I am trying to calculate tritium breeding ratios in a FLiBe sphere for different thicknesses and material (Li) compositions. For this I am initially defining a neutron point source at the centre of a spherical shell of FLiBe. I have the following questions:
is choosing isotropic correct and sufficient to define a point source?
how do I correctly track the amount of tritium bred in my sphere? I have read several other threads here and the manual, but I am not sure whether I should use USRTRACK, USRYIELD or USRBDX or RESNUC?
What libraries should I not miss?
How do I then process the data depending on the detector? Can I do a spherical tracking?
Thank you in advance,
Alejandra
Input files
Please upload all relevant files. (FLUKA input file, Flair project file, user routines, and data files)
Isotropic source - for your simple model this is correct and sufficient.
If you wanted to work with a more complex geometry (i.e. a full blanket segment), you could also create a simple plasma source, using BEAMPOSit to create a ring source, and add blackhole regions to segment.
Ensure you have the low-energy libraries for the pointwise treatments installed.
In addition check in your transport settings that you have LOW-PWXS on, and to keep the neutron threshold low (PART-THR).
Using the physics card, check EVAPORAT and COALESCEnce are on.
Processing
If using RESNUCLEI, you will get tritium/primary - so in order to get the value as a tritium breeding ratio you’ll have to normalise with number of primaries.
Regarding the spherical tracking, do you mean to get the angular dependence?
In this case you could either segment your sphere and track by region.
Or use USRBIN which allows you to score in Cartesian coordinates, you would have to convert this then to its spherical dependence (there is no spherical meshing unfortunately) .
Thank you very much for your response. I managed to implement all of the above and am now struggling to interpret the results. Where do I find an explanation of the formats / contents of the .rnc plot and the sum.lis and tab.lis it generated? Thank you in advance and best regards, Alejandra
The values in the .rnc file have units of Bequerels and the interpretation of the results depends on the irradiation profile you have used. For the .lis file, the results are always normalized per unit primary weight and the error that is cited is generally in percents.
It shows the fluence in units of cm ^{-2} per GeV per primary weight. The normalisation per cm ^{-2} depends on whether you specified the area between the regions in the USRBDX card.
Not sure to understand. I am using RESNUCLEi for yield tracking, not USRBDX. The RESNUCLEI produces sum.lis and tab.lis files. The values in them represent the yield and not a fluence, correct? Is the content of these two files described anywhere in the documentation?
The numbers in the lis file generated by RESNUCLEI are activities in the region in units or Bequerels. This is for residual activation only. The USRBDX lis file contains the fluences for particles that escape (prompt or after cooldown).
Dear Benoit, sorry to insist on this but are you sure the .lis files from RESNUCLEI show activity and not yield? The file itself mentions yield nut it is unclear. Also Kate indicated I could track produced Tritium using RESNUCLEI. I have not created an irradiation profile in my input. The values I obtain are consistent with yields I find in literature. Is it possible it is indeed number of Tritiums per primary in the region that the RESNUCLEI . lis file is producing?
If the RESNUCLEi scoring is not associated by DCYSCORE to a cooling time, referring in turn to an input irradiation profile, the respective results are indeed yields per beam particle. These are divided by the region volume if the latter has been specified in the RESNUCLEi card. In the _sum.lis and _tab.lis files you can read the aforementioned yields and the associated statistical error in percentage.
Thank you! This is helpful. Is this information available somewhere in the documentation or is the forum the only way to find out? I am finding it hard in general to progress with FLUKA as I get stuck and cannot find any information in the documentation, especially regarding output files. What is in general the approach for users other than joining the FLUKA courses, which only happen ever so often?
There is currently a big effort in the collaboration to prepare new, more accessible, documentation to better support users. Among others, we are working on a beginner’s guide. In the mean time, I am sorry to say that your best options are still indeed the manual, the official FLUKA courses content and the forum. That said, over the year, hundreds of questions have been posted on the forum and it is now more likely than ever that you will find a discussion on your topic of interest.
