Download - 2 NTW - Safety Assessment of Ageing
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Safety assessment ofnuclear reactors ageing
Frederic Menage
NTW - Exploratory workshop
"Ageing of nuclear power
plants: a threat to nuclearsafety? "
19thMarch 2014
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Who is IRSN?
IRSN, Publicassessment
Research
into risks
Stakeholders(CLIs)
THE PUBLIC
Operator
Designers and constructors
Publicauthorities
Parliament
ASN, ASND
Supreme Committee for Transparencyand Information on Nuclear Safety - HCTISN
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Who is IRSN?
Safety assessment of nuclear reactors ageing
The French TSO,
Independent from operators
Detailed knowledge of installations
Safety watchtower (operational experiencefeedback monitoring)
Conducts its own independent research on safetyissues, including ageing management
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Introduction
Safety assessment of nuclear reactors ageing
Most NPPs have been designed with a givenlifetime in mind (e. g. 40 years in France)
For economical reasons, most operators want tooperate NPPs beyond this timespan
Meanwhile
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Safety assessment of nuclear reactors ageing
EXPERIENCEFEEDBACK
R&D
Opportunities for
improvement
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Safety assessment of nuclear reactors ageing
MORE STRINGENTSAFETY
OBJECTIVES
Coexistence of old
and new reactors
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Under what safety conditions can aprolonged reactor operation be accepted,
taking into account the fact that safertechnology is available ?
Managing timedependent effects
Reducing the safetygaps between old
and new plants
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Managing time-dependent effects
Ageing management
Ability to prevent, anticipate and cope withdiscrepancies
Plant modifications
Obsolescence management
Human resources and knowledge management
Coping with industrial and environmental changes
Key issues of long term operation
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Reducing the safety gaps between old
and new plants
Operating experience feedback
Periodic safety reviews
Enhancing prevention of accidents
Reducing radiological consequences of accidents
Enlarging the scope of PSA studies
Improving operation conditions
Key issues of long term operation
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Summary /Conclusions
1. LEVEL
2. Level
3. Level
4. Level
Title of presentation
Ageing management
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Ageing management : objectives
Safety assessment of nuclear reactors ageing
To maintain availability andeffectiveness of all SSCs importantfor safety
Replaceable SSCs
Non-replaceableSSCs
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Ageing management : key issues
Knowledge of degradation mechanisms
Experience feedback, R&D
Evaluating the effectiveness of scheduledmaintenance to detect these mechanisms
If necessary enhancing maintenance effectiveness
Plant monitoring (especially when degradationmechanisms are not well known)
Repairing/replacing before safety issues occur
Key issues of long term operation
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Expanding qualification durability
Qualification : demonstrating the ability of SSCs towork in extreme conditions resulting fromaccidents (pressure, temperature, dampness)
Usually these demonstrations make assumptionsabout the lifetime of the SSC
If the lifetime is extended, so shall be thedemonstration.
Safety assessment of nuclear reactors ageing
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Periodic safety
reviews
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Periodic safety reviews : objectives
Safety assessment of nuclear reactors ageing
To assess the cumulative effects of plant ageingand plant modifications, operating experience,technical developments and siting aspects.
Including an assessment of plant design andoperation against current safety standards andpractices
To ensure high level of safety throughout theplants operating lifetime.
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Periodic safety reviews
Safety assessment of nuclear reactors ageing
By nature, PSRs are the mostefficient way to reduce the gap
between old and new plants
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Enhancing preventionof accidents
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Enhancing prevention of accidents
: objectives
Safety assessment of nuclear reactors ageing
To search for high impact solutions, able
to prevent severe accidents (i.e. coremelt) and mitigate consequences moreefficiently
To enlarge the scope of design accidentsand the robustness of their assessment
Design basis accidents
Severe accidents
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Enhancing prevention of accidents
: key issues
Safety assessment of nuclear reactors ageing
Adding new plausible accident scenarii to the safetyanalysis report
For example, accidents specific to shutdown states
Lengthening the time limit for operator actions.
20 30
Design basis accidents
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Enhancing prevention of accidents
: key issues
S f t t f l t i
Using PSAs to identify ways of improvement andcheck their effectiveness.
Ways of improvement depend on the state of thedesign :
Improving the reliability of electrical sources
Increasing water storage for safety functions
Post Fukushima improvements
Severe accidents