WPEC SG 21: Assessment of Neutron Cross-Section Evaluations for the Bulk
of Fission Products

**Y-91**

Reviewed by Shen Qingbiao CIAE, February, 2003

**1. Files**

***ENDF/B-VI***: Evaluation was made in 1974 for ENDF/B-V. It was
converted to ENDF/B-VI in 1990.

***JENDL-3.2***: The evaluation was completed in 1990.

***JEF-2.2***: ENDF/B-V was adopted. The charged particle production
cross sections were added from REAC-ECN-4 library in 1989. The data were
compiled in 1992.

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

Figs: <http://www.nndc.bnl.gov/~sirakov/fp/fp21/htm/Y91.htm#mt1>

**2. Thermal and resonance region**

\(1\) Resolved resonance parameters

***ENDF/B-VI***

No resolved resonance parameters are given.

***JENDL-3.2***

No resolved resonance parameters are given.

***JEF-2.2***

No resolved resonance parameters are given.

***CENDL-3***

No resolved resonance parameters are given.

\(2\) Unresolved resonance parameters

***ENDF/B-VI***

No unresolved resonance parameters are given.

***JENDL-3.2*** (380 eV - 100 keV)

The neutron strength function S1 was based on the systematics of
Mughabghab S.F.\[Mu81\] and S1 and S2 were calculated with CASTHY code
\[Ig91\].

***JEF-2.2***

No unresolved resonance parameters are given.

***CENDL-3*** (380 eV - 100 keV)

JENDL-3.2 was adopted.

\(3\) Recommendation/conclusion for resonance region

***JENDL-3.2*** (***CENDL-3***) is recommended. The background cross
sections of ***JENDL-3.2*** below 380 eV and ***ENDF/B-VI***
(***JEF-2.2***) below 526.07 eV fall down largely and suddenly as energy
decreases. ***CENDL-3*** changes the above suddenly falling down
situation to smoothly changing. But they have the same thermal capture
cross section and ***CENDL-3*** and ***JENDL-3.2*** have the same
thermal total and elastic scattering cross sections. It seems that the
thermal radiative capture resonance integral of ***CENDL-3*** is too
large. In my opinion, it is better that the resonance parameters
obtained by SAMMY code are used in whole low energy region for unstable
nuclei or the resonance parameters of stable nucleus Y89 are used to
unstable nucleus Y91.

**3. Fast neutron region**

\(1\) Methodology

***ENDF/B-VI***

Theoretical calculation was widely used. The optical potential of
Moldauer was adopted.

Inelastic scattering was calculated with COMNUC-3 code, and the capture
cross section with

NCAP code. No direct inelastic was considered. No threshold reaction
cross sections are given.

Isotropic distributions were given to the elastic and inelastic
scattering.

Evaporation spectra were given to the continuum inelastic scattering.

***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 29 levels
up to 3.2840 MeV were considered for the inelastic scattering. No direct
inelastic was considered. Other reaction cross sections were calculated
with a preequilibrium and multi-step evaporation code PEGASUS. Sum of
the threshold reaction cross sections were considered as a competing
reaction cross sections in the CASTHY calculation.

Angular distributions of elastic and inelastic scattering were
calculated with CASTHY code. Isotropic distributions were assumed to the
other reactions.

The energy distributions were calculated with PEGUSUS code.

***JEF-2.2***

ENDF/B-V data were adopted. The charged particle production cross
sections were added from REAC-ECN-4 library in 1989.

***CENDL-3***

Calculated with SUNF code and DWUCK4 code \[Ku94\]. The optical model
parameters were determined with APOM code. The 11 levels up to 2.0666
MeV were considered for the inelastic scattering. The direct inelastic
scatterings of 7 levels were calculated by DWUCK4 code.

Angular and energy distributions of neutrons were also calculated with
SUNF code.

\(2\) Total cross section (MT=1)

Y89 is the closed stable odd A nucleus of Y91.The total cross sections
of ***CENDL-3*** are in good agreement with the experimental data of Y89
than other libraries. (see the following figure)

![](media/image1.png){width="6.490277777777778in" height="6.31875in"}

\(3\) Capture cross section (MT=102)

No experimental data are available for Y91 capture cross section. The
shapes of the capture cross section of ***JENDL-3.2*** and ***CENDL-3***
are better than other libraries.

