Hungary in the mid of ’90-s introduced the concept and obligatory of the periodic safety review (PSR) for its nuclear facilities. The Paks NPP successfully finished the first PSR in two steps (for units 1&2 in 1995-1997 and for units 3&4 in 1998-2000).

The paper outlines the following essential topics:

• International background of the PSR, mean features.
• The Hungarian legal framework.
• General schedule of the national safety review/report activities.
• The 50-SG-O12 IAEA Safety Guide, as the basis of the Paks PSR.
• The safety factor concept and the principal areas of the review.
• National guidelines (importance of the guidelines, goals, regulatory requirements, scope, procedure, documentation).
• The PSR execution process (preparation, performing at the NPP, communication with the authority during its assessment, possible post-PSR activities).
• Team organization and computer support.
• PSR work volume indicators (effort, manpower, estimated cost).
• The most important results of the PSR according to certain safety factors.
• Corrective actions (number, content, priorities and deadlines of safety improvement).
• Utilization of PSR results.
• Public information about the PSR.
• The Hungarian PSR and safety improvement experience response in the world.

The Paks Nuclear Power Plant is the only NPP in Hungary. The NPP consists of 4 units, type VVER-440/V-213 (second generation), which were put into operation between 1982 and 1987. The Paks NPP successfully finished the first PSRs in two steps (for units 1&2 in 1995-1997 and for units 3&4 in 1998-2000).

The PSR concept started its development 30 years ago:

1970-1985	Several IAEA member states are introducing comprehensive PSR
1974	Launch of the NUSS (Nuclear Safety Standards) program by IAEA
1978-1986	Issue of about 60 safety guides…
-1988	… and their review and modification
1991	Conference on Nuclear Safety in IAEA “Strategy for future”.  The periodic safety review concept getting international support.
1994	Issue of the Periodic Safety Review of Operational Nuclear Power Plants, Safety Series No. 50-SG-O12

• systematic safety reassessment of an operational NPP in regular (near 10 years) intervals,
• to get an overall picture about the unit nuclear safety,
• to deal with cumulative effects of plant aging, modifications, operation experience and technical developments.

In Hungary first it was the decree of minister in 1993 that required the performance of PSR for nuclear installations. The PSR for Paks NPP 1&2 units in 1995-1996 has been performed in accordance with this decree. The new Act on nuclear energy entered into the force at 1997. This Act and the related regulations already contain the obligation of performing PSR, including as well the main conditions of its accomplishment. That was the legal background for PSR of Paks NPP 3&4 units in 1998-1999. In both of cases the role of PSR within the plant licensing was the same and essential: the review procedure is to be the basis for the renewal of the permanent operation license.

In the Table 1. one can see, how the PSR fits into the middle range general schedule of several safety review/report activities at Paks NPP. The Preliminary Safety Analysis Report (PSAR) called that time SAR Before Construction, and the Final Safety analysis Report (FSAR) called SAR Before Startup.

The national AGNES (Advanced and General New Evaluation of Safety) project was the most important precursor for the PSR. Its original aims could be summarized as follows:

• a state of the art report on the reassessment of the nuclear safety of Paks NPP,
• those deterministic analyses of design basis accidents and severe accidents as well as probabilistic analyses should be carried out that are necessary for the preparation of the report,
• the priorities of safety enhancement measures should be determined,
• preparations for elaborating an up-to-date safety report should commence.

Since 2001 the yearly update of the FSAR is obligatory.
 

Unlike other countries starting the PSR earlier, Hungary had a very good opportunity in 1994 to use the brand new, just issued IAEA Safety Guide. This guide has been generalized several approaches. On the basis of this 50-SG-O12 document Hungary developed its own national guidelines, and carried out the review itself.

According to the IAEA Safety Guide a comprehensive assessment of overall plant safety is a complex task. It can be facilitated by dividing it into a number of elements. These are the so called safety factors, covering with certain favorable overlapping all important aspects of the nuclear installation safety.

For the units 1&2 of Paks NPP the PSR included nine principal areas, or safety factors. In fact that was a subset of the full eleven safety factors suggested by the appropriate IAEA Guide. The reason of missing of two factors originated in the those days valid Hungarian licensing task and responsibility distribution. The former nuclear regulatory body wasn’t responsible for all areas, so they limited the scope according to their competence. By the time the re-regulation and partial reorganization of the Hungarian nuclear authority have been taken. An important novel addition in comparison to the previous approach in PSR for the units 3&4 of Paks NPP was that the scope of the review has been supplemented by the two additional areas. Now the scope of the PSR is fully identical to IAEA recommendations.

The eleven safety factors are:

1. the actual technical condition of the installation,
2. the qualification of the equipment,
3. safety analyses,
4. aging management,
5. the evaluation of the characteristics of safe operation, and utilization of own operational experience,
6. utilization of operational experiences of other facilities, and the achievements of research and development
7. regulations (procedures)
8. organizational and administrative factors,
9. human factor,
10. analysis of environmental radiological effects,
11. prevention of nuclear accidents.

