MCNP simulation of TRR-II cold neutron source design

摘要

A cold neutron source (CNS) for the modified Taiwan Research Reactor (TRR-II) was designed using the MCNP code. Liquid hydrogen at 20 K is selected as a moderator. The moderator cell has a structure of a cylindrical annulus in which the outer shell contains liquid hydrogen and the inner shell has only hydrogen vapor. The moderator cell is made of a 6061 aluminum alloy and is located in the position of thermal neutron flux of 1.45 x 10(14) n/cm(2)s. Parametric analyses, such as the thickness of liquid hydrogen in the outer shell. the thickness of D2O gap between the vacuum chamber of CNS and the window of the BT-8 beam tube. void ratio and ortho/para ratio in the liquid hydrogen, were done. The cold neutron gain and the cold neutron brightness at the entrance of the cold neutron guide are also evaluated and compared with other facilities. The nuclear heat load of the CNS was calculated by considering fast neutrons from the core. prompt fission gamma rays, delayed gamma rays, and beta decay from Al-28. The results show that TRR-II CNS has a good performance for the study of condensed matter and fundamental physics using cold neutrons. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 8]