What is the position of SNSA on requiring a Periodic Safety Review comparable to those periodic review processes mandatory in a number of countries in Europe?

The question whether to insert into the new legislation (which is under preparation) a requirement on Periodic Safety Reviews is still under consideration. If a positive decision will be taken the required scope of the PSR programme would follow the IAEA guides and the International experience.

(See also the response to a French question on Article 6 and to a Italian question on Article 7).

Which position do Technical Support Organisations (TSOs) have in the assessment and verification process? What is the qualification assessment process for TSOs?

Based on the 1980 Act the organisations were appointed for giving support to the regulatory body in different fields related to nuclear safety. They are also responsible for assessment and verification of the safety of nuclear facilities. SNSA has developed criteria for qualification and is also performing QA audits in these organisations with the frequency of two years.

Please clarify the following two statements on page 50 of the National Report: Due to that, there is no comprehensive verification that all the aspects are completely, regularly and adequately addressed. As a conclusion, Slovenian regulations and practices are in compliance with the obligations of Article 14?

The conclusion that there is no comprehensive verification that all important safety aspects are completely, regularly and adequately addressed refers to the legislation. Additionally to the NPP Krsko, SNSA has a complete regulatory control over all the safety issues and their applicability and implementation at the plant. Based on this Slovenia does comply with the provissions of the Article 14.

(See also the response to a French question on Article 6 and to a Italian question on Article 7).

PSA study initiated ..... quite extensive plant improvements ....
Are any safety improvement measures already considered in the PSA or reflects the result of CDF = 2.7E-4/ry (see page 11) the situation without the improvement measures?

The overall CDF of 2.7E-4/ry considered the overall CD frequency for the on-power internal/external initiators and average CDF for the shutdown modes of operation for the NPP Krsko. The given result reflects the initial state of the design/plant operation practice of NPP Krsko, e.g. without the implemented improvement measures.

The modifications and improvements in the plant design have mostly resulted from the PSA Level 1/Level 2 study of NPP Krsko, and as such are planned/applied as the backfitt action to the original design after the study has been done.

As the example, the following modifications can be mentioned:

• Separation fixes of the air supply to certain AOVs;
• 125V DC power supply extended capacity (from 2hr to 4 hr);
• IA control air tanks backup modification for important control AOVs;
• AMSAC system modification;
• SW trains raw water filters modification;
• Various small fixes related to the seismic based events (fixations, equipment supports, equipment/components interaction reduction, etc.);
• FP fire area modifications with rerouting, fire barriers and FP system protection annunciation and actuation modifications;
• Rx "Dry cavity" to "Wet cavity" design modification.

Once implemented, which will be the scope of the PSR (Periodic Safety Review) programme in Krsko NPP and which will be the duties of each involved party ?

PSR is not yet required and scope of PSR and responsibilities of each involved party has not been defined yet.

(See also the response to a French question on Article 6 and to a Italian question on Article 7).

The report states that : The licensing process and licensing requirements are defined in the national regulation (the 1984 Act and Regulations E-1 and E-2) covering the aspects of siting, design, construction and operation. The missing requirements are covered by the regulation from the countries of technology origin. What are these missing requirements ? Are they identified in an inventory document ?

Slovenian legislation is complete and is covering most of the requirements in the nuclear energy and safety area. Slovenia however has not developed specific standards, technical criteria and quality norms for the design and construction of nuclear facilities. In the case of Krsko NPP US codes and standards were applied directly as per Section 37 para 2 and 3 of the 1984 Act which allows in such case that technical criteria or quality norms, rules established by international or foreign technical regulations or international and foreign standards may be applied.

Verification

Since the Periodic Safety Review is not yet adopted and despite many analyses and re-assessments performed, the report underlines that a systematic approach was not followed. Consequently, there is no comprehensive verification that all important safety aspects are completely, regularly and adequately addressed. 

