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More broadly, during inspections, ASN verifies that the
licensee complies with the STE and, as necessary, checks
the compensatorymeasures associatedwith any temporary
modifications. It also checks the consistency between the
normal operating documents, such as instructions and
alarm sheets, the STE and the training of the persons
responsible for implementing them.
Examination of modifications
made to the equipment
To improve the industrial performance of its production
facility, process anydeviations detected, implement design
changes following periodic safety reviews or operating
experience feedback, EDF regularly makes changes to its
facilities. ASN is notified of those changes liable to affect
nuclear safety or environmental protection before their
implementation, and they are examinedbeforeASNissues
its correspondingpositionstatement. The changesdesigned
to remedy conformitydeviationsmade in response toASN
prescriptions, in particular those resulting from the stress
tests, are granted particularly close attention.
ASNchecks theways inwhich the changes it has approved
are implemented,more specificallyduring reactor refuelling
and maintenance outages.
2.2.2 Incident or accident operations
Chapter VI of the RGE comprises all the reactor operating
rules for an incident or accident situation and prescribes
how the reactor is to be controlled in these situations. ASN
must be notified of any changes to Chapter VI of the RGE
liable to affect nuclear safety before they are implemented.
Chapter VI of the RGE changes in order to take account
of experience feedback from incidents and accidents and
to take account of modifications made to the facilities, in
particular those resulting fromthe periodic safety reviews.
ASNalso regularly checks the incident or accident operating
rules andhow they are implemented. Todo this, ASNruns
simulations with the facility’s shift crews. It thus checks
that the operating instructions applied are consistent with
the rules of Chapter VI of the RGE, the implementation
methods for these documents, and themanagement rules
for specific equipment used inaccident operating situations.
2.2.3 Operation in a severe accident situation
If the reactor cannot be brought to a stable condition after
an incident or accident and if a series of failures leads
to core degradation, the reactor is said to be entering
a severe accident situation. To deal with this type of
unlikely situation, various steps must be taken to enable
the operators to safeguard the containment in order to
minimise the consequences of the accident (see point 1.3.1
of chapter 5). The operators then drawon the skills of the
emergency response teams set up at both the local and
national levels. These teams use the On-site Emergency
Plan (PUI) plus the severe accident operation guide and
the emergency teams action guides in particular.
ASN periodically examines the strategies presented by
EDF in these documents, in particular for the reactor
periodic safety reviews.
2.3 Fuel
2.3.1 Developments in fuel design and management
Inorder toenhance the availability andperformanceof the
reactors in operation, EDF, together with the nuclear fuel
manufacturers, researches and develops improvements to
fuels and theiruse in the reactor. The latter isknownas “fuel
management” and is described in point 1.2.
ASN ensures that each change in fuel management is
the subject of a specific safety case for the reactors
concerned, based on the specific characteristics of
the new fuel management. When a change in the fuel
or its management model leads to EDF revising an
accident study method, this requires prior review and
cannot be implemented without ASN approval. When
significant changes are made to fuel management, their
implementation is dependent on a resolution being
issued by the ASN Commission.
2.3.2 Monitoring the condition of fuel in the reactor
Fuel behaviour is an essential element in core safety
in normal operation or accident conditions, and its
reliability is of prime importance. The leaktightness of
the fuel rods, of which there are several tens of thousands
in each core and which constitute the first containment
barrier, are therefore the subject of particular attention.
During normal operation, leaktightness is monitored
by EDF by means of continuous measurement of the
activity of radioelements in the primary system. Any rise
in this activity level beyond predetermined thresholds is
the sign of a loss in fuel assembly leaktightness. During
shutdown, EDFmust look for and identify the assemblies
containing leaking rods, whichmay not then be reloaded.
If this activity in the primary system becomes too high,
the RGE require reactor shutdown before the end of
its normal cycle.
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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