What is the approach concerning storage of spent fuel?

Presently the NPP Krsko spent fuel is stored on site in the Spent Fuel Pit with the capacity of 828 positions. End of 1998 530 spent fuel assemblies were stored. Remaining capacity would suffice for the next 5 years of operation. Short term solution for storing the spent fuel is to increase the capacity of the SFP by replacing the existing fuel racks with denser ones. Long term policy is still under consideration.

19.4 Anticipated operational occurrences and accidents

The report states that :?The Krsko NPP has developed and applied the full set of Abnormal Operating Procedures (AOP) and Emergency Procedures (EOP)?. Are these sets of procedures reviewed by SNSA ? Are modifications to these procedures systematically checked during the operator?s simulator training?

SNSA has not performed a complete review of the AOPs and EOPs. The procedures are exposed to continuous verification process through operator's requalification training as well as through continuos WOG EOP programme. Each revision of NEK EOP procedures is first validated on the simulator. This will be further enhanced with the use of new plant specific simulator. Current revision of NPP Krsko EOP is Rev.7. SNSA is approving yearly programme of the operator?s training and auditing the simulator training.

19.8 Radioactive wastes

Information concerning spent fuel storage is missing. Could Slovenia give information on this subject?

Presently the NPP Krsko spent fuel is stored on site in the Spent Fuel Pit with the capacity of 828 positions. End of 1998 530 spent fuel assemblies were stored. Remaining capacity would suffice for the next 5 years of operation. Short term solution for storing the spent fuel is to increase the capacity of the SFP by replacing the existing fuel racks with denser mesh. Long term policy is still under consideration.

What is the granted license time after the commissioning period is completed?

Operating license has no explicit time limitation. Implicitly the life time of the plant is limited by the FSAR, which is a licensing document, by the design lifetime of the reactor vessel 32 EFPY which is estimated to be approx. 40 years of normal operation.

Which is the SNSA review and control process for design modifications being implemented by the operator? Is there an independent review?

All proposed changes to the plant hardware and software are sent to SNSA (in the form of the Change Summary Description and associated safety evaluation document according to 10 CFR 50.59) prior to the implementation. SNSA reviews each proposal and decides whether formal licensing is necessary. If safety evaluation presented by the NPP involves TS Change or unreviewed safety question existence licensing is obligatory.

How is the authorisation process applied when completing major renovations or modifications?

For each of the major changes in the licensing basis documents (Technical Specification, FSAR) the technical basis documents are independently reviewed by authorised organisation. Based on that review independent evaluation is prepared and submitted to SNSA together with licensing application (proposed FSAR, TS changes with technical background documents - analyses, etc.).

(See also response to Spanish question above).

Which is the scope and layout of the emergency operating procedures? How are they verified and validated?

NEK specific emergency operating procedures have been developed based on generic Westinghouse Owners Group EOP procedures. Initially generic procedures have been developed based on Westinghouse engineering simulator verification as well as full scope simulator and other available analytical tools. NEK plant specific EOP procedures have been validated on two loop PWR simulator which have been used for NEK operators requalification training (Kewaunee) at the end of 80s. It has to be pointed out that EOP procedures are exposed to continuo verification process through operator's requalification training as well as through continuos WOG EOP programme. Each revision of NEK EOP procedures are first validated on the simulator. Current revision of NPP Krsko EOP is Rev.7.

Modification activities are important for old and middle age plants to keep their safety and operation capabilities updated. On the other hand it is possible that these activities influence some aspects of the basic concepts in original design.

What are criteria to initiate and implement modification requests in NPP Krsko?
Is there ranking of the requests based on safety or based on any other benefits of the proposed modification?

Who is responsible for approving plant modification based projects and who is involved in verification?

What measures are used to preclude adverse influence of planned modification activity on basic safety concept of the plant and/or on the some part of the plant not being subject of modification?

Criteria

Officially a request for some modification is started through the Initiation of Engineering Evaluation and Assistance Request (EEAR). Request could be initiated by anybody on the plant, however his Superintendent should approve it before release. EEAR is submitted to the Technical Operation Manager who is classifying approved request depend of the kind of the request. E&DC Superintendent who will determine responsible engineer (RE) for the evaluation will review such request. RE have to prepare the evaluation and obtain the concurrence of the proposed solution with the EEAR initiator and System Engineer. After the E&DC Superintendent approval, the proposed solution is presented in a front of Krsko Operating Committee (KOC) which shall give the concurrence to the proposed solution. After such approval the RE will start with development of Design Modification Documentation.

Small problems (low budget) resolutions can be started without the previous presentation in front of KOC, however the final resolution have to be approved by KOC.

Ranking

In the initial phase the EEAR request will be ranked in accordance of the subject of request through following criteria:

• Priority 1A: require immediate action to keep plant running, could have an effect on nuclear safety, require immediate response to a regulatory action.

• Priority 1B: require promptly action due to the procurement related EEAR?s from QA, TO, etc.

• Priority 2A: regulatory or licensing commitment (due date < 1 year).

• Priority 2B: requests for drawing, document, procedures etc change.

• Priority 3: regulatory or licensing commitment (due date > 1 year).

• Priority 4: long term improvement in production, reliability etc.

• Priority 5: preferential request for routine item or activity.

• Priority 6: low priority request (no action just for record).

In addition with ranking (see above) the procedure for the Prioritisation of requests for the Design Modifications will be prepared. This procedure is in the review phase and will be approved in the first half of this year. The intention of this procedure will be to prescribe the uniform approach to the prioritisation of EEAR?s requests from the following prospective:

• Increasing of Nuclear Safety (PSA will be used as a tool)

• Increasing of the reliability (enhancement of operation process)

• Increasing of Safety on Work

• Enhancement of ALARA

• Improvement or enhance of maintenance

• Cost benefit (benefit will be compared with the required estimated costs)

Approval and verification team

In accordance with Prioritisation procedure (in review) the team consisting of Technical, Operation, Maintenance and Engineering Managers will be responsible for the projects start approval. Basically the same group is also currently approving projects. When the Design Modification Package is prepared it is reviewed by several reviewers: System Engineer, Peer Reviewer, other reviewers (ALARA, EQ...), QA and E&DC Superintendent. Each modification should be approved before the implementation also by KOC and by Krsko Safety Committee, if Safety Evaluation was performed for the particular modification.

Influence to the basic safety concept

Modification Process in NPP Krsko is covered by set of Engineering Procedure giving an uniform approach how to prepare particular Design Change Documentation. During the preparing of Design Change Documentation each Responsible Engineer (RE) should prepare a design input document, which define the design inputs, bases and other considerations for particular Design Modification. Procedure ESP-2.604 Design Considerations, Bases and Inputs is giving detail instructions for preparing this document (Design Inputs, DI). After the review of DI and approval the RE can proceed with the design of plant modification in accordance with approved DI. In addition to the DI shall RE complete a Design Impact Evaluation Form to determine whether the plant design modification affects or is affected by key plant design analyses or regulatory programme requirements. If any design documents or drawings are affected and require revision as a result of the Design Impact Evaluation the RE shall identify and revise the drawings and documents.

For each modification also Screening process in accordance with 10 CFR 50.59 have to be performed. During executing of Safety Evaluation and Screening (SES) and (if required) Safety Evaluation (SE) possible influence to the Safety of the Plant should be recognised. Each SES and SE has to be submitted to the Licensing department for approval. After licensing approval each SES and SE are reviewed by KOC and KSC. 

If SE was performed it should be submitted also to SNSA. NPP Krsko has to get approval of SE from SNSA before implementation of modification.