1 6 th Review Meeting of the Convention on Nuclear Safety SLOVENIA Country Group 3 24 March 2014, Vienna

Outline Basic information on the national programme Changes in the legislation since the last Review Meeting Significant events since the last Review Meeting Action on challenges and planned measures from the last Review Meeting Current Challenges Questions Raised from Peer Review of National Report Updates to National Report to 6th Review Meeting Conclusions

Basic information on the national programme

Nuclear Slovenia NPP Krško TRIGA Mine

Krško NPP Westinghouse PWR, 2 loop 700 MWe Commercial operation since 1983 Ownership 50:50 Slovenia- Croatia Without major problems Life time extension after 2023 is foreseen Intensive post Fukushima improvements

Other facilities TRIGA research reactor Central Interim RW Storage Former Uranium Mine Looking for the LLIW Repository >1000 sources of ionizing radiation

Slovenia, the smallest nuclear country We have everything the big country has … … but we have to manage it with less resources!

Dynamic period! Krško NPP operation was without major problems, however March 2011 has drastically changed the focus of nuclear safety related activities

Post-Fukushima activities New mobile equipment’s Mobile DG’s - various power (from 3 KW up to 2 MW) Mobile Air Compressors Mobile FP pumps Stress tests and National Action Plan Long term improvements:  Comprehensive Safety Upgrade Programme: Filtered Containment venting – implemented Passive Autocatalitic Recombiners – implemented Additional SI and FW pumps – by 2018 Additional heat sink – by 2018 External control room – by 2018 Dry spent fuel storage – by 2018

Fire Equipment Fire truck with a hydraulic fire-fighting arm Tanks: 8500 l of water & 1500 l of fire-extinguishing foam

First actions of the Krško NPP Testing the spraying of the “imaginary SFP” 30 m 3 /hr, 32 bar 2 discharge connections

First actions of the Krško NPP Fuel (diesel, gasoline) stored on-site Mobile and portable diesel generators

Other improvements 3 rd safety related diesel generator  Reduces risk primarily from the Station Blackout Sequence and from seismic events Upgrade of flood protection dikes.  Protects against more demanding Probable Maximum Flood Reactor pressure vessel head replacement  In response to industry events involving Alloy 600 penetrations and 82/182 weld material

Safety Related Diesel Generator

Other developments Aging management programme approved  It makes operation after 2023 possible  One more Periodic Safety Review have to be done before first 10 year life extension Second Periodic Safety Review is concluded, to be approved by June 2014 KI iodide tablets distributed in 10 km radius around the Krško NPP.

Improvements in the plant Replaced main generator rotor Upgraded of 400 kV buses and undervoltage protection Replaced main feedwater isolation valves actuators Upgraded fire protection detection system, Refurbished residual heat removal and essential service water systems.

Post Fukushima actions Operator immediately started with improvements The SNSA issued three decisions to the Krško NPP:  to perform an extraordinary PSR in line with specifications for European Stress Tests  to reassess the severe accident management strategy and implement safety improvements for prevention of severe accidents and mitigation of its consequences  to review bases for emergency planning and response including emergency planning zones

Stress tests analyses Evaluation of seismic and flooding margins, Additional station blackout analyses, Drain cycle of the 1E batteries, Water heatup and evaporation rate in the spent fuel pool, Evaluation of spent fuel pool criticality.

Stress test conclusions Krško NPP was well designed and constructed, Potential external events were taken into account during preparation of protective and mitigating measures. A single recommendation after Peer Review: “The regulator should consider requesting to update the seismic design basis for future design modifications and consequently the associated PSA model.”

Post Fukushima Action plan Its core is the Krško NPP’s Safety Upgrade Program Implementation of upgrades foreseen already in 2009 Implementation of Short-Term Improvements (accelerated B.5.b Requirements Actions):  Procurement of AC diesel generators, pumps and compressors, implementation of quick connection points for this equipment, additional fire protection equipments, including high capability fire truck  Amendments to the emergency operating procedures and severe management accident guidelines

Krško NPP Safety Upgrade Programme Safety upgrade of AC power, Additional FW pump, Additional heat sink (AHS), Additional SI pumps with a dedicated water supply, Containment filter vent system and passive autocatalytic recombiners, Emergency control room, Fixed spray system around the spent fuel pit,

Krško NPP Safety Upgrade Programme (cont’d) Mobile heat exchanger with provisions to quick connect, Flood protection upgrade, New technical support center, Upgrade of existing operational support center.

