Gyttja, a low-level, high-organic reference material

Gyttja, the bottom sediment from Perch Lake at Chalk River Nuclear Laboratories, was collected to prepare a low-level, high-organic standard radioactivity reference material. In the natural state it contained about 92% water and when dried the residue was about 50% organic material. The surface layer of this sediment contains small quantities of 60Co, 90Sr, 137Cs and 239Pu. The material was collected from depth using a sludge pump and the radioactivity content adjusted with addition of surface-layer material. It was then dewatered by centrifuge and freeze-dried. The overall exercise was a demonstration of co-operation between the National Bureau of Standards, Washington, D.C., Atomic Energy of Canada Limited, the Ontario Department of Labour, the Environmental Protection Service of Environment Canada, the Department of Agriculture, the Atomic Energy Control Board and two commercial firms, Rush Engineering and Freeze-Dried Foods, Incorporated.