Creating the geometry using MNCPX VisEd

[ugata88]

TL;DR

I'm having problems creating the geometry using MNCPX VisEd

I'm working on the MSFR design and want to calculate keff. I'm trying to use the MNCPX VisEd program included with MCNP 6.1 to create my geometry. The reactor I'm designing doesn't contain fuel rods or moderator structures. The molten salt fuel circulates within the cylindrical reactor core.

I'm having problems creating the geometry using MNCPX VisEd. VisEd allows for easy drawing of nested sphere, cylinder, or rectangular prism cells. However, when you want to draw a torus section within a cylinder or deviate from the geometries found in conventional reactor designs, creating surfaces and cells in CSG format is not user-friendly.

I've tried importing 3D geometries with the .SAT extension into VisEd from programs like ANSYS Design Modeler, SolidWorks, and AutoCAD, but I haven't been able to open the files. Can you recommend a method for creating an input file for the geometry below using VisED or another viewing/drawing program?

 

[DEvens]

My experience has been that VisEd is only useful to view your MCNP inputs. Trying to edit within VisEd is not worth it. For example, I would get frequent crashes that required me to delete a bunch of files created by VisEd in order to get it to start again.

If you are trying to use the 3D viewing feature of VisEd, I found it could only handle the simplest of geomtries. If you started getting things like hundreds of cells, or complicated structures like pipes through tanks, it got confused. In the 2-D view it usually did quite well.

The way I did it was to type in the MCNP input in a text editor. Then save the file. Then open it in VisEd.

The files I used for my main work were too large for VisEd and I had to use the built in plotting functions in MCNP. There is a special mode you start it in and it will graph your model. You can persuade it to produce limited diagnostic information during this as well. The commands for this are in the MCNP manual. It winds up looking very much like VisEd. I only ever got it to work with LINUX and only with the X-Windows emulator running. And then only with the help of the sys admin doing a lot of tweaking. I never got the plotter working on MS Windows.

You mentioned torus. There are some issues with torus shaped cells in MCNP. It loses particles. You should not try to use a torus to model a corner in a pipe, for example.

There was a project to convert a CAD program's file to MCNP. I don't know where they got to. This was before COVID, and the project was not very far. If you Google for it you might find it. I think it was a Japanese group. They were all set to send me a free copy of their prog, but then COVID caused everybody to be disrupted. We had an analysis program that could export its geometry to MCNP. The problem was it tended to produce thousands of cells when it should have only used two or three.

I am not sure but I have been told that the very latest version of MCNP has CAD ability. But I have never used it, so I could easily be completely wrong.