Issue with restarting burnup

Hello all,

I have run into a weird problem. I am trying to restart a burnup calculation. Before restart, the last value of k-eff is 1.54 but when I restart the burnup, I get a value of k-eff which is less than 0.3. Restart file which I am using is attached here.

Any help will be appreciated. Thanks. (1.0 KB)

I have an MTR type assembly. When I make a unit cell the restart capability works fine but when I model the whole assembly and perform depletion and then try to use the restart capability, the scenario which I explained in my earlier post happens.

any takers @paulromano @andrewjohnson

thank you…

One thing I noticed is your fission source spans what appears to be a single assembly. Do you define the fission source across the entire domain for the restart run? If that assembly or region is overly depleted and does not reflect the “average” composition of the core, your source distribution may be off.

Can you also try loading the geometry with Geometry.from_xml? I know the depletion operator re-writes the geometry file before running openmc, which writes the statepoint file. But maybe something isn’t quite right there.

Hye Andrew

Thanks for the reply. Yes, I am modelling a single fuel assembly of MTR type reactor and trying to do burnup calculations. About overly depleted, for IAEA MTR benchmark I need concentration of isotopes at 50% burnup. The number of days i used in my first calculation gave me about 40% burnt uranium so I am restarting the calculation so I don’t think this is the issue of average to overly burnt assembly. what do you suggest?

regarding your suggestion of loading geometry from xml rather than statepoint, it is not showing any difference. still same sad story…

I run into similar problem here as well with large SFR Oxide-3600 core. And here’s the result