La-138

Reviewed by T. Nakagawa, JAERI, January 2004

**1. Files**

***ENDF/B-VI***: No data are given.

***JENDL-3.3 and JENDL-3.2***:

The same data as JENDL-3.2 are given in JENDL-3.3. The evaluation was
made by JNDC FPND working group \[Ka92\] for JENDL-3.1 in 1990. The data
were taken over to JENDL-3.2 and JENDL-3.3.

***JEFF-3.0 and JEF-2.2***:

JEF-2.2 has no data for La-138. JEFF-3.0 adopted the data of JENDL-3.2.

***CENDL-3***: No data are given.

***BROND-2***: No data are given.

**2. Thermal and resonance region**

***JENDL-3.3 and JENDL-3.2***

Resolved resonance parameters were based on Mughabghab et al. \[Mu81\] A
negative resonance was added to reproduce the thermal capture cross
section of 57.25.7 \[Mu81,Mi76\].

In the unresolved resonance region from 330 eV to 100 keV, neutron
strength functions were calculated with the optical model. Average level
spacing was adjusted to the capture cross section calculated with the
statistical model code CASTHY.

***JEFF-3.0***

The same as JENDL-3.3.

**[Recommendation/conclusion for the thermal and resonance
region]{.underline}**

***JENDL-3.3*** is recommended.

**3. Fast neutron region**

**(1) Methodology**

***JENDL-3.3 and 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 gamma-ray strength function was determined from the
systematics of the radiation width (0.085 eV) and the level spacing
(24.5 eV). Fifteen excited levels up to 0.836 MeV were adopted for the
inelastic scattering cross section. The direct/semi-direct capture was
calculated from a simple formula of Benzi and Reffo \[Be69\]

Other reaction cross sections were calculated with the preequilibrium
and multi-step evaporation code PEGASUS. The (n,p) and (n,) reaction
cross sections were normalized to 5.16 mb \[Fo86\], and 2.29 mb \[Fo86\]
at 14.5 MeV. 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 the CASTHY code. Isotropic distributions were assumed to
the other reactions.

The energy distributions were calculated with the PEGASUS code.

***JEFF-3.0 and JEF-2.2***

Same as JENDL-3.3.

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt1)La138.htm#mt1

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt102)La138.htm#mt102

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt2)La138.htm#mt2

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt4)La138.htm#mt4

Discrete levels considered in the evaluations are as follows:

JENDL-3.3, JEFF-3.0 15 levels up to 0.8360 MeV

The direct inelastic was not considered.

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt16)La138.htm#mt16

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt103)La138.htm#mt103

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

See Fig:
[http://www.nndc.bnl.gov/sg21/fp21/htm/](http://www.nndc.bnl.gov/sg21/fp21/htm/La138.htm#mt107)La138.htm#mt107

**(9) Other reactions**

The following reaction cross sections are given:

JENDL-3.3, JEFF-3.0 (n,3n), (n,n), (n,np), (n,nd), (n,nt), (n,d), (n,t),
(n,^3^He)

**[Recommendation/conclusion for the fast energy region]{.underline}**

***JENDL-3.3*** is recommended.

**References**

\[Be69\] Benzi V. and Reffo G.: *CCDN-NW/*10 (1969).

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

\[Ka92\] Kawai M. et al.: *J. Nucl. Sci. Technol.*, **29**, 195 (1992).

\[Mi76\] Michael H., Neubert A., Wagner R. and Blair A.J.: *Int. J.
Appl. Radiat. Isotopes*, **27**, 533 (1976).

\[Mu81\] Mughabghab S.F. et al.: *Neutron Cross Sections, Vol. 1, part
A*, Academic press (1981).

\[Mu03\] Mughabghab S.F.: "Thermal Neutron Capture Cross Sections
Resonance Integrals and g-Factors," *INDC(NDS)*-440 (2002)

Table 1 Summary for Resolved and Unresolved Resonance Region: La-138

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Library RRP URP Remarks

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> JENDL-3.3 330 eV, MLBW 0.33 -- 100 keV
>
> JEFF-3.0 330 eV, MLBW 0.33 -- 100 keV the same as JENDL-3.3

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Table 2. Thermal Cross Sections and Resonance Integral: La-138

Units: barns

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Library/Experiment Total Elastic Capture Res.Integ.

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JENDL-3.3 70.06 12.98 57.08 364

JEFF-3.0 70.06 12.98 57.08 364

Mughabghab et al. \[Mu81\] 57.25.7 40990^\*1^

Mughabghab et al. \[Mu03\] 57.25.7 36225

Michael et al. \[Mi76\] 57.25.7 38490^\*2^

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\*1) Mughabghab et al. recommended I^c^ of 36030 barns also.

\*2) Resonance integral of non-1/v part. Total resonance integral is
41090 barns.