Studies on neutron generated activities in the bombardment of 0.5, 1.0 and 1.5 GeV protons on massive targets using chemical sensors

A renewed interest in spallation has arisen with the proposals of accelerator-driven transmutation of long-lived radioactive waste and the so-called energy amplification. To investigate the neutron yields in massive targets, a series of experiments has been carried out at the Synchrophasotron of the Joint Institute for Nuclear Research (JINR), Dubna, using proton beams of energy between 0.5 GeV and 1.5 GeV on solid lead (φ 8 x L 20 cm) and uranium targets (φ 3.6 x L 21 cm) surrounded with Pb-rings (2.2 cm), both targets were surrounded by a 6 cm thick paraffin moderator. To measure the proton beams, a new monitor system was developed and used in the present work. On the outer surface of moderator a number of small U and La sensors was placed to register the neutron induced activities. The neutron distribution on the outer surface of moderator has its maximum flux about 5 - 10 cm downstream of the entrance point of the incident particles into the massive target. The transmutation rate of long-lived nuclear waste 129I and 237Np induced by the spallation neutrons was also studied in the present work. (author)