Design of On-line Rare Isotope Production System for the RAON Facility

Abstract

The Rare Isotope Science Project (RISP) in Korea is developing the Rare Isotope (RI) Accelerator, RAON. The RAON is planned to be an advanced RI beam using Isotope Separation On-line (ISOL) with a high power target. The key feature of ISOL facility is to provide high intensity and high quality beams of neutron-rich isotopes with the atomic mass number in the range 80 - 160 by means of a 70 MeV proton beam directly impinging on uranium carbide (UCx) thin-disk targets. We are developing the ISOL target system to produce the neutron-rich RI, which consists of 1.3 mm thick uranium carbide disks and cylindrical tantalum heater, to be installed in the new facility of RISP in Korea. The intense neutron-rich nuclei are produced via the fission process using the UCx targets with a 70 MeV proton beam. The fission rates were estimated to be 1.5 × 1013/sec, 7.3 × 1013/sec and 1.5 × 1014/sec for 10 kW, 35 kW and 70 kW proton beam, respectively. The target system has been designed to be operated at a temperature of 2000 ℃ so as to improve the release efficiency. In the ISOL target area, major radiation hazards are related to prompt radiation fields (mainly neutrons) and residual radioactivities due to the interaction of the primary beam and/or secondary radiation (neutrons) with the beam line, the target stations and their surroundings. The UCx target is the most critical item of the facility from a radiation safety point of view due to the high levels of radioactivity induced by the fission reactions. In order to reduce the dose rate below the RISP’s design limit of 5 μSv/h (radiation worker area), 400 cm, 330 cm and 270 cm thick concrete shields are required in the forward, side and roof directions, respectively.