Contribution to Subgroup 21

Eu-155

Reviewed by A.Ignatyuk, March, 2004

**1. Files**

***ENDF/B-VI***: Evaluation was made in 1979 for ENDF/B-IV and
transformed to ENDF/B-V in 1980. Resonance parameters were revised for
ENDF/B-VI in 1988 and once more in 1991. Unresolved resonance parameters
were added in 1998 and negative resonance parameters were revised to
correct thermal cross sections.

***JENDL-3.3***: Evaluation was made for JENDL-2 in 1984. JENDL-2 data
were revised in 1990 for JENDL-3.1, modified for JENDL-3.2 in 1993 and
transformed to JENDL-3.3 in 2001 with minor corrections.

***JEF-3.0***: ENDF/B-VI Release 7 was adopted in 2002.

***CENDL-3***: Evaluation was performed in 1999.

**2. Thermal and resonance region**

***(1) Resolved resonance parameters***

***ENDF/B-VI*** (1.0e-5 -- 37.5 eV)***)***: The resonance parameters
below were based on the compilation of Mughabghab \[Mu84\]. MLBW
formalism was used. Negative resonance parameters were adjusted to
reproduce the thermal capture cross section and the resonance integral
measured by Sekine et al. \[Se87\].

***JENDL-3.3*** (1.0e-5 eV -- 29.7 eV): The resonance parameters were
evaluated for JENDL-2 by Kikuchi et al. \[Ki86\] on the basis of the
data measured by Anufriev et al. \[An79\]. MLBW formalism was used.
Negative resonance parameters were adjusted to reproduce the thermal
capture cross section and the resonance integral \[Se87\].

***CENDL-3*** (1.0e-5 eV -- 97.2 eV): JENDL-3.2 was adopted.

***(2) Unresolved resonance parameters***

***ENDF/B-VI*** (37.5 eV -- 10 keV): Energy independent parameters were
adopted. The average radiative width of 94 meV was taken in accordance
with the Mughabghab recommendations \[Mu84\]. The neutron strength
functions S0=2.3, S1=0.5 and the resonance spacing of 4.1875 eV were
adopted.

***JENDL-3.3*** (29.7 eV -- 100 keV): Energy dependent parameters were
used. The neutron strength functions S0=2.3, S1=0.5, S2=2.3 were
estimated from the optical model calculations and the average radiative
width of 94 meV were taken from the Mughabghab \[Mu84\]. The resonance
spacing was determined to reproduce the capture cross section at 70 keV
calculated with the CASTHY code.

***CENDL-3*** (97.2 eV -- 100 keV): JENDL-3.2 was adopted.

***(3) Thermal cross sections and resonance integrals*** (in barns)
calculated for the corresponding files are compared in the following
table:

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Library/Experiment Total Elastic Capture Cap.Res.Integ.

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

ENDF/B-VI 3777.9 17.7 3760.2 15288

JENDL-3.3 3675.0 6.57 3758.4 15600

CENDL-3.2 3675.0 6.57 3758.4 15600

Mughabghab \[Mu84\] 3950(125) 23200

Sekine et al. \[Se87\] 3760(170) 15300(2700)

Holden \[Ho94\] 16000(2000)

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

***(4) Recommendation/conclusion for resonance region***

Experimental data are available only for the thermal cross sections and
neutron resonances below 35 eV. Both independent evaluations ENDF/B-VI
and JENDL-3.3 are very similar. The main difference between them relates
to values of effective radius for unresolved resonances that define the
total and elastic cross sections. There are no criteria nowadays to
select a better estimation. Some preference can be given to JENDL-3.3
due to an extension of the unresolved resonance energy region to higher
energies (100 keV instead of 10 keV).

**3. Fast neutron region**

***(1) Methodology***

Statistical model calculations were widely used for all evaluations.
However the optical potential parameters and the corresponding
statistical codes were rather different that reflected into the obtained
results.

