valve broken shaft in a valve in the main steam line was found.
At the end of refueling outage pressure test of RCS revealed that a number of valves in the lines of clean condensate to filters of reactor coolant clean-up system were leaking -> Reduction in margin against "interface LOCA". There was only one other valve providing a barrier between high and lowpressure system.
During refueling outage an HPCI pump was used to fill the refueling pool. The pump had to be stopped after 6 minutes due to its heating and damage of bearing. A blinder was found at a valve in a cooling line of its motor. The pump might be inoperable for some unidentified time period, because there were no recirculation lines for testing ECCS pumps.
Following a start of the unit a large replacement of reactor coolant was carried out to decrease boron concentration. Due to increase in coolant letdown into the sump, its water siphon was expelled and gas activity in service rooms was increased.
Organized leak from RCS through the seals of main isolation valves at reactor coolant loops caused water expulsion from a siphon at the tank of organized leaks room with this tanks.
Cristallization of boron was found at both inner sealing rings. Leaks from reactor main sealing plane are a recurrent problem of WWER 440/V230.
During test the motor of HPCI pump failed to start. A second start 24 min. later was successful. Cause of the failure was the resistance of the pump after a long back-up mode.
Room with control instrumentation was flooded and contaminated from a leak in an instrument line for measuring the pressure difference in a mixed bed filter of reactor coolant clean-up system.
During repairing cracked welds at RPV nozzles some foreign objects dropped into the RPV, and were found at the bottom.
Inspection during refueling outage revealed a lot of cracks in the austenitic built-up welding of 6 RPV nozzles.
During inspection, some bolts were found in two nozzles of RPV originating from inspection work.
Overexposure of a worker during refueling (115 mSv) because of manipulations with exposed in-core parts.
During refueling outage a facility for inspecting in-reactor parts was charged into the reactor. Some parts broke and fragments fell into the RPV.
In 1997 in Bohunice-1 and 2 23 events labelled with INES 0 and 2 events labelles with INES 1 occured according to the UJB annual report.