The required periodicity of PSR in earlier legislation was 12 years. The current figure is 10 years, which has better match with the international good practice.

As it was mentioned already the overall philosophy and scope of the Hungarian PSR have very good correspondence with the international recommendation and national rules. At the same time in the procedures themselves there are some differences.

One of the most characteristic features of the Hungarian PSR is the strong national guideline issued by the regulatory body prior to the execution of PSR. It is a 50-70 page document, describing all important conditions of the review, giving clear requirements, preventing later misinterpretation between the licensee and authority. The preparation, consultations and issue of such a document requires a great deal of work. Nevertheless it is worth the effort, because the good quality and detailed guideline makes the tasks very clear, decreases the need for the intensive communication between the two parties during the performance of the review..

These documents were: The Guidelines for Periodic Safety Review of Paks NPP 1&2 units (Supplement to Decision RE-1498 of Nuclear Safety Authority Inspectorate from 15 August 1995) and Paks NPP 3&4 units (Supplement to Decision RE-2086 of Nuclear Safety Directorate from 9 June 1998). The main aspects addressed in these guidelines were the following: goal, legal background, technical basis, reference documents, scope, schedule and reference basis (the plant state and snapshot of ongoing activities at the given date), basic principles and responsibilities, safety factors (for every safety factor requirements derived from domestic and modern international safety regulations and requirements to the review content), procedure, list of post-PSR activities and documentation of PSR.

The practical steps of PSR execution process at NPP, as an outcome of the guideline and the general project management rules are as follows:

a) Preparation phase

• study of requirements, guides and recommendations, other plant PSR activities,
• planning (general economic and manpower planning),
• development and issue of NPP CEO’s decree and QA program, PSR team building,
• methodical studies, training, trial activities (only for selected safety factors), search for data sources, development of detailed content (3-4 decimal levels),
• splitting and delegation of tasks, scheduling, taking into consideration of parallel activities in working groups, allocation of manpower among working groups,
• establishment of the computer support (hardware, software),
• contracts with external TSOs, bonus awards to team members.

• compilation of certain parts, working group meetings, editing of the draft,
• tracking of progress of team work, progress reporting to plant Technical Council, solutions of conflicts in task delegations and delays,
• audit of the PSR team QA activities,
• editorial commission sessions of ready drafts for each safety factor, internal and external independent review of the draft (for example: consultation with the WANO follow-up mission members on internal regulations and procedures),
• final corrections, layout, printing, bookbinding, archives, preparation of the chapters on magnetic data carrier, submission to the regulatory body.

• receipt and elaboration of the regulatory body preliminary comments, consultations
• regulatory body final decision (with conditional renewal of operating license),
• grouping and prioritization of the corrective actions,
• updates and modifications following the regulatory body comments, issue of the 2^nd edition on paper, CD-ROM,
• submission to the regulatory body, attestation clause to be made by regulatory body, preparation of summary for the public,
• file translation into HTML intranet format, setup of the PSR intranet application,
• performance of the postponed with permission of authority parts
• prioritizing, splitting and allocation of the corrective actions, execution of the scheduled corrective actions, follow up the progress of the corrective actions reporting the fulfilled corrective actions to the regulatory body.

All the PSR activities have been fulfilled at the plant by a two level team. The upper level of the team incorporated all responsible persons for the every safety factors. Review made by working groups and resulted separate chapters in the documentation. On the lover level of the team were the working groups Several staff took part not only in one working group, which in limited cases leaded to conflicts and needed coordination.

All the documentation (not only the text but the graphics part too) have been prepared on computers. In the QA paper of the team have been fixed the editor program, version, the valid digital picture formats. For the exchange of the written drafts the participants intensively used the plant LAN. The team disposed dedicated file server and the team leader was the supervisor of this server. He organized a file directory system according to hierarchy of the team. Every team member had an individual directory with full rights. One level higher the working group leaders were maintaining the chapter directories. The other team members in this directories had only rights for reading. The communication among team members was mainly electronic too, using notice boards on the network and e-mails. All the files of the project every day moved into the backup. This rules and tools nowadays are already commonly used, but for the Paks NPP it was the first big computerized document preparation session, started 6 years ago.

At the NPP some 200 operation, maintenance, technical support etc. engineers and technicians worked in the PSR team, aside their everyday tasks. The portion of involvement for each person was varying in a broad range (2-60% of their work time). The overall documentation size made for a twin unit PSR was about 7000 printed pages.

The round cost of performing the PSR was about 1 million USD for a unit, resulting in 4 millions for the whole plant. In this estimation several facts shall be taken into account:

• The AGNES project previously carried out approximately for 2 million USD (with less then 10% external aid). The PSR mainly utilized and partly updated the project results.
• Because of this except of special safety analysis calculations the PSR has been performed mainly by the NPP personnel itself. The major part of the work was the reconfiguration of the existing at the plant records into the formats required by the PSR and the evaluation of the collected data.

