Summary

The Lithuanian State Nuclear Safety Inspectorate (VATESI), had requested support from EU's Technical Support Organisations (ISO) in the fields of core safety surveillance, assessment of KC equipment and systems and ageing management.

The Lithuanian regulator VATESI has the task of establishing regulatory requirements for the safety of nuclear facilities as well as licensing of nuclear facilities and safety-related activities. The three fields considered under this project: Core integrity, Upgrading of control systems and Management of ageing form an essential part of the regulatory assessment process within the licensing of Ignalina NPP.

To assist VATESI, the Lithuanian TSOs have a clear role providing technical and analytical support. Although the TSOs have technical competence in performing thermo-hydraulic analysis, structural integrity assessment and in other scientific fields, their experience in the areas selected for this project were limited. Therefore, VATESI had a strong need to improve the capability of its technical support organisations in order to have efficient support of regulatory activities.

Task 1 - RBMK core safety surveillance

The overall objective of Task I was to provide training for VATESI and its TSOs in the use of modern methodology and modern tools for core physics calculations to obtain a better understanding for the calculations presented by lgnalina and to improve the possibilities to perform independent audit calculations.

New 2-group macroscopic cross section libraries were generated by the lattice codes WIMS8A and HELIOS. The application of the new libraries using the 3D-core-model QUABOX/CUBBOX showed, that an important step was made in generating cross section libraries for RBMK-1500 core calculations independently from Russian producers.

The core calculations based on WIMS8A showed, that the void reactivity effect is underestimated and the fuel reactivity is slightly overestimated in comparison to results from the RRC KI cross- section library or to plant data. Since the void reactivity effect is small the influence on the total reactivity behaviour is also small in general. Therefore the WIMS8A library can be used for core calculations, when the influence of void reactivity is of limited relevance. However, still improvements of the WIMS library are recommended for increased possibilities to use the code.

The HELLOS library shows a stronger under-prediction of the void reactivity effect and a stronger over-estimation of fuel reactivity, than the WIMS data. An application of the HELIOS library for core calculations would require an improved cross section library.

Based on the qualification and verification results performed with the code QUABOX/CUBBOX some improvements of the cross section libraries could be achieved, but still more efforts are necessary to overcome the detected problems. Since the results from safety analyses with 3D-core models are dependent from the quality of the cross-section data, which are used as input, sufficient qualified nuclear data are of safety relevance. Therefore, it is recommended to perform additional investigations to improve the cross-section libraries for RBMK core calculations.

The training courses for the application of the lattice codes WIMS8A and HELIOS to generate 2- group cross-sections and their integration into the 3D-core model QUABOX/CUBBOX for RBMK core analyses have been performed as planned.

Task 2 — Licensing related assessment of modern l&C equipment important to safety

The overall objective of Task 2 was to enhance the capabilities of VATESI and its TSOs to assess and review the introduction of modern state of the art i&C components and/or systems including software-based technology. Such introductions can be made either due to normal maintenance programs or due to upgrading of the plant. Assessment of new systems must take into account not only the function of the new system itself but also compatibility with existing systems of older technology and also how to assess quality assurance in development of software based functions.

The work was carried out by using existing material and experience, and then discussed and develop them in meetings and seminars into new documents for VATESI. These were the Assessment Review Handbook to be used by VATESI and an Assessment Guide to be used by the utility. During the work VATESI and the Lithuanian TSOs enhanced their capability in understanding how to use modern l&C in nuclear power plants for system with security function.

The MC SYSTEMS ASSESSMENT REVIEW HANDBOOK and the l&C SYSTEM SAFETY ASSESSMENT GUIDE were delivered as draft versions, and VATESI will develop and introduce them into Lithuanian regulation.

Task 3 — Assessment of INPP ageing management system related to safety

The overall objective of Task 3 was to assist VATESI with technical support and training of Lithuanian TSOs in the assessment of the ageing management programme (AMP) developed by INPP.

The scope of the Task 3 has covered electrical equipment, mechanical components and structures of the pressurised coolant circuit excluding core internals. The main part of the work was performed jointly with Lithuanian TSOs.

Within the Task 3, training was provided to enhance the Lithuanian TSOs' understanding of the ageing degradation mechanisms and limitations in qualified life to different components and the review process, methods of assessments, mitigation measures, prioritising of equipment and safety classification of systems/equipment.

Furthermore, three common position reports were drawn up together with the TSOs, regarding conclusions and recommendations to the VATESI requirements document VD-E-05-99, and the INPP Ageing Management Programme and its effectiveness relating to mechanical and electrical systems/components.

A final "Guide for Assessment of Implementation of Ageing Management Programme for Systems and Components Important to Safety of Nuclear Facilities", was developed/compiled by the TSOs with assistance from the project.

Beneficiary Organizations Details

http://www.vatesi.lt

Project Aims

The primary objective of the project was to improve the Lithuanian TSO's capabilities and to provide efficient support to the nuclear safety authority within the following areas:

• RBMK core safety;
• instrumentation and controls;
• management of ageing

It included both direct support in licensing processes and development of national regulations taking into account the western countries experiences in these fields.

Project Results

The work included comparison/review if international practises and practises within the EU countries.
The work was performed in full agreement with VATESI and the Lithuanian TSO coordination council, regarding the detailed content of the task, selection of cases and policy recommendations. The needed support in each step of the licensing procedure was agreed with VATESI.
Lithuanian TSO's worked together with the Contractors staff within ongoing licensing tasks. The RISKAUDIT guided the Lithuanian TSO's in how to structure the work and lead the scrutinising process. A Lithuanian TSO leader was selected within each technical area. The Lithuanian TSO made the main part of the review and assessment work.. Western experts' main task was to transfer a good reviewer/assessment workmanship approach.
The project practised a step by step approach where a basic capacity was developed within this project and further steps and obstacles are identified. The long-term perspective were taken into account where sustainable TSO capability was in focus.

The budget for this project was 750 000 euro.

Further Project Results

Further information on the project could be sought from the beneficiary organizations.