The Unreflected Reactor in Age Theory

The simple reactor model we propose for these analyses may be defined in terms of the following assumptions  

As mentioned, our first model is based on the assumption of monoenergetic fission sources. The use of a monoenergetic spectrum for the fission neutrons as a first model seems justified in view of the fact that the actual spectrum is a sharply peaked function (see Fig. 4.25). Thus a delta function placed in the vicinity of the peak will yield a reasonable description of the fission spectrum, especially in regards to its influence 

The combined slowing-down diffusion equations which will be used for the study of the multiplying medium are 

The purpose of the present section is to solve the differential equations (6.54) for two cases of the source function S(r,w). For the first case we use the monoenergetic fission source given by (6.55) and look for the solution to (6.54) which satisfies certain boundary conditions. In a system of finite extent these conditions are specified on the outer surface of the medium. An appropriate set of such conditions was discussed in Sec. 5.le 

It is convenient in developing the solution to Eqs. (6.54) to rewrite equation (a) in terms of the slowing-down density 9(r,u) in place of the fast fiux In the present case of a monoenergetic neutron source, 

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