Arc Nucleart’s irradiator in Grenoble
Editorial revision 2026
France has a facility that is unique in Europe for the preservation of heritage objects. It is the NUCLEART regional conservation workshop in Grenoble. Created in 1969 on the initiative of Louis de Nadaillac, an engineer at the French Atomic Energy Commission, it is today a “Public and Cultural Interest Group”.
Irradiation chamber
Exploded-view diagram of the irradiation facility. The pool where the cobalt-60 source is stored when not in use can be seen; the water provides protection from radiation. The source is mounted on a trolley that allows it, when required, to be raised from the pool into the irradiation chamber.
© Arc Nucléart
It should be noted that there is a similar facility at CEA Saclay (the one that treated RAMSES), the Poséidon irradiator.
The Poséidon irradiator at CEA Saclay. Note the blue luminescence at the bottom of the pool (Cherenkov effect). CEA Saclay
The organisation’s restoration activities have diversified, but its main distinctive feature is that, since its beginnings, it has had a large-scale Cobalt-60 irradiation facility.
Irradiation takes place in a shielded chamber. The Cobalt-60 rods that constitute the source are stored in a 4-metre-deep pool. This depth is sufficient to allow the source to be observed safely when it is in its resting position. A rail system moves the rods from the pool to the chamber during irradiation. They return to the pool afterwards. As irradiation does not generate radioactivity, the chamber can be entered and the objects handled as soon as the treatment is completed.
Monitoring the irradiation
Lead-glass window of the irradiation chamber and control panel with remote manipulators.
© Arc Nucléart
A lead-glass viewing window allows the inside of the chamber to be seen and the consolidation or disinfection process to be monitored.
The advantage of consolidation by irradiation lies in the ability to control the heat released by the polymerisation reaction within the object by modifying the dose rate of gamma radiation. The reaction is started with a dose rate of around 1 kilogray/hour, and when the temperature inside the wood reaches around 60–70°C, the dose rate is reduced by moving the object away from the radiation source, in order to lower this temperature. The total duration of the process is around 48 hours, with variable dose rates to prevent the temperature within the object from exceeding 70°C. A dose of approximately 20,000 Grays (Gy) is required for radio-polymerisation.
In the case of disinfection, the doses vary considerably: 500 Gy to sterilise wood-boring insects and 2,000 Gy to stop the growth of certain fungi, 10,000 Gy or more for disinfection. There is nothing to prevent several objects from being treated at the same time. Disinfestation by irradiation is particularly well suited to the mass treatment of ethnographic objects of various shapes and made from different materials. For example, around one hundred m3 of furniture from the storage collections of the Musée Dauphinois in Grenoble was treated in batches of 2 m3.