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handle case with neutron being in the lowest energy grid bin or below

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walshjon 2014-09-09 18:47:44 -04:00
parent 39e272cd63
commit 20cffb0c4a
1 changed files with 16 additions and 5 deletions
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21
src/physics.F90
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@ -884,13 +884,24 @@ contains
i_E_up = nuc % grid_index_0K(union_grid_index)
! interpolate xs CDF since we're not exactly at the energy indices
m = (nuc % xs_cdf(i_E_low) - nuc % xs_cdf(i_E_low - 1)) &
& / (nuc % energy_0K(i_E_low + 1) - nuc % energy_0K(i_E_low))
cdf_low = nuc % xs_cdf(i_E_low - 1) + m * (E_low - nuc % energy_0K(i_E_low))
if (i_E_low == 1) cdf_low = ZERO
! cdf value at lower bound attainable energy
if (i_E_low > 1) then
m = (nuc % xs_cdf(i_E_low) - nuc % xs_cdf(i_E_low - 1)) &
& / (nuc % energy_0K(i_E_low + 1) - nuc % energy_0K(i_E_low))
cdf_low = nuc % xs_cdf(i_E_low - 1) &
& + m * (E_low - nuc % energy_0K(i_E_low))
else
m = nuc % xs_cdf(i_E_low) &
& / (nuc % energy_0K(i_E_low + 1) - nuc % energy_0K(i_E_low))
cdf_low = m * (E_low - nuc % energy_0K(i_E_low))
if (E_low <= nuc % energy_0K(1)) cdf_low = ZERO
end if
! cdf value at upper bound attainable energy
m = (nuc % xs_cdf(i_E_up) - nuc % xs_cdf(i_E_up - 1)) &
& / (nuc % energy_0K(i_E_up + 1) - nuc % energy_0K(i_E_up))
cdf_up = nuc % xs_cdf(i_E_up - 1) + m * (E_up - nuc % energy_0K(i_E_up))
cdf_up = nuc % xs_cdf(i_E_up - 1) &
& + m * (E_up - nuc % energy_0K(i_E_up))
! values used to sample the Maxwellian
E_mode = kT