Type: VVER-440 Model V230 and VVER-1000
Units: Six; units 1-4 are the VVER-440 Model V230, and units 5-6 are VVER-1000s
Total megawatts (net): 3,526
Location: Kozloduy, Bulgaria
Dates of initial operation:
For an overview of the principal strengths and deficiencies of Soviet-designed plants, see Soviet Nuclear Power Plant Designs.
Kozloduy, which is now run by the National Electric Company, had a troubled operating history in the early 1990s.
Radioactive Contamination. An International Atomic Energy Agency (IAEA) mission in 1990 noted that several serious incidents had occurred, one of which resulted in the radioactive contamination of groundwater on the site.
The mission also found that 217 workers had received excessive exposure to radiation over the plant's operating life. More recently, at least five "hot spots"--areas of radioactive contamination--have been found in the plant.
Poor Physical Condition. A June 1991 IAEA mission found Kozloduy's four VVER-440 units in such poor physical condition, and safety deficiencies so serious, that it recommended they be shut down until improvements were made.
Following the mission, the Bulgarian Committee on the Peaceful Use of Atomic Energy announced that Unit 4 had been shut down for safety-related improvements and that Unit 3--which was being refueled--would remain shut until improvements were made. Unit 4 resumed operation in August 1991 and Unit 3 in November. Unit 1 was shut in September for backfitting, followed by Unit 2 in November.
Staffing Problems. Unit 5 was plagued by staff shortages which--together with a maintenance and refueling outage--kept it out of service for much of 1991. Full staff levels have now been reached, allowing operation of Unit 5 and the recently commissioned Unit 6.
Management Changes. In 1991, the Bulgarian government twice changed Kozloduy's management in an attempt to improve the work and safety culture at the plant.
In 1991, Bulgaria requested financing from international lending organizations--the World Bank, the European Bank for Reconstruction and Development--as well as from such bodies as the European Communities to pay for technical improvements by Western companies to the four VVER-440 units at Kozloduy.
Technical improvements under way and completed are discussed in the section on International Exchange/Assistance.
The Bulgarian Energy Committee has said it plans to announce a tender for bids to upgrade Kozloduy units 5 and 6. In addition to Westinghouse Corp., which presented an upgrading program in 1995, the committee expects Germany's Siemens, France's Framatome and Russia to bid on the project.
In addition, the Kozloduy plant is funding numerous improvement projects, including a four-phase project to upgrade the autonomous radiation control system at units 5 and 6. A U.S. consortium of Westinghouse and Sorrento Electronics will provide 18 new detectors and 16 new radiation processors. Under the first phase of the project, the central unit and two radiation processors are expected to be delivered in 1996.
WANO Membership. Kozloduy is a member of the World Association of Nuclear Operators (WANO), and plant representatives hosted a visit by staff of Consumers Power Co.'s Palisades plant May 5-12, 1990. Kozloduy staff, in turn, visited Palisades June 17-24 of that year.
Because of Kozloduy's WANO membership, plant management appealed to the organization for help following the visit of IAEA design and operational safety review teams in early 1991. WANO agreed to help, offering to provide spare parts and equipment from the closed VVER-440 units at Greifswald in eastern Germany.
In November 1995, at the invitation of the Kozloduy plant management, a team of experts from WANO carried out a peer review of units 5 and 6. The review covered such areas as operating practice, maintenance, technical support, radiation protection, training, and organization and management.
IAEA Training Seminar. An IAEA training seminar is scheduled to be held at Kozloduy April 8-10, 1997, to demonstrate the practical use of the ASSET analysis procedures for self-assessment of operational events in advance of the October ASSET peer review mission to the plant.
EC Assistance. In July 1991, the European Communities (EC) announced that it had earmarked 11.5 million ECU ($14.5 million) through its PHARE program for emergency aid to improve safety at Kozloduy.
The aid focused on three areas:
The immediate repairs needed to restore the units to their original operating condition.
A three-year improvement program, starting with a six-month phase consisting of on-site advice by an international team of nuclear engineers to achieve two objectives:
"Twinning" Kozloduy with nuclear power plants in EC countries for ongoing exchanges of technical and operating information.
Within a month of the EC announcement, the team of nuclear engineers had arrived at Kozloduy, and by November of that year, units 1 and 2, the two oldest, had been shut down for extensive repairs.
