Hello!

So I ran this neutron-photon coupling calculation during a depletion calculation. I am tallying with the card energy_mode=âenergy-depositionâ, and I get a tallies.out file like this one:

Material 1

Particle: neutron

Total Material

Flux 13.9520 +/- 0.00166268

Fission Rate 0.320254 +/- 6.91290e-05

Nu-Fission Rate 0.887214 +/- 0.00019191

heating-local 6.51791e+07 +/- 13585.7

heating 5.78842e+07 +/- 12480.8

(I get one of those as well for photon, electron and positron).

I read the openmc_simulation_n*.h5 files for each depletion step, and so I processed the heating and heating-local cards (which they are in eV/source-term). Now, I am depleting at constant power a 2D fuel pin (fuel, cladding and coolant) assuming full reflective conditions. Such power is the power of the whole domain, and I would expect that the sum of the different heating components of the tallies at each burnup step would give exactly the power at which I am burning. So I set the power to be 17373 [W]. In order to get the real energy from the tallied heating and heating-local components of the particles for each material of the pin, I am first computing the following normalization factor (at each depletion step):

A = ((TOT_POWER_DOMAIN) * Nu-FissionRate)/(Keff * sum(heating from all particles and materials))

Therefore, if I want to get for instance the true power in Watts of each material and for a certain particle, I just do the following, e.g.: fuel_neutron = (heating_neutron)*A/6.242e18

So my idea is to get the energy deposited in each material and for neutrons and photons. Thus, at every burnup step the sum of all the materials power (both by neutrons and photons) should give the original 17373 [W] power of the domain (since I am depleting at constant power). Now, it seems I get very close values but not exactly the 17373 Watts. Moreover, I tend to oscillate such total power estimation as a function of burnup around the constant power value of the domain (see my attached figure).

I also realized that what is actually consistent is the heating and heating-local values. So for the heating-local ones, there are only values related to neutron energy deposition. The total addition in power coming either from a normalization performed by heating or heating-local is the same. Is just that is strange for me that the sum does not corresponds exactly to the original power of the domain. To give you an example, I did this benchmark with SERPENT2 and there you always conserve the addition of the different materials and particles energies to the original value of the domain. My OpenMC version corresponds to a compilation I did in mid-July this year (when there was a fixed-issue for depleting with neutron-photon coupling). Could you take a look at this?

Many thanks!!