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[en] The use of Sr-85 as an indicator of the skeletal location and relative amount of bone demineralization which occurs during immobilization of the body or body parts, bed-rest or space flight was studied. The bone mineral replacement which occurs after immobilization was measured rather than the bone loss which occurs during immobilization. In a study with two adult beagle dogs, the Sr-85 uptake in a leg which had been immobilized for two months was 400 percent higher than the uptake in the legs in regular use. This increased uptake probably resulted from only a few percent loss in bone mineral and indicates that losses less than one percent can be easily detected and located. The sensitivity, simplicity, and low radiation dose associated with the use of this method indicates that it should receive consideration for use on humans in bed-rest and space flight studies. Methods for measuring changes in total body nitrogen and in assisting the Johnson Space Center in calibrating a whole body counter for total body potassium measurements were also investigated

[en] A state-of-the-art radiation detector system consisting of six individually mounted intrinsic germanium planar detectors, each 20 cm² by 13 mm thick, mounted together such that the angle of the whole system can be changed to match the slope of the chest of the person being counted, is described. The sensitivity of the system for counting uranium and plutonium in vivo and the precedures used in calibrating the system are also described. Some results of counts done on uranium mill workers are presented. 15 figs., 2 tabs

[en] Significant advances in the measurement of ²³⁹Pu, ²⁴¹Am, ²³⁵U, and ²³⁸U have been obtained over the past several years due to the availability of the Livermore Lung phantom and the mock plutonium study. Further improvements obtained through the use of arrays of high-purity planar germanium detectors were published. Even further improvements are needed if we are to achieve the ability to reliably measure pure ²³⁹Pu lung burdens of 16 nCi or less in the average size radiation worker. Although there are many approaches that could provide improved measurement capability, only five of the more important ones will be discussed in this paper to stay within the time restraints. 8 refs., 7 figs

[en] The extensive use of liquid sodium as the primary coolant for fast breeder reactors presents human safety hazards from both the chemical toxicity of the sodium oxide and the radioactive toxicity of the large quantities of ²⁴Na and ²²Na in case of a rupture in the liquid sodium piping. Although the effects of the chemical toxicity are expected to be very immediate and more severe, the radioactive toxicity is also of significant concern. Other sources of radioactive sodium contamination exist in the nuclear industry. This paper describes some procedures which can significantly reduce the radiation dose to the body from ²⁴Na and ²²Na which might be accidentally inhaled or ingested. Studies with rats indicate that the retention time of the sodium isotopes which have exchanged with the body sodium pool can be reduced by a factor of 10 by ingestion of high levels of stable sodium. In addition, the ingestion of a sodium salt at the time or immediately after the inhalation incident could result in at least 60 percent or more of the inhaled radioactive sodium to be excreted before it exchanges with the body sodium pool. The combined effects of both immediate and sustained sodium ingestion in rats can result in a radiation dose from ²²Na of only 4 percent or less of that which would result if no additional salt is administered. The dose reduction for ²⁴Na would not be as much as that for ²²Na but would be significant. The tolerance for high levels of stable sodium intake in humans will be discussed and optimum intakes will be suggested which will provide the maximum radioactive sodium excretion with minimum harm to the physiological processes of the body

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[en] The total body calcium in humans was determined by measuring expired Ar-37 after neutron irradiation. The excretion of Ar-37 from humans was found to be much slower than the excretion from rats and dogs, and to be related to the age of a person. A study of the uniformity of the Ar-37 production throughout the thickness of the body was studied using phantoms. The results indicate that it should be possible to obtain a uniformity within plus or minus 3 percent for the production of Ar-37 per unit of calcium by using a bilateral irradiation. New low background, large volume proportional counters were developed and constructed, for more sensitive measurement of Ar-37 in the expired air from patients. A new irradiation enclosure was developed for measuring total body calcium in rats by the Ar-37 method. With this enclosure the Ar-37 production per gram of calcium is constant with a standard deviation of plus or minus 2.8 percent for any size rat between 100 and 500 grams. The use of Na-22 as measure of bone replacement in the fractured femur of a dog was not successful