WPEC SG21: Assessment of Neutron Cross-Section Evaluations for the Bulk
of Fission Products

> **48-Cd-111 Review**

Mike Herman, BNL, April 11, 2003

#### General

**Properties**

Stable nucleus, natural abundance 12.80%, fission yield substantial.

**EXFOR data**

Very scarce experimental information. Limited data available for total,
elastic, capture, and (n,p). Only those for (n,p) can be considered
sufficient to fix excitation function shape and magnitude. Other
reaction channels not measured.

Evaluations:

-   **ENDF/B-VI** year of origin 1993, authors J. McCabe, A.B. Smith
    and J. W. Meadows.

-   **JEF-2** year of origin 1982, authors H. Gruppelaar, E.Menapace,
    last revision 1989. Data based on the old ENEA/CEA evaluation from
    1977 and ENDF/B-V.

-   **BROND-2** none

-   **JENDL-3.2** year of origin 1990, last revision 1993

-   **CENDL-3** none

# Thermal and resonance region

*** ***

#### ENDF/B-VI

-   RR range from 1.0E-5 eV to 2.4 keV. The MLBW formalism used with the
    RR parameters taken from S.F. Mughabghab et al (1981) and from
    Musgrove et al (1982)).

-   UR absent

**JEF-2**

-   RR -- up to 2.32 keV. The original JEF-1 (ENEA/CEA) evaluation
    maintained. No more information provided.

#### JENDL-3.2 

-   RR (MLBW formula) up to 1.8 keV. Resonance parameters taken from
    JENDL-2, and modified. JENDL-2, evaluation was based on experimental
    data of Liou et al. (1974) and Wasson and Allen (1973) The average
    radiation width for s-wave levels was assumed to be 0.102 eV.
    Scattering radius of 6.5 fm was assumed on the basis of systematics
    of measured values. A negative resonance was added in order to
    reproduce thermal capture and elastic cross sections given by
    Mughabghab et al. (1981). The capture data measured at ORNL were
    renormalized by factor of 1.208). The neutron and/or radiation width
    were revised to reproduce the normalized capture area for each
    resonance above 2.76 eV

-   UR region: 1.8V - 100 keV. The parameters from JENDL-2 were used as
    initial values and adjusted to reproduce capture cross sections
    calculated with CASTHY above 15 keV and those measured by Musgrove
    et al. below 15 keV. The effective scattering radius was obtained
    from the fit to the calculated total cross section at 100 keV.

**Recommendation/Conclusion**

**Total** -- all three evaluations practically identical up to 0.1 eV.
Above, JENDL has more resonances than the other two and JEF has more
than ENDF. The ENDF background appears to be systematically lower than
in the remaining two evaluations. All three evaluations ignore a single
experimental point by Vertebnyj, which seems too low.

**Elastic** -- up to 25 eV all three evaluations have similar shape but
differ in magnitude by about 30% (ENDF being the lowest and JEF the
highest). In the resolved resonance region JENDL appears to be the most
detailed and ENDF background is systematically lower. Shifts between the
resonances in different evaluations are observed. JENDL reproduces
within an experimental uncertainty the measurement by Vertebnyj.

**Capture** -- all three evaluations identical up to 0.28 keV, except of
the two resonances present in the JENDL file only. For higher energies
the evaluations differ with JENDL revealing the most detailed resonance
structure. All three evaluations agree with the recently recommended by
Mughabghab (2001) value thermal energy and ignore a single experimental
point by Vertebnyj, which seems too low.

JENDL-3.2 evaluation is recommended in the low energy region.

# Fast neutron region

#### ENDF/B-VI methodology

-   The direct reaction contribution to inelastic scattering calculated
    assuming a one-phonon vibrational model using coupled-channels code
    ANLECIS.

-   Weisskopf model used for inelastic scattering to continuum and for
    the radiative capture (code ABAREX). Width fluctuations within the
    frame of the Moldauer approach.

-   Preequilibrium effects in the inelastic scattering approximated by
    Weisskopf calculations with increased nuclear temperature

-   (n,2n), (n,p), and (n,alpha) and other minor channels reactions
    calculated with code GNASH

-   Non-isotropic angular distributions for elastic only.

#### JEF-2 methodology

-   Pretty old modeling and scarce information on evaluation methodology
    available. Obsolete codes CERBERO and ERINNI used.

-   MT=16 and 91 distributions assumed isotropic.

#### JENDL-3 methodology

-   Methodology fairly up-to date, all important effects taken into
    account.

-   Spherical optical and statistical model calculation performed with
    CASTHY including preequilibrium effects.

-   OMP\'s for neutron determined to reproduce total cross sections
    measured on natural Cd by Foster and Glasgow (1971) and others.

