state-of-the-art in environmental monitoring

Why Electricité de France decided for the GammaTRACER system

The French national power supplier Electricité de France (EDF) was looking since a long time for a gamma probe able to measure radioactive radiation in the vicinity of her power plants.

Since the early 90s France is already equipped with a national early warning and survey network, called TELERAY, based on Rados gamma probes. A number of 180 of these probes are installed on the highest mountains, on the top of Mont Blanc 4000 m, and in the major towns. Additionally, each of the 25 nuclear sites from EDF, COGEMA and CEA is equipped with four to eight Saphimo probes placed in the main wind directions.

Nevertheless EDF's problem was:

• to report monthly to the national authority on the dose rate around the site of the NPPs
• to be prepared to monitor the radioactivity level around the NPP in case of emergency

To fulfil this second target, the device required was supposed to be

• independent from external power supply and from defined communication means, as phone or cellularphone lines will be saturated and radiolinks do not work everywhere,
• fast in operation
• not expensive

EDF was seeking for such a device for a long time! In December 1994 Saphymo finally came out with its GammaTRACER autonomous system for long-term environmental surveillance. After testing the unit EDF found the "white elephant" (in French "mouton à cinq pattes") they were looking for!

In July 1995 Saphymo and its French distributor MTE Instruments went into an agreement with EDF to install GammaTRACER probes in all French twenty nuclear power plants operated by them. The decision of EDF was to equip each NPP with ten probes and install them around the fence of the site, ready to be used elsewhere in an emergency case.

The official French authority, OPRI, agreed to such a strategy and on the GammaTRACER solution. One GammaTRACER is hanging on a tree branch at the entrance of the OPRI site in Vesinet - Paris. The conditions to equip EDF with GammaTRACER probes were:

• positive experience in Cattenom NPP where ten probes were installed in July 1995
• ability to get official homologation which was achieved through the French CTHIR
  (Centre Technique D'Homologation de L'Instrumentation de Radioprotection)

Due to the successful homologation and the very satisfactory experience at the NPP site in Cattenom and OPRI the management of EDF decided to install 400 GammaTRACER probes in all twenty French NPPs: ten around the fence of each site, 2 x 5 pieces in emergency vehicles, ready for intervention in case of an accident. In the meantime Chooz NPP was the second plant where the full number of systems was installed, to be followed by Dampierre

NPP, Superphénix and all the others to follow. The final installation of the complete number of probes is planned to be finished within the first part of 1997.

Installation itself is fast and easy to handle as neither cabling nor drill holes are required. Mounting can be done very simply on existing structures or with a firm mast support of stainless steel which stands wind speeds up to 200 km/h. With a warranty period of three years the GammaTRACER probe is practically maintenance free. Battery lifetime could even go up to five years, thus cost of further maintenance is kept at a minimum level regarding external cost and manpower.

All GammaTRACER probes are compatible with the GammaVIEW software of each NPP. Thus in an emergency situation several thens of probes will be available to cover a large region. The measurements recorded by the ten probes on the fence are reported monthly to the OPRI for official information.

There are many other applications for the unique GammaTRACER system which make the probe universal for its range of users:

• use in an high-dose environment (20 nSv/h - 10 Sv/h)
• in extreme temperature ranges (- 40° to + 70° C)
• with modules for wireless data transmission (brand name "SkyLINK") These are already studied by NPP security managers, in particular for use in the fuel building and on the top of refrigerant towers, using radio and cellular phone links.