The abnormal level of tritium measured in the Loire this year is probably related to a problem of sampling methodology, said Thursday the Institute for Radiation Protection and Nuclear Safety (IRSN), which will continue its investigation.
The association for the control of radioactivity in the West (ACRO) announced in June, after a measurement campaign, a high level of tritium (radioactive isotope of hydrogen) including Saumur.
Taking stock of its investigations in an information note, the IRSN considered “unlikely” that this is an incident in the discharge process of EDF nuclear power plants, which are several on the Loire . Power plants have the right to reject tritium within the limits set by the authorities.
The hypothesis of a rejection by a source other than EDF is for its part “difficult to consolidate”.
Experts believe that a “problem with the sampling methodology” is “the most likely hypothesis”.
More specifically, the most likely cause lies in sampling outside the so-called “good mixing” zone, that is to say in which the tritium concentration is homogeneous.
“At the date of detection by ACRO of the peak concentration in Saumur, the main source of discrepancy between the measurement resulting from regular monitoring and the model would be attributable mainly to a delay in the homogenization of releases from the central of Chinon “, indicates the IRSN.
It intends to continue its investigation, with the ASN, by launching a new measurement campaign under conditions “as close as possible” to those that led to the measurement of ACRO in Saumur (in winter, in a period of low water).