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

**36-Kr-86 Review**

I. Sirakov, INRNE, February 24, 2003

######## **[Files]{.underline}**

***ENDF/B-VI:*** Year of origin 1972, taken from ENDF/B-V, no revisions
since then

***JEF-2:*** Year of origin 1982, data taken from ENDF/B-V, last
revision 1989

***JENDL-3:*** Year of origin 1984, taken from JENDL-2, last revisions
1990, 2002

***CENDL-3:*** Year of origin 1999, last revision 2001

######## **[Thermal and resonance region]{.underline}**

***ENDF/B-VI, JEF-2:*** Resolved resonance parameters up to 13.0 keV;
SLBW representation for the single resonance at 2.73 keV with parameters
GN=34 eV and GG=168 meV based on data of Mann and Watson (1959);
scattering radius 7.47 fm. No unresolved resonance region (Table 1).
Computed resonance integral 141 mb. ***JEF-2:*** Flag changed to MLBW
representation, which does not change anything in this case of a single
resonance.

***JENDL-3*:** Resolved resonance region up to 640 keV; MLBW
representation for 33 s-, 113 p- and 59 d-wave resonances with resonance
parameters based on experimental data (Carlton 1988, Raman 1983);
scattering radius 7.5 fm from BNL-325 (1981); a negative