Hello, everyone!
Now I have a problem about transport-correction scatter matrix.
When I was calculating a quarter core, I found a negative cross section in the P0 transport modified scatter matrix of my moderator (boron-containing water), which is not the case for other materials, the calculation was 7 energy groups, and when I reduced the energy group to a three-energy group, the negative cross section of the moderator disappeared. Why? Is there any way to fix this?
I was very anxious, I was hoping someone could answer that for me.
Thanks and regards,
lichw
The layout of a quarter core is shown below.
Hi lichw
“I am encountering the same issue where setting too many groups causes the cross-section to become negative. Could you please tell me how you adjusted P3 to correct this?”
You may misunderstand my meaning, I mean when I use P0 to modify the scattering matrix, if the energy group number is set to 7, I will find that my scattering matrix has negative numbers, and if I change the energy group number to 3, the scattering matrix will not have negative numbers, I did not use P3 correction.
I apologize, I might have misunderstood. By the way, do you know if it is possible to prevent the cross-section from becoming negative when using the same number of energy groups
According to me, if you replace the water with another moderator material you should be able to get a P0-modified scattering matrix of group 7 without negative cross sections, or you can use higher order cross sections, such as the P3 modified cross section you just mentioned, but the higher order cross sections will also have negative cross sections, depending on how you use the cross sections and what program you use the cross sections in. (My understanding of this aspect is still shallow, if there are mistakes and omissions hope to understand)
Thank you very much for your response. I will keep trying to achieve the desired results."