Nevertheless the report concludes that Slovenian regulations and practices are in compliance with the obligations of Article 14. Could Slovenia comment ?

The conclusion that there is no comprehensive verification that all important safety aspects are completely, regularly and adequately addressed refers to the legislation. Additionally to the NPP Krsko, SNSA has a complete regulatory control over all the safety issues and their applicability and implementation at the plant. Based on activities and programmes for verification of safety as described in the report Slovenia does comply with obligations of Article 14.

Does Krsko NPP intend to adopt the Periodic Safety Review in a near future ? If not, how Krsko NPP will proceed to identify those of the safety aspects which remain to be addressed ? Has a methodology been established for this purpose ?

Periodic safety review is scheduled to be implemented in the NPP Krsko after the steam generator replacement project is completed.

Control of modifications (this paragraph is included in Article 7)

According to the Slovenian legislation, nuclear facilities are obliged to notify modifications and changes of FSAR to SNSA. The report mentions that the legislation does not define the criteria and procedures for each type of modification. What are the modifications that require an approval by the SNSA before implementation?

Change of plant Technical Specifications, unreviewed safety question (based on safety evaluation), changes in organisation and changes in Plant Emergency Preparedness Programme, require an approval of SNSA. Additionally, SNSA can require licensing procedure for any other modification, if its assessment show that there is a safety impact. Namely NPP sends all planned modifications for screening to SNSA. For changes of the FSAR three categories are recognised in the legislation similar to 10CFR50.59.

Are improvements performed by other countries in similar designs being assessed in a systematic way by SNSA or Krsko, to consider the implementation in Krsko NPP?

Yes, one of the responsibilities of the Independent Safety Engineering Group (ISEG) in NPP Krsko is to follow industry experience according to the Operating Experience Assessment Programme. Industry event reports from various sources (like: United States Nuclear Regulatory Commission (NRC), World Association of Nuclear Operators (WANO), Institute of Nuclear Power Operation (INPO), Westinghouse Owner Group (WOG), vendors, units of similar design, etc.) are screened for applicability and significance for the plant. The Krsko Operating Committee further approves evaluations with proposed corrective actions. Implementation of the corrective actions is further followed until completion.

SNSA is also assessing industry and regulatory experience from other countries, through the IAEA or through direct contacts. According to the results of those assessments SNSA can propose or request solutions for improvements in nuclear safety at the NPP Krsko. A sistematic screening is also performed for USNRC Generic Letters.

Is the risk information being used to ensure adequacy of the NPP maintenance programmes?

The risk information is being used in NPP Krsko in the process of scheduling the on-line maintenance. The information relates to all relevant aspects of risk impact, i.e. instantaneous, temporary and cumulative impacts. Risk information is also used for scheduling the maintenance performed during the outage periods.

Is there a systematic programme, agreed with the SNSA, for the management of ageing and plant life extension in Krsko NPP?

There is no systematic programme agreed with the SNSA for management of ageing and plant life extension in Krsko NPP. However Krsko is participating in the Westinghouse Owner?s Group Plant Life Extension and License Renewal Programmes which will result in such a programme.

It is not clear from the Report, what are the documents that establish/specify the periodicity of NPP safety assessment.

See response to the next question.

It is mentioned that Periodic Safety Review is not adopted yet. Which are the plans for introducing PSR?

The question whether to insert into the new legislation (which is under preparation) a requirement on Periodic Safety Reviews is still under consideration. If a positive decision will be taken the required scope of the PSR programme would follow the IAEA guides and the International experience.

Is there a full time safety review group which reports directly to the plant manager and/or owner of the NPP Krsko?

Yes, the Independent Safety Engineering Group (ISEG) is composed of at least five, dedicated, full-time engineers located on site. Monthly report of ISEG activities including recommendations for the improvement of plant safety and reliability is prepared and distributed each calendar month to the NEK Board of Directors (owner representatives) and NPP Krsko Director General.