Modeling Triso Particles in CSAS6-Shift with Randommix

[Chris Lemke]

Hello,

I am tying to perform some calculations on an annular TRISO compact. I was hoping to make use of the newer randomgeom/randommix functionality to stochastically fill an annular cylinder with TRISO particles but I am getting an error when doing so that says "randommix can only be used with a single region". Am I doing something wrong or is this even possible to us it this way?

Best,

Chris

[Chris Lemke]

Additionally, I am wondering if it is possible to read in a material composition from an .f71 within a Triton sequence input? 

[Rike Bostelmann]

Hi Chris,

In the SCALE 6.3 release, the randomgeom/randommix capability is supported only for solid spheres, cylinders, and cuboids. Annular geometries will be supported in SCALE 7 beta versions (for example, SCALE 7 beta 11 will support placement in spherical shells).

 

Please also note that the packing fraction that can be achieved with the randomgeom/randommix in SCALE 6.3 is limited to around 20% because the underlying algorithm is a simple throw-and-rejection algorithm. For SCALE 7, we are working on enabling higher packing fractions with reasonable packing times (for example, SCALE 7 beta 11 will support packing fractions of up to ~55%).

If you have any other experiences with this new capability, we'd be happy to hear about it. Especially because we are currently working on extending the capability, any user feedback is much appreciated.

Best regards,

Rike

[Rike Bostelmann]

Regarding your second question:

As of now, TRITON does not support direct loading of nuclide concentrations from an F71 file. This will be enabled for a future SCALE 7 beta version.

Some options until then:

• In the case that you have access to a SCALE beta version, you can use command-line utility OBIWAN to print concentrations from a F71 file directly in SCALE's standard composition input format: "obiwan view -format=csv my.f71".
• With SCALE 6.3, you can still use OBIWAN to print concentrations from a F71 file. You can use command "obiwan view -format=csv -units=atom my.f71" together with additional flags to specify precision, nuclide id form, and the time step. The print-out should be fairly easy to convert to a SCALE composition input.
• With SCALE 6.2 or SCALE 6.3, you can use OPUS to extract concentrations from a F71 file. There will likely be more formatting necessary because OPUS prints data in a specific format. 

Note that the selection of nuclides for inclusion in a material specification is relevant. Some nuclide filtering is required to capture all relevant nuclides, but to remove nuclides that cannot be included in the composition input:

• ORIGEN tracks a large list of nuclides. However, the TRITON composition input can only contain nuclides for which cross section data is available on the MG or CE library.
• A good list of nuclides to include is the list of nuclides considered with ADDNUX=4. This guarantees that for all nuclides, cross section data is available, and that low-density, but neutronically relevant nuclides are included.

I should note that such a procedure does not perform an actual restart of a TRITON depletion calculation. ORIGEN tracks many nuclides for which nuclide densities will not be correctly restarted when using a selection of nuclides in TRITON's composition block. Depending on the model and the target output quantities, this may or may not have a noticeable impact.

[Chris Lemke]

Dr. Bostelmann, 

Thank you very much for your responses and clarification. 

If it is alright with you I would like to ask a follow up question regarding the methods you suggest to generate the composition input.

As I have access to version 6.3 and already have some Obiwan inputs that will spit out the nuclide concentrations at the final time step, I think the second method you suggest would be the simplest to implement. Ultimately I want I want to pull in the composition for the depleted material and then combine that with a potion of fresh/un-depleted material to have a new material that can then be depleted again. I was trying to do this using stdcomp but it doesn't appear that format supports the us of both vf and aden. With that being said, is there a composition format that you think would be the "easiest" to use in that manner? Or perhaps I am approaching this in the wrong way and there is a simpler way? Any suggestions you have would be greatly appreciated. 

Best, 
Chris