National Report of the Slovak Republic - Radiation and Nuclear Safety , September 1998

4.5.6 ÚJD Requirements with Respect to NPP Mochovce WWER 440/V-213 Reactors Safety Upgrade

The construction of the nuclear power plant Mochovce started in 1984 when the former Czechoslovak Atomic Energy Commission (CSKAE) approved, by Resolution No 23/1984, the issuance of the building permit for NPP Mochovce, based on a review of the safety documentation pursuant to Act No. 28/1984 Coll.

The construction of NPP Mochovce was suspended in 1990 due to unclarified issues concerning the instrumentation and control system and also due to lack of funds needed for the completion of the construction. The construction of the two first units was resumed in 1996 offer both above mentioned difficulties have been resolved.

After 1989, NPP Mochovce used own means and assistance of international expert missions to make a number of steps to reassess the safety of the original NPP design.

Several international missions were invited to NPP Mochovce since 1994 to review the nuclear power plant safety level. The document "Technical Specification of Safety Measures" (TSSM) was developed based on the recommendations of the international expert missions (IAEA, Riskaudit, EDF) in 1995. The document has become a basic reference for the development of the safety upgrade program for NPP Mochovce. Terms of Reference for design amendments have been developed based on TSSM, and they are expected to be implemented even before the commissioning of the NPP. The amendments mainly concern design adjustments in response to the most serious faults identified upon the safety review of the original project.

The numbers of measures included in TSSM (87) corresponds to the numbers of measures stated by the IAEA document "Safety Issues and their Ranking for WWER 440, Model 213 NPPs", IAEA-EBP-WWER-03. All the measures suggested by Riskaudit have been included in the 87 measures which represent a more comprehensive understanding of the safety level. The difference in the numbers of measures shown in Riskaudit report and TSSM is due to a different structure of both materials. The TSSM document, similarly as that of IAEA, distinguishes between three categories of safety upgrading measures based on their safety relevance.

The role of ÚJD is to assess the level and the status of the NPP safety and the degree to what the NPP meets the requirements and recommendations of the national and/or accepted international regulations and instructions. Based on such a review, ÚJD approves the license to be issued by the Building Authority (District Environmental Office).

ÚJD has consistently monitored and reviewed the implementation of safety upgrading measures since the time of their formulation. Operator is responsible to submit monthly reports on the implementation of those measures. With respect to category three measures (there was no category four) measure which are not fully realized prior to the start of operation, ÚJD shall require satisfactory substitutional measures to be taken prior to the start of operation. Such substitutional measures shall be assessed and controlled by ÚJD. All the original measures aimed at safety upgrading shall remain a precondition for approval of commercial operation. In other words, any category 1 measures, even if of less safety relevance, will have to be implemented by or during the first fuel reloading on unit one.

The most comprehensive review of the implementation level of safety-related measures was conducted by ÚJD prior to the approval of the first fuel loading. Another comprehensive review was performed prior to approving the commercial operation.

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