Sorption of radionuclides on sodium sampling vessels

Determination of radionuclides in KNK primary sodium yielded different results when ceramic crucibles instead of nickel crucibles were used for sodium sampling. It was shown that adsorption of some radionuclides on nickel crucibles was the reason for this effect. Small cylinders and metal coupons were introduced into the KNK primary sodium sampling station for radionuclide deposition studies. These deposition samples, made of different types of stainless steel, nickel, tantalum, titanium, and molybdenum, were exposed to the contaminated, flowing primary coolant for times up to 24 hours. Gamma spectrometric measurements indicated a strong adsorption of 65Zn on all nickel samples; the activities of 51Cr, 54Mn, 60Co, and at low temperatures (4730K) even of /sup 110m/Ag were higher on nickel samples than on any other material exposed to the primary sodium. These results were confirmed for the adsorption of radionuclides on crucibles of various metals. Consequently, stainless steel crucibles will be used for sampling primary sodium in order to determine radionuclides at KNK-II