CIELO Pu-239
Date: 27 January 2014
Place: Phone conference
Time: 16:00 (Paris, GMT+1), 8:00 (Los Alamos, GMT-7)
Participants:
CEA: G.Noguère, O.Bouland
LANL: M.Chadwick, T.Kawano, A.Kahler, P.Talou
ORNL: L.Leal
NEA: E.Dupont
The objective of this phone conference is to share progress and plans on the 239Pu evaluation for theCIELO pilot project. A short-term milestone is to have a starter file by May 2014.
M.Chadwick opened the discussion and proposed to build upon the work performed within Subgroup 34
on the evaluation of 239Pu in the resonance region.
Measurements
T.Kawano, M.Chadwick and P.Talou reported on a multi-year experimental programme to study thefission of 239Pu at LANSCE. The capture cross section was measured below 1 keV using DANCE andfinal results are available (to be published in PRC). The fission cross section will be measured using thenew TPC. The emission of prompt fission neutrons and gammas is measured with the Chi-Nu
spectrometer. However, these data will not be available in the coming months.
Resolved resonance region
G.Noguère reported on the work performed in the framework of SG34. L.Leal re-analysed all data tocreate a single consistent set of resonance parameters up to 2.5 keV. These new resonance parameters
were included in the JEFF-3.1.1 evaluation for benchmarking against integral parameters from ICSBEP
and from experiments in MINERVE (including trends on K1). A specific validation study dedicated toPrompt fission neutron spectra (PFNS) was made by Y.Peneliau (cf. ND2013 draft on the SG34webpage1).
A.Kahler reported on complementary benchmarking work using the new resonance parameters andENDF/B-VII.1 that he presented during the WONDER 2012 workshop2. This work will be described in
the SG34 report.
M.Chadwick commented that JEFF-3.1.1 nu-bar at thermal energy is rather low compared toexperimental data and to the value used by the standard group. G.Noguère answered that JEFF-3.1.1(and ENDF/B-VII.1) were only used as bases to validate the new SG34 resonance parameters and that
there is probably room for improvement in JEFF-3.1.1 nu-bar (which is briefly described in JEFF Report213). In particular, it would be interesting to see if the thermal value can be increased when adjusting thenu-bar fluctuations and the PFNS at the same time while keeping good integral performance.
A.Kahler and M.Chadwick proposed to include in the starter file the new SG34 resonance parameters
together with JEFF-3.1.1 nu-prompt below 650 eV.

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www.oecd-nea.org/science/wpec/sg34
www.oecd-nea.org/science/meetings/wonder20123
www.oecd-nea.org/dbdata/nds_jefreports2

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Unresolved resonance region
G.Noguère mentioned that the existing averaged resonance parameters evaluated by H.Derrien
reproduce nicely the existing data, especially the intermediate structure below 4 keV (which areconfirmed by the recent data measured at LANSCE by F.Tovesson). He recommended performing newmeasurements at high resolution facilities (e.g. RPI, Geel, n_TOF) in order to further improve thedescription of these fluctuations in the unresolved region.
T.Kawano commented that the use of the LSSF flag still needs to be discussed. He proposed to use
LSSF=1, which means that the URR parameters are used only for self-shielding calculations.
Continuum region
T.Kawano reported on modelling activities performed in part within the IAEA group that studies theinelastic scattering and capture cross section data of major actinides in the fast neutron region. There arestill large differences in inelastic channels that need to be studied further. He asked whether the JEFF3.2 test file could be made available to facilitate comparisons. E.Dupont answered that test files arereleased outside the JEFF project on a case-by-case basis and that he needs to check with the authors4.
G.Noguère recommended using information from the averaged resonance parameters in the modellingof the continuum. T.Kawano agreed and explained that he plans to keep the existing averaged
parameters in MF2 (in order to calculate self-shielding) and to make sure that the MF3 cross sections are
consistent with reference data and other experimental data (as well as URR parameters) down to the keV
region.
E.Dupont inquired about the time schedule for the new modelling of the continuum and about theavailability of model parameters. T.Kawano answered that new results will be presented by the next
WPEC meeting in May. On the second question, he commented that (phenomenological) model
parameters are not very useful without the associated model/code, but noted that the IAEA started tocollect such materials.
Prompt Fission Neutron Spectrum (PFNS)
P.Talou reported on experimental and modelling activities related to PFNS. The last meeting of theIAEA CRP on PFNS took place in October 2013. Contributions to the final report are expected until theend of 2014. He noted that experimental data at low energy are absolutely required to constrain themodels, which are not predictive enough. At higher energy, new PFNS evaluations are now available
and new Chi-Nu data will be used to improve them.
Starter file – Integral validation
It was agreed to include in the CIELO starter file the new SG34 resonance parameters together withJEFF-3.1.1 nu-prompt below 650 eV, and to use ENDF/B-VII.1 for other data (including PFNS). The
file will be updated with new continuum and PFNS data when available and the integral performances
will be monitored.
Adjourn

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The file is now available at www.oecd-nea.org/science/wpec/sg40-cielo.

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