BOXER3: a three dimensional integral transport code for PHWR supercell

This report describes BOXER3, three dimensional computer code for solving the integral transport equation. The code uses a combination of the collision probability and the interface current methods. It uses mixed rectangular and cylinderical coordinates and can therefore treat cylindrical fuel channels and reactivity devices within a rectangular 'supercell' of a Candu PHWR. The report describes the details of computation of collision probabilities and the solution of the neutron balance equations. The latter can be done iteratively or by direct matrix inversion. It is shown that the iteration scheme is convergent. Comparisons of the results of BOXER3 and those obtained by other transport and diffusion codes in one, two and three dimensional geometries are also presented. (author)