Transmutation of radioactive waste by means of relativistic heavy ions

A series of experiments was carried out at the synchrophasotron of the Joint Institute for Nuclear Research (JINR), Dubna, using 3.67 GeV protons and 18 GeV 12 C ion beams. Two solid lead and uranium targets surrounded by paraffin moderator were irradiated. The outer surface of the moderator contained a number of small U and La sensors, and also solid-state nuclear track detectors. Both experimental techniques identify independently approximately 28 low-energy neutrons per 3.67 GeV proton hitting the Pb target. Theoretical estimations based on LAHET and DCM/CEM computer codes show considerably smaller fluences. A similar problem seems to appear in analogous experiments at the Centre des Recherches Nucleaires (CERN), Geneva. In addition, long-lived radioactive waste nuclides, such as 129 I (T 1/2 = 1.57 . 10 7 a) and 237 Np (T 1/2 = 2.14 . 10 6 a), in the form of well-sealed targets (approximately 1 gram each) were placed in different geometrical positions during the 3.67 GeV proton irradiations The transmutation rates are substantial: a 10 mA, 3.67 GeV proton accelerator is able to transmute at least 30 % of 237 Np and 1% of 129 I per month, under the given geometrical conditions.