Reactor physics studies of various advanced neutron source reactor core configurations

The current conceptual design for the core of the advanced neutron source (ANS) reactor is a vertically split, annular geometry composed of involute, thin (1.3-mm) fuel plates and thin (1.3-mm) heavy-water coolant channels. The core would have a heavy-water reflector, and estimates of the total fueled core volume have ranged from 30 to 60 ell. Due to control rod and materials irradiation position constraints, the inner radius of the annulus is expected to be at least 110 mm. A goal of the ANS project is to design a facility in which the peak thermal flux in the reflector is 5 to 10 x 1019 n/m2·s. To achieve this goal while maintaining adequate thermal-hydraulic margins, a variety of core configurations have been proposed, two of which are shown. For both the two- and three-element designs, coolant flowing through any single element does not enter the other element(s). The use of three elements allows the length of each element to be smaller - reducing pressure drop and inlet/outlet temperature differential. However, the engineering complexity and cost of the three-element design exceeds that of the two-element design. This paper discusses the relative merits of these designs from a neutronics viewpoint