Nuclear Science and Engineering / Volume 20 / Number 3 / November 1964 / Pages 331-337
Technical Paper / dx.doi.org/10.13182/NSE64-A19578
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The ‘intermediate resonance’ formulation of slowing-down problems is extended to nonhomogeneous systems by means of formulating the integral transport equation for the problem and comparing with the analogous homogeneous system equations. Heavy-atom slowing down in a heterogeneous system is accounted for in this formulation, yet quite concise expressions for resonance integrals are obtained. Numerical results are compared with a Monte Carlo calculation for a specific lattice, and good agreement is obtained. The comparison of homogeneous and nonhomogeneous system equations not only establishes the so-called ‘equivalence relations’ but also clearly brings out the approximations involved in these relations and permits a determination of some of the errors involved. In particular, the ‘flat-flux approximation’ is discussed in detail.