0
$\begingroup$

As we know, the relationship between atomic weight and neutron energy loss can give the number of collision between a neutron and nucleus to slow down (average logarithmic energy decrement.)

I was wondering if this can be a good factor of selecting materials for fast and thermal reactor. I have not found the any relevancy between the relationship mentioned above and the material selection of the reactors.

Can anyone please explain how the relationship between atomic weight and neutron energy loss can be relevant to the selection of materials between fast and thermal reactor? Or, can anyone give me any link/sites to know about it more?

$\endgroup$
2
  • $\begingroup$ "As we know, the relationship between atomic weight and neutron energy loss can give the number of collision between a neutron and nucleus to slow down." Can you explain more what process/ relationship your thinking of? I don't understand it as is $\endgroup$ Mar 21, 2021 at 18:49
  • $\begingroup$ I have acquired this concept from this (I do not know its the correct concept or not)- lanl.gov/org/ddste/aldgs/sst-training/_assets/docs/PANDA/… (page 360). (kinetic energy of thermal neutron formula) $\endgroup$ Mar 21, 2021 at 19:06

2 Answers 2

0
$\begingroup$

The average logarithmic energy loss ("xi") is very important for selecting good moderators. If a neutron can lose a lot of energy by colliding with the material, it will be a good moderator. However, "xi" is not the only factor involved. You also have to consider the scattering and absorption cross sections of the moderator. In addition to "xi", a good moderator should also have a high scattering cross section and a low absorption cross section.

if you put these together, you can define a "moderator effectiveness" as xi*sig_scat/sig_abs. If you do this, you will find that heavy water is usually defined as the "best" moderator.

This is covered in many nuclear engineering textbooks. See for example, Table 8-1 in Duderstadt and Hamilton.

$\endgroup$
0
$\begingroup$

A moderating material slowing down neutrons is all the more effective when the slowing down is done in a minimum of shocks; For that, the neutron in slowing down must meet nuclei of mass as close as its own: at this moment, it loses half of its energy at each shock. But this is not the only fact to take into account to have a good retarder : it must be not very absorbent towards the slowed down neutrons. Also to be taken into account, the economic cost and the ease of technological use. Hence the choices for the different reactor types .

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.