Characterization of a Neutron Collimator for Neutron Radiography

At the ENEA TRIGA research reactor (Casaccia Research Center, Rome), a new neutron collimator has been designed and installed at the neutron tangential channel. This collimator, that is part of a neutron/X-ray facility for NDT analysis, was experimentally characterized and optimized in terms of thermal neutron flux, its spatial/energetic distribution, photon air KERMA and effective beam diameter. This paper shows the methodologies and the results of the experimental analysis that was carried out. TRIGA RC-1 DESCRIPTION The TRIGA Mark II nuclear reactor, named “RC-1” as Reactor Casaccia 1, was build in the early sixties from General Atomics, with original power of 100 kW, increased by the ENEA staff to 1 MW in 1967. It is a pool thermal reactor having a core contained in an aluminium vessel and placed inside a cylindrical graphite reflector, bounded with lead shielding. The biological shield is provided by concrete having mean thickness of 2.2 m. Demineralized water, filling the vessel, ensures the functions of neutron moderator, cooling mean and first biological shield. Reactor control is ensured by four rods: two shims and one safety fuelled follower rods, and one regulation rod. Produced thermal power is removed by natural water circulation trough a suitable thermohydraulic loop comprehending heat exchangers and cooling towers. In Tab. 1 are listed some irradiation facilities.