As part of the backfit effort, Germany announced in September 1991 that it was sending $11 million worth of spare parts to Kozloduy from VVER-440s at the closed Greifswald plant.
Electricité de France (EdF) had already agreed in June 1991 to "twin" Kozloduy and EdF's Bugey nuclear plant, making that pairing the first under the emergency aid effort.
As part of the six-month safety review of units 1-4, Bulgaria's Committee of Energy and the EC selected firms to carry out the most urgent work, which included assessing the structural integrity of the primary vessel and pipework and the effects of vessel annealing. Among the firms awarded contracts under the EC's 11.5 million ECU PHARE program for Bulgaria were the U.S. company Westinghouse, Empresarios Agrupados of Spain, EdF/Siemens, and Belgatom. A separate contract was awarded to a consortium of Western European nuclear safety expert organizations led by France's IPSN (Institute of Nuclear Protection and Safety).
The consortium, together with WANO, Kozloduy operators and Bulgarian regulators, agreed on a three-year outage management program that would cover plant restoration, equipment requalification, engineering, documentation, operational feedback, formation of a safety committee, and training.
In March 1992, the annealing (a heat-treatment process that can help restore the ductility of metal) of Unit 2's pressure vessel began. Annealing was completed in April. In addition, Western non-destructive testing methods were used to check the condition of the primary circuit, and cracked isolating valves were replaced. Fire-detection equipment was replaced, and fire protection--including fireproof doors and protection for electrical cables--was installed. The EC provided $15 million for improvements to Unit 2, while the Bulgarian government provided $10 million.
Following a full inspection of Kozloduy 2's safety-related systems and equipment by an international consortium and a Bulgarian government commission, the unit was approved for restart in late December 1992. Following a complete check of the primary circuit and analysis of the pressure vessel, Unit 1 was restarted in December 1993.
As part of the upgrading effort, a consortium of Belgatom and Finland's IVO International carried out projects aimed at improving training, operating procedures and documentation at Kozloduy.
The National Electric Company is owed millions of dollars by Bulgarian industrial electricity consumers. As a result, money needed by Kozloduy to complete the plant's overhaul has not been provided by NEC.
EBRD's Nuclear Safety Account. In January 1993, members of the G-24's Working Group on Nuclear Safety met at Kozloduy to decide on the next steps in the plant's assistance program. Also in January, Bulgarian officials reported that the European Bank for Reconstruction and Development (EBRD) had agreed to supply 24 million ECU ($30.2 million) to upgrade the Kozloduy plant. The grant was conditional on the earliest possible shutdown of units 1-4.
The Bulgarian government said it intended to shut down units 1 and 2 as soon as upgrading work on either unit 5 or 6 was completed and a pumped storage plant was built, probably by 1997. It added that units 3 and 4 would operate until both units 5 and 6 were upgraded and three district heating cogeneration plants were upgraded, which--given sufficient financing--could be done by 1998.
In June 1994, tenders were invited for a wide range of equipment, most of it intended for units 3 and 4. The U.K.'s Nuclear Electric received a $600,000 grant from the European Union to help the National Electric Company manage the upgrading program.
Under a contract financed by the NSA grant, the French company Sebim will supply pilot-operated safety relief valves for units 1-4.
In early October 1995, Bulgarian deputy prime minister Tsochev told the managers of the EBRD's NSA that the government was prepared to place Kozloduy Unit 4 in special shutdown in the spring of 1996 for the installation of safety-related equipment financed by an NSA grant.
Other Assistance. In 1992, the Bulgarian government requested funding from the World Bank for a review of nuclear safety at Kozloduy. The purpose was not to duplicate the work planned under the EC program, but to indicate what could and should be done at the plant. The review, carried out by EQE International, identified short-term modifications and longer-term improvements to Kozloduy that would enable safety levels at the plant to approach those of nuclear plants in the West.
The EQE International recommendations included four modifications that would significantly enhance safety: adding a segregated, hazard-protected bunker to house all functions needed to shut down the plant; adding fast-acting main steam isolation valves; providing additional protection against hazards such as earthquakes, fires and wind; and providing a filtration system and improving the existing venting capability. According to Bulgaria's chief nuclear regulator, the study demonstrated that the difference in operational risk between units 1-2 and units 3-4 is small and does not justify the early shutdown of units 1 and 2.
