1. of the Muse-4 Experiments with the JEF-2.2 and JEFF-3.1 libraries
Comparative Analysis of Selected Aspects
of the Muse-4 Experiments with
the JEF-2.2 and JEFF-3.1 libraries   
1J.F. Lebrat - 2M. Plaschy - 1J. Tommasi
1C.Suteau - 1D. Plisson-Rieunier - 1C. De Saint-Jean  
1CEA/DEN/DER, St Paul lez Durance, France
2PSI, Villigen, Switzerland
Presented by J.M. Ruggieri, CEA (France)

2. The MUSE-4 Program:
The aim of the MUSE-4 experiment was to test and develop new measurement techniques specific to the evaluation of reactivity in an ADS and to define a reference calculation route for such systems.
The experiment has already been fully analyzed with the JEF-2.2 library (submitted to NSE).
We focus here on two configurations to study the impact of the new JEFF-3.1 library on the calculation results and C/E agreement.

3. MUSE4-reference and MUSE-4 SC3-Pb configurations:

4. Calculations route with ERANOS-2.1:
JEF-2.2 and JEFF-3.1 evaluated libraries
The JEFF-3.1 Nuclear Data Library is the latest version of the Joint Evaluated Fission and Fusion Library. The complete suite of data was released in May 2005, and contains general purpose nuclear data evaluations
ECCO cell code with 62 energy groups
TGV/VARIANT (XYZ) and BISTRO (RZ) deterministic transport code
Specific analysis modules for beff, L, traverses, perturbations analysis,…

5. We observe that both libraries provide comparable results on the
Reactivities:
We observe that both libraries provide comparable results on the
Reference configuration, whereas there is a –400 pcm effect on SC3-Pb

6. Perturbation Analysis of Reactivity Calculations:
We consider the calculations performed with JEF-2.2 as the reference case and the use of JEFF-3.1 as a perturbation to that situation. The ERANOS perturbation module allows to split the reactivity effect of the library change in all the isotopes and reactions.   
the small total effect is the compensation of large positive and negative components (several hundreds of pcm’s each),
the large positive component comes mainly from the capture of 240Pu, 239Pu, 55Mn, 57Fe and 241Am,
the large negative component comes mainly from the elastic scattering of 56Fe and 52Cr,
There are quite large effects from the fission of 239Pu and 240Pu, capture of 59Co, scattering of 23Na, 56Fe, 238Pu and 238U,
In Muse4-SC3-Pb there is a large negative contribution of Pb scattering

9. Spectral Indices:
Several spectral indices have been measured with fission chambers in the lead or the fuel of the MUSE-4-Reference configuration - with an experimental uncertainties of 2 to 3% - and compared to calculations.
We observe that the new library ameliorates the C/E for all the spectral indices in the fuel and for most of them in the lead except for 238U and 243Am

10. Kinetic Parameters:
We see that the influence of the library is negligible, whereas the increase from 6 to 8 precursor families increases the beff of 5.6 pcm.
These values are in good agreement with the measurement of beff = 331  6 pcm.
The generation time L has also been calculated with JEF-2.2 and JEFF-3.1 and the value is 0.50 ms in both cases.

11. The library change does not affect the fission rate traverse more than 1.5%
in the middle of the reflector and does not improve the C/E agreement

12. Conclusions:
The analysis of some selected experiments of the MUSE-4 program with the ERANOS-2.1 code system using either the JEF-2.2 library or the more recent JEFF-3.1 one has shown limited improvements of the newest libraries.
This is not obvious since some compensating effects - especially on reactivities - are hiding the improvement, which is particularly obvious for all the spectral indices except for 238U and 243Am in the lead zone.
The MUSE4 Pb configuration is predicted with less accuracy with JEFF3.1 than JEF2.2 but still within the experimental uncertainty.