Absorption of uranium-233, neptunium-237, plutonium-238, americium-241, curium-244, and einsteinium-253 from the gastrointestinal tract of newborn and adult rats

Absorption of the nitrates of 233U, 237Np, 238Pu, 241Am, 244Cm, and 253Es by the adult rat was estimated at 0.03 percent, 1.0 percent, 0.006 percent, 0.012 percent, 0.04 percent, and 0.014 percent, respectively; absorption of the oxides of 241Am and 244Cm was estimated at 0.01 percent and 0.003 percent, respectively. These estimates are based on retention in skeleton and liver. Absorption of the nitrates of 237Np, 238Pu, 241Am, 244Cm, and 253Es by the newborn rat was estimated at 6.6 percent, 2.9 percent, 5.0 percent, 2.0 percent, and 5.1 percent, respectively; absorption of the oxides of 241Am and 244Cm was estimated at 1.1 percent and 1.7 percent, respectively. The amount retained by the lower small intestine of newborn rats was frequently several times more than the amount absorbed, which could be a significant factor in evaluating the hazard potential of these radionuclides. (U.S.)