Aftermath of the INES-3 Incident at Paks NPP on 10th April, Lajos Vöröss Hungarian Atomic Energy Authority 7th Annual Meeting of NERS IAEA, Vienna, 23-24, September 2004.

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3 Main Tasks to Perform After having stabilised the situation inside the reactor hall there have been two main tasks to perform: 1. Recovery of service shaft No.1 of Unit 2. (SS) where the incident occurred 2. Restart of Unit 2. as soon as possible

4 - Recovery project and team established at Paks NPP - Tendering process won by Russian consortium led by TVEL; FRAMATOM had bidden as well months preparatory, 2-3 months implement phases planned, excluded licensing time - significant delay now - Special tools for manual removal of debris are to be used - Manipulation is to be carried out from a movable platform placed above the cleaning tank - Some experiments to clarify behaviour of debris for planned removal actions performed Recovery of SS

5 Recovery outline – FRA / GER crane air filter manipulator working rod suction control panel container cleaning tank 2 versions removal of the cleaning tank and fuel in one step (dismissed later – difficult, does not give final solution) removal of the cleaning tank and fuel in parts with clips, bending tools, manipulators, vacuum soakers, cutters

6 Recovery outline – RUS shell container different - water level, - boron concent- ration, - contami- nation ГИ ВНИПИЭТ ГП НИКИМТ ПО Маяк НПФ Сосны structure winner mostly manual removal moving platform

7 - Separation of SS from spent fuel pond and from other systems of Unit 2.became necessary - Autonomous cooling device and emergency boron injection system for SS have been installed - Mobile water cleaning device (NURES,Finland) was used to clean the water especially from the uranium and trans- uranium isotopes Recovery of SS (cont’d)

8 - Reliable neutron flux and boron concentration measurement in SS installed - Increased radwaste storage capacity constructed - Free positions made available for capsules/cartridges containing debris in spent fuel pool - Preparatory actions for regulatory licensing process - regulatory requirements for recovery developed - review and assessment in large number of modifications and fabrication of equipment performed

9 Restart of Unit 2. - After long-term shut-down status with intact main equipment but contaminated by uranium and trans-uranium isotopes - special cleaning was necessary (completed) - Interrupted refuelling and maintenance occurred during the incident - RPV used as temporary storage tank of spent fuel assemblies - Low enrichment fresh FE supply and rearrangement of spent fuel pool became necessary - Reuse of cleaned spent fuel assemblies is limited

10 Restart of Unit 2. (cont’d) - C onception for short term operation cycle developed - refuelling and yearly maintenance completed - suitable core for operation during the preparatory phase of the recovery is possible (about 4 months long) - regulatory requirements for restart/operation phases developed, licence given on 16. July, nearly full power operation started on 02 Sept Keen interest from media and public follows

11 International Assistance - IAEA - two international missions provided at Paks NPP - GAN (Russian Regulator) - on basis of contractual arrangement, focuses to review QA of Russian contractors - US NRC/IAEA - gives advice to review conditions of restart of Unit 2. NOTE: In spite of the incident, lifetime extension and power uprating of the units are still insisted on