Lessard to Thiessen, MD
-2-
lecember 17, 1980
1.
acute dose reassessment,
2.
3.
4.
5.
chronic dose reassessment,
analysis of plutonium and strontium in urine and teeth,
analysis of Castle Bravo fallout, and
diet and living pattern study.
The acute dose reassessment from Castle Bravo fal out on Rongelap and
Utirik Atolls is partially complete and uses three inde endent approaches: 1)
biological samples, 2)
soil samples and 3)
weather da a obtained during the
1954 thermonuclear test experiment at Bikini Atoll.
Each approach requires
the evaluation of large volumes of data, the developmen of mathematical models, and the performance and verification of numerous cilculations.
Additionally, we are considering other factors such as the soluoility 0: lodine isotopes in fallout, the possible contribution from neutro: Induced activity, the
impact of thyroid seekers other than fodine isotopes on dose, and confidence
levels for values of derived quantities such as airborne
activity concentrations and thyroid dose equivalents for different age groups.
The chronic dose reassessment is completed and results for the population averages are avatlable (Le 80).
This work has application to the ongoing
radiological safety program on Rongelap and Utirik Atol'’s and is useful in
predicting future dose equivalents to persons who return to Eneu Island at
Bikini Atoll and to Enewetak Atoll.
Individual dosimet:ic data is maintained
in a data base at Brookhaven National Laboratory.
Analysis of plutonium in urine and teeth has led
o large uncertainty in
the estimate of the true mean value for the sample popu ation due to the fact
that measurements are at or near the lowest limit of de-ection.
The practical
significance of this has led us to optimize our procedu-es and to employ a
variety of techniques for measurement.
Our main goal will be to achieve measurements at a level which impacts insignificantly on tie dose estimate for
blood forming organs.
Currently we are attempting to obtain a small amount of Castle Bravo
fallout which has been kept in Japan following its removal from the Lucky
Dragon, a Japanese fishing vessel which had satled through the tropospheric
Bravo cloud in March, 1954.
Analysis of this ash could lead to a verification
of the fodine isotope yield per unit fission.
This could be analyzed by neutron activation (as were the historic soil samples which were used in the
acute dose reassessment) {tn order to quantify the long lived fission product
I-129.
The todine isotope production 1s a varlant according to weapon design
and its value has a major impact on acute exposure thyruid dose equivalent estimates.
The evaluation of diet and living patterns among the inhabitants of the
Northern Marshall Islands and the data gathered on their anthropometric and
physiologic characteristics are used as input to the e>cternal and internal