Correction of Fe-55 activity measurements due to interference of other low energy photon emitters

Abstract

Measurement of 55Fe in reactor waste samples by chemical separation of Fe is subject to interference by 58Co and 54Mn because these nuclides are produced in copious quantities in reactors, they emit K x-rays of essentially the same energy as 55Fe x-rays, and chemical separations of Fe are not pure enough to assure their absence. Fortunately 58Co and 54Mn also emit high energy gamma rays that can be used to detect and quantitate their presence in separated samples. x-Ray fluorescence yields of 58Co, 54Mn and 55Fe can be used to correct count rates and provide corrected measurements of 55Fe. This technique has been used successfully to correct measurements of 55Fe in reactor wastes, especially spent ion-exchange resins though most corrections have been only a few percent.