Transfer of radium-228, thorium-228 and radium-226 from forage to cattle and reindeer

Concentrations of radium-228, thorium-228 and radium-226 were measured in different natural forage materials and in feed supplements. The activity concentrations of these nuclides were then determined in the bones of domestic farm animals, with emphasis on their distributions within the skeleton and humerus. Feeds added in recent years to the forage of domestic animals alter the concentrations of the naturally occurring radionuclides. The modified daily radium uptakes associated with the various feeds are reflected in the radium concentrations observed in the different layers of the humerus. Radium uptake and retention are highly dependent on calcium metabolism. We propose a method for calculation of nuclide retention coefficients via an approach which simplifies their assessment and provides important information on radium metabolism. The data obtained here are of value in dosimetric assessments related to these natural radionuclides. (author)