Conceptual design for TRR-II neutron guide system

Abstract

The Taiwan Research Reactor modified Project (TRR-II) is going to construct the neutron guide system (NGS) in order to transport cold neutrons, with well-defined angular and energy characteristics, from cold neutron source (CNS) to the distant guide hall of 30×60 m 2. The conceptual design of NGS will optimize the performance and safety of the whole system considering the scientific and engineering options. The NGS starts from a specialy designed cold neutron beam tube (BT-8) that looks onto the CNS and contains four primary neutron guides, whose cross sections are 6×15, 5×20, 6×15 and 6×17 cm 2, respectively. These neutron guides are coated with either Ni-58 mirror, or 2 θ C or 3 θ C supermirrors. In the guide tunnel of the reactor building, the primary neutron guides are connected to the curved guides in order to remove the gamma rays and fast neutrons. A curved neutron guide is subdivided into two up and down guides by inserting two partition mirrors and separated from each other by the opposite curved guides. In the guide hall, neutron beams are supplied to each instrument using benders or monochromators. The design parameters of the neutron guides are optimized using the neutron guide simulation code. The safety concepts of the NGS are also described in this paper.