IRSN, Institut de radioprotection et de sûreté nucléaire

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Enhancing Nuclear Safety


Experimental facilies and means

OPERA network


As part of its monitoring brief, IRSN carries out regular measurements of radioactivity levels in the environment, employing high-performance investigation means for the quantification of trace amounts. This mission is one of the components of the territorial surveillance carried out by IRSN throughout France with the participation of nuclear operators and various associations on a regional and/or local level. It therefore closely complements the information from the automatic warning station network Teleray, which would react instantaneously in the event of high contamination but with a lower level of sensitivity. 




Observatory station of Rhône in Arles (SORA)
during hydrological calm period (September 2006)
Credit : Olivier Seignette/Mikaël Lafontant/IRSN



Issues at stake


The data obtained, in particular from the OPERA-Air network (permanent radioactivity observatory), also serves as a support to the numerous research and expertise studies on the time and spatial variations of stocks and fluxes of radionuclides in the environment. Apart from the characterisation of the lowest measurable levels, the targeted objective is to understand the mechanisms governing those distributions and the transfer of radionuclides of natural and artificial origin within the atmospheric compartment and from the atmosphere to other compartments of the environment. Knowledge of these mechanisms will then enable IRSN to conceive, consolidate and validate the modelling of radionuclide transfer processes in order to better estimate what would be the impact of an accidental release into the environment and the consequences on the use of the environment and human activities. 




Observatory station of Rhône in Arles (SORA) during flood 
in November 2002 (8010 m3.s-1). The water samples are made at 50 cm under river surface, thanks of an underwater pump and a float (white triangle upstream from red and white sign buoy) linked to the station by an articulated arm. The station continually takes off water 3 m3/hour
so as to feed on open supply circuit and the different samples collecting spots.

Credit : Olivier Seignette/Mikaël Lafontant/IRSN



Facilities and structures

The observation of the atmospheric compartment (OPERA-Air network) is conducted from around fifty atmospheric dust sampling stations in France. These stations permanently filter the air over periods ranging from several days to a week (using a turbine and a filter). The filters are then sent to IRSN's metrology laboratories. The results are obtained after one to two weeks after sending the filters. The network of observatories has made it possible to search for the time variation of levels of the main natural (7Be, 210Pb, 22Na, 228Ac, 40K, 234Th) and artificial radionuclides (134Cs, 137Cs, 131I, 60Co, 110mAg, 54Mn, 106Rh) over a period of more than 50 years in the atmosphere.

Such network was started in 1959 for the atmospheric domain (aerosols, precipitation) and, since 1984, has also covered the French coastline (coastal sediments and fauna), since 1993 the land environment (soils, plants, animals) and, since 1998, the river environment (water, suspended solids). This long period of observation has enabled the constitution of chronological series indispensable for scientific studies on the variability of the levels observed. 




Implantation of the sampling stations of OPERA network (2009)


Upgrading of the network

The renovation of the OPERA-Air network is scheduled between 2011 and 2015 in order to increase its sensitivity (detection of small scale events). Forty stations are therefore going to be equipped with turbines that are ten times more powerful, thereby enhancing the sensitivity and detection thresholds tenfold, either to replace existing stations or in new sites to reinforce the national cover. In addition, they will be equipped with an iodine sampling line enabling gaseous sampling in crisis situations. The remaining ten or so stations have already very high volume samplers (up to 700 m3/hour). These stations were in particular very active in the days following the Fukushima accident, detecting the very first signs of the arrival of masses of faintly contaminated air in France. Routinely, they make it possible to characterise the background radiation levels of certain artificial radionuclides, such as 137Cs, as well as any rise, even minimal, in radioactivity levels. These stations will also be equipped with an iodine sampling line in the near future.  


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