FGXS t6-depl-SHIFT issue calculating currents

[inigo...@gmail.com]

Dear SCALE team,

I have encountered several issues regarding the FGXS block when using T6-DEPL-SHIFT (SCALE 6.3.2, Feb 2024), and I would appreciate some clarification.

1. FGXS block definition (documentation vs. actual behavior) 

The SCALE version I’m using is SCALE 6.3.2,  2024-02. According to the manual attached, version SCALE 6.3.2 User Manual Feb 2023, it says that the FGXS block should be defined inside the tallies block, like this:

read tallies

read fgxs 1

response=macro_nodal

grid=2

time 0 1 2 LAST end

energy=5

end fgxs

read fgxs 2

response=macro_nodal

shape=1

time ALL end

energy=5

end fgxs

end tallies

But this does not work in reality. What works is the previous definition of FGXS block defined in SCALE 6.3.1 User Manual Feb 2023, where FGXS block should be defined as an independent block, for example:

read fgxs

 energy        id=1 1.00000E-05 0.625E+00 2.00000E+07 end

 tallyset t16  id=1

 shape cuboid  id=1 0 -1.43 1.43 -1.43  50 -50

end fgxs

Could you confirm whether this is a known inconsistency between the documentation and the current implementation?

2. Available tallysets and documentation gaps

The SCALE 6.3.1 User Manual Feb 2023 says: “the only supported type is currently tallyset t16 to request the full set of nodal data”. But  the validation tab in Fullcrum shows the following if tallyset t16 is not defined:

[ "tallyset" "total" "transfer" "absorption" "capture" "fission" "nu" "chi" "kinetics" "kappa" "diffusion_osc" "diffusion_cmm" "transfermatrix" "current" "flux" "reactiontoken" "eddington" ]

No information is given in the manual on how to use these tallies.  Our interest is specially on the fluxes and currents at the faces of the fuel assembly (we are modelling PWR FA for nodal and pin calculations). 

Is there documentation available for these additional tallies?
Are there plans to extend SHIFT capabilities for assembly flux and current calculations? 

3. Zero boundary currents in t16 data

The tallyset t16 nodal response shows that currents at the boundaries of the assemblies are zero. We studied this case, simplifying the input to an array of 2x2 with 2 pin cells and water moderator on the right side. Here is the input:

=t6-depl-shift parm=(centrm,addnux=4)
Currents FGXS Issue
ce_v7.1_endf
read composition
'FUEL PIN CELL COMPOSITIONS PIN 001
'Fuel pellet composition
 uo2     401    den=10.257   01.0   579.65
         92234    0.027269
         92235    3.2
         92236    0.01472
         92238    96.758011 end
'Fuel gap composition
 he   801   den=0.000179 1 579.65 end
'Cladding composition
 zirc4   1201   den=00006.56 1 579.65 end
'Moderator composition
 h2o   1601     den=0.71243    0.9987   579.65 end
 boron   1601     den=0.71243    0.0013   579.65 end

'FUEL PIN CELL COMPOSITIONS PIN 002
'Fuel pellet composition
 uo2     402    den=10.257   01.0   579.65
         92234    0.027269
         92235    3.2
         92236    0.01472
         92238    96.758011 end
'Fuel gap composition
 he   802   den=0.000179 1 579.65 end
'Cladding composition
 zirc4   1202   den=00006.56 1 579.65 end
'Moderator composition
 h2o   1602     den=0.71243    0.9987   579.65 end
 boron   1602     den=0.71243    0.0013   579.65 end

'GUIDE TUBE PIN
'Moderator composition
 h2o   1603     den=0.71243    0.9987   579.65 end
 boron   1603     den=0.71243    0.0013   579.65 end
end composition


read burndata
 power=36.7 burn=2.725    nlib=1  end
end burndata

read depletion
401 402
end depletion

read model

read fgxs
 energy             id=1 1.0E-05 0.625E+00 2.0E+07 end
 tallyset t16       id=1
 shape cuboid  id=1 0 -1.43 1.43 -1.43  50 -50
end fgxs

read parameter
gen=100
npg=6000
nsk=10
sig=0.01
run=yes
end parameter

read geometry
unit 1
com="Fuel rod left down corner"
 cylinder 10  0.4555 2p50  
 cylinder 20  0.4655 2p50  
 cylinder 30  0.5375 2p50  
 cuboid   40  0.715 -0.715 0.715 -0.715 2p50
 media    401 1 10
 media    801 1 20 -10
 media    1201 1 30 -20
 media    1601 1 40 -30
 boundary 40

unit 2
com="Fuel rod left down corner"
 cylinder 10  0.4555 2p50  
 cylinder 20  0.4655 2p50  
 cylinder 30  0.5375 2p50  
 cuboid   40  0.715 -0.715 0.715 -0.715 2p50
 media    402 1 10
 media    802 1 20 -10
 media    1202 1 30 -20
 media    1602 1 40 -30
 boundary 40

unit 3
com="Guide tube regular"
 cuboid   10  0.715 -0.715 0.715 -0.715 2p50
 media    1603 1 10
 boundary 10

unit 4
com="Guide tube regular"
 cuboid   10  0.715 -0.715 0.715 -0.715 2p50
 media    1603 1 10
 boundary 10

global unit 1000
com="Assembly unit"
 cuboid   10  1.43  -1.43  1.43  -1.43 2p50
 array    1 10 place 1 1 1 -0.715 -0.715 0
 boundary 10
end geometry


read array
 ara=1 nux=2 nuy=2 nuz=1 typ=cuboidal
  fill
  1 3
  2 4
 end fill
end array

read bounds
 ZFC=mirror
 +xb=mirror
 -xy=mirror
 +yb=mirror
end bounds


read volume
type= random
batches= 5000
points= 100000
end volume

end data

end model

end

Here non-zero values are expected on the east side of the tally defined, yet the currents remain zero.

Is this a known limitation of the current implementation?
Or could this be related to how boundary conditions or FGXS regions are defined?

Thank you for your time and support.

Best regards,

Iñigo Gayo