[en] Within the time interval from July 1978 to June 1980, the FRN-reactor had been operated for 567 shifts at an energy release of 2460 MWh and a number of 2007 pulses. In this period, about 14000 samples had been irradiated at the reactor. The establishment of a new core configuration turned out to be necessary in the end of 1979 because of severe reactivity problems. The set-up of the new core was contrived by replacing the remaining 11 graphite dummies in the G-ring by fresh fuel elements, thus gaining approx. 1.6 $ of additional excess reactivity. The emphasis of operational duties lay in the investigation upon the emission of further radionuclides in the exhaust air with very low concentrations in comparison to the Ar-41 activity. Except for natural radioactivity neither aerosols nor halogens were found above the detection limits of ∼ 5 x 10^-16 Ci/m³. The emission rate of C-14 was determined to be 1.8 x 10^-6 Ci/MWh, which corresponds to an annual C-14 delivery from the reactor of about 2.2 mCi. Its radiological influence is totally negligible compared to the natural C-14 activity. (author)