Transmutation of radioactive waste with the help of relativistic heavy ions

A series of experiments was carried out at the Synchrophasotron, LHE, JINR, Dubna, using 3.67 GeV protons and 18 GeV 12C ion beams. Two massive lead and uranium targets surrounded by paraffin moderator were irradiated. The outer surface of the moderator was some small U- and La-sensors, to be studied by radiochemistry activation techniques, and also by solid-state nuclear track detectors. Both experimental techniques independently give approximately 28 low energy neutrons on the outer surface of the moderator per 3.67 GeV proton hitting the Pb-target. Theoretical estimations based on LAHET and DCM/CEM computer codes give considerably smaller fluences: approximately 7-9 low energy neutrons (<0.1 keV) and 34-35 neutrons at all energies in the same geometrical positions. A similar problem seems to appear in analogous experiments at CERN. In addition, long-lived radioactive waste nuclides, such as 129I(T1/2=2.4 days), could be identified radiochemically as well as other spallation products. The transmutation rates are substantial: a 10 mA accelerator of 3.67 GeV protons could transmute at least 30% of 237Np and 1% of 129I per month under the given geometrical conditions