MEASUREMENTS OF C-14 FROM NUCLEAR-POWER-PLANTS WITH THE AMS TECHNIQUE

One of the most important radionuclides spread from nuclear power plants to the surroundings is C-14 because of its long half-life and its incorporation in living organisms, To measure the emission of C-14 in the ventilation air from the stacks is difficult, not only because it is a pure beta-emitter but also because the ventilation air normally contains much higher activity concentrations of noble gases and activation products. These problems can be overcome if the activity concentration of C-14 can be measured with accelerator mass spectrometry (AMS). Air samples have been taken from the stack of the Swedish nuclear power station Forsmark 1. An automatic sampler for continuous sampling for up to 14 days has been constructed. For measurements with the AMS technique only about 10 mg of carbon is needed, this corresponds to 0.050 m3 of air, which makes this method favourable considering the several m3 which are needed for on-line sampling for beta-spectrometry. The first measurements show that the activity concentration in stack air is about 15-20 Bq/m3.