SAFETY EVALUATION OF VVER

In the framework of the TACIS programme, the Commission of the European Community (CEC) signed a contract with RISKAUDIT IPSN/GRS International establishing a first phase Safety Evaluation Contract for VVER 440/213, Rovno units 1 -2, and VVER 1000/320, Rovno unit 3.
Rovno NPP is situated in the north-west part of Vladimeretz district of Rovno region of the Ukraine, on the right bank of the Styr river.
The two pressurized water reactors present the first units of the WWER-440/W-213-type in the former Soviet Union. These units were put into operation 1980 respectively 1981.
They were built as double-unit plants in which two reactors are located in one common reactor hall. A common turbine building serves all four turbines (two per unit).
In contrast to the containment of unit 3, the reactor building of the W-213 plants is connected to pool-type pressure suppression systems (bubble condenser).
The main production building is supplemented by auxiliary buildings: in particular the diesel generator station, the service water pumping house, processing plants for water purification and waste treatment.

The objectives of the project were as follows:
•Identification of current Safety Plant Status and determination of the differences between already analyzed VVER NPP (Greifswald, Stendal, Loviisa, etc.) to Rovno,
•Preliminary assessment of:
o safety design,
o plant operation status,
o operating experience feedback,
•Transfer of Western experience and practices in carrying out a Probabilistic Safety Assessment,
•Transfer of knowledge on Western regulatory requirements on Safety Analysis Report,
RISKAUDIT was acting as consultant for a consortium of 6 European Technical Safety Organisations. Each organization was in charge of two technical items.
General coordination was performed by RISKAUDIT. Technical management was handed over to GRS (Rovno Units 1 -2, VVER 440/213) and IPSN (Rovno unit 3, VVER 1000/320).

