Shielding Cask for a ²⁵²Cf Ion Source

S.I. Baker; E.F. Moore; R.C. Pardo; and G. Savard (Argonne National Laboratory)

A dual-purpose cask provides shielding for an intense radioactive source during transport and use. Design considerations are presented for such a cask for the proposed ²⁵²Cf upgrade to the ATLAS accelerator at Argonne National Laboratory. A 37 GBq ²⁵²Cf fission source yields neutron-rich isotopes. These fission fragments stop in a gas catcher, are extracted into an electron cyclotron resonance ion source to increase the charge state, and then accelerated in the ATLAS superconducting linac. The technique is expected to produce accelerated beam intensities of up to one million ions per second on target, greatly enhancing the physics capabilities currently available worldwide to study neutron-rich nuclei. Also, experience gained in handling radioactive fission fragment beams is applicable to the Rare Isotope Accelerator. As currently planned, after shipment of the ²⁵²Cf source from ORNL in a conventional cask, transfer to the dual-purpose cask takes place in a hot cell at Argonne before movement of the source to the ATLAS accelerator. At ATLAS the cask ascends to the high voltage platform and opens remotely to allow the bare ²⁵²Cf source to move forward and mate with the gas catcher. Borated polyethylene slows down and absorbs the neutrons and reduces the weight lifted. For facilitating maintenance, a removable insert collects the fission fragments stopped inside the cask as well as any loose source material. Also, elements of the gas catcher are modular for radiation exposure reduction during repair.

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