TACIS/U/TSO/VVER/01 Licensing Related Assessments

This project is the continuation of the project UK/TS/01 A (see the relevant PRS) dedicated to safety assessment of the NPPs at the Rovno site.
Since March 1993 the EC was funding some technical assistance to Ukraine under TACIS programme in order to strengthen the Ukrainian Nuclear Regulatory Administration (NRA) and to improve the safety of the Ukrainian Nuclear Power Plants.
In a first step, the site of Rovno was selected for the implementation of the assistance. This site of Rovno has three units under operation, two VVER 440-213 and one VVER 1000-320.
A consortium of six Western Technical Safety Organisations (TSOs) carried out an independant safety assessment of the three units under operation at Rovno NPP. The work was performed in close cooperation with the Regulatory Authority and with the participation of technical experts from the NPP and also from the Russian and Ukrainian design organisations. It led to the identification of safety issues and corresponding recommendations were issued for their correction or for a deeper evaluation through specific studies. Results are summarised in the PRS of the project UK/TS/01 A & B.
Subsequently a TACIS contract was awarded in 93 to assist the Rovno operator in the improvement of the plant safety in the area of design, operation and organisation. This on site assistance was provided by EdF. One of the actions performed under this later umbrella was to propose a modernisation programme of the existing plant (units 1.2), and to submit it for approval to the Ukrainian Safety Authority.
This project was implemented to support the licensing related assessment of this modernisation programme.
However, after some discussion with the NRA, it was decided that the modernisation programme to be considered in this project was an old long term modernisation programme edited by the NPP before 1993.

Two major objectives were given to the project, namely:

• To provide technical support of Western TSOs to the NRA during the process of improvement and licensing of Rovno operating units.
• To ensure transfer of know-how and methodology to the experts of NRA and its TSOs by active involvement of Ukrainian Experts in the different phases of the licensing project.

RISKAUDIT was the Contractor of this project. The following Organisations were part of the consortium: GRS, IPSN, Agenzia Nazionale per la Protezione dell'Ambiente (ANPA), and Centro de Investigaciones Energeticas, Medioambientales y Technologicas (CIEMAT).

KFKI Atomic Energy Research Institute (AEKI) of Hungary was a subcontractor of Riskaudit for some activities as well as the Ukrainian TSO SSTC.

Achievements (With reference to the TORs)

The project was organized in the following tasks:

• Evaluation of modernization programme,
• Transfer of know-how on the following aspects:
• QA for NSSS data base and input deck development,
• Performance of a T/H safety analysis (Main Steam Line Break),
• Analysis of dry containment,
• PSA.

The following deliverables were issued:

• Report n.1: Modernization programme - Definition of safety objectives to be met after implementation of the modernization programme
• Report n.2: Methodology for prioritization of existing recommendations,
• Report n.3: Prioritization of the existing recommendations,
• Report n.4: Joint ANPA/CIEMAT/GRS/IPSN evaluation of Rovno 1-2 Modernization programme,
• Report n.5: SSTC evaluation of Rovno 1-2 Modernization programme,
• Quality Assurance/NSSS data base,
• Quality Assurance/Input deck development,
• Initial and boundary conditions for MSLB calculations,
• Result of the MSLB analysis,
• Result of Rovno 3/Analysis of dry containment,
• PSA/Transfer of know-how,
• PSA/Evaluation of Rovno 1-2.

In relation to the report n.1, safety objectives were defined in terms of defense-in-depth. In particular the proposed model of defense in depth concept was centered on several independent levels of protections, including successive barriers preventing the release of radioactive materials to the environment. The overall objective of the modernization of Rovno 1 & 2 units was proposed to be that improved design arrangements, equipment classification, quality and operation practice prevent accidents with a high confidence. “It must be ensured that, for all accidents taken into account in the design of the plant, even those of very low probability, radiological consequences, if any, would be minor; and the likelihood of severe accidents with serious radiological consequences would be extremely small”.

Therefore, through use of reliable structures, components, systems and procedures, accident prevention was considered of first priority.

It was stated that the safety evaluation of the modernization programme which had to be performed should take as a basic assumption that essential design and operational safety weak points for this type of reactors were previously identified through the work performed on Rovno 1 & 2 reactors by Riskaudit under TACIS contract.
The objectives of the safety evaluation were stated as in the following:

• to verify the completeness of the proposed modernization measures,
• to access the implementation schedule of the proposals, in order to provide an independent judgment of the safety of the modified plant in front of Western practices.

Therefore an approach for the evaluation based on the IAEA documents INSAG3 and INSAG 10 documents was established by Riskaudit. The basic philosophy of the approach is that:

• the more frequent the excepted occurrence of the initiating event is,
• the more serious the potential consequences are,
• and the more unreliable the safety function is,
• the more urgent and necessary is the need for improvement.

In relation to the Report n.2, the proposed prioritization method was established based on following process:

• Determine the safety function affected by the issue,
• Determine the initiating events to be considered, if more than one consider following steps for each one and then select the worst result,
• Determine the expected frequency of corresponding initiating event considering to the adverse effect of the issue: Expected, Possible, Unlikely or Remote,
• Determine the capability to fulfil the safety function considering adverse effect of the issue: Robust, Adequate, or Inadequate,
• Estimate and categorize potential consequence considering adverse effect of the issue: Tolerable, Significant or Intolerable,
• Determine with decision matrix (see table 1) category of the issue.

In relation to the Report n.3, it was intended to provide a basis for further assessment of Rovno-1 & 2 modernization Programme by experts from RISKAUDIT and SSTC.
During the Phase I (see UK/TS/01) of Rovno 1,2,3 TACIS Project RISKAUDIT and other participating Western technical safety organizations developed a Final Report identifying for Rovno 1,2 (and 3) important safety issues and recommendations for safety improvements. The report categorized these recommendations to ensure further systematic approach to the assessment of Rovno-1,2 Modernization Program. The result of the prioritization and estimates made by the SSTC experts was provided, covering the following technical areas:

• Core design and fuel management
• Pressurized components
• Electrical supply
• Instrumentation and control
• Containment
• Internal hazards
• External hazards
• Accidental analysis
• System analysis
• Operating experience feedback
• Plant operation

At the end of each Chapter a summary table provided the status of the issues and all the recommendations relevant to that technical area.
Report n.4 and 5 provided the evaluation results achieved by the Western TSOs and the SSTC on the basis of the application of Western practice to the modernization program for RNPP. The evaluation results were presented for each technical area, and the safety issues were examined in order to evaluate if acceptable proposals were given in the Modernization programme (MP), according to the following grid:

• Safety issue presentation (or recall of previous recommendation),
• NPP proposal given in the MP (if any),
• Evaluation (i.e technical safety comments),
• Conclusion/Recommendation given by Riskaudit
• (The NPP position was sometimes added).

Also, a classification of the urgency for implementation of proposed measures was given (which was not comparable to the classification of safety issues performed by the IAEA)
According to the SSTC position, the Safety Upgrading Program, if updated and implemented in accordance to the recommendations provided in reports, would significantly increase the safety level of Rovno WER-440 model 213 Units 1 and 2.

Comments

(Quality of the results, Lesson learned, Recommendations for follow-up)

The project met the objectives stated in the TORs and represented a major step forward in an agreed identification of the safety issues and their remedies for the Rovno plant.