Opal neutron beams shutters

Full text: The Opal Reactor has five beam tubes for neutron beams. Of these 5 tubes, two come from a cold neutron source, another two from thermal sources, and a fifth is ready for a future hot neutron source. Neutron guides come from the cold and thermal beam tubes. Neutron beams are enabled/disabled through shutters located inside the reactor pool's radial shield. These shutters were specially designed by INVAP for the OPAL reactor. They comprise fixed and movable shields. The movable part allows neutron beam enabling or disabling. The design of these shutters demanded the construction of prototypes that were further submitted to comprehensive tests to be qualified in light of the strict movement precision and high reliability requirements involved. The shielding material - a plastic and steel mix - was also specifically designed for this facility. The design required great efforts as to shield calculation and energy deposition. A heat removal system was designed to dissipate the energy absorbed by the shields. The cold and thermal beam shutters are built following a single vertical axis design. The hot shutter, due to different requirements, was designed with a horizontal axis