Urinary and fecal excretion of 144Ce was studied for 15 days following subcutaneous, intramuscular, intraperitoneal and intravenous injection of 144CeCl3 to the rat. From the third to the 15th day, the daily urinary excretion of 144Ce following all the routes of administration was expressed in the first approximation by a single exponential function, regardless of the difference of the routes. It means that the initial body burden of 144Ce can be estimated from the daily urinary excretion of 144Ce during this period using an identical formula. Tissue distribution of 144Ce 15 days postinjection was also studied. After 15 days following subcutaneous and intramuscular injection, 57 and 38 percent of the injected 144Ce were found at the sites of injection, respectively. The transported 144Ce was deposited mainly in the liver and bone regardless of the routes of administration.
Cerium-141 given orally was retained in the whole-body for much more prolonged time by suckling than by weanlings or adult rats. Distribution study showed 141Ce given orally to suckling rats was associated with the intestinal tract and little was transferred to the other organs or tissues, although the intestinal absorption rate was much higher than that of adult rats. Intestinal radiation doses of the suckling, weanling and adult rat by orally given 141Ce were calculated on the assumption that 141Ce was practically distributed uniformly in the intestinal tract with contents. The results showed that the intestinal dose of the suckling rat was much greater than that of the weanling or adult rat. Because of the greater intestinal dose and the high intestinal absorption of 141Ce in the suckling rat, the radiocerium should be considered as more hazardous than previously regarded.
A description is given of work carried out to determine the optimum condition for maximum extraction of a number of alpha emitting radioactive elements with dinonyl naphthalene sulfonic acid from urine dissolved in perchloric acid. The extraction yield of plutonium, thorium, uranium, and their mixture is about 90% using this procedure. Emphases are given to the acidic effect of the aqueous phase, the concentration effect of the organic phase, and the shaking and the settling time.
With the development of peaceful uses of atomic energy, the works dealing with uranium compounds have recently increased in the country. In the uranium refinery, there are several uranium compounds dusts in the air and workers there may encounter hazards to inhale the dusts. The concentrations of uranium in the air of a uranium refinery and in the urine of the workers were measured. Uranium was found to be in the range of 9.6×10-11-3.7×10-9g/l in the air of the refinery and, in the urine of the workers, in the range of 3.9×10-7-3.6×10-6g/l. The concentrations in the air are higher than that of natural level by order of two to four and those in the urines higher than those of the general public order of one. It is considered that these high levels in the urine are due to inhalation in higher concentrations of air borne uranium of the working environment.
Problems of environmental contamination by 85Kr are investigated. 85Kr is produced by fission of nuclear fuels and most of it is discharged to the atmosphere during the reprocessing of spent fuels. Because it is a rare gas, it is difficult to retain it by the conventional method. Once discharged, it remains for a long time in the atmosphere and results in global contamination as well as local contamination. The discharge rate at currently-operating reprocessing plants is about 4×103 Ci·d-1 per t·d-1 and the annual average concentration of 85Kr at a few kilometers is about 5×103pCi·m-3 and the corresponding average gonad dose and skin dose are 85μrad·y-1 and 10.5 mrem·y-1 respectively. The concentration of 85Kr in the atmosphere is about 15pCi·m-3 in 1970, but for the year 2000 the predicted value is 2500pCi·m-3 and the corresponding annual skin dose is 5200μrad. The status of the work on 85Kr removal and the uses of recovered one are also reviewed.