- 148 --


where

                      T (r)
               G(T) =   g   (T')dT'                (8.44)
                       T0



        In most cases of practical interest, simple analytical expressions for the opacity of the fuel, coolant, or mixed plasma regions are not available. The temperature dependence of these opacities will be determined from experimental measurements or theoretical calculations. In such cases, numerical methods must be used to obtain temperature distributions.


Composite Opacity with Arbitrary Temperature Dependence

        Let the opacity with arbitrary temperature dependence be denoted by KR = K R(T). The corresponding diffusion coefficient is


                    K16cT                          (8.45)
                    R(T)    3K R(T)


The energy balance equation (8.9) is expressed as


                 V •(K R(VT) + S = 0               (8.46)

Substituting (8.45) into equation (8.46) and using the identity


V . (uVv) = uV2v + Vu - Vv


(8.47)