抄録
USEPA has conducted a series of surveys of disused U. S. radioactive waste sites at the Atlantic and Pacific Ocean. The author joined the surveys in 1976 and 1978. A characteristic method of the survey was the use of submersibles to collect samples of sediment, biota etc. and to recover radioactive waste packages at deepsea bottoms.
Cement-solidified radioactive wastes packaged in drums were recovered during the surveys in 1976 at depth of 2, 800m in the Atlantic Ocean, in 1977 at 900m in the Pacific Ocean and in 1978 at 3, 800m in the Atlantic Ocean, respectively. The recovered packages have been investigated at Brookhaven National Laboratory.
An 80 gallon package disposed of in 1960 and recovered in 1976 contained a cylindrical container (99×16.5cm∅) made of steel in the center of the package. Three pieces of fiber filters were enclosed in the steel container and a cement-liquid waste composite including 162μCi of 137Cs was found to surround it. It was estimated that the amount corresponding to the cumulative leach ratio ca. 56% was released during its stay on seabed for 16 years.
It was found that ca. 1/3 of the drum was buried in the sediment. As a result of the investigation average corrosion rate of steel plate of the drum was 0.030±0.006mm/year for the sea water side and 0.046±0.006mm/year for the sediment side, respectively.
