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depending on the reactors, can range from a few tenths
of a degree to several degrees. This warming is regulated
by ASN resolutions.
Since 2006, changes have beenmade to these resolutions
for advanced definition of the operations of NPPs during
exceptional climatic conditions thatwould lead to significant
warming of the river. These special provisions are however
only applicable if the security of the French electricity
grid is at stake.
2.6.4 Consideration of fire risk
In the same way as the other BNIs, NPPs are subject to
an ASN statutory resolution on the control of fire risks
(ASN resolution 2014-DC-0417 of 28th January 2014).
Controlling the fire risk in nuclear power plants is built
around the principle of defence in depth, based on three
levels: facility design, prevention and fire-fighting.
The design rules should prevent the spread of any fire and
limit its consequences. This is primarily built around “fire
zoning”, that is the principle of dividing the facility into
sectors designed to contain the firewithin a givenperimeter,
each sector being bounded by sectoring elements (fire
doors, fire-walls, fire dampers, etc.), offering a specified
fire resistance duration. The main purpose is to prevent
a fire from spreading to two redundant equipment items
performing a fundamental safety function.
Prevention primarily consists of the following:
•
ensuring that the nature and quantity of combustible
material present in the premises remain below that of
the scenarios used for zoning;
•
identifying and analysing the fire risks in order to take
steps to avoid them. In particular, for all work liable to
cause a fire, a “fire permit”must be issued andprotective
measures must be taken.
Finally, fire detection and fire-fighting procedures should
enable a fire to be tackled, brought under control, and
extinguished within a time compatible with the fire
resistance duration of the sectoring elements.
ASN checks that the fire risk is taken into account in
the NPPs, notably through an analysis of the licensee’s
baseline safety requirements, monitoring of significant
events notified by the licensee and inspections performed
on the sites.
2.6.5 Consideration of explosion risks
An explosion can damage elements that are essential for
maintaining safety ormay lead to failure of the containment
with the release of radioactive materials into the facility,
or even into the environment. Steps must therefore be
taken by the licensee to protect the sensitive parts of the
facility against explosions.
ASN checks these prevention andmonitoringmeasures,
paying particular attention to ensuring that the explosion
risk is included in EDF’s baseline safety requirements
and organisation. ASN also ensures compliance with
the “Explosive Atmospheres” (ATEX) regulations with
respect to worker protection.
2.7 Maintenance and testing
2.7.1 Regulation of maintenance practices
ASNconsiders that preventivemaintenance is an essential
line of defence inmaintaining the conformity of a facility
with its baseline safety requirements.
In order to improve the reliability of the equipment
contributing to safety but also to industrial performance,
EDF regularly seeks to optimise itsmaintenance activities
in light of best practices used in the industry and by NPP
licensees in other countries.
In2010, EDF thus informedASNof its intention todeploy a
newmaintenancemethodologydevelopedby theAmerican
licensees, called AP-913.
Deployment of AP-913 is based on implementation of the
following six processes:
•
identification of critical equipment anddefinition of the
associated maintenance and monitoring programmes;
•
definition of equipment monitoring and maintenance
requirements;
•
equipment and systems performance analysis;
•
definition and oversight of corrective measures;
•
continuous improvement of baseline requirements and
oversight of reliability;
•
equipment lifecycle management.
The various steps in thismethodology and theorganisational
conditions for its deployment in theNPPswere examined
by ASN, which is in favour of its adoption.
The main benefit of this method is to aim for improved
equipment reliability through in-service monitoring, in
order to improve preventive maintenance and through
sharingofmaintenancepractices among theNPPs.However,
ASNconsiders that proactive stepsmust be takenwith the
NPPs to allowcorrect implementationof this newmethod
and ensure that it is effective. EDF must in particular
more closely oversee the implementation of AP-913 in
its various NPPs and allocate the necessarymanpower to
this task. EDFmust also ensure that all participants follow
the recommendedmethods for filling out the equipment
monitoring indicators, for the preparation, performance
and write-up of field visits and for the traceability of
maintenance decisions.
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CHAPTER 12:
EDF NUCLEAR POWER PLANTS (NPPs)
ASN report on the state of nuclear safety and radiation protection in France in 2015