***ENDF/B-VI***

The total and the elastic scattering cross sections were calculated for
the Moldauer's optical potential parameters \[Mo63\] adjusted to
experimental data on the total cross sections for natural europium.
Inelastic scattering and capture cross sections were calculated with the
COMNUC-3 code. The capture cross section above 1 MeV was adopted the
same as for Eu-153. The threshold reaction cross sections were
calculated with the TRESH code. The temperature approximation was used
for neutron evaporation spectra.

***JENDL-3.3***

The total, elastic and inelastic scattering, and capture cross sections
were calculated with the spherical optical model and the statistical
model code CASTHY. The contribution of preequilibrium processes was
taken into account through the PEGASUS code. Capture cross sections at
high energies were estimated according to the direct-collective capture
model of Benzi and Reffo \[Be69\] and normalized to 1 mb at 14 MeV. The
threshold reaction cross sections were calculated with the PEGASUS code.
The (n,p) and (n,) reaction cross sections were normalized to the
systematics of Forrest \[Fo86\] at 14.5 MeV. PEGUSUS calculations were
also used for evaluations of secondary neutron energy spectra.

***CENDL-3***

The total, elastic and inelastic scattering cross sections were
calculated with the spherical optical model and the contributions of
direct processes were taken into account with the DWUCK-4 code. The
inelastic scattering and all threshold reaction cross sections were
calculated with the statistical model code SUNF. The same code was used
for calculations of angular and energy distributions of secondary
neutrons.

***(2) Intercomparison of evaluations***

**Total cross section** (MT=1, Fig:
http://www.nndc.bnl.gov/sg21/fp/nucl/Eu155/Eu155tot.htm):

All calculations performed with the optical model are rather similar.
They reproduce the available experimental data on the total cross
section for natural europium at energies above 10 MeV. CENDL-3 seems
preferable due to more consistent description of inelastic cross
sections.

**Capture cross section** (MT=102, Fig.:
http://www.nndc.bnl.gov/sg21/fp/nucl//Eu155/Eu155cap.htm):

All evaluations are very similar and there are no criteria to prefer one
evaluation to another.

**Inelastic scattering** (MT=4, Fig.
http://www.nndc.bnl.gov/sg21/fp/nucl//Eu155/Eu155inl.htm):

ENDF/B-VI and JENDL-3.3 calculations certainly give too low inelastic
scattering cross sections above 10 MeV. Both of them seem two low at
energies below 4 MeV. CENDL-3, which includes the direct and
preequilibrium processes, looks preferable for the whole energy region.

**(n,2n) cross section** (MT=16, Fig:
http://www.nndc.bnl.gov/sg21/fp/nucl//Eu155/Eu155n2n.htm):

All evaluations are close enough and CENDL-3 looks preferable a little
owing to a more correct estimation of inelastic cross sections.

**(n,p) and (n,) cross sections** (Figs.
http://www.nndc.bnl.gov/sg21/fp/nucl//Eu155/Eu155np.htm ,
http://www.nndc.bnl.gov/sg21/nucl//Eu155/Eu155na.htm):

Charge-particle production cross sections have very low importance for
reactor applications. Experimental data are absent. JENDL-3.3 looks
preferable owing to normalization to the Forrest systematics.

***(3) Recommendation/conclusions for fast neutron region***

CENDL-3 could be considered as preferable ones on the basis of a
comparison with evaluations and available experimental data for
neighbouring nuclei.

**References**

\[An79\] V.A.Anufriev et al., Sov. At. Energy, 46, (1979) 182.

\[Be69\] V.Benzi, G.Reffo, Report CCDN-NW/10 (1969).

\[Fo86\] Forrest R.A.: Report AERE-12419 (1986).

\[Ho94\] N.E.Holden. Nucl. Data for Science and Technology (Gatlinburg,
1994), ORNL, v. 1, p. 742.

\[Mu84\] S. Mughabghab. Neutron Cross Sections, Vol.1, Part B, Academic
Press, 1984.

\[Se87\] T. Sekine, S. Ichikawa and S. Baba, Appl.Rad.Isotopes 38,
(1987) 513.