WRITTEN QUESTION P-2820/97 by Nuala Ahern (V) to the Commission (1 September 1997)

Subject: Proposed completion of the Rovno Unit 4 and Khmelnitsky Unit 2 (k2/r4) nuclear reactors under the Memorandum of Understanding between G7 and Ukraine

Concerning the proposed completion of the k2/r4 nuclear reactors in Ukraine, do the safety proposals at each of the costing, least-costing, evaluation and construction phases of the project incorporate a completely new instrumentation and control system, a full probabilistic safety assessment, and the separation of all power and control cabling as dictated by the lessons of the Browns Ferry cable-tray fire of 1975, all of which are being undertaken on the similar reactors in Temelin, and if not why not?

Further, will all the requirements to meet the implications of the Three Mile Island and Chernobyl disasters be included, and if not, why not?

How is it proposed to deal with pressure vessel embrittlement, and safety against air-crashes?

Can the Commission clarify how the Risk Audit safety assessment (Report No 52) could possibly be used as a basis for any final decision on this matter, since there seems to have been no complete analysis of existing work on these reactors, and certain problems are left for future resolution, or for implementation after start-up? How therefore could the PHARE/TACIS Nuclear Safety Expert Group possibly have given safety approval for the project last year, and why did it take more than 6 months for the Risk Audit report to be made publicly available?

Answer given by Mr Van den Broek on behalf of the Commission (1 October 1997)

In the Commission's view, the final safety level to be achieved at the Rovno 4 (R4) and Khmelnitsky 2 (K2) reactors is of critical importance. With the assistance of the Tacis programme, a modernisation programme has been prepared for both reactors. Riskaudit, an organisation composed of independent technical safety organisations from France and Germany, has evaluated this modernisation programme on the basis of guidelines produced by the International atomic energy agency (IAEA) and on the basis of approved practices in similar reactors operating in the Community and has assessed that the proposed modernisation programme represents the state of the art and is fully consistent in itself.

In this context, it is clear that the status of the present construction is important. As the plant construction has been interrupted for some years, a careful assessment of the actual plant status has been initiated. If this qualitative inspection identifies weak points, corrective measures will be taken. The inspection reports and the corrective measures will also be independently evaluated by Riskaudit.

The implementation of the resulting modernisation programme, which includes the recommendations made by Riskaudit, completed by additional specific measures by the Ukrainian organisations, and of the specific recommendations resulting from the qualitative inspection, will guarantee a safety level comparable to that achieved in western plants of the same vintage design, upgraded on the basis of subsequent improvements in safety standards. The safety level will therefore be equivalent to that of many reactors operating now in western countries.

With regard to the specific questions raised for the R4K2 reactors results of probabilistic safety assessments (PSA) on similar reactors have been used. A full scope PSA is foreseen on the basis of the modernised installation.

The instrumentation and control (I& C) as foreseen in the original project has a certain number of shortcomings which have been identified through assessment and operating experience. They are subject to specific corrective measures. At Temelin, the choice has been made to fully replace the I& C. The separation between cabling for I& C and cabling for power supply is not a safety related requirement. However, the separation of the redundant trains of safety systems needs to be achieved either by geographical or physical separation. Both principles will be used concurrently at R4K2 to achieve independence of trains.

In answer to the general question, it is obvious that the lessons from the Three Mile Island and Chernobyl accidents have been taken into account.

With regard to the pressure vessel embrittlement, the exposure of the VVER-1000 reactor pressure vessel wall to neutron flow is in the same range as in the western pressurized water reactor vessels of the same vintage. Additional measures will be implemented through the modernisation programme so as to reduce the fluence (irradiation) and the number of thermal shocks. A surveillance programme will be developed in order to determine the residual lifetime of the vessel.

The modernisation programme includes the assessment of the probability of an aircraft impact on the reactor building. If the value obtained from the assessment exceeds the internationally accepted value, administrative measures with respect to air corridors will be enforced.