6th Review Meeting of the Convention on Nuclear Safety SLOVENIA

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6th Review Meeting of theConvention on Nuclear
Safety SLOVENIA

• Country Group 3
• 24 March 2014, Vienna

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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

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Basic information on the national programme
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Nuclear Slovenia
TRIGA
Mine
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Krško NPP

• Westinghouse PWR, 2 loop
• 700 MWe
• Commercial operation since 1983
• Ownership 5050 Slovenia-Croatia
• Without major problems
• Life time extension after 2023 is foreseen
• Intensive post Fukushima improvements

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Other facilities

• TRIGA research reactor
• Central Interim RW Storage
• Former Uranium Mine
• Looking for the LLIW Repository
• gt1000 sources of ionizing radiation

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Slovenia, the smallest nuclear country

• We have everything the big country has
• but we have to manage it with less resources!

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Dynamic period!

• Krško NPP operation was without major problems,
  however ...
• ... 11. March 2011 has drastically changed the
  focus of nuclear safety related activities

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Post-Fukushima activities

• New mobile equipments
• Mobile DGs - 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

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Fire Equipment

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

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First actions of the Krško NPP
30 m3/hr, 32 bar 2 discharge connections
Testing the spraying of the imaginary SFP
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First actions of the Krško NPP

• Fuel (diesel, gasoline) stored on-site

Mobile and portable diesel generators
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Other improvements

• 3rd 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

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Safety Related Diesel Generator
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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.

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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.

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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

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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.

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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 ReviewThe
  regulator should consider requesting to update
  the seismic design basis for future design
  modifications and consequently the associated PSA
  model.

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Post Fukushima Action plan

• Its core is the Krško NPPs 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

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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,

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Krško NPP Safety Upgrade Programme (contd)

• Mobile heat exchanger with provisions to quick
  connect,
• Flood protection upgrade,
• New technical support center,
• Upgrade of existing operational support center.

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Changes in the legislation
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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

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Significant events since the last Review Meeting
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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

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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

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Trip due to the loss of external load

• 23 March 2011 (during Fukushima!)
• Spurious activation of bus protection in the
  NPPs 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

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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.

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Trip due to steam isolation valve stem failure

• Broken MSIV stem

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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.

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• 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

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Action on challenges and planned measures from
the last Review Meeting
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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!

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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!

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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
• SNSAs quality management system,
• An inter-ministerial committee chaired by SNSA
  for coordination of emergency planning
• Communications system used during emergency
  situations

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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.

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Reactor Head Replacement

• Done in 2012!

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Upgrade of Flood Protection and Installation of
New Diesel Generator

• Done in 2011-12!
• 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.

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Upgrade of flood protection dikes

• Plant sitewould remain dry

Upgrade of dikes upstream of the plant to protect
the plant to the flood flows beyond the Probable
Maximum Flood
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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

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The Krško QA System and Compliance with IAEA
GS-R-3

• The latest revision of Quality Assurance Plan in
  2011.
• 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,

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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
• ...

44
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 06-12 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.

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Future Planned Measures to Improve Safety
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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

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Current and Future Challenges
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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

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Questions Raised from Peer Review of National
Report
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Questions from Peer Review

• The complete set of answers to the questions
  raised by other CP is available at the SNSA site
  http//www.ursjv.gov.si/fileadmin/ujv.gov.si/pageu
  ploads/si/Porocila/NacionalnaPorocila/KJV_6th_answ
  ers.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,

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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

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Updates to National Report to the Review Meeting
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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

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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

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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 OP?T (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

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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