Trapping of thermal neutrons, (2). Miscellanea

With the help of formula obtained in Part 1, effects of mixing light and heavy water are examined. The maximum trapping factor as well as the optimum radius of the mixture varies monotonically with the mixing ratio. Contrary to the mixing case, D₂O surrounded by a H₂O layer as a blocking layer for trapped thermal neutrons will give a higher trapping. A central cavity in a trapping medium can hardly enhance the trapping effect. Effects of a reflector enclosing an active shell are discussed. A thick D₂O reflector will be most effective in view of criticality, provided that the active shell is thin enough. In a trapping medium, the fast neutron importance rather than the thermal importance will be affected by the existence of an reflector. (author)