According to siting the team identified only 2 changes requiring re-evaluation and separate actions: the extremely low water level of Danube river, and the seismic risk. The actual technical condition of the installation found good. The equipment qualification showed in 84% suitable, in 11% partly suitable and in 5% non-suitable results. The main areas of safety analysis shown in the Table 2. There were no unknown or new major safety issues, nevertheless there were a need for many significant improvements. In the aging management the review detected shortcomings in uniform treatment and common methodology. The safety performance was generally good. The PSR showed also the importance of the regular invitation of international safety missions. The internal regulation in general worked well at the NPP, but in several fields there was over-regulation. Important issue is to introduce the symptom oriented EOPs. The organization and administration needed some improvement. The training of the personnel was appropriate, but it was necessary to maintain the staff aging, and preparation of the replacement. The radioactive releases to the environment was pretty low under the limits. Some problems could be meet in waste storage if case of delay of the national repository. The emergency preparedness organized well, but further analysis of certain severe accident scenarios and introduction of new accident management procedures were necessary.
 

The process for addressing main issues and necessary corrective actions was based on safety significance. Usually the PSA (contributions to the core damage frequency) helped to make decision about the priorities. The safety upgrading modifications should be scheduled according to time needed for the project and licensing activities, and outages.

As a result of PSR the licensee itself suggested corrective actions, and the authority prescribed them with a slight modification of the list of measures and priorities. The number of corrective actions by safety factors for units 1&2 were 12+13+17+5+8+6+5+ 8+10 (licensee) +14 (regulator), the same figure for the units 3&4 is 13+7+11+9+0+1+0+0+3+1+9 (licensee) + 29* (regulator).

The following priority groups made by authority:

• highly important - 23 / 15 items (the delay in carry out suspends the license),
• important - 12 items / 50* items (no influence to the operation license),
• others - 63 items /18* items.

The measures can be grouped by content as administrative (organizational consequences, partial renewal of internal regulation, training activities), and technical (further analyses, hardware modifications).

The Table 3. shows the major safety improvements and their schedule. Due to the measures implemented, the safety of the units was significantly increased. The risk of core melt-down - that is the most characteristic safety indicator of nuclear power plant units - has been reduced by an order of magnitude.
 

On one hand to carry out the PSR needs substantial effort and it is a long and costly task. On the other hand the PSR results should be utilized several ways. The benefits for the licensee are the following. The PSR is first of all a necessary instrument for license renewal. It requires the update of the all relevant technical documents (what is very significant from the point of view of the training and education), it is a good tool for identification of the safety upgrading priorities and basis for the management investment decision. The documents can be used also for the International Safety Convention national report preparation. Generally the PSR gives higher confidence in safety to general public and in international level.

PSR also helps for the regulator by its comprehensiveness, systematic approach and good documented character. The review provides a legal framework for the accomplishment of the necessary measures, gives good opportunity to find the most significant ways for maintaining of the plant safety.

The new Act about the nuclear energy states: “The safety of nuclear facilities, adherence to safety requirements and the level of risk shall be fully analyzed and evaluated, and the results shall be made public by the licensee and the regulatory authority…”

For that purpose a short (20 pages) summary of the PSR have been prepared about the goals, content, methodology and main results for the plant visitors and the general public. Attention have been taken to use of simple language as well to avoid the special terminology. At the plant site and authority headquarters for interested persons the organized access is available – if necessary, conducted with explanations – to all PSR documentation. The key points are: to assure such public access to the documents which requires certain effort from the interesting people (e.g. not to put the full reports on the internet); to give all the documentation, but to give it only in case of explicit request to reduce the possibility for misinterpretation and misuse; to make possible written notes, but not to allow to photocopy the content.

Our assessment was the foremost full PSR for VVER type (soviet planned PWR) plants, and we were among the firsts who almost fully followed the IAEA guidance. The IAEA recognizes our effort, and in recent years is inviting our experts as lecturers to many regional workshops (in Czech Republic, Hungary, and China) to present our experience. Last March we contributed at advisory group meeting on PSR in Vienna. It is very honorable for us that the Korean experts are interesting too. In October of 2000 we received a Korean delegation investigating our PSR in Hungary. It is very grateful to present our paper in this conference and consult with experts in Korea.

The Western European Nuclear Regulators' Association (WENRA) is representing the heads of the nuclear regulatory authorities of Western European countries with nuclear power plants. In their last October assessment “Nuclear safety in EU candidate countries” they gave the following status about Hungary: “The regulatory regime and regulatory body in Hungary are comparable with Western European practice. A well-defined licensing process according to Western practice is in place.” Regarding to Paks units 1-4 (VVER-440/213) they diagnosed: “A major safety improvement program has been implemented at Paks units 1-4, bringing these units to a safety level that is comparable to that of Western European reactors of the same vintage.”

The Hungarian Nuclear Safety Directorate as the result of PSR conditionally extended the permanent operating licenses of the affected units for the next 10 years. The conditions are the scheduled implementation of the identified and prioritized safety improvements.