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Fixed survival biasing with probability tables. Closes #103 on github.
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Paul Romano
parent
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1 changed files with 49 additions and 71 deletions
120
src/physics.F90
120
src/physics.F90
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@ -325,97 +325,75 @@ contains
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! FISSION EVENTS (ANALOG) OR BANK EXPECTED FISSION SITES (IMPLICIT)
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if (nuc % fissionable) then
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! If survival biasing is turned on, then no fission events actually occur
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! since absorption is treated implicitly. However, we still need to bank
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! sites so we sample a fission reaction (if there are multiple) and bank
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! the expected number of fission neutrons created.
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if (survival_biasing) then
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! If survival biasing is turned on, then no fission events actually
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! occur since absorption is treated implicitly. However, we still need
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! to bank sites so we sample a fission reaction (if there are
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! multiple) and bank the expected number of fission neutrons
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! created.
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if (nuc % has_partial_fission) then
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cutoff = prn() * micro_xs(index_nuclide) % fission
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prob = ZERO
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i = 0
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do while (prob < cutoff)
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i = i + 1
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! Check to make sure partial fission reaction sampled
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if (i > nuc % n_fission) then
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message = "Did not sample any partial fission reaction " // &
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"for survival biasing in " // trim(nuc % name)
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call fatal_error()
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end if
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rxn => nuc % reactions(nuc % index_fission(i))
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! if energy is below threshold for this reaction, skip it
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if (IE < rxn%IE) cycle
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! add to cumulative probability
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prob = prob + ((ONE-f)*rxn%sigma(IE-rxn%IE+1) &
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+ f*(rxn%sigma(IE-rxn%IE+2)))
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end do
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else
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! For nuclides with only total fission reaction, get a pointer to
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! the fission reaction
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rxn => nuc % reactions(nuc % index_fission(1))
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end if
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! Bank expected number of fission neutrons
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call create_fission_sites(index_nuclide, rxn)
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else
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! If survival biasing is not turned on, then fission events can occur
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! just like any other reaction. Here we loop through the fission
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! reactions for the nuclide and see if any of them occur
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cutoff = prn() * micro_xs(index_nuclide) % fission
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prob = ZERO
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end if
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if (micro_xs(index_nuclide) % use_ptable) then
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if (micro_xs(index_nuclide) % use_ptable) then
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! In the case that the particle is in the unresolved resonance
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! region and probability tables are being used, we should only
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! check the first fission reaction
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! In the case that the particle is in the unresolved resonance region
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! and probability tables are being used, we should only check the
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! first fission reaction
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prob = prob + micro_xs(index_nuclide) % fission
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if (prob > cutoff) then
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rxn => nuc % reactions(nuc % index_fission(1))
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call create_fission_sites(index_nuclide, rxn)
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prob = prob + micro_xs(index_nuclide) % fission
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if (prob > cutoff) then
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rxn => nuc % reactions(nuc % index_fission(1))
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call create_fission_sites(index_nuclide, rxn)
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! With no survival biasing, the particle is absorbed and so its
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! life is over
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if (.not. survival_biasing) then
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p % alive = .false.
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p % event = EVENT_FISSION
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return
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end if
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end if
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else
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! With no probability tables, we need to loop through each fission
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! reaction type -- note that this loop still works even if there is
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! only one fission reaction
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else
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FISSION_REACTION_LOOP: do i = 1, nuc % n_fission
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rxn => nuc % reactions(nuc % index_fission(i))
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! With no probability tables, we need to loop through each fission
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! reaction type
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! if energy is below threshold for this reaction, skip it
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if (IE < rxn%IE) cycle
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do i = 1, nuc % n_fission
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rxn => nuc % reactions(nuc % index_fission(i))
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! add to cumulative probability
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if (nuc % has_partial_fission) then
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prob = prob + ((ONE-f)*rxn%sigma(IE-rxn%IE+1) &
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+ f*(rxn%sigma(IE-rxn%IE+2)))
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else
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prob = prob + micro_xs(index_nuclide) % fission
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end if
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! if energy is below threshold for this reaction, skip it
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if (IE < rxn%IE) cycle
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! Create fission bank sites if fission occus
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if (prob > cutoff) then
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call create_fission_sites(index_nuclide, rxn)
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! add to cumulative probability
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if (nuc % has_partial_fission) then
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prob = prob + ((ONE-f)*rxn%sigma(IE-rxn%IE+1) &
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+ f*(rxn%sigma(IE-rxn%IE+2)))
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if (survival_biasing) then
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! Since a fission reaction has been sampled, we can exit this
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! loop
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exit FISSION_REACTION_LOOP
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else
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prob = prob + micro_xs(index_nuclide) % fission
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end if
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! Create fission bank sites if fission occus
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if (prob > cutoff) then
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call create_fission_sites(index_nuclide, rxn)
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! With no survival biasing, the particle is absorbed and so
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! its life is over
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p % alive = .false.
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p % event = EVENT_FISSION
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return
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end if
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end do
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end if
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end do FISSION_REACTION_LOOP
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end if
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end if
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end if
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! ==========================================================================
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