EQE Bulgaria was established in 1992 to provide Western seismic and safety analysis expertise to Kozloduy. Among its projects, variously funded by the International Atomic Energy Agency, the World Bank, EQE and Kozloduy itself, are: the seismic qualification of information backup system data recording equipment for units 5 and 6; the design and implementation of seismic upgrades for electrical, instrumentation and control equipment, walls and buildings and the interim spent fuel storage building; a top-level risk study of units 1-4 to analyze safety as initially built and after reconstruction work carried out between 1990 and 1994, and to identify further modifications that could be carried out in the short term; and the evaluation, design and cost-benefit studies of potential safety improvements to units 1-4.
Electricité de France. EdF signed a cooperative agreement with the National Electric Company in 1993 to improve safety at the Kozloduy plant. EdF also contributed FF 10 million ($1.97 million) for equipment and spare parts purchases. The utility is also advising NEC on corporate strategy, fuel supply, training, pricing policy and linking the Bulgarian and Western European grids. In July 1993, the Kozloduy plant asked EdF to help analyze potential improvements to the instrumentation and control systems of units 5 and 6.
In January 1994, EdF agreed to continue its cooperation with NEC aimed at improving the safety of the Kozloduy plant. Under this agreement, EdF would concentrate on upgrading the plant's two VVER-1000 units. The proposed modernization of units 5 and 6--developed by NEC, Energoproject and EdF--was reviewed by an IAEA team in June 1995 during a visit to the Kozloduy plant. The team compared the proposal with an IAEA-developed list of VVER-1000 generic safety concerns, and concluded that the proposal--together with some recommendations from the team itself--would greatly contribute to improved plant safety.
Siemens. Germany's Siemens agreed in 1993 to provide $45 million worth of equipment for Kozloduy's upgrading in exchange for Bulgarian chemical products and exported electricity. NEC, which negotiated the arrangement for Bulgaria, said it was owed several million dollars by Bulgarian chemical manufacturing companies. In June 1995, Siemens said it planned to install a newly developed water and steam leak monitoring system at Kozloduy.
European Bank for Reconstruction and Development. In 1993, Bulgaria held informal talks with the EBRD about negotiating a $100 million credit to use for upgrading Kozloduy units 5 and 6. In April 1995, the head of the Committee on Power Supply announced that Bulgaria planned to request a credit of $200 million for rebuilding and modernizing units 5 and 6, which are operating only at about 65 percent of their capacity.
United States. Under the United States' International Nuclear Safety Program, Kozloduy has received two emergency diesel generators and two fire trucks, one to pump water and one to pump chemical suppressants. In November 1995, Westinghouse Corp. proposed upgrading Kozloduy units 5 and 6, with the Bulgarian government providing 15 percent of the funding, and the U.S. Export-Import Bank guaranteeing the remainder. ABB Combustion Engineering, working with Bulgaria's Energoproekt, has completed a study of confinement structures at units 1-4 to assess the technical and economic feasibility of installing a filtered vent system. The study, funded by the U.S. Trade and Development Agency, concluded that vent systems are financially and technically feasible and desirable.
Inetec. Croatia's Inetec has several long-terms contracts with Kozloduy. Under one, the company will carry out eddy current testing of the plant's steam generators until 1999. Depending on the results of testing, it will also carry out tube plugging until 1999. The company will use advanced ultrasonic testing, eddy current testing and visual techniques to carry out in-service inspection of the plant's pressure vessels to the year 2001.
Russia. In December 1995, Russian Deputy Minister of Atomic Energy Viktor Sidorenko reportedly said that Russia was prepared to help Bulgaria develop a modernization program for all six reactors at Kozloduy and, if Bulgaria chose to carry out such a program, to provide support.
Kozloduy's Unit 1--which underwent upgrading in 1992--was shut down in February 1995 for a five-month check of its safety systems. Two European safety institutes--France's IPSN and Germany's GRS--submitted a report to the Bulgarian regulatory authority in mid-September that maintained the resistance of Unit 1's pressure vessel to large thermal shock had not been adequately demonstrated. They recommended that samples be taken from the vessel for examination and analysis before the unit was restarted.
In late September, the ambassadors of the G-7 nations met with Bulgarian Deputy Prime Minister Kiril Tsochev to express their concern about Kozloduy Unit 1. They asked that the unit not be restarted unless the condition of its pressure vessel could be ascertained to the satisfaction of Western safety experts. NEC responded that it could not ensure normal power supplies if any one of the units at Kozloduy did not operate, and the Bulgarian government rejected the G-7 request. Following the government's rejection, Electricité de France, which had been providing assistance to Kozloduy since 1991, said it would withdraw its remaining staff from the site if Unit 1 were restarted.
Subsequently, two Bulgarian parliamentary committees--on power supply and environment--met to discuss the G-7 request. The committees concluded that Bulgaria's nuclear regulator--the Committee on the Peaceful Use of Atomic Energy--should have the final say on Unit 1's restart.
At the end of September, the Committee on the Peaceful Use of Atomic Energy issued a statement noting that all the studies carried out independently by Bulgarian institutes, the Russian designer of Kozloduy and the pressure vessel manufacturer had concluded that the pressure vessel could be operated with sufficient safety margins until the next refueling in March or April 1996.
On Oct. 3, a team of IAEA experts met with representatives from Bulgarian and Russian nuclear bodies as well as IPSN and GRS in an attempt to resolve their differences over Unit 1's restart. The discussions focused on the condition of the reactor pressure vessel, with a review of recent information from Bulgarian and Russian institutes. While recognizing the information's value, the European institutes maintained that further analysis and examination were necessary before restarting the unit.
At the meeting, the Bulgarian nuclear safety authorities described licensing-related requirements for the unit's restart, consisting of a three-step program of operation: a reduced operating cycle of about six months; a special operating regime to include constant power operation to avoid system transients, revised operating procedures, special operator training, and increased supervisory control; and a comprehensive program to prepare to take samples and/or anneal the reactor pressure vessel after the shortened operating cycle. On Oct. 5, the Bulgarian regulator gave approval for restart.
In mid-October, the European Parliament passed a resolution calling for the immediate shutdown of Unit 1. In response, the chairman of Bulgaria's parliament told the European Parliament that samples from Unit 1's pressure vessel would be analyzed in the spring of 1996.
In December 1995, Bulgarian officials reported that, following a meeting with the Commission of the European Union ( EU) in Brussels, the EU would fund the tests on Unit 1's pressure vessel, which could cost up to $500,000. Bulgaria said it could not close the unit for tests before April or May 1996 unless the EU compensated it for electricity losses. EU, Bulgarian and Russian experts met in January 1996 to discuss the program of tests to be carried out on Unit 1. They agreed that six metal samples would be taken from the vessel for chemical and mechanical analyses. The conditions and sources of finance for the tests will be agreed at a later date.
The Bulgarian government has requested IAEA inspections of all six operating units at Kozloduy.
OSART Mission (Unit 5). The first IAEA inspection was an Operational Safety Review Team (OSART) mission to Unit 5 Oct. 15-25, 1990. The team focused on several key issues--operations, maintenance and technical support--in what it termed a "mini" OSART and scheduled a full-scope OSART for the following year.
In its review, the team recommended:
The team also pointed out that improvements would be difficult to make without the support of the Bulgarian government.
ASSET Mission (Units 1-4). An IAEA Assessment of Safety Significant Events Team (ASSET) mission visited units 1-4 Nov. 7-21, 1990. The team noted a lack of attention to preventing operational events and said that safe operation demanded major improvements by plant management. In particular, the team criticized management's emphasis on production of electricity over operational safety.
The team stressed the seriousness of the situation at Kozloduy and said that Bulgaria must supply the resources needed for the plant's safe and reliable operation. Noting that it could not complete its review because of a lack of information, the team called for another ASSET mission when the necessary information was available.
OSART Mission (Units 1-4). The IAEA OSART mission to Kozloduy units 1-4 during June 3-21, 1991, identified many operational problems, including:
The findings were so devastating that the team suggested that continued operation of units 1-4 would be imprudent.
OSART Mission (Unit 5). A month later, July 15-Aug. 2, an OSART mission visited Kozloduy 5. The team said that despite the unit's good operational performance, fundamental changes were needed to break with past practices and establish a safety culture.
ASSET Mission (Units 1-4). An ASSET mission visited Kozloduy June 1-5, 1992, to help plant management implement previous ASSET recommendations on quality control, preventive maintenance, surveillance, root-cause analysis, and repairs and remedies.
The team noted that the plant management had paid proper attention to the recommendations of the 1990 ASSET mission. Some recommendations had been carried out immediately, and others were included in general programs for improving operational safety.
The team observed that plant management was fully dedicated to making technical and organization changes, and was taking full advantage of the international assistance offered for this effort. The team added that the importance of quality assurance and safety culture was understood at the top management level.
Singling out the recommendation on installing fast-acting valves to isolate the main steamlines, the team emphasized that this action should have higher priority than it had been given under the plant's improvement program. The team also noted that while progress had been made in enhancing the safety awareness of maintenance personnel working on safety-related equipment, improvements were still needed to achieve a satisfactory level of safety awareness.
In addition, the team noted that quality assurance was a relatively new concept at the plant, and suggested that while WANO exchanges had improved attitudes toward quality assurance, workshops, seminars and on-the-job training would also help.
Follow-Up OSART Mission (Units 1-4). An OSART follow-up mission visited Kozloduy April 26-30, 1993. The purpose of the mission was to determine the status of actions taken in response to the findings of the 1991 OSART mission to the plant as well as the actions taken in response to the issues identified as part of the IAEA's program on the safety of VVER-440 Model V230 reactors.
The team concluded that the plant had made reasonable progress in responding to the recommendations of the 1991 mission and the more generic issues identified by the IAEA program. Given the significance of the 1991 findings, the team said, the progress represented the fruits of a major effort by, among others, the Bulgarian utility, Kozloduy staff and the Bulgarian regulatory body.
The team noted that about two-thirds of the operational safety issues were moving toward completion. The team identified improvements in:
The team pointed out, however, that a considerable amount of work remained to be done to resolve the issues raised by the 1991 mission. The team urged renewed management drive to ensure that sufficient resources were available to develop and manage the plant's training program, and that plant staff received appropriate training in emergency response when following the recently improved emergency plan.
Follow-Up ASSET Mission (Units 1-4). An ASSET follow-up mission visited Kozloduy Sept. 20-Oct. 1, 1993, to review operating experience, assess the appropriateness of corrective actions, and exchange views on improving the management of incident prevention. The team noted that all 13 recommendations made by the 1992 ASSET mission had received appropriate consideration. Six had been fully addressed and carried out; progress was being made on the other seven.
The team reviewed 93 reported events between December 1990 and May 1993. Of these, 73 were considered by the team to be safety relevant; 14 were classified as Level 1 and the rest, as Level 0.
The team offered several recommendations:
As the plant organization evolves, management should ensure that each department has a clear definition of its interfaces, responsibilities and resources.
Departments within the plant should be encouraged to increase the level of shared information.
Management should consider whether surveillance programs for equipment that has failed should be assessed to determine whether extensive testing is beneficial.
Management should consider expanding the sharing of information with plants of similar design and origin to include the sharing of critical spare parts when necessary.
The team commended three plant practices:
ASSET Mission (Units 5 and 6). An ASSET mission visited Kozloduy units 5 and 6 Nov. 14-25, 1994. The team reviewed 425 reported events, of which 177 were considered to be of safety relevance. One event was classified as Level 2 on the International Nuclear Event Scale, 31 were classified as Level 1, and the rest as Level 0. The team noted that the number of events per year was declining and the proportion of events discovered by surveillance programs was rising--both positive trends.
The team identified 12 safety problems that had developed over the life of the units, of which six had been resolved. Satisfactory solutions were being implemented for the remaining six.
In its recommendations, the team emphasized further enhancement of the units' surveillance programs and the training of staff.
Safety Review Mission (Units 5 and 6). A Safety Review Mission visited units 5 and 6 June 25-July 1, 1995. The purpose of the mission was to review the safety aspects of the units' modernization program. The review covered plant design and operational safety as proposed in the program. Upgrading measures, which are aimed at improving plant availability, were not reviewed.
Because of variations in the content and descriptions of individual measures in the program, the team could not judge the sufficiency of some proposals. It concluded that a certain number of measures need to be improved, and some measures need to be added to the program. The team recommended that the proposed improvements be examined to ensure that they do not cause adverse effects.
Planned Safety Review Mission (Units 1-4). A Safety Review Mission to units 1-4 is planned for the first quarter of 1996.
Planned OSART Mission (Units 1-4). An OSART mission to units 1-4 is planned for the first half of 1997.
Planned ASSET Mission (Units 5 and 6). An ASSET peer review mission to units 5 and 6 is scheduled for Oct. 6-10, 1997. The mission will review the plant's analysis of events reflecting safety culture issues based on ASSET procedures.
January 1996
