EXPANDA-4, 1-D Neutron Diffusion in Slab, Spherical Geometry from JAERI Fast-Set with Criticality Calculation

1 - Nature of physical problem solved: EXPANDA-4 solves the one-dimensional diffusion equation in slab, cylinder or sphere geometry. As the coefficients of the equation, it calculates effective cross sections from the library data of JAERI-Fast set in 25 group structure before it automatically transfers the control to the criticality calculation. The criticality adjustment is, if necessary, done by adjusting the thickness of one of the reactor regions. Adjoint equation can also be solved. 2 - Method of solution: The central difference approximation is adopted for the differential coefficients. The three points difference equation is solved by the ordinary set of two points recurrence formulae