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After decommissioning the steam generators and the
primary system, ASN, through its resolution of 3rdMarch
2014, authorised decommissioning of the reactor vessel
which is planned to start in 2016.
The preparatory work for decommissioning the Chooz A
reactor vessel started in 2015. The reactor cavity gates
were dismantled and the pressuriser, dismantled in
2013, was removed.
With regard to the environment and nuclear safety,
ASN considers that the decommissioning operations
are being carried out satisfactorily.
Regarding radiation protection, in 2015 ASNobserved the
progress made by EDF under the action plan implemented
in 2014. ASN considers that EDF must maintain its
training and awareness-raising efforts for its outside
contractors in this area.
Several incidents occurred during operations on
electrical distribution panels in 2014 and 2015 due
to insufficient preparation of the activities concerned
and to concomitance of activities.
EDF must have completed the periodic safety review
of Chooz A in 2017. ASN examined the orientations
of this safety review in 2015.
2.1.6 The Superphénix reactor
and the Fuel Evacuation Facility (APEC)
The Superphénix fast neutron reactor, a sodium-cooled
industrial prototype, is located at Creys-Malville. It
was definitively shut down in 1997. This installation is
associated with another BNI, the Fuel Evacuation Facility
(APEC), which consists primarily of a storage pool in
which the spent fuel removed from the Superphénix
reactor vessel is stored, and storage for packages of
soda concrete from the Sodium Treatment Installation
(TNA).
ASN considers that the safety of the Superphénix reactor
decommissioning operations and of APEC operation is
satisfactorily ensured. The progress ASN observed in
2014 with regard to operating rigour and monitoring
the performance of maintenance operations and periodic
tests was maintained in 2015.
In addition, following the detection of anomalies in 2014,
the licensee has listed the retention structures on the
site and defined corresponding inspection programmes.
Nevertheless, in 2015 ASN asked EDF to rapidly set up
an organisational structure enabling it to remove and
treat, as rapidly as possible, the hazardous substances
that could accumulate in the retention structures.
Lastly, ASN has verified that the organisation and
provisions with regard to occupational radiation
protection and the transport of radioactive substances
complied with the regulations.
Examination of the file transmitted for the authorisation
to treat the residual sodium from the reactor vessel and its
filling withwater revealed no blocking points. Preparation
and performance of these operations represent the main
risk activities for the coming year. The periodic safety
review files for the Superphénix reactor and the APEC
were submitted in 2016. ASNmade a statement in 2014
on the orientations of the then forthcoming periodic
safety reviews and will start the technical examination
of the files received.
The implications of decommissioning
the PWR vessel
The Chooz A reactor is a Pressurised Water Reactor (PWR)
like EDF’s 58 reactors in operation. It is therefore the first reactor
using this technology to be decommissioned in France by EDF
and the first shut down reactor to have its vessel dismantled.
Decree 2007-1395 of 27th September 2007 authorising
decommissioning of the Chooz A reactor set four hold points:
dismantling of the primary system, dismantling of the reactor
vessel, start of stages 2 (surveillance phase) and 3 (demolition
and redevelopment of the site), considering that the change
of stage operations require a specific examination.
ASN thus authorised dismantling of the reactor vessel in 2014.
The main challenges of dismantling the reactor vessel are:
1 - Worker radiation protection is a major issue. This is because
the reactor vessel, the metal of which has been activated,
cannot be decontaminated beforehand (unlike the already
dismantled steam generators) to reduce the dose rate.
EDF has therefore planned to carry out the operations
to remove the elements from the vessel and cut up
of the vessel under water in the reactor cavity, using
remotely operated means.
2 - There is a risk associated with the handling of large
components (the vessel weighs about 200 tonnes).
3 - New facilities must be built to treat and package the waste.
4 - Waste management represents a major challenge since
the activated waste, once characterised and packaged, must
be transferred to ICEDA (activated waste packaging and
interim storage installation). This facility will therefore have
to be put into service within a time frame compatible with
the progress of vessel dismantling.
To cope with these challenges, EDF has the benefit of
international experience feedback from reactors of identical
technology on which this same procedure has been used,
particularly the Zorita NPP in Spain.
UNDERSTAND
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CHAPTER 15:
SAFE DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS
ASN report on the state of nuclear safety and radiation protection in France in 2015