1 6 th review meeting of the convention on nuclear safety slovenia country group 3 24 march 2014,...
TRANSCRIPT
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6th Review Meeting of theConvention 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
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 ...
... 11. 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 m3/hr, 32 bar2 discharge connections
First actions of the Krško NPP
Fuel (diesel, gasoline) stored on-site
Mobile and portable diesel generators
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
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 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
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.
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
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.
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
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 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,
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 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 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
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 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/pageuploads/si/Porocila/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
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