The aim of the project was the analysis of the VVER safety documentation to assess the status of the technical basis for the safety of the VVER reactors. The project was expected to provide results for VVER 440/230, VVER 440/213 and VVER 1000. The purpose of this documentation analysis was to provide the CEC with the necessary sound basis for decision making about further work on VVER safety improvement.
The review specially aimed at reviewing the documents related to the engineering solutions chosen by Rosenergoatom.
The project provided the results of the review of available documents for the VVER 440 - V230, VVER 440 - V213, VVER 1000 - VI 87, VVER 1000 - V320, and VVER 1000 - V338 NPPs.
A systematic plan for the categorization and assessment of the documentation was developed, which has already been used for the analysis of Western documentation. This reliable methodology was applied to the Russian documentation. The first step of the analysis reflecting the status of the information was summarized in the Topical Report “Safety analysis, systems, component, and operation”.
Individual conclusions have been drawn for each technical area, based on the analysis performed. The overall conclusions about the status of the available safety documentation for both types of VVER reactor, the VVER 1000 and the VVER 440, were presented.
Finally, the reports established summarize the recommendations for future studies to assist in determining the existing needs of the VVER reactors.
The available documentation consists of a wide range of basic information, ranging from general VVER information to detailed information specific to a particular plant.
The “Master List” developed contains 484 documents with all aspects of design, safety, and operational matters. The review covered a total of 24.000 pages, dealing with assessment, concerns and measures not yet implemented in Russian NPPS.
In terms of technical scope, according to the method used, a certain lack of information was found. During the execution of the review, several meetings and exchanges between MOHT and Western experts were held. The status of the assessment measures taken into account in the document database, on the basis of the international measures contained in IAEA recommendations, was evaluated.
From this status, recommendation lists were drawn up for each type of reactor design and a selection of the most important recommendations was made by joint agreement between the project partners.
The following tasks, identified by both MOHT and Contractor, have been carried out with high priority. However, the amount of work to be performed on each reactor design may vary, due in particular to the different life expectancies of the different plants:
A leak-before-break follow-up programme for the VVER 1000 design, particularly for the secondary side;
Primary to secondary leak: a follow-up programme for the VVER 1000 design;
Thermal insulation: a follow-up generic programme for the replacement of the thermal insulation on pipe work within the containment/confinement (VVER 1000 and 440);
System design upgrades for the VVER 440/230 design, with provision of a two-line safety injection system, upgrades to the essential electrical systems and the service-water system, to improve redundancy and diversity. This should be performed during the detailed front-end engineering work;
A containment analysis, follow-up programme for detailed front-end engineering work;
A follow-up generic programme for I&C revamping, in addition to the large volume of technical work already done, to prepare the procurement specifications.
Finally, for the VVER units the priority needs according to the findings of this project are considered in the following areas:
Primary system breaks, both breaks in the primary system per se and primary-to-secondary leaks. This point includes broad-scale actions ranging from the application of the LBB concept to the design of leak-detection systems, without forgetting the aspects of the post-accident procedure;
Revamping of the I&C systems, for which detailed engineering work must now lead to the definition of a progressive installation programme. For this, it is necessary to draw up specifications by function that enables consulting the manufacturer, so as to obtain better cost and schedule information;
The analysis has also revealed specific needs for the heat-insulation techniques, notably employed for the primary system. In this field, immediate action must be envisaged;
Finally, to manage all of the upgrading documentation, the Russian institutes now have available a database that should be kept up-to-date as the safety enhancement work goes forward.