\(4\) Elastic scattering cross section (MT=2)

This cross section was obtained as (total cross section) -- (sum of
partial cross sections) in the all

libraries.

\(5\) Inelastic scattering cross section (MT=4, 51 -- 91)

Excited levels considered in the files.

> ENDF/B-VI 8 levels up to 1.5800 MeV
>
> JENDL-3.2 29 levels up to 3.2840 MeV
>
> JEF-2.2 8 levels up to 1.5800 MeV
>
> CENDL-3 11 levels up to 2.0666 MeV

The shapes of total inelastic scattering cross section of ***CENDL-3***
and ***JENDL-3.2*** are reasonable, but the total inelastic scattering
cross sections of ***CENDL-3*** are in better agreement with the
experimental data of Y89 than other libraries. (see the following
figure)

![](media/image2.png){width="6.490277777777778in"
height="5.5784722222222225in"}

\(6\) (n,2n) reaction cross section (MT=16)

No experimental data are available for Y91 (n,2n) cross section. The
shapes of the (n,2n) cross section of ***JENDL-3.2*** and ***CENDL-3***
are reasonable.

\(7\) (n,p) reaction cross section (MT=103)

No experimental data are available for Y91 (n,p) cross section. The
shapes of the (n,p) cross section of ***JENDL-3.2*** and ***CENDL-3***
are reasonable. Their less values than Y89 is reasonable in physics.

\(8\) (n,) reaction cross section (MT=107)

No experimental data are available for Y91 (n,) cross section. The
shapes of the (n,) cross section of ***JENDL-3.2***, ***JEF-2.2*** and
***CENDL-3*** are reasonable. Their less values than Y89 is reasonable
in physics. But it seems that the value of ***CENDL-3*** is too little.

\(9\) Other reactions

The following other reaction cross sections are given in the files.

> JENDL-3.2 (n,3n),(n,n), (n,np), (n,nd), (n,nt), (n,d), (n,t)
>
> CENDL-3 (n,3n),(n,n), (n,np), (n,d), (n,t), (n,He-3)
>
> JEF-2.2 (n,d), (n,t), (n,He-3), (n,2p)
>
> ENDF/B-VI no

\(10\) Recommendation/conclusions for fast neutron region

***CENDL-3*** or ***JENDL-3.2*** is recommended. The total and the total
inelastic scattering cross sections of ***CENDL-3*** is in better
agreement with the experimental data of the closed odd A nucleus Y89
than ***JENDL-3.2,*** but it seems that the (n,) cross section value of
***CENDL-3*** is too little. ***ENDF/B-VI*** has no threshold reaction
cross sections and ***JEF-2.2*** has no important (n,2n), (n,p)
reactions.

**References**

\[Ig91\] Igarasi S. and Fukahori, T., JAERI 1321 (1991).

\[Ku94\] Kunz, P. D., 'Distorted Wave Code DWUCK4', University of
Colorado, 1994.

\[Mi60\] Milton G. et al., J, CJP, 38, 1690 (1960).

\[Mu81\] Mughabghab S.F. et al.: "Neutron Cross Sections, Vol.1, Part
A," Academic Press (1981).

Table 1. Summary for Resolved and Unresolved Resonance Region: Y-91

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

Library RRP URP Remarks

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

ENDF/B-VI No RRP No URP

JENDL-3.2 No RRP 380 eV-100 keV

JEF-2.2 No RRP No URP

CENDL-3 No RRP 380 eV-100 keV taken from JENDL-3.2

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

Table 2. Thermal Cross Sections and Resonance Integral: Y-91

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

Library/Experiment Total Elastic Capture Res.Integ.

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

ENDF/B-VI 5.098 3.698 1.400 1.66671

JENDL-3.2 7.100 5.700 1.400 2.85

JEF-2.2 5.098 3.698 1.400 1.66671

CENDL-3 7.100 5.700 1.400 10.3926

Mughabghab et al. \[Mu81\] 1.40.3

Milton et al. \[Mi60\] 1.40.3\*1

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

\*1) Spectrum averaged

**[Attachment 2]{.underline}**

Figs: <http://www.nndc.bnl.gov/~sirakov/fp/fp21/htm/Y91.htm#mt1>