Boxes
"Flaws
in safety culture" and "Failure
in operating procedures" at the ATPu
These stinging conclusions from the DSIN followed
an incident which occurred in March 1992, classed at level two on
the International Nuclear Event Scale (INES) 1.
A spot inspection by the safety authority revealed the presence of
an excessive number of "centering cages", devices making it possible
to handle fissile materials and prevent the risk of criticality, in
a storage area of the ATPu. "Criticality" means a situation in which
a sufficient mass of fissile material is brought together in a configuration
favorable to the triggering of an uncontrolled nuclear reaction. This
serious anomaly in operation did not have any radiological consequences,
but such "flaws in safety culture" and "failures in installation
operating procedures" had "severe potential consequences"
according to the DSIN, which suspended then the facility's activities.
The improvements "proposed" by the operator covered operating
procedures, monitoring, and raising of awareness among personnel;
they led to the lifting of the DSIN's restriction one month after
the accident. Nine years later, nothing had apparently changed as,
on 18 April 2001, the Provence-Alpes-Côte d'Azur DRIRE —
in a press conference on the status of safety at Cadarache in 2000
— recalled the "lack of rigor of the operators of the installations."
2
The more recent incident, on 17 December 1997, casts
doubt on the measures adopted by the operator: "a mass of fissile
material 50 per cent greater than that authorized by safety requirements"
was placed in the centering cages. This failure to obey safety requirements
may stem from a somewhat lax attitude on the part of operators and
a lack of awareness of the "safety culture", but other factors directly
incriminate the operating procedures themselves. Some operations,
for which the degree of control varies, expose operators to potential
risks. A look back over the history of operation of the ATPu and LPC
highlights systematic loss of confinement causing contamination by
plutonium of the premises and of personnel (reaching the Annual Limit
of Intake (ALI) ). This was not the result of confinement failures
but rather of contact with protruding metal objects in glove boxes,
able to pierce the vinyl envelopes and operatives' gloves (even though
these are lined). These recurring incidents led the safety authority
to state, in its safety bulletin of January 1998, that "in spite
of all precautions taken, such piercing of gloves could not be totally
avoided." Two years later, a technician from LPC was contaminated
again 3, with exposure at "around
the Annual Limit of Incorporation." The incident was classed at
level two on the INES, given the "significant contamination of
areas accessible to personnel." It originated from the
piercing of the double envelope of a package containing the residues
of mixed uranium and plutonium oxide pellets and powdered plutonium
oxide. On 25 April 1999, a level one incident at the ATPu involved
piercing of an operator's protective glove by a metal shard.4
Such loss of confinement caused by piercing of vinyl envelopes has
given rise to a number of incidents at the CFCa, two of which were
classed at level two on the INES and in which the Annual Limit of
Incorporation was reached for operators.
Another event confirms the flaws in the procedures
at the ATPu. This time it was removal of materials that was pinpointed
by the safety authority: 5 "failures
in the procedures for removal of materials present in the installations"
were revealed in a level one incident that occurred on 18 October
1991. Inspection of a truck "revealed that 40 Rapsodie type assemblies
each containing 1.800 grams of depleted uranium were delivered in
1970 and never irradiated!"
Notes:
1 The International Nuclear Event Scale (INES) is used to indicate the
gravity of any event occurring in nuclear power stations or other facilities.
Level two corresponds to:
- significant on-site consequences: significant contamination, overexposure
of a worker,
- degradation of defense in depth: incident with significant failure
in safety provisions.
2 Provence-Alpes-Côtes d'Azur DRIRE, "Press
Conference on Nuclear Safety at CEA Center at Cadarache in 2000",
18 April 2001.
3 See Contrôle review, January 1990.
4 See Contrôle review, June 1999.
5 See Contrôle review, December 1991.
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