Flux calculation for fixed source in shielding calcs

User Support
1

I am trying to calculate flux due to a reactor at some dsitance away from the core(specifically at just RPV edge). I applied shielding to it and checking the flux after shield. Now I made the core a homogeneous cylindrical source(settings changes to fixed source as I am not doing k eff calc). Now I am getting no flux in my tally so I tried checking the flux at core edge as well. There also I am not able to get any flux. My geometry is all good as I can see from the plots.

SOURCE DEFINITION

----------------------

source = openmc.IndependentSource()
source.space = openmc.stats.CylindricalIndependent(
r=openmc.stats.PowerLaw(0.0, R_core, 2),
phi=openmc.stats.Uniform(0.0, 2*np.pi),
z=openmc.stats.Uniform(-H_core/2, H_core/2),
origin=(0.0, 0.0, 0.0)
)
source.energy = openmc.stats.Watt(a=0.988, b=2.249)

I specified source like this since its uniformly distributed in a cylinder. Can someone help me in this.

2

Did you applied any variance reduction technique.?

3

No I did not. Actually I am totally new to MC simulations but I have heard from my superiros that theres a weight window concept in mcnp but not in openmc so how to do that? Also if I am checking the flux at just core edge Do I relly need to incroporate variance reduction technique?

4

There is weight window concept in openmc. Update to version 0.15.2. Please see neutronics-workshop/tasks/task_14_variance_reduction at main · fusion-energy/neutronics-workshop · GitHub

5

okay thank you. But I am struggling to understand that at just the core edge I should have gotten some flux even without var red techiques. Shouldnt it?

6

If possible please share your model.

8

openmc default energy unit is in eV.
class openmc.stats.Watt(a=988000.0 , b=2.249e-06 )

secondly energy bins range is .0005eV to 10eV.
are you sure with values of parameters a and b and energy range?