Long-term accumulation and microdistribution of uranium in the bone and marrow of beagle dog.

The accumulation and microdistribution of uranium in the bone and marrow of Beagle dogs were determined by both neutron activation and neutron-fission analysis. The experiment started immediately after the weaning period, lasting till maturity. Two animal groups were fed daily with uranyl nitrate at concentrations of 20 and 100 microg g(-1) food. Of the two measuring techniques, uranium accumulated along the marrow as much as in the bone, contrary to the results obtained with single, acute doses. The role played by this finding for the evaluation of radiobiological long-term risks is discussed. It was demonstrated, by means of a biokinetical approach, that the long-term accumulation of uranium in bone and marrow could be described by a piling up of single dose daily incorporation.

A new statistical method for transfer coefficient calculations in the framework of the general multiple-compartment model of transport for radionuclides in biological systems.

A new and simple statistical procedure (STATFLUX) for the calculation of transfer coefficients of radionuclide transport to animals and plants is proposed. The method is based on the general multiple-compartment model, which uses a system of linear equations involving geometrical volume considerations. By using experimentally available curves of radionuclide concentrations versus time, for each animal compartment (organs), flow parameters were estimated by employing a least-squares procedure, whose consistency is tested. Some numerical results are presented in order to compare the STATFLUX transfer coefficients with those from other works and experimental data.

Energy levels in 139La from the decay of 139Ba.

The gamma-ray spectrum of 139La following the beta- decay of 139Ba has been studied using both singles and gammagamma coincidence spectroscopy techniques. The energies and intensities of 30 gamma-transitions have been determined, which include three new transitions placed in the level scheme. Two new levels at 1524.6 and 1900.3 keV excitation energies are proposed and a number of gamma-transitions have been confirmed. On the basis of these results a precise decay scheme is proposed.

Transfer coefficient measurements of uranium to the organs of Wistar rats, as a function of the uranium content in the food.

Groups of animals (Wistar rats) were fed with rations doped with uranyl nitrate at concentrations ranging from 0.5 to 100 ppm. The uranium content in the ashes of the organs was measured by the neutron-fission track counting technique. The most striking result is that the transfer coefficients, as a function of the uranium concentration, exhibit a concave shape with a minimum around 20 ppm-U for all organs. Explanations to interpret this finding are tentatively given.