Changes in the legislation

Changes in the legislation since the last Review Meeting New Act on Liability for Nuclear Damage issued Amendments of the Act on Ionising Radiation Protection and Nuclear Safety comprising:  requirements of Nuclear Safety Directive,  the restriction of the right to go on strike,  provisions on physical protection,  duplications in the area of radiation practices,  availability of inspectors and professional officers, etc. Resolution on Nuclear Safety

Significant events since the last Review Meeting

Events in the Krško NPP Activation of false alarms in the seismic monitoring system, Inoperability of the service water system, Trip of auxiliary feedwater pump, Inoperability of Chilled Water System, Reactor vessel head cable bridge incident, Extensive fuel damage

Reactor shutdowns Reactor trip and safety injection actuation system due to the loss of external load Main steam isolation valve stem failure Shutdown due to large amounts of debris in the Sava river Malfunctioning of primary temperature measurement system

Trip due to the loss of external load 23 March 2011 (during Fukushima!) Spurious activation of bus protection in the NPP’s 400 kV switchyard, Rapid pressure decrease in the main steam line, Safety injection (SI) signal on low steam line pressure, Diesel generators started automatically, No other problems

Trip due to steam isolation valve stem failure 25 February 2013 Sudden closure of main steam isolation valve (MSIV) – valve stem break, Increased steam flow in another line resulted in pressure drop actuating the safety injection system and the reactor trip, Similar event occurred 1997, Replacement and redesign of MSIV.

Trip due to steam isolation valve stem failure Broken MSIV stem

Shutdown due to debris in the river 28 October 2012 The flow of the river Sava rose very rapidly High river washed down materials from river banks, The inlet of the condenser cooling system was clogged, Condenser cooling water flow was reduced, Temperature and pressure in the condenser increased and vacuum in the condenser deteriorated. Operators carried out manual preventive shutdown of the reactor.

Trip due to the malfunctioning of the primary temperature measurement system and Extensive fuel damage See last part of this presentation with updates to the National Report

Action on challenges and planned measures from the last Review Meeting

Problems of domestic TSOs – Reliance on foreign TSO Not all technical aspects could be covered by domestic Technical Support Organizations (TSOs) Operator is seeking expertise from anywhere Reducing number of domestic experts No systematic support to nuclear fission related research, experts are growing older... Challenge remains!

Financial and Human Resources for the SNSA SNSA is financed only by the state budget, Due to the crisis funds are decreasing, No new employments! SNSA had to abandon ISO9001 certification SNSA is fulfilling its mission, but has already publicly announced what risks are increasing due to restrictions Challenge remains and is growing bigger!

IRRS in 2011 Between 25 September – 4 October 2011 The SNSA Strengths  Adequate legal framework  SNSA has in place an effective process for carrying out this responsibility,  Response to the accident at the TEPCO Fukushima Daiichi power plant has been prompt and effective. Good practices  SNSA ’ s quality management system,  An inter-ministerial committee chaired by SNSA for coordination of emergency planning  Communications system used during emergency situations

IRRS in 2011 A need to develop a national policy and strategy for nuclear safety - done Possible alternative methods of financing SNSA – decided not to go for independent agency! SNSA needs competencies and resources – see previous challenge Necessary steps to be taken for the Low and Intermediate Level Waste Repository – SNSA has actively pushed for it, some progress Transition between the emergency phase to long term recovery operations and the post-accident phase,... and some others.

Reactor Head Replacement Done in 2012!

Upgrade of Flood Protection and Installation of New Diesel Generator Done in ! Flood protection  Upgrade by up to 1.8 meters of flood protection dikes along the river Sava.  Seismic criteria the same as for the Krško NPP  Safety margin of 0.75 m. Third Diesel Generator Class 1E 3.5 MW diesel generator Increases safety in case of a seismic event and loss of offsite power.

