Hello, I was wondering whats the most effective method to model spacer grids? Does anyone have an example code for it ? Thanks.
Hi AEjder, welcome to openmc community.
Regarding modelling spacer grid, you might want to look at some benchmark cases such as MIT BEAVRS case
or from vera benchmark
I am forgot if both benchmark use the separated spacer grid part (cell) on its fuel pin lattice or is it also consider to simplified the model into making a homogenized mix of spacer grid material and water (based on their volume fraction) at specific fuel heights.
I think the recommended model will be separated spacer, but I also remember that I read some paper or documents that also consider to homogenized the spacer material with coolant. Sorry
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Smearing the grid with water is a common approach, and it will save you ray tracing time.
Seven or eight years ago I did some VERA core physics benchmarks in OpenMC using an explicit spacer grid model (spacergrid.py). This model makes the lazy approximation that the mass of the spacer grid is evenly distributed in a rectangular tube around the outer edge of each pincell in the lattice. Essentially, this makes the outer edge a little too thin and the grid a little too thick, but it’s closer to reality than smearing.
Obviously, you can make the model of the grid arbitrarily complicated, but there are diminishing returns. You can quickly do a unit cell with smeared grid and an explicit grid as a worst-case scenario.
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