Contribution to Subgroup 21

Sm-150

Reviewed by A.Ignatyuk, March, 2003

**1. Files**

***ENDF/B-VI***: Evaluation was made in 1974 for ENDF/B-V. The resonance
parameters were revised in 1992 for ENDF/B-VI, the unresolved resonance
range was added.

***JENDL-3.2***: In 1984, the evaluation was made for JENDL-2. JENDL-2
data were revised in 1990 for JENDL-3.1. The inelastic scattering and
capture cross sections were revised in 1994 for JENDL-3.2.

***JEF-2.2***: ENDF/B-V evaluations were adopted in 1982. The resonance
parameters were revised in 1986. In 1989 the missing charged-particle
emission cross sections were included from REAC-ECN-4.

***BROND-2***: Evaluation was made in1987.

***CENDL-3***: Evaluation was performed in 1999. The file was compiled
in 2001.

**2. Thermal and resonance region**

**(1) Resolved resonance parameters**

***ENDF/B-VI*** (1.0e-5 eV -- 1.6 keV): The parameters were taken in
accordance with the recommendation of Mughabghab \[Mu84\]. MLBW
formalism was adopted. The negative resonance parameters were corrected
to reproduced the thermal cross sections.

***JENDL-3.2*** (1.0e-5 eV -- 1.538 keV): The parameters were taken from
JENDL-2, which was evaluated by Kikuchi et al. \[Ki86\] on the basis of
experimental data \[El74, An77\]. MLBW formalism was used. A negative
resonance was added to reproduced the thermal capture cross section.

***JEF-2.2*** (1.0e-5 eV -- 0.593 keV): The parameters were taken in
accordance with the recommendation of Mughabghab \[Mu84\]. MLBW
formalism was adopted.

***BROND-2*** (1.0e-5 eV -- 0.5 keV): The parameters were taken in
accordance with the analysis of Zakharova et al. \[Za82\]. MLBW
formalism was used. A negative resonance was included to reproduce the
thermal cross sections. The upper limit of resolved resonance range is
estimated by the condition of a small resonance missing.

***CENDL-3*** (1.0e-5 eV -- 1.538 keV): JENDL-3.2 was adopted.

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

***ENDF/B-VI*** (1.6 -- 100 keV): The neutron strength functions were
based on the compilation of Mughabghab \[Mu84\], the radiative strength
functions were fitted to experimental data on the neutron radiative
capture.

***JENDL-3.2*** (1.538 -- 100 keV): The neutron strength function S0 and
the average radiative widths were based on the compilation of Mughabghab
\[Mu84\], S1 and S2 were estimated from the optical model calculations.
The resonance spacing D0 was fitted to reproduce experimental data on
neutron radiative capture.

***JEF-2.2***: There is no the unresolved resonance region.

***BROND-2*** (.5 -- 20 keV): Statistical model was used with the
parameters fitted to experimental data on the capture cross sections.
The experimental data were corrected in accordance with current changes
of the standard and monitor cross sections used in old measurements.
Erroneous values of radiative widths are available into the file
distributed by IAEA, which were corrected into the national version of
the BROND-2 library.

***CENDL-3*** (1.538 -- 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 122.9 19.0 103.9 337.8

JENDL-3.2 116.9 8.34 108.6 325

JEF-2.2 124.7 21.3 103.4 338.8

BROND-2 118.2 8.85 109.3 331.4

CENDL-3.2 116.9 8.34 108.6 325

Mughabghab \[Mu84, Mu03\] 104(4) 358(50)

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

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

There are no essential differences in the parameters of resolved neutron
resonances. However, starting from 1 keV the missing of resonances
manifests in the experimental data that was taken into account by
BROND-2 evaluations, but leaved out of consideration by other ones. For
higher energies all evaluations look reasonable for the available
dispersion of experimental data. As a whole JENDL-3.2 (CENDL-3) seems
preferable due to a better agreement with the recent experimental data
\[Wi92, Du99\].

![](media/image1.wmf){width="4.7131944444444445in" height="3.25625in"}

Fig. 1. Calculated group cross sections for the unresolved resonance
region.

**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 deformed optical model was adopted for calculations of the total
cross sections and the elastic scattering angular distributions. The
revised total cross sections are based on the measurements \[Sh80\].
Inelastic scattering and the capture cross sections were calculated with
COMNUC-3 code. The capture cross sections between 100 keV and 3.5 MeV
were corrected to agree with the experimental values \[Ko78, Zu84\]. The
(n,2n), (n,3n), and charge-particle production cross sections were
calculated with THRESH code. The temperature approximation was used for
neutron evaporation spectra.

***JENDL-3.2***

The total, elastic and inelastic scattering, and capture cross sections
were calculated with the spherical optical model and statistical model
code CASTHY. The contribution of direct inelastic scattering to the
excitation functions of the low-lying collective levels was calculated
within the coupled-channels model code ECIS88. The gamma-ray strength
function was adjusted to reproduce the capture cross section of 420 mb
at 30 keV measured by Macklin et al. \[Ma63\]. Other reaction cross
sections were calculated with a preequilibrium and multi-step
evaporation code PEGASUS. The (n,p) and (n,α) reaction cross sections
were normalized to the systematics of Forrest \[Fo86\] at 14.5 MeV. The
energy spectra of secondary neutrons were calculated with PEGUSUS code.

***JEF-2.2***

The total, elastic and inelastic scattering cross sections were
calculated with the spherical optical model and the statistical model
code SASSI-RCN. The capture cross section was calculated with code
FISPRO-RCN. The original evaluations were adjusted on the basis of STEK
and CERMF integral data. Charge-particle production data are included
from REAC-ECN-4 library. The temperature approximation was used for
neutron evaporation spectra.

