Improved monochromator concrete shielding for the cold neutron triple-axis spectrometer at HANARO

The cold-neutron triple-axis spectrometer (Cold-TAS) installed at CG5, high-flux advanced neutron application reactor (HANARO) has undergone an optimization process in the segmented shield and sample table owing to a slight deformation in 2013. A rapid deformation of the Cold-TAS guide shield was recognized when the reactor was shut down for a long time, and other deformations were confirmed in several monochromator concrete shields in 2015. To ensure safety of the experimental environment, it was decided to redesign the monochromator concrete shield. In the redesigning process, the structure of the segmented and borated polyethylene shield, beam dump, and the shield around the monochromator was changed to improve shielding performance. To improve the load-supporting structure, the outer shape of the monochromator concrete shield was changed from vertical to horizontal. When the mechanical design changed, the proper material, thickness, and density were determined based on the shielding performance results. The improved monochromator concrete shield, Cold-TAS Mark III, was installed at CG5 again. The inspections of the mechanical installation and operations of the sample table and analyzer were completed in the end of 2016. (author)