I would like to know whether FLUKA is able to simulate the 232Th(n,2n)231Th reaction cross section.
My goal is to compare the experimentally measured 232Th(n,2n)231Th cross section with the theoretical values obtained from simulations. Is it feasible to perform such simulations using FLUKA?
（This image is taken from the Experimental Nuclear Reaction Data ).
In my output file, the following message appears: “Total number of inelastic interactions (stars): 0”. I believe this is incorrect, and I am unsure whether this indicates a problem in my setup.
FLUKA simulates the indicated reaction channel, but is not designed to extract microscopic cross sections;
For low energy (<20 MeV) neutrons, there is a dedicated treatment and their inelastic interactions are not accounted as ‘stars’, hence it’s normal to read 0 there, while a not null value is reported in the respective line a bit below.
The aforementioned treatment is based on data libraries, hence for low energy neutrons the simulation reflects the latter and does not give ‘theoretical’ values.
The JEFF-3.3 (n,2n) cross section on 232Th used by default by FLUKA is shown in the following revision of your plot:
Thank you for your helpful guidance. If I would like to obtain the results shown in your figure, how should I read the .out file? I look forward to your reply.
You do not find those cross section numbers in the .out file, rather in the respective library file. For this specific case ((n,2n) on 232Th), it’s JEFF-3.3/Inelastic/F04/90_232_Thorium.z in the data/neutron directory of your FLUKA installation.
Thank you for your guidance, which has given me a deeper understanding of the database. I have one further question: since FLUKA retrieves cross-section data for low-energy neutrons directly from evaluated nuclear data libraries, does this mean that FLUKA cannot provide cross sections for low-energy neutron reactions when no experimental data are available?
For example, I attempted to define a broad-energy neutron source (0.1 eV–200 MeV, with a significant flux below 20 MeV) and tried to obtain the cross section for producing $^{225}$Ac from neutron-induced reactions on a thorium target. I am unsure whether this approach is conceptually incorrect.
On the other hand, if the goal is simply to calculate the resulting $^{225}$Ac activity from irradiating a thorium target with such a broad-energy neutron source, would this setup be acceptable?
If there is any misunderstanding on my part, I would greatly appreciate your clarification. Thank you again for your kind guidance.
The adopted libraries are pretty complete.
On the other hand, a <20 MeV neutron cannot generate 225Ac on a thorium target, being the physical threshold of this reaction channel above 30 MeV. At those energies (>20 MeV neutrons), FLUKA uses its own reaction cross section parameterization and reaction model.
While - as already pointed out - FLUKA is not designed to extract microscopic cross sections, ways to estimate the latter have been already discussed at length in this forum, including a thread initiated by yourself.
As for the 225Ac activity in a thorium target irradiated by a broad-energy neutron source, it can certainly be calculated by FLUKA.