***BROND-2***

The deformed optical model was used for calculations of the total,
elastic and inelastic scattering cross sections on low-lying collective
levels. The optical potential parameters were fitted to the total cross
sections measured by Shamu et al. \[Sh80\]. The inelastic scattering
excitation functions were taken from EVDF/B-V, but the cross sections
for the first and second levels were corrected in accordance with
calculations performed. The capture cross section was obtained by
adjustment of the RCN evaluation to available experimental data
\[Be84\]. The capture cross section above 5 MeV was estimated in
accordance with the systematics based on the direct-collective radiative
capture model \[Be84\]. The (n,2n) and (n,3n) cross sections were taken
from BOSPOR evaluations \[By82\]. The temperature approximation was used
for neutron evaporation 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 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 neutrons.

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

**Total cross section** (MT=1, Fig:
http://www.nndc.bnl.gov/sg21/fp/nucl/sm150/sm150tot.htm):

The deformed optical model (ENFB/B-VI and BROND-2) reproduces the
experimental data only and the calculations with the spherical model
(JENDL-3.2 and CENDL-3) are too low for energies below 1 MeV. Some
artificial changes of the optical potential parameters in JEF-2.2 are
badly justified for energies, where there are no experimental data
(above 1 MeV). So ENFB/B-VI and BROND-2 look as preferable ones.

**Capture cross section** (MT=102, Fig.:
http://www.nndc.bnl.gov/sg21/fp/nucl//sm150/sm150cap.htm):

Kononov et al data \[Ko78\] are definitely to high for energies below
0.1 MeV. All other experimental data are reasonable described by all
evaluations. JENDL-3.2 is better confirmed by the recent experimental
data \[Wi93, Du99\] for energies below 1 MeV, but seems too high at the
energy range between 4 and 9 MeV. CENDL-3 seems too low at the energy
range between 0.5 and 3 MeV and ENFB/B-VI and JEF-2.2 are too high at
energies above 10 MeV. However, the high-energy differences have a
negligible effect for reactor applications. So all evaluations should be
considered as acceptable ones and some preference could be given to
JENDL-3.2.

**Inelastic scattering cross section** (MT=4, Fig.
http://www.nndc.bnl.gov/sg21/fp/nucl//sm150/sm150inl.htm):

JEF-2.2 evaluation is certainly wrong above 8 MeV and both ENDF/B-VI and
JEF-2.2 look too low at energies between 3 and 8 MeV. The shapes of
total inelastic scattering cross section are rather similar for BROND-2,
JENDL-3.2 and CENDL-3. However, JENDL-3 seems too high for both the
cross section value at maximum and the cross section at a high-energy
region. A reason of a such overestimation of the inelastic scattering is
not clear. So BROND-2 and CENDL-3 evaluations look reasonable ones only.

**(n,2n) cross section** (MT=16, Fig:
http://www.nndc.bnl.gov/sg21/fp/nucl//sm150/sm150n2n.htm):

ENDF/B-VI is two high at energies above 15 MeV and CENDL-3 seems
slightly overestimated at these energies too. JENDL-3 and BROND-2 look
as the most reasonable.

**(n,p) and (n,α) cross sections** (Figs.
http://www.nndc.bnl.gov/sg21/fp/nucl//sm150/sm150np.htm;
http://www.nndc.bnl.gov/sg21/nucl//sm150/sm150na.htm):

Charge-particle production cross sections have very low importance for
reactor applications. Experimental data are available for energies about
14.5 MeV only. JEF-2.2, JENDL-3.2, and CENDL-3 are similar enough and
all look as acceptable ones.

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

For the total, inelastic and (n,2n) cross-section evaluations BROND-2
looks preferable, however, the capture cross section seems slightly
overestimated below 200 keV and the charge-particle production cross
sections are not included into BROND-2 too. So for most applications the
CENDL-3 file, which coincide with JENDL-3.2 for the resonance region,
can be recommended as an optimal one.

**References**

\[An77\] V.A. Anufriev et al.: Proc. 4th Conf. on Neutron Physics, Kiev,
1977, v.2, p. 263.

\[Be84\] Belanova T.S. et al.: Radiative Neutron Capture -- Handbook.
Moscow, Energoatomizdat, 1986.

\[By82\] V.M.Bychkov et al. Cross Sections of Threshold Reactions --
Handbook. Moscow, Energoatomizdat, 1982.

\[Co88\] F. de Courte, A.Simonitz. Nuclear Data for Science and
Technology (Mito 1988). JAERI, 1988, p.583.

\[Du99\] B.Duamet et al. J. Nucl. Sci. Tech., 36 (1999) 865.

\[El74\] H.M.Eiland et al.: Nucl. Sci. Eng., 54, 286 (1974).

\[Ki86\] Y.Kikuchi et al. JAERI-M 86-30 (1986).

\[Ko78\] V.N.Kononov et al. Sov. J. Nucl. Phys., 27 (1978) 5.

\[Ma79\] Macklin R.L. et al.: Nature 197 (1963) 369.

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

\[Mu03\] S. Mughabghab.Thermal Neutron Capture Cross Sections, Resonance
Integrals and G-factors. Report INDC(NDS)-440, IAEA, Vienna, 2003.

\[Sh80\] R.E.Shamu et al. Phys. Rev., C22 (1980) 1857.

\[Wi92\] K.Wisshak et al. Report KFK 5067 (1992).

\[Za82\] C.M.Zakhatrova et al. Report FEI-161, Obninsk, 1982.

\[Zu84\] Zhou Zu-Yimg et al. Chin. J. Nuc. Phys., 6 (1984) 174.