Abstract
Concentrations of 234U and 238U in the groundwater samples from Musashino-daichi, western Tokyo have been measured by alpha-spectrometry. Observed range of 234U and 238U concentrations were about 0.2-3.5 and 0.3-9.3 dpm/100l, respectively, with the 234U/238U activity ratios of 1.4-5.0 The presence of excess 234U, together with the observed linear correlation with 238U concentrations, indicates both excess 234U and238U have been supplied by source materials which are uniform with respect to the ability of supplying recoilgenic 234U and 238U into the groundwaters. High tritium concentrations in many of the samples (Tanaka, 1983) indicate the groundwater samples were composed of two distinct water components: one with fairly long age of contact with U containing minerals (orders of 1000 yrs or more) and one with fairly short tritium age (less than about 30 yrs).
