Bohunice :	|	Operating History	|	Technical Activities	|	Accomplishments	|

Technical/Upgrading Activities

In April 1992, the Slovak government reviewed a technical and economic analysis of the units' operation, and requested studies on three options: safety upgrading, conversion of the units to combined cycle, and closure of the units and their replacement with a new combined cycle plant. Studies of the three options concluded that safety upgrading of the units would entail lower capital and operating costs than the other two options.

The Slovak regulatory authority asked that the proposed upgrading be reviewed by international experts. In July 1993, the IAEA convened such a meeting. After hearing presentations by Slovak safety authorities and Bohunice management on safety improvements already made and the options for future major upgrades, the experts agreed that a major safety upgrade was technically feasible and would significantly raise the plant's level of safety. The experts made a number of recommendations on various options to help Slovak authorities make a final decision.

SE proposed that upgrading be carried out gradually in two phases, during extended refueling outages. In January 1994, the republic's Nuclear Regulatory Authority laid out the conditions that would have to be met so that the two units could be licensed after each refueling.

International Exchanges and Assistance

SE contracted with Western companies for a number of safety- related improvements:

• In 1986, Germany's Siemens/KWU supplied loose-parts monitoring systems and component vibration-monitoring systems for Bohunice-3 and -4.
• In 1990, Siemens/KWU supplied component vibration-monitoring systems to Bohunice-1 and -2, and a year later, delivered leak-monitoring systems for the two units.
• In 1990, the utility commissioned Siemens/KWU to analyze the reactor safety systems at Bohunice-l and -2. Areas covered included safety-system design, reactor performance under accident conditions, and instrumentation and control technology.
• The CSFR government said in April 1992 that a study of instrumentation and control system replacement in VVER- 440 Model V213 reactors would be carried out under the European Cornmunities' PHARE program. The study found that extensive I&C refurbishing or replacement was needed at Bohunice Units 3 and 4, and a contract was signed with the U.K.'s NNC Ltd. in 1993 to provide full technical specification of the I&C system.

Recently, international assistance has included studies for the construction of a safety parameter display system, and upgrade of a plant analyzer model. In upgrading plant analysis capabilities, Bohunice staff are working with staff from the Brookhaven National Laboratory to provide upgraded hardware and software for plant analysis and relevant training. Also, BNL and the U.S. firms General Physics and Sonalysts are assisting the Trnara Training Center staff with the development of training programs.

Bohunice :	|	Operating History	|	Technical Activities	|	Accomplishments	|