Diving into nuclear power plants is specific to only a few companies
rigorously selected by the operators. For this reason and to ensure
relevant information, I have contacted Patrick Lucon, the diving
manager of “Onet Technologies CN”, a company specializing in these
activities, headquartered in Marseille, France. who provided me with
a presentation I have adapted for this article. Note that in addition to
services to the nuclear industry, this group, which operates
worldwide, is specialized in the design and production of specific
communication systems, asbestos removal, waste management
services, and many other activities.
The diving department of “Onet Technologies CN” was initially
“COMEX Nucleaire”, a company created in 1990 by the COMEX group
that was bought in 1999 by “Onet Technologies CN”.
The need to work and dismantle installations in contaminated
nuclear pools created this diving activity that initially employed
divers who previously worked on military experimentation sites.
SOGETRAM, a subsidiary of the COMEX group that specialized in
interventions in unhealthy surroundings in addition to onshore and
inland diving operations, was one the 1st company involved with this
market in France before the creation of “COMEX Nucleaire” (Note that
SOGETRAM no longer exists).
The company operates for clients such as EDF (1), ORANO (2), and
CEA (3), and all types of diving work are done in their nuclear
facilities (mechanical, inspection, welding, etc.). These interventions
can be anticipated or incidental, requiring continuous personnel and
Nuclear diving is an activity in a radioactive environment, and no
school trains divers for it. For this reason, Onet Technologies CN
trains its divers in specific gestures and procedures to allow them
to work in the very closed nuclear industry environment safely.
Trainings are regularly carried out in the COMEX swimming pool in
Marseille, France, or in pools similar to those of the nuclear facilities
in service at the "Centre d'expérimentation des techniques
d'intervention sur les chaudières nucléaires" (Experimentation
centre for technical interventions on nuclear boilers), also know
under the acronym "CETIC". This makes it possible to carry out the
most appropriate gesture for saving time and limiting the ionising
radiation dose absorbed by the diver during his exposure time
(measured by dosimetry).
The study and manufacture of suitable equipment are necessary.
For this reason, a close collaboration is established with the Onet
Technologies design office and the well-known nuclear power plants
manufacturer "Framatome" (4). Also, based on the 30 years of
experience acquired by the company, the diving department
continuously improves the diving systems, which are standardized
Fully sealed reinforced rubber dry suits, like those made by
"Viking" or "Gates", equipped with waterproof rubber gloves, so
that no part of the body is exposed to the water, are the only
type of suits used currently. Note that for ionising radiation
exposure reasons, the diving team uses only one suit, which
result that the divers of a team should be of similar
mensuration to be able to use this suit safely.
The helmets used are continuous flow types. The company has
successfully used the Aquadyne AH3 and AH4 in the past, and
now the AH5, which is the latest evolution of this helmet
(Aquadyne is a Brand of JFD). However, the exhaust valve of
these helmets has been modified as the original model did not
allow working in any position without water intrusion: As a
reminder, this adjustable exhaust valve is provided with a "Head
button" that can be operated by a movement of the head for the
accelerated evacuation of the air contained in the suit, allowing
the diver to quickly adjust his buoyancy and avoid an
uncontrolled ascent (blow-up). As water intrusions were
noticeable when the diver operated this button in the laid
position, and because a perfect sealing is essential, this exhaust
valve had to be modified. This problem has been solved with
the help of COMEX Pro diving systems designers and then
those of COMEX Nucléaire.
In addition to the above, the company has closely worked with
Beat Engel (Composite - Beat Engel) on designing a new helmet
better adapted to its nuclear diving activities. This project,
started five years ago, results in a new model equipped with a
removable weight that allows additional comfort during the
diver's long dressing and undressing phases. These long
phases are linked to the fact that the diver must be fully
assisted during the dressing phase, as he must never touch the
outside of the suit for obvious contamination reasons. It is the
same for the undressing phase, where in addition, a thorough
decontamination must be done by the assistants to guarantee
an undressing without risk before being allowed to get out of the
suit. As the helmets are calculated to have a neutral buoyancy,
they are quite heavy outside the water. For this reason, a helmet
with a removable weight has been considered an advantage
regarding comfort and, thus, fatigue of the diver.
