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BROOKHAVEN NATIONAL LABORATORY Upton, New York 11973 Manager, Human Health Studies Program Division of Biomedical & Environmental Research One of the key studies in the Dose-Reassessment for Rongelap and Utirik is the determination of 1291 in soil samples that were collected from Rongelap and Utirik soon after the fallout from the BRAVO test had ceased. 1291, the long-lived radionuclide, is the only isotope of the iodine series that would still be present today in the above samples (collected in 1954) in detectable quantities. Knowing the concentration of 1291 in these soil samples and also knowing the isotope fractionation (or ratios) for a given yield, we can estimate the other short-lived iodine isotopes. In addition, the iodine isotope ratios could be used to estimate other fission products as well. ever, the accuracy in determining the 1291 concentration depends on the type of sample used. The historic samples analyzed in this study, so far, have been soil samples collected from Rongelap and Utirik by the University of Washington. It is to be noted that the amount of fallout particles in such samples is extremely small when compared to the bulk of the particles that make up the to detect very small quantities of 1291 in the sample. fallout sample as exemplified by the "Bikini Ash" (1) which fell on the Japanese fishing vessel "The Lucky Dragon" would be an excellent sample to analyze for 1291 and thus serve as a benchmark to which other samples could be compared. this connection, the procurement of a small sample (3-5g) of the "Bikini Ash" would be extremely useful in strengthening the accuracy of our 1291 determination in the historic soil samples. authorities who have studied the sample extensively but have not yet analyzed the same for 1291. Also, the reciprocity of our analytical data would indeed benefit all in the true characterization of the fallout particles from the BRAVO test. The samples, I believe, are in the custody of the Institute of Physical and Chemical Research, Japan. In such cases, the analytical method must be extremely sensitive Also, the data would prove useful to the Japanese
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I sincerely appreciate your continued interest in this unique study. Ref. (1) Radioactive dust from the Nuclear Detonation, Bulletin of the Institute of Chemical Research, Kyoto University, Encl.: Copy of letter to Dr. Shun’ichiHisamatsu, Akita University for