Corrosion product behaviour in the primary circuit of the KNK nuclear reactor facility

During nuclear operation of the KNK facility from 1972 until September 1974 the composition and behaviour of radionuclides occuring in the primary circuit were investigated. Besides traces of 140Ba/140La, no fission product activity was detectable in the KNK primary circuit. The fuel element purification from sodium deposits (prior to transport to the reprocessing plant) did not yield any indication of a fuel element failure during KNK-I operation. The activity inventory of the primary loop was exclusively made up of activated corrosion products and 22Na. The main activity was due to 65Zn, followed by 54Mn, 22Na, sup(110m)Ag, 182Ta, 60Co and 124Sb. It was found that the sorption of 65Zn and 54Mn on crucibles made from nickel was condiserably higher than on vessels made from other materials. This observation was confirmed both in tests with material samples from the primary circuit and for disks of gate valves of the primary circuit. sup(110m)Ag did hardly exhibit any sorption effects and had been dissolved largely homogeneously in the hot primary coolant. In the first primary cold trap which was removed from the circuit after some 20,000 hours of operation, only 65Zn and 54Mn were detected in addition to traces of 60Co and 182Ta. (author)