Search for Pu-244 in deep-sea sediment

'Now-extant' Pu-244 discovered in a Precambrian bastnaesite by D.C. Hoffman et al. in 1971 was explained by K. Sakamoto in 1974 as due to possible inflow to the earth as an interstellar dust component from supernova remnants, not as due to survival of the primeval Pu-244 nor cosmic ray component. A search for the 'live' Pu-244 has been started with a 80 kg of wet sediment from 5.8 km in depth off Hawaii to see the inflow of the extra-Solar System material, and a preliminary result by alpha counting and AMS measurement for Pu-244 separated from a portion corresponding to 400 g of dry sediment sets a limit of 1 x 106244Pu atoms (i.e., 0.3 nBq) (kg-dry sediment)-1 for extraterrestrial deposition. Magnetic materials, slightly soluble silicates and manganese nodules separated from the sediment were also subjected to analyses for Pu-244. (author)