Proposals for setting possible limits on intake of transuranium radionuclides absorbed from the gastrointestinal tract

The absorption of transuranium elements (238Pu, 241Am, 252Cf) from the gastrointestinal (GI) tract as influenced by physiological factors (e.g. age) and physical and chemical properties of compounds incorporated has been studied in 600 white mongrel rats. Average values of absorption have been determined for simple salts and a complex citrate. A number of factors increasing absorption have been found. Thus, originally bound compounds contained in the meat of animals incorporated with 238Pu and 241Am when alive, 241Am-containing potato juice and green oat stalks enhanced absorption by a factor of 5 to 30 as compared with an adequate control. Ethanol administered orally as a 20% solution increased the absorption of americium nitrate by 60% and that of citrate by 23%. Oral administratio of 241Am nitrate solution together with ferric chloride changes the metabolic kinetics of the nuclide completely. The total absorption of americium from DI tract is 7.1 times that of the control, but a considerable fraction absorbed into blood is excreted with urine (4.2% over 8 days). Among physiological factors age effects the absorption of transuranics from the GI tract to acertain degree. The absorption of 252Cf in 7 day-old young rats proves to be 8.1 times that of adults. Gestation brought about a 2.7 fold increase of 241Am absorption