Specific and strict operational procedures must be in place:
A radiation dosimetry must be conducted to identify and quantify
the nature and impact of the radiological risks to which the divers
will be exposed before starting the diving campaign.
A map identifying the radiation context is established under the
responsibility of the Radiation Protection Department of the site:
A first mapping is carried out from the surface before any
diving campaign. absorbed in real time. This makes it possible
to better manage the traveling and gestures of the diver.
In function of the cartography, more precise measurements
are carried out at the start of the dive in areas inaccessible
from the surface.
The volumetric activity of the water and the nature of the
radioelements* are also requested. (*Radioelements = Element
that are radioactive). For information, underwater, the
radiological dose rate decreases by a factor of 2 when moving
away from 10 cm. This is why nuclear diving is considered
Another point to take into account is that the water of nuclear pools
is often hot (consider temperatures between 24 and 34 °C). For
safety reasons (hyperthermia), the company considers that the
water temperature for diving intervention should be below 28 °C.
Depending on the intervention criteria, a specific study by the
hyperbaric doctor and the company's hyperbaric prevention advisor
can be considered.
The composition of a diving team is 5 people, organized as follows:
- 1 diving supervisor
- 1 working diver
- 1 standby diver
- 2 divers operating as tenders
Therefore, the functions of the team members are identical to those
in force in the offshore industry, with a diving supervisor managing
the dive and a standby diver ready to intervene as quickly as
possible in an organized manner on the supervisor's instruction in
case of an incident or accident. For this reason, the standby diver is
not involved in any other activity than waiting for the instruction to
rescue the diver at work, and is partially equipped, as it is the case
in the offshore industry.
In addition to the precautions already mentioned, the intervention of
the diver is organized to manage and minimize the radiological risks:
The diver’s suit is provided with several radiological probes
(one on each foot, one on each wrist, one at chest level, and one
in the back), allowing the diving supervisor to know the
radioactive dose absorbed in real time. This makes it possible to
better manage the traveling and gestures of the diver.
The diver moves along a path previously defined in the work
procedure according to the radiological mapping of the
A precise radiological survey is carried out in the intervention
area, and the diver is equipped with a radiological probe for this
reason. This submerged probe must remain available and close
to the diver throughout the intervention.
Nuclear diving remains a particular activity where errors are not
allowed. For this reason, in addition to the working methodology and
intervention procedures mentioned above, the mentality of the
divers contributes to working safely in this very closed field of
Orano SA is a multinational company headquartered in
Châtillon, France, specializing in uranium mining, conversion,
and recycling. The company also provides logistical,
engineering, and intervention services to the nuclear industry.
EDF is the acronym of “Electricite De France” (Electricity of
France), a French multinational electricity producer mainly
owned by the French state and headquartered in Paris, France.
The company operates various types of power plants
worldwide and is one of the major operators of nuclear power
CEA stands for “Commissariat a l'energie atomique” (Atomic
Energy Commission). As suggested by its name, it is a French
public research organization initially specialized in the civil and
defense nuclear industry whose function is to create
synergies between fundamental research and advanced
technology, including designing nuclear reactors and
manufacturing specific systems. For a few years, the mission
of the commission has been extended to the study of other
energies, resulting that its name is now changed to
“Commissariat a l'energie atomique et aux energies
alternatives” (Alternative Energies and Atomic Energy
Commission), without changing the acronym under which it is
Framatome is a nuclear systems and power plants
manufacturer operating worldwide and headquartered in
Patrick Lucon: LuconP@onet.fr
The document “Diving protection against nuclear contaminants”,
published in 2020 by Nicusor Chiripici, Amil Avram, & Laurentiu
Mocanu can be read in the section “Diving equipment”
Underwater welding training in a swimming pool
New Composite Beat Engel helmet model DSL B2 CN.
Note the removable weight also acting as a protector.
Diver dressing (above) and cleaning before undressing
(below). Note the protective suits of the assistants.
Launching the dive in a reactor pool
Intervention in a combustible pool
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