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Processing of
incident-neutron sub-library from ENDF/B-VII.1, JENDL-4.0 and JEFF-3.1.1
13th Int Conf Nuclear Reaction Mechanisms, Varenna, 15 June 2012
Mary Chin Alfredo Ferrari
Vasilis Vlachoudis
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Radiation transport calculation
DISCRETE ORDINATE
MULTIGROUP TREATMENT
POINTWISE, UNCORRELATED
POINTWISE, FULL CORRELATION
More challenging in terms of code development
Higher detail and precision mandatory for some applications
Not necessarily longer runtime variance reduction techniques are available
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achieved so far in FLUKA
MULTIGROUP TREATMENT
POINTWISE, FULL CORRELATION
All other particles from eV to TeV
Neutrons > 20 MeV all isotopes
Neutrons < 20 MeV 1H, 6Li, 10B, 14N, 40Ar Cd and all Xe isotopes for gamma cascades in capture
Neutrons < 20 MeV all isotopes except those already in pointwise
we aim for full correlation even with low-energy neutrons 3 download
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APPLICATIONS requiring correlation 1. Single Event Upset (SEU) electronics are becoming vulnerable to neutrons < 20 MeV 2. Tissue Equivalent Proportional Counters (TEPC)
low-density and thin gas chamber energy deposited via kerma by low-energy neutrons lone peak appears as artefact in pulse-height spectra respective contribution by C, N, O recoil not differentiable
3. Neutrino detection at Gran Sasso artefact in energy spectra
4. Damage and DPA calculations, and more 4 download
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CORRELATED NOT CORRELATED E, p, A, Z conserved at each
point of interaction
Each particle has a uniquely-defined parent; each sibling (if any) is uniquely identified
Kinship is lost
Doesn’t matter if we want averaged estimations eg. dose
or fluence – same outcome
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EVALUATE analyse, fill in gaps,
data reduction, parameterisation
PROCESS NJOY / PREPRO
USE monte carlo etc
ENDF PENDF
Preparing POINTWISE LIBRARIES
Reported in 2010, issue fixed in the new version
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Some issues remain 93Nb (n,p) 94Nb (n,g) similar in 93Nb (n,a); also Tl (n,n’a), (n,a) and (n,p)
similar in 94Nb (n,el) 95Nb (n,el) and (n,g) 99Mo (n,el) and (n,g)
148Pm (n,g)
249Cm (n,el) similar in (n,g) and (n,fis)
95Nb (n,n’a) similar in (n,p); also 99Mo
(n,n’a) and (n,p); 94Nb (n,el)
NJOY99u364 PREPRO2010
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Often, differences are due to something in the endf (unexpected absence/presence of certain contents)
rather than the algorithm itself
THE ENDF6 FORMAT supposed to be the standard;
in practice, however, it is more to the best endeavour
NJOY and PREPRO
supposed to be inert to library releases/versions (ENDF/BVII.1, JEFF3.1 etc);
again, to the best endeavour
128Pm (n,el)
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It is not our real intention to compare NJOY and PREPRO.
This is just a tangential QA exercise to spot vulnerabilities,
to balance between automated (bound to miss details)
and manual (bound to make mistakes)
handling of the sea of numbers.
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ELASTIC SCATTERING (MT=2)
ANGULAR DISTRIBUTION (MF=4)
PURELY ISOTROPIC (LTT=0, LI=1)
ENDF/B-VII.1 2011 Dec
none
JENDL-4.0 2010
none
JEFF-3.1.1 2009
74 materials
* So, is JEFF3.1 out-of-date? Well, it contains 78-Pt and 81-Tl (absent in ENDF/B-VII.1 and JENDL-4); and it goes up to higher energies for H-1, Sc-45, Fe-54, Fe-56, Fe-57, Fe-58, Ge-70, Ge-72, Ge-73, Ge-74, Ge-76, Tc-99, Rh-103, I-129, Pb-208, Bi-209, Pu-239 and C-0.
ISOTROPIC WITHIN TABULAR/LEGENDRE
DISTRIBUTIONS (LTT=1, 2 or 3)
PROBABILITY DISTRIBUTION BY LEGENDRE
REPRESENTATION
ENDFB/VII.1 LEGENDRE JENDL4.0 LEGENDRE ENDFB/VII.1 TABLE JENDL4.0 TABLE
LEGENDRE ORDER FROM LOW (DARK COLOUR) TO HIGH (BRIGHT COLOUR)
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ISOTROPIC ≠ ‘NO DISTRIBUTION AVAILABLE’ ENDF/BVII.1 tables (LTT=2)
‘too complicated to be represented even by Legendre’
JEFF3.1
purely isotropic (LTT=0, LI=1)
* barns/sr obtained from combining MF=2 and MF=4 11 download
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example: 91-Pa-231 (ENDF/BVII.1)
so complicated that 64 (the max) Legendre orders have to be used
example: 8-O-16, 150 MeV (ENDF/BVII.1)
at some point, increasing the
Legendre order doesn’t help anymore
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REPRESENTING ANGULAR DISTRIBUTIONS
LEGENDRE POLYNOMIAL
SERIES
TABULAR DATA
PARAMETERISED LEGENDRE
COEFFICIENTS
BYTES SAVING
FURTHER BYTES
SAVING
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THE FIRST LEGENDRE COEFFICIENT if we get this right we get the average energy loss right
ENDFB/VII.1 JENDL4.0
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dcX
e
baY +−
++=
1low energy (dark) to high energy (bright) low A (dark) to high A (bright)
outlier: 61-Pm-148
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a1
A
periodic peaks and dips common grid drawn from 10 keV to 20 MeV 16 download
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design priority of FLUKA Enforce conservation laws at each step
Adopt microscopic models wherever possible
Ensure consistency between all reaction steps and/or channels
Benchmark against measurements at single-interaction level where available
Apply a minimal set of fine-tuned parameters uniformly throughout all energy-target-projectile combinations
(as opposed to local tweaking)
Final prediction from complex simulations should emerge naturally from underlying physics models
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