-   Direct and semi-direct mechanisms considered in the calculations of
    the capture cross sections. Gamma-ray strength function adjusted to
    reproduce capture cross section at 90 keV as measured by Musgrove et
    al. (1978)

-   Calculated (n,p) and (n,alpha) cross sections normalized to the
    experimental values

-   L[e]{.underline}gendre polynomial coefficients for angular
    distributions, calculated with CASTHY, are given for MT=2 discrete
    inelastic levels, and MT=91. For other reactions, isotropic
    distributions are assumed.

-   Energy distributions of secondary neutrons were calculated with
    PEGASUS code for inelastic scattering from overlapping levels and
    for other neutron emitting reactions.

Comparison of ENDF/B-VI, JEF-2, and JENDL-3

-   MT=1,2. Substantial differences among the three evaluations can not
    be resolved because of the lack of experimental data.

-   MT=4. . No experimental data for comparison. Substantial differences
    between the evaluations can not be resolved. JEF is missing
    preequilibrium component, which appears to be stronger in the ENDF
    evaluation than in JENDL. Independent EMPIRE-II calculations support
    JENDL (also below 5 MeV)

-   MT=16. No experimental data for comparison. Substantial differences
    between the evaluations. can not be resolved. JEF shape unrealistic.

-   MT=102. JENDL-3.2 follows the only set of experimental data by
    Musgrove (1978) closer than the remaining evaluations.

-   MT=103. ENDF reproduces experimental data much better than the other
    two evaluations.

-   MT=107. No experimental data available. All three evaluations
    strongly discrepant.

# Recommendation/Conclusion

JENDL-3 uses fairly up-to date physics, which, in the fast energy
region, is superior to the approach used in the ENDF/B-VI evaluation.
Both JENDL-3.2 and ENDF/B-VI can be recommended but there is a slight
preference for JENDL (consistence with the resonance region
recommendation).

[Table 1.]{.underline} Summary for Resolved and Unresolved Resonance
Region for 48-Cd-111

+------+---+---------------+-----+---+---------------------------------+
| Lib  | Y | First Authors | RRR | # | Remarks                         |
| rary | e |               |     |   |                                 |
|      | a |               |     | U |                                 |
|      | r |               |     | R |                                 |
|      |   |               |     | R |                                 |
+------+---+---------------+-----+---+---------------------------------+
| E    | 1 | J. McCabe, A. | 2.4 |   | > RR parameters taken from S.F. |
| NDF/ | 9 | B. Smith      | keV |   | > Mughabghab et al (1981) and   |
| B-VI | 9 |               |     |   | > from Musgrove et al (1982)).  |
|      | 3 |               | M   |   |                                 |
|      |   |               | LBW |   |                                 |
+------+---+---------------+-----+---+---------------------------------+
| J    | 1 | H.            | 1.8 |   | > The original JEF-1 (ENEA/CEA) |
| EF-2 | 9 | Gruppelaar,   | k   |   | > evaluation                    |
|      | 8 | E. Menapace   | eV\ |   |                                 |
|      | 2 |               | \   |   |                                 |
|      |   |               | M   |   |                                 |
|      |   |               | LBW |   |                                 |
+------+---+---------------+-----+---+---------------------------------+
| J    | 1 | FP NUCLEAR    | 1.8 | 1 | > RR based on experimental data |
| ENDL | 9 | DATA W.G.     | k   | 0 | > of Liou et al. (1974) and     |
| -3.2 | 9 |               | eV\ | 0 | > Wasson and Allen (1973)       |
|      | 0 |               | \   | k |                                 |
|      |   |               | M   | e |                                 |
|      |   |               | LBW | V |                                 |
+------+---+---------------+-----+---+---------------------------------+

[Table 2.]{.underline} Thermal Cross Sections for Cd-111

+--------------------------------------+---------+-----------+--------+
| File/ Experiment/Evaluation          | # Total | # Capture | # E    |
|                                      |         |           | lastic |
+--------------------------------------+---------+-----------+--------+
| ENDF/B-VI                            | 28.6779 | 24.0289 b | 4.649  |
|                                      | b       |           | b      |
+--------------------------------------+---------+-----------+--------+
| JEF-2                                | 29.8116 | 23.7105 b | 6.1011 |
|                                      | b       |           | b      |
+--------------------------------------+---------+-----------+--------+
| JENDL-3.2                            | 29.0388 | 23.9412 b | 5      |
|                                      | b       |           | .09754 |
|                                      |         |           | b      |
+--------------------------------------+---------+-----------+--------+
| Vertebnyj (1968)                     | 1       | 7.7(8) b  | 5.2(3) |
|                                      | 3.0(15) |           | b      |
|                                      | b       |           |        |
+--------------------------------------+---------+-----------+--------+
| BNL-325 (1981)                       |         | 24(3) b   |        |
+--------------------------------------+---------+-----------+--------+
| S.F.Mughabghab, INDC(NDS)-424,       |         | 24(3) b   |        |
| (2001)                               |         |           |        |
+--------------------------------------+---------+-----------+--------+