Diffusion Theory

  • Thread starter EngNewbit
  • Start date
  • #1
1
0
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)
 

Answers and Replies

  • #2
Astronuc
Staff Emeritus
Science Advisor
18,932
2,258
One has to write the diffusion equation (in spherical coordinates) with a constant, distributed source, and apply the boundary conditions, that the flux [tex]\phi[/tex] is finite at r = 0, and 0 at r = R.

The current should also be 0 at r = 0.
 

Related Threads on Diffusion Theory

Replies
15
Views
32K
Replies
1
Views
4K
  • Last Post
Replies
4
Views
4K
  • Last Post
Replies
9
Views
1K
  • Last Post
Replies
7
Views
12K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
16
Views
8K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
5
Views
1K
Top