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Restart of Unit 2


In view of the importance and volume of the expected licensing activities, the Nuclear Safety Directorate of the Hungarian Atomic Energy Authority (NSD) created a workgroup dealing with the regulatory activities related to the preparation of the restart works of unit 2 of the Paks NPP. The workgroup has set up the safety requirements for the restart. The document takes into account the valid Nuclear Safety Codes, the recommendations of a study prepared by the KFKI Atomic Energy Research Institute (AERI) and the Hungarian Electric Power Research Institute (VEIKI), the conception plan of the Paks NPP, the valid legal rules and the planned modifications. The set of safety requirements is based on the review mission of the International Atomic Energy Agency and comprises 30 items covering all safety relevant factors originating from the special condition of unit 2. It lists in detail those demanded safety assessments and tests that could reveal potential adverse effects of a long-time shutdown period. At present the Paks NPP is planning the restart of unit 2 based on these requirements. NSD has approved an actual yearly refuelling maintenance plan of unit 2, which is in harmony with the requirements. Beyond the actual maintenance works it includes the finishing of the activities interrupted by the serious incident in 2003. NSD approved the onload of core into the reactor after its reactor physics suitability has been demonstrated by the Paks NPP. The normal maintenance works of unit 2 were completed by 1th April 2004 and indispensable cleaning activities and preparatory works for reaching higher operational modes and technological conditions have been started. NSD approved the cleaning program of unit 2 after the amendments that took account of the regulatory comments also. In the course of the cleaning process the reactor pressure vessel and the primary system are cleaned in several consequent phases by the ion exchanger resin bed of the operational water cleaning system. The program implies rigorous control points in the starting and ending of each phase. A report shall be submitted to NSD about each phase of the cleaning program and NSD inspects the performance of the phase. The cleaning cycle is planned to be performed three times. Based on the safety assessments completed so far parameters of unit 2 following the three cleaning cycles will be similar to that of the other units and unit 2 will be ready to restart. On 18th May the Paks NPP submitted a license application aiming at putting unit 2 into operation. The application document comprises the expert’s reports by the Russian Kurchatov Institute Scientific Centre and the Hungarian AERI and also the mandatory independent expert’s report prepared by the Hungarian BME Nuclear Technology Institute validating the restart of unit 2. The Paks NPP demonstrates in detail in its application how the set of requirements for restart is fulfilled. In answer to the request by NSD, the Paks NPP will amend the submitted application taking account the NSD comments. NSD will issue a resolution in mid July provided the application amendment will be submitted in time. For the restart of unit 2 beyond the resolution it will be necessary to put into operation the emergency borating system under preparation at service pool 1 of unit 2 as well as the autonomous systems ensuring the subcriticality and cooling of service pool 1 independently from the operating mode of the unit. Then restart of unit 2 for a 130-day campaign can be initiated in accordance with an elaborated program. The NSD will elaborate detailed inspection plan to control fulfillment of its resolution.