Moderator Temperature Coefficient

User Support
1

Hello, everyone.

I have been trying to find the moderator temperature coefficient of a reactor core by varying the temperature of the coolant from 500 to 650K, increasing the temperature by 5K at each step. The temperature of the other materials in the core is set to constant. However, the result I am getting is not desired and it hardly varies. I am using the following algorithm:

  1. Calculate k1 at coolant temperature T1
  2. Calculate k2 at coolant temperature T2
  3. MTC = (k2-k1)/[k2 k1 (T2-T1)]
    I have used the same algorithm for the fuel temperature coefficient and that value is coming as desired. It is the moderator temperature coefficient which is showing problem.
2

Have you changed the density of moderator also or just temperature?

3

If you change the temperature of the nuclide, you are changing the cross section curve. In case of the full you can see the doppler effect. In the case of the moderator, there are probably no noticeable changes in the scattering and absorption shock session curve.

For you to collect correct results (both for the fuel and the moderator) you need to vary the temperature and also the density (the density as a function of temperature).