**50-Sn-126 Review**

Keiichi SHIBATA, JAERI Nuclear Data Center, January 10, 2003

1.  **Files**

ENDF/B-VI: Year of origin 1974.

JEF-2.2: Year of origin 1982; charged-particle emission cross sections
taken from REAC-ECN-4 in 1989; other quantities taken from ENDF/B-V
(=ENDF/B-VI).

JENDL-3.2: Year of origin 1990.

1.  **Thermal and Resonance Region**

ENDF/B-VI: No resonance parameter is given. The elastic scattering cross
section was calculated as 4πR^2^. The capture cross section was assumed
to be 1/v form.

JEF-2.2: No resonance parameter is given. The elastic scattering cross
section was calculated as 4πR^2^. The capture cross section was assumed
to be 1/v form.

JENDL-3.2: No resolved resonance parameter is given; unresolved
resonance parameters are given between 2 and 100 keV. The elastic
scattering cross section was assumed to be constant below 2 keV. The
capture cross section is in the 1/v form. The thermal cross sections
were determined by the systematics of the neighboring nuclei.

Thermal cross sections and resonance integral for Sn-126 (300K)

  -------------- -------------- -------------- -------------- --------------
                 Total (b)      Elastic (b)    Capture (b)    Cap. R.I. (b)

  JENDL-3.2      4.11022E+00    4.01881E+00    9.00397E-02    1.29588E-01

  ENDF/B-VI      4.91382E+00    4.61381E+00    3.00015E-01    1.59774E-01

  JEF-2.2        4.92053E+00    4.61381E+00    3.00132E-01    1.59564E-01
  -------------- -------------- -------------- -------------- --------------

**Recommendation**

There is a difference between the JENDL-3.2 and ENDF/B-VI cross
sections. However, it is impossible to judge which the best evaluation
is, since no experimental data are available on this nucleus. The
ENDF/B-VI and JEF-2.2 data are essentially the same.

2.  **Fast Neutron Region**

    1.  **Methodology**

[ENDF/B-VI]{.underline}

Optical and statistical model calculations were performed. The library
contains the total, elastic and inelastic scattering, and capture cross
sections. The elastic scattering cross section was obtained by
subtracting the inelastic scattering and capture cross sections from the
total cross section.

[JEF-2.2]{.underline}

Charged-particle emission cross sections ((n,p), (n,d), (n,t),
(n,^3^He), (n,α), and (n,2p)) were taken from REAC-ENC-4, but no detail
in given. Other cross sections are the same as those in ENDF/B-VI.

[JENDL-3.2]{.underline}

Optical and statistical model calculations were performed. The library
contains the cross sections for the (n,n'), (n,2n), (n,3n), (n,nα),
(n,np), (n, γ), (n,p), (n,d), (n,t), and (n,α) reactions together with
the total and elastic scattering cross sections.. The DSD process was
considered for the capture reaction in a phenomenological way. The
elastic scattering cross section was obtained by subtracting a sum of
reaction cross sections from the total cross section.

1.  **MT=1**

The ENDF/B-VI and JEF-2.2 cross sections increase above 7 MeV up to 20
MeV. This behavior seems unreasonable as compared with the total cross
section in this mass region. I cannot judge which the best evaluation
is, since there is no experimental data. However, it seems me that
JENDL-3.2 is preferable.

2.  **MT=2**

The ENDF/B-VI and JEF-2.2 cross sections increase above 7 MeV up to 20
MeV. This behavior seems unreasonable as compared with the elastic
scattering cross section in this mass region. I cannot judge which the
best evaluation is, since there is no experimental data. However, it
seems me that JENDL-3.2 is preferable.

3.  **MT=4**

I cannot judge which the best evaluation is, since there is no
experimental data. However, the shape of the ENDF/B-VI and JEF-2.2 cross
sections is somewhat strange.

4.  **MT=16**

Only JENDL-3.2 gives cross sections. According to the experimental data
/ik88/, /kl63/ on Sn-124, the 14-MeV cross section is about 1.45 b,
which is almost consistent with the JENDL-3.2 evaluation for Sn-126.

5.  **MT=102**

I cannot judge which the best evaluation is, since there is no
experimental data.

6.  **MT=103**

JENDL-3.2 and JEF-2.2 give cross sections. I cannot judge which the best
evaluation is, since there is no experimental data.

7.  **MT=107**

JENDL-3.2 and JEF-2.2 give cross sections. I cannot judge which the best
evaluation is, since there is no experimental data.

**Recommendation**

JENDL-3.2 is recommended, since it has no obvious drawback for the
reactions considered.

**References**

/il88/ Y. Ikeda et al.: JAERI-1312 (1988).

/kl63/ A.P. Klyucharev, **46**, 1483 (1963).