The plant had been turned off at 9 November, because in the quarterly evaluation of the carbon isotope 14C casted in from of CO2, measurement values had approached the limit set for the balanced output.
14C is a radioactive carbon isotope with a half-life of 5730 years and is formed continuously in the atmosphere by cosmic radiation. In archeology the 14C method is used to determine the age of organic materials.
In nuclear installations 14C is produced in routine operation by a nuclear reaction of neutrons with the oxygen isotope 17O. This is a non-radioactive oxygen isotope which is found in water with an incidence of 0.048 per cent. If the oxygen isotope 17O captures another neutron, it turns to 14C.
For the emission of 14C, an upper limit of 2 x 1010 Becquerel per year was defined in the nuclear construction licence of the Research Neutron Source Heinz Maier-Leibnitz (FRM II). This limit has been set extremely low. Therefore, there are no radiological relevant effects on the environment.
The increased emission of 14C in 2012 compared to the past years is due to a more frequent drying of the ion-exchange resins that are used to clean the deuterium oxide. In future, the 14C load can be minimizedby a simple chemical leaching of CO2.
Press contact
Petra Riedel, presse officer, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Tel. ++49 (0)89 289 12141, E-Mail: presse(at)frm2.tum.de