Abstract
Raw milk and skim milk powder collected monthly from several districts in Japan (from June 1956 to May 1957) were burnt to ashes and their total radioactivities were measured.
As a result, total radioactivities showed 40_??_50cpm per 1g of ash. There was neither sea-sonal variation nor regional variation in the total radioactivity.
Skim milk powder (or whole milk powder) collected every season from six districts in Tanan (August, October in 1957, Fubruary, May in 1958) was burnt to ashes and its Sr-90 concentration was measured.
Results obtained showed that Sr-90 concen-tration in skim milk powder manufactured in the northern districts were higher than those in the central or southern districts of Japan.
The Sr-90 concentrations are as indicated in the following districts.
Hokkaido:4.2_??_6.7 Sr-90uuc/g of Ca
Tohoku: 0.9_??_2.0 Sr-90uuc/g of Ca
Kanto: 1.0_??_1.4 Sr-90uuc/g of Ca
Chubu: 0.8_??_2.2 Sr-90uuc/g of Ca
Kinki:0.5_??_1.3 Sr-90uuc/g of Ca
Chugoku and Shikoku: 1.0_??_1.6 Sr-90uuc/g of Ca
The authors wish to thank Dr. Yamazaki and Mr. Hashizume, Physical and Chemical Research Institute, for having taken charge of counting in the measurement of Sr-90 concen-tration, and to Dr. Asari, Japan Inspection Co. Ltd., for his valuable counsel and good offices given in the measurement of Sr-90 concentration.
