222 Health Physics madeonthe raw (1.e., unseparated) sample. The detector efficiency for measuring gammaemissions from '*'T was estimated to be 39% at the time ofthe first reporting of results******% and later modified by Harris to be 35%." Analyses of other radionuclides were also conducted at LASL as described by internal LASL reports from 1954.***** These included beta ray measurements of dried urine samples and analyses of plutonium in urine. Analyses for plutonium were based on an unidentified means of chemical isolation which was the procedure in use at LASLatthat time, followed by alpha counting for 80 min.**** Assumptions for estimation of radioiodine intake August 2010, Volume 99, Number 2 Another assumption made in 1954 was that ingestion was the primary modeof intake.** This conclusion follows from various arguments including the relatively large size of particles deposited at Rongelap, which would tend to preclude inhalation and has been subsequently supported by Lessard et al. (1985) and Simonet al. (2010b). Based on these various assumptions, the intake (Bq) of radioiodine on the day of intake can be simply estimated by the quotient of the '*'I activity measured in the total daily urine output (decay corrected from time of measurement back to time of collection) and the frac- tional excretion on the day of collection per unit of intake (unitless). Intake and internal radiation dose calculations can be made with varying degrees of complexity and realism, and though few parameters are needed to makeestimates of intake, calculations generally require assumptions, some that can be made with good assurances and others that can be difficult to verify. One assumption inherentin The urinary fractional excretion on any single day following intake can vary, however, among individuals (1954**), was that the excretion followed a single intake in urine from an acute intake. Hence, for the most part, due to differences in individual metabolism, differences in ambient temperature, and differences in water losses from the body, primarily through the skin (Maoetal. 1990, 2001; ICRP 2002). There are few reported long- the interpretations of the ''I assay data by Harris term empirical data (beyond a few days) of '*'I excreted of radioiodine from Bravofallout. This appears as a good assumption because the last test depositing fallout at Rongelap prior to Bravo wasthe Kingtest in 1952 (Beck et al. 2010), and there were no further tests depositing fallout before the urine samples were collected in midMarch of 1954. While the simplest assumption concerning time of intake is to assume that intake occurs at the onset of deposition, other assumptions are clearly possible. For example, the total estimated intake could be partitioned into fractional intakes at various time following deposition, e.g., at meal-times. Though differences in assumptions about time of intake are not extremely important for the daily excretion fraction must be predicted from a biokinetic model. Various radioiodine biokinetic models have been published over the years. For example, the International Commission on Radiological Protection (ICRP 1989) published basic metabolic data for iodine in the body based on the description by Riggs (1952) and used that data to develop a three-compartment model with explicit representations for blood, thyroid, and the rest of the body. These models, however, were not available at the time of the exposures to Bravofallout. The estimated excretion fraction from an acute intake of '"'T (i.e., fraction of original intake excreted on For example, Lessard et al. (1985) calculated total day f) used by Harris in 1954** was 0.001 on H+16 d and H+17 d based on the advice of biokinetics expert, Joseph Hamilton (see, for example, Hamilton and Soley wasingested 5.5 h post-detonation (H+5.5 h or ~12:15 data on the long-term excretion of radioactive iodine ‘ST, partitioning the total intake may be modestly impor- tant for dosimetry of the shorter-lived iodine isotopes. intakes based on the assumption that one-third of the '*'] pm) and two-thirds at H+12 h (~6:45 pm). In the earliest LASL assessment by Harris,** no such assumptions were made. In the work of Simon et al. (2010b), intake was considered to occur at the midpoint of the period of deposition which typically takes place for a period of time somewhat less than the elapsed time between detonation and onset of fallout (Simon etal. 2010b). #2 Tog Alamos Scientific Laboratory, Memo R3574, “Data on plutonium results from urine samples collected in the Marshallese.” Undated. Declassified by Atomic Energy Commission, 3/23/1972. Obtained from archives of U.S. DOE Environmental Measurements Laboratory. 1939, 1940; Hamilton 1948). However, because good were not available at that time, the value of 0.001 was recognized as only an estimate and radioactive decay between time of intake and time of sample counting was accounted for in the decay factor of eqn (1). Values of the excretion fraction of '*'I used by later investigators have varied within a range of two-fold; however, all these implicitly included radioactive decay between day of intake and day of sampling. For example, Lessard et al. (1985) provided an estimate of 1.4 < 10 * for the early LASL samplesas derived from ICRP (1979) and Johnson (1981). Goetz et al. (1987) estimated that the excretion fraction for the American military men on Rongerik was 3.07 X 10* on day 17 as derived from