40 Upgrade of flood protection dikes Plant site would remain dry Upgrade of dikes upstream of the plant to protect the plant to the flood flows beyond the P robable M aximum F lood

Harmonization of Legislation with Good Practice in EU WENRA Reference Levels are fully transposed into Slovenian legislation, Slovenian legislation is harmonized with the EU Nuclear Safety Directive and EU Nuclear Waste Directive

The Krško QA System and Compliance with IAEA GS-R-3 The latest revision of Quality Assurance Plan in In line with Slovenian Rules JV5 and IAEA GS-R-3 requirements Covers Safety Culture, Self-Assessment, Human Performance, Industrial Safety The bases for the revision were:  Changes of the Slovenian regulatory requirements and licensing documents,  SNSA inspection requirements,  Changes of international standards,  Conclusions of the first PSR,

PSR 2 to be completed in 2013 PSR2 was completed There were no major issues which would prevent further safe operation 15 safety factors were reviewed An action plan is being developed and will be implemented in the next 5 years. Some issues from the action plan: Procedures periodic review Root cause analysis Temporary modification survey Generation of solid radioactive waste Potential tube wear from secondary side loose parts...

Cyber Security Threats and Airplane Crashes Krško NPP has prepared and implemented Cyber Security programme SNSA has trained its people Airplane Crashes  No-flight zone in place around the NPP Krško  NEI B.5.b requirements was one of the inputs to post Fukushima action plan and those consider also airplane crash  Bunkerized structures for DG3 and future safety equipment  Alternative Spent Fuel Pool cooling system,  Fire fighting of airplane fuel fires capabilities  Improved SAMGs.

Future Planned Measures to Improve Safety

46 Future Planned Measures to Improve Safety Most of those measures are within the Safety Upgrade Programme (see post-Fukushima related slides) Upflow conversion in the reactor vessel Improvements in off-site emergency planning together with Croatia Inviting peer review missions:  WANO, IRRS-FU, OSART, EPREV

Current and Future Challenges

Challenges Individual actions of the Safety Upgrade Program as well as other National post- Fukushima Action Plan (NAcP), including Design Extension Codition (DEC) implementation Reassessment of alternative spent fuel strategy (part of NAcP) Preservation of knowledge and competencies:  Financial and Human Resources of SNSA  Domestic TSOs

Questions Raised from Peer Review of National Report

Questions from Peer Review The complete set of answers to the questions raised by other CP is available at the SNSA site: NacionalnaPorocila/KJV_6th_answers.pdf NacionalnaPorocila/KJV_6th_answers.pdf Questions were evenly distributed among articles, with the exception two:  “regulatory body”: the decreasing SNSA budget, challenge to keep competency due to small nuclear programme, ageing of the SNSA staff, sharing information to the public of the SNSA activities  “assessment and verification of safety”: PSA, PSR, SAMG, response to Fukushima, performance indicators,

Questions from Peer Review The other questions referred to.  Post-Fukushima upgrades (plan and status)  Management system of the licensee  Emergency preparedness in Slovenia and Croatia and review of emergency plans in the light of Fukushima  Incident reporting system by the operator  Assessing safety culture  Transparency and communication to the public by the licensee

Updates to National Report to the Review Meeting

Fuel leakage and cladding failure Discovered during outage in October 2013, Six fuel assemblies were leaking, 50 cm long segment of the fuel rod found in the fuel transfer channel

Fuel leakage and cladding failure Open defects in 8 fuel rods of three fuel assemblies, Primary cause debris fretting, baffle jetting and grid- to-rod fretting Extensive inspection of fuel assemblies and the core baffle plate Corrective action: armoring of fuel assemblies with dummy stainless steel rods at exposed positions Prior to the start of operation an extended Failed Fuel Action Plan was prepared

RTD – Spurious electrical signals caused reactor trip Resistance Temperature Detectors Bypass was eliminated during outage 2013 After the outage signal “spiking” caused reactor trip due to creation of OPΔT (for a split second) Corrective actions:  Installation of “surge suppressors”  Some equipment was tagged out until the problem was resolved  The vendor will analyze lead/lag filters used in processing the signals and redesign appropriate circuits

CONCLUSIONS The only NPP operating safely Slovenia has Legislative System harmonized with best practices Regulatory Supervision is efficient and effective, although the risks due to lack of resources are increasing Slovenia and its Nuclear Facilities fulfill requirements of the Convention on Nuclear Safety