© Forsmarks Kraftgrupp AB
Sweden’s LWR activities
IAEA TWG-LWR meeting Vienna, 18-20 June, 2013
Sekretessklass: Öppen (S1)
2013.06.19
© Forsmarks Kraftgrupp AB
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Contents
• Regulatory activities
• Swedens Post-Fukushima actions
• R & D program - Reactor Safety
• The phase-event at Forsmark 3
• Future Role & Initiatives on LWRs in Sweden
• Proposals for future IAEA-activities
© Forsmarks Kraftgrupp AB
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Regulator activities
• Swedish government requested in 2010 SSM to make a safety
evaluation of the existing plants called ”Investigation of long-term safety
in the Swedish nuclear power industry and measures regarding the
accident at Fukushima Dai-ichi”
• The scope was:
- Compliance and effect of the implemented safety upgrades
- Operation beyond 50 years. Identify necessary safety upgrades.
- Key parameters for long term operation (LTO)
- Evaluation of the Swedish regulatory framework (ie. international bench mark)
- International experience of safety enhancements to allow LTO
- Addition 2011: Fukushima: Stress test, actions taken and further investigations
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| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Conclusions of Regulatory evaluation
1. Needs for further safety improvements:
• Up until 30 June 2012, altogether for the ten reactors’ modernisation programmes, approximately 60 per cent of the decided measures had been implemented to fulfill the requirements in the regulations
• The power plants needs to strengthen resilience against extreme natural phenomena, a loss of power and a loss of main heat sink
• Systems for independent coolant makeup needs to be built
• Protection against sabotage needs to be strengthened further
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| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Conclusions of Regulatory evaluation
2. Ageing management and long-term operation
• Establishment of programmes that effectively detect early indications of safety deficiencies due to ageing
- Special attention to effects that can substantially increase the
rate of embrittlement of reactor pressure vessels for PWRs
- The condition of tendons and steel liners in reactor
containments
- Degradation mechanisms that can influence reactor
containments’ concrete and metal parts
- Possibilities for reliable inspections and testing of reactor
containments
- The validity of environmental qualifications of electrical,
instrumentation and control equipment as well as parts with
polymer construction materials
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| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Conclusions of Regulatory selfassessment
3. Needs for changed regulation and regulatory supervision
• The model stands up relatively well in relation to international standards and practice, but it needs to be developed in various respects
• The results of the IRRS review points out areas for improvements such as regulatory framework, in the form of regulations and regulatory supervision
- The regulatory framework needs to become more comprehensive and be based on international safety standards and European practice
- Define the areas of supervision for which different supervisory strategies are to be developed
|
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Overview Post-Fukushima Actions
• Present investigations to determine measures,
how they shall be implemented and when.
• Investigations to be completed 2013, 2014 and
2015
• Fukushima actions are considered in relation
to other safety upgrades that are in progress or
are planned
• Recognise the importance of strategy for core
melt mitigation
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
New postulated events
New postulated events are needed for the design of back fitting
measures to enhance prevention of severe accidents.
• “Extended Loss AC Power” (ELAP) and “Loss of DC-power”
• Loss of ultimate heat sink (LUHS, total loss of the plants connection to
all sea water sources)
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
Suggested principles for a independent ECCS
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Probability
Consequence
Compensatory measure
Instructions
Mobile equipment
Functions Fixed installations
SAR 4.8
External impact
SAR 4.6
SAR 4.7
Initiating events and accepted consequences
SAR 4.10
Protection against sabotage
Countermeasures
Permanent safety functions
Independent ECCS Mitigating
system
DB Slow sequences BDB
Implemented measures
Further actions
PC2,3 PC4 PC5 Complex sequences (CCF)
ELAP, LUHS
Core mealtdown
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| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 | 10
R & D program - Reactor Safety
Network Issues Partners
NPSAG Risk assessment
PSA, Failure data
SSM, Fortum, TVO, OKG, RAB,
FKA (SAFIR- contact,OECD-
contacts)
NORTHNET Thermohydraulic
In fuel, In-vessel,
Containment
SSM, Fortum, Westinghouse, OKG,
RAB, FKA, KTH, CTH, VTT, (SAFIR-
contact)
APRI Severe Accident SSM,KTH, RAB,OKG, FKA
(SAFIR-contacts, SARNET-contacts)
NBSG Fire prevention SSM, RAB, OKG, FKA
( OECD-contacts)
BWR-club Support
R & D activities
20 different utilities and vendors in
Europe and Japan
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The event at Forsmark 3 2013-05-30
Switchyard FT46 –
400kV for F1 and F2
Forsmark 1
Forsmark 3
Forsmark 2
Switchyard –
FT47 400 kV for
F3
Gasturbine 70 kV
Switchyard - 70kV
Forsmark 3 was
in outage with
external 400 kV
busbars
connected to the
plant
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
The event at Forsmark 3 2013-05-30
400 kV
Maintanance work
on the generator
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
The event at Forsmark 3 2013-05-30
400 kV
Signal to open the
400kV breaker
was sent
unexpected
The reason is
an inaccurate
instruction
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
The event at Forsmark 3 2013-05-30
400 kV
Two out of
three breakers
opens
The reason is
a loose cable
to the 400kV
breaker
tripping device
Pumps for
residual heat
removal stops
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
© Forsmarks Kraftgrupp AB
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
What happened?
• Equipment on safety and non-safety busbar with protection for “phase-disconnection” stopped
automatically. This includes the pumps for residual heat cooling. Electrical machines lacking protection
for “phase-disconnection” did not stop and some of them got minor damages.
• The under-voltage protection on the diesel busbar did not measure < 65 % voltage with only one phase
connected (the internal voltage is above 65 % due to the generator step-up transformer coupling.
- No automatic signal to start the Emergency Diesel Generators (EDG) on any trains
• Operators separated manually the safety busbar from the external grid (opened the breakers).
- The load on the busbar was automatical disconnected and protection safety device was manual
and automatic reset and the EDG:s started as expected and energized the safety busbars
• The residual heat cooling was in operation after 16 minutes
• Analyses shows that there was time in the day scale to restore cooling before start of boiling
© Forsmarks Kraftgrupp AB
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Future Role & Initiatives on LWRs in Sweden
• Modernisation aim at 50 -60 years life time of Swedish
plants
- New regulations to support licensing of new reactors
- New strategy for the regulatory work
- Safety enhancements to support Long term Operation
• Actions after Fukushima
- Power supply: Improved reliability (grid, gas turbine etc)
- Spent fuel pool cooling
- Independent core cooling
- Handle events with all units affected
© Forsmarks Kraftgrupp AB
| Sweden's LWR activities | Patrik Svantesson | 2013-06-19 |
Proposals for future IAEA activities
Identify new events outside design base
• Support member states to achive better understanding of not yet fully
assessed events
- Experience shows that the events that occurred in reality is often a
complex combination of events that not have been foreseen.
• Create methods to combine probabalistic and deterministic safety
assessments by comparing differences and similarities between
member states
- Support development of methodologies to identify critical complex
event scenarios by dynamic PSA or other methodologies
- Increase benchmarking between countries on identificaion of critical
complex scenarios (Benchmarking of PSAs and FSAR)