Numerical improvements of the exact kernel method in transport theory

The formalism of the exact DSN method also called the I method, is recalled. A fully analytical integration is proposed to compute the three-dimensional array I(k,l,m), which is the crucial point of such a theory. Comparisons with the numerical quadratures proposed so far show that a significant CPU time savings is achieved (a factor of 1000 for S/sub 8/), and, moreover, a few symmetry properties relax the storage requirements by a factor of 4