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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