 # Lattice pitch for heterogeneous elements

Hi all,

I need some guidance regarding creating a lattice similar to the mtr design in which the two outer most plates are of greater thickness than all the other plates while between each two fuel plate, there exists a water channel of another variable thickness.

What pitch must I give for this type of geometry, as for the water channel it will automatically be assigned but, when all channels will be placed in the lattice, but I am getting error when trying to place plates of different thicknesses.

Let’s say the outermost two plates are of thickness 2 cm while there are 10 other inner plates of thickness 1.5 cm, and I need to give a water channel between each of the consecutive fuel plates of thickness 2.5 cm. The total height in y direction is 51.5 cm, and for the plates if I create 2 universes for each plate with infinite water at its outer should I give the pitch as 4.0833 if I consider 1.25cm of water at both sides of each plate considering the lattice lower left at -49/2. I tried this approach and this should’ve worked but it doesn’t.

Can someone please correct me where I am wrong, because I seem to get an error that tuple index is out of range and from where I have understood, it occurs whenever I place an incorrect entity in the lower left or pitch of the lattice.

Kind Regards.

@Issacc do you perhaps have a picture/figure showing the geometry you’re trying to model? From what I understood, it sounds like your pitch should be the sum of the inner plate thickness and the water channel thickness, so 4 cm. If the outermost plates are part of the lattice, you would have to adjust the planes in that universe accordingly so that you still have a 2.5 cm water channel between the outer and inner plates.

To put it simply, above is for example a case I am trying to model, like I need to repeat two plates of varying thicknesses into a lattice but I am unsure of what pitch to take, in the hand sketch as you can see the outermost plate is of thickness 1 cm while the second plate is of greater thickness, now if I use a pitch of 1+2.3 cm the lattice does not get filled at all except with the root material. How do I design a heterogeneous plate lattice, can you please guide me.

Regards.

Another case is as follows:

Here is somewhat the case I have describes in the question, lets say I have two plates of different thicknesses, the outermost plates are of thickness 1.5 cm while the inner plates are of thickness 1 cm and I need coolant in between these. now what pitch must I use to put these plates into a lattice so as to get 0.8 cm of coolant on both outer sides of the outermost plates while 2 cm of coolant between each plate.

Regards.

Specifically what approach must I use to design such a model, I also tried to create a cell1 using planes and placed each type of plate between two planes (3 planes in total and two universes) and created the cell1 of thickness 2.3 cm, then I used it into a universe1 then repeated the universe1 in a lattice. but this would give me plate 2 as the outermost plate from the bottom, this is not what I want, I want the outermost plates to be plate 1 only, I did adjust the lattice window to cut out plate 2 from the bottom and take only plate 1 as the outermost plate, but the problem lies with creating the cell1, it’s centre is not origin and this creates a problem in fiiling this into another cell or even into a lattice

``````heightp = 3.3  #cm
pl1 = openmc.YPlane(y0=-2.3)
pl2 = openmc.YPlane(y0=0.0)
pl3 = openmc.YPlane(y0=+1.0)

pl4 = openmc.XPlane(x0=-3.0)
pl5 = openmc.XPlane(x0=+3.0)

plate1 = openmc.Cell(region=+pl4 & -pl5 & +pl2 & -pl3, fill=univ_plate1)
plate2 = openmc.Cell(region=+pl4 & -pl5 & +pl1 & -pl2, fill=univ_plate2)

univ_plate3 = openmc.Universe(cells=[plate1, plate2])  