National Report of the Slovak Republic - Radiation and Nuclear Safety
, September 1998
2.1.2 Safety Assessment of Bohunice V-1 Units
The following safety review missions have been conducted during the operation of the Bohunice V-1 units:
- IAEA Fact Finding Mission, Sept. 3 - 7, 1990; the objective of the Mission was to document safety measures taken to improve safety of operation of units 1 and 2 throughout their operation time: operation control, facility improvements, staff training, and control and testing activities.
- Mission of the Siemens company to assess the project and safety level, August - November, 1990. Based on deterministic assessment of the project and safety level, the group of experts provided recommendations for safety improvements; they were accepted by the operator, and included in the "Small Reconstruction" program.
- Commission of the CSFR government and Federal Ministry of the Environment - August - September, 1990. The aim was to asses the current status of nuclear safety of V-1 units and to review the impacts and possibilities to resolve the energy situation of Czechoslovakia if a need should occur to immediately shut down V-1 units because of insufficient safety. Based on the report, CSKAE conducted a comprehensive assessment of V-1 units current condition. The reports clearly stated that there was no need to immediately shut down the power plant, in spite of certain deficiencies, in particular concerning V-1 design. CSKAE issued the Resolution No.5/91 to change approvals on permanent operation of both units, issued by CSKAE in 1980 and 1981, and it regulated the further operation of the units. The operation of the units is now subject to annual approvals based on the progress of upgrading. In addition, the necessary safety improvements to be implemented were defined.
- Austrian Expert Commission, August - October, 1990. The objective of the Commission's visit was to collect information on V-1 unit's safety and to recommend to the government of the Republic of Austria how to further proceed in negotiations with the CSFR government.
- IAEA ASSET (Assessment Of Safety Significant Events Team), October 1-12, 1990; the objective was to review the accident (operation events) prevention concept, to assess the adequacy of measures taken, and to recommend areas for improvements. All events have been reviewed which occurred since the start of operation of the units, and safety significant events were identified. Any of the events, as stated, had no radiological impact on the environment. The activities of the Breakdown Commission for Investigation of Nuclear Installations Events as well as the measures taken immediately were considered adequate. Recommendations were extended for improved process efficiency as well as for quality assurance, staff training and design improvements.
- IAEA Safety Review Mission, April 7 - 26, 1991 within the "IAEA WWER-440P230 Nuclear Power Plants Safety Program, in the framework of which the first conceptual review of these units has been performed in February, 1991. This was followed by missions to the individual power plants. The objective of the program was to review the design and the operation, considering specific conditions of the power plant, and to formulate recommendations (classified into four classes according to their safety significance) which were expected to assist in decision-making concerning the achievement of a higher safety level. The safety significant problems identified during the missions were incorporated into the document TECDOC-640. The approach of the operator who develops its own plan to deal with the issues identified, was positively assessed as a good practice in safety culture.
- IAEA Safety Review Mission in Relation to the Design of Seismic Upgrading for Bohunice NPP, September 2 - 6, 1991; the objective of the mission was to review criteria and design documentation developed for seismic upgrading of V-1 and V-2 units. The mission appreciated the high professionality of the staff involved in the seismic upgrading project, and suggested recommendations concerning structures, systems and components the application of which would secure safe shut-down of the power plant and its maintaining in a safe condition after an earthquake.
- IAEA Safety Review Mission, April 27 - 30, 1992; the objective was to review the implementation of the recommendations and suggestions of the preceding mission (April, 1991) and to evaluate activities performed in response to the Technical Report of the mission. Also, the Report contained an evaluation concerning safety issues identified by IAEA and published in TECDOC-640 document and their degree of implementation under the "Small Reconstruction". The Mission Report considered the activities of the power plant a satisfactory progress, and numerous safety-related issues were considered as eliminated.
- IAEA Seismic Safety Review Mission Relating to the Seismic Upgrading of Bohunice NPP, May 5 - 7,1992; the objective of the Mission was to check the implementation of the recommendations of the preceding Mission of September, 1991, to review the implementation of works relating to the seismic upgrading project of V-1 units. It was stated that the seismic risk of the V-1 power plant has been substantially reduced due to the previous upgrading works, and recommendations were extended concerning problems identified during the preceding review, and issues were pointed out accordingly.
- IAEA Seismic Safety Review Mission Relating to the Seismic Upgrading of Bohunice NPP, April 5 - 8, 1993; the objective of the Mission was to review the project and the implementation of V-1 units upgrading works as recommended by preceding IAEA Missions (September 2 - 6, 1991 and May 5 - 7, 1992) The Mission Report appreciated the volume of works done to seismically upgrade both units, and pointed to the need to continue dealing with issues identified by the preceding Missions.
- IAEA Peer Review Mission to Review the Probabilistic Assessment of V-1 Units Safety Study, March 8 - 12, 1993; the first review stage has very positively assessed the extent, organization, quality assurance, identification and grouping of initiation events, development of event trees of the Level 1 Probabilistic Safety Assessment Study, and defined certain issues to be dealt with in the next steps. The Level 1 PSA Study was developed in cooperation of the operator with the company Electorate Engineering Services, United Kingdom.
- IAEA ASSET (Assessment of Safety Significant Events Team Follow-up Mission), July 5 - 9, 1993. Its objective was to review the implementation of recommendations of the ASSET 1990 Mission and of those of the ASSET Advisory Group meeting of July, 1991, to identify the efficiency of the Conception of the prevention of power plant operation events since 1990, and to extend further recommendations to improve event prevention efficiency. The Mission Report has appreciated the energetic response to the preceding recommendations, and noticed significant progress in the safety improvements of both units. Extensive plans of safety improvement were highly commended, and continuous taking of measures has been recommended, the implementation of which not been could completed due to their significant time-consuming nature.
- IAEA "Small Reconstruction" Assessment Mission, July, 1993. The Report has stated that a significant progress had been achieved with respect to the definition and implementation of safety improvements since TECDOC-640 was issued. At the same time the need was pointed to revise the strategy and safety implications of suggestions on the "main reconstruction program".
- The IAEA Site Safety Review Mission to Review the Design Basis Seismic Input for Bohunice and Mochovce NPP Sites - October 18 - 22, 1993. The aim was to assess data and methods used in determining the impacts of design earthquake and to provide recommendations for further activities in the seismic upgrading area.
- Review of the "Leak Before Break" Concept Application to the Bohunice WWER- 440/230 NPP, consultation meeting; February 28 - March 2, 1994. The aim was to evaluate LBB analyses conducted, consequent changes in equipment and application, as well as the general adequacy of the LBB program to meet the set safety requirements. The technical aspects and the LBB concept programs were assessed as suitable, and the results of the analyses conducted have provided evidence for meeting the criteria ;and that, some unavoidable project adjustments have been made. Operation control programs concerning the main circulation pipe are adequate.
- IAEA Peer Review Mission to evaluate PSA NPP V-1 Study, February 28 - March 11, 1994. The final evaluation continued the preceding March 1993 Mission. Two PSA models have been reviewed: PSA Level 1 - before and after "small reconstruction" including internal fires and floods. It has been stated that the method, technique and PSA data used follow standard practices as recommended by IAEA Guidelines.
- A seminar organized by ÚJD in cooperation with IAEA to evaluate embrittlement and baking of the WWER 440 reactor pressure vessel (RPV) - March 29 - 31, 1994. The aim was to discuss issues of the integrity of WWER-440/230 reactor pressure vessels, the previously taken measures, ongoing activities and plans for the future. The evaluation report of the workshop contains recommendations with respect to RPV integrity of this reactor type.
- Consultation Meeting on Safety Improvements to WWER-440/230 NPPs) - September 26 - 30, 1994, Vienna. The meeting reviewed the previous results of the dealing with safety problems of WWER-440/230 units identified by the preceding missions, and updated the IAEA database of the status of the problem solving at the various power plants. It is evident from the assessment that among all the units, the best progress in safety improvements had been achieved at the Bohunice power plant.
- IAEA Safety Mission to Slovakia: Seismic Safety Review for Bohunice and Mochovce NPPs - October 31 - November 4, 1994. The aim was to review the tectonic stability of the subbase and to review the design parameters of earth movements for the Bohunice and Mochovce NPPs. This mission was a continuation of the October 1993 mission, and it provided recommendations for further proceeding.
- IAEA Technical Safety Review Mission - May 6 - 8, 1996 - the aim was to update information available to IAEA on the implementation of safety improvements and to review activities of the power plant with respect to safety problems resolution (both operating and design problems) identified by the preceding missions. The mission has stated that all safety measures contained in the IAEA TECDOC - 640 document concerning design and operation improvements had been reflected in the V-1 NPP reconstruction program.
- IAEA Gradual Reconstruction Review Mission - June 15 - 19, 1998 - a continuation of the 1991 - 1996 Safety Review Missions . The Mission´s focus was on the evaluation of the implemented and/or planned modifications of NPP V-1 units under the gradual rehabilitation program, in particular from the aspect of the dealing with the safety significant problems of the WWER 440/230 units defined in the TECDOC 640 document. The Mission appreciated the previous approach as well as the further implementation of the safety upgrade program as far as the scope and the adequacy of the measures are concerned. The Mission also defined certain recommendations, including an invitation for an IAEA Mission which would comprehensively assess the treatment of safety significant problems after the completion of the gradual rehabilitation program beyond 1999.
Copyright © UJD SR, 1998
Copyright © SE, a. s., 1998