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## Main Question or Discussion Point

This is in the beginning of a long set of problems, and I am lost. I don't get anything like this answer. Any guidance? I have a feeling its simple but haven't done much of these.

Write down the diffusion equation for the neutron flux in a multiplying sphere of radius R containing a constant distributed source of strength Q neutrons/cm3/s. Assuming that the flux vanishes at the sphere surface and that it remains finite at the origin:

Solve the diffusion equation when k inf = 1 and show that the neutron flux is given by:

(Q/6D)(R^2 − r^2)

Write down the diffusion equation for the neutron flux in a multiplying sphere of radius R containing a constant distributed source of strength Q neutrons/cm3/s. Assuming that the flux vanishes at the sphere surface and that it remains finite at the origin:

Solve the diffusion equation when k inf = 1 and show that the neutron flux is given by:

(Q/6D)(R^2 − r^2)