SR-90 ACTIVITY IN MONTHLY MILK SAMPLES FROM GREECE

The present study evaluated after the Chernobyl nuclear accident the a ctivity of Sr-90 in commercial bovine milk sampled monthly from 1987 t o 1994. Monthly mean activities (0.04 to 1.25 Bq/L) were comparable wi th those reported for other countries of the European Union (0.05 to 0 .9 Bq/L), but maxima were higher, and the range of values was wider. M ilk samples were also compared against samples of bovine milk in Greec e that were collected before the Chernobyl accident during the period from 1969 to 1983 (0.04 to 1.37 Bq/L) and from 1985 to 1986 (0.04 to 0 .30 Bq/L). The data were fit exponentially utilizing the chi-square st atistic. The goodness of fit for the curve was 65%. Based on this resu lt, the effective half-life of Sr-90 in milk was estimated to be 308 /- 57 d, which is very short compared with the physical half-life of 1 0,410 d for Sr-90. Since the second half of 1992, the decay curve of t he measured mean activity approximated a threshold of 0.09 +/- 0.03 Bq /L, which is close to the low limit of detection by beta-scintillation .