Achievements (With reference to the TORs)
For carrying out the safety assessment, working groups involving experts from Western, and Eastern institutions were established. About sixty experts from the following Eastern organisations took part in the discussions:
•GANU (Nuclear Safety Authority of Ukraine),
•Scientific Technical Centre from GANU (Technical support organization of GANU),
•NPP Rovno (Utility),
•Energoprojekt Kiev (Designer),
•Gidropress Podolsk-Russia (Constructor),
•Kurchatov Institute (Russian scientific support for design and commissioning).
The technical leadership of these Eastern organizations was taken first by GANU former deputy leader and later on by a GANU representative.
Working groups were established; their tasks were related to:
•identification of the plant status and differences with already analyzed VVER's,
•development of a preliminary assessment using, among the others, results of previous evaluations,
•transfer of know-how for performance of a PSA,
•transfer to the GANU of Western know-how on regulatory requirements on Safety Analysis Report.
After a first round of meetings, an interim report was prepared (RISKAUDIT Report no 3) and submitted to CEC and to the GANU. The insights presented in this report were based only on technical discussions with Eastern experts.
In order to complete the basis of information for further review, a limited amount of documentation was translated into English, and then analyzed by the Western experts in order to prepare a second series of working group meetings of 10 days each, which were held in Rovno NPP for September to December 1993. Deeper discussion with Eastern specialists were organized to complete the review work.
A project meeting was held in Berlin the 20th and 21st of January in order to harmonize the results of the review.
In order to finalize the draft review report, a review committee involving senior experts of Western safety organizations and senior experts of Eastern partners was also planned.
Reference standards were taken as from the IAEA. In particular, the “satisfactory safety level” was assumed based on a reference plant design complying with internationally acknowledged and adopted standards, as well as on a documented quality of realization and strict conditions. Each of these factors being necessary but not sufficient in itself, according to the "Basic Safety Principles for Nuclear Power Plants" published by IAEA in 1988 (75-INSAG-3).
The intended safety approach used for this evaluation was to ensure that with the solvability of identified safety issues, a final safety level of this plant with current international requirements and acceptable according to various national Western practices could be obtained.
The final technical report contained the draft results of the analysis performed within the frame of this contract. The identification of the safety issues was presented and recommendations were developed for discussions. For each technical item, the following was presented:
•Basis for evaluation,
•Information on the status at Rovno NPP,
•Assessment,
•Recommendations for improvements,
•Recommendations for complementary studies to be performed by NPP,
•Proposals for future evaluations to be performed by the Consortium within the 2nd part of the contract.
For each of the technical items, two types of recommendations were proposed. The first one was dealing with the weaknesses for which improvements (or development a of compensatory measures) were necessary in order to reach a "Western safety level" in the concerned area. The second one was dealing with the issues for which a safety demonstration was usually provided by the NPP's in the West, but they were lacking in Rovno. Additionally, taking into consideration some incompleteness of the information received during this stage, a complementary evaluation to be performed by the Consortium was proposed. This evaluation should have represented the first part of the tasks to be fulfilled within the following contract.
The following areas were examined:
•Design safety status,
•Operational and management practices,
•Operational experience feedback.
The general conclusions were the following:
•Except for the VVER's 1000 generic problem on control rods blockage which occurred also during tests in Rovno 3, no major technical safety deficiency which would lead to shut down immediately one of the units was identified. The main issues for which improvements have to be developed and implemented in the shortest term are linked with the following:
oquality of some equipment (electrical equipment such as breakers and relays, mechanical equipment such as tightness devices of valves, ...) ;
o documentation (drawings, Safety Analysis Report, technical specifications, etc.) ;
o quality assurance;
o safety culture (punishment system, etc.)
o spare parts availability;
o foreign dependence (spare parts, waste, etc.) ;
o overpressurization protection devices (primary and secondary) ;
o common mode failures potentialities (14.7 m platform level for units 1-2), and fire protection (cables segregation, fire hazard in turbine hall for units 1-2).
• Concerning the weaknesses in the safety demonstration, the behaviour of the bubbler condenser of units 1-2 under accidental situation should be studied with a top priority. This issue is a generic one, common to all the plants of the same type. International programmes under preparation by CEC are encouraged.
Some general recommendations were also issued in the conclusions of the final report:
•After further discussions with the Eastern experts for clarification of the safety issues, it was proposed as a second part of the future Consortium activities, within the frame of a follow-up contract, to perform a classification of the recommendations, depending on their importance for safety. However, due its complexity, such work was not possible to be concluded during this step, also for the need to discuss this classification with the NPP.
•The proposed recommendations for improvements and for complementary studies should represent a basis for definition by the NPP of an upgrading programme of the plant, in order to reach a Western safety level. Such a programme could be prepared with the help of a Western utility. It should have absolutely to be supported, for implementation, by West European funding.
•It is proposed that CEC continue also to ensure continuity of the support of Western technical safety organization in order to provide help to the Ukrainian Safety Authority for the review of this programme and for the regulatory surveillance of its implementation. This should constitute the third part of future Consortium activities. It is expected that, through this exercise, a licensing procedure should be developed in Ukraine.
•Concerning the Probabilistic Safety Assessment activities, transfer of methodology for elaboration of a specific data base was fulfilled. In addition, an action plan for the realization of a Rovno 3 PSA was proposed. In view of the situation in Ukraine, such an action should be realized under the responsibility of both the utility and the Ukrainian Safety Authority, with Western support from the industry side. However, this task was considered only as second priority action. The Consortium proposed to limit its action to the on-line review of this PSA. This should constitute a fourth part of a follow-up contract.
•In parallel to the actions performed by the Consortium for the safety evaluation of Rovno NPP, a support to the Ukrainian Safety Authority was also given on the definition of the Safety Analysis Report content (SAR). This action was complementary to the actions taken within the RAMG frame activities in Ukraine. The Ukrainian Safety Authority asked the plant to establish a SAR for Rovno units 1 -2 and unit 3. To be fulfilled, such task would have necessitated the participation of Eastern and Western industrial actors which could be coordinated by NPP and its Western utility support. Within the frame of the EC on-site assistance projects, EDF was planning to assist specifically Rovno NPP for the establishment of the SAR chapters on site and technical specifications for operation. It was proposed that the Western technical safety organizations provided also an on-line review to support the GANU during the establishment of the SAR and evaluate later on the final product.

Comments

(Quality of the results, Lesson learnt, Recommendations for follow-up)
The project met the objectives stated in the TORs.
Unfortunately, some of the documents provided by the Beneficiary for analysis were not well translated into English; this fact often made their understanding difficult, if not impossible. This documentation inadequacy together with some language problems and some cultural differences between the evaluators, plant designers and operators made the task of developing the report quite difficult in the short time available.