For 10 years, 14C measurements have been performed around French nuclear power plant sites, both in zones influenced and zones not influenced by gaseous releases. Examining the results from these measurements in the terrestrial environment shows that the discharges have a very slight impact on the radiocarbon level (with a relative increase in the specific activity of the order of 3 Bq kg-1 C in the influenced areas). In
correlation, there is a near-negligible increase in dose, on average less than 0.1 microSv yr-1, with reference to a dose from background radiation, which is of the order of 10 mSv yr-1. The delta13C values are very similar between the influenced zone and the non-influenced zone, with a mean of -27per mil. The mean delta14C varies from 101per mill in the non-influenced zone to 123 per mil in the influenced zone. Moreover, a general reduction in 14C concentration was found, with a time constant of the order of 95 years. The current level of 14C specific activity in terrestrial environment is estimated to be 242 +/- 6 Bq kg-1 C.
a Laboratoire d’Etude Radioecologique du milieu Continental et Marin, Institut de Radioprotection et de Surete
Nucleaire, DEI/SESURE/LERCM, Cadarache, Bat.153, B.P. 3, 13115 St-Paul-lez-Durance Cedex, France
b EDF R&D, De´partement LNHE, 6 Quai Watier, B.P. 49 F-78401, Chatou Cedex, France
c Laboratoire de Mesure de la Radioactivite dans l’Environnement, Institut de Radioprotection et de Sureté
Nucleaire, DEI/STEME/LMRE, Bois des Rames, Baˆ t. 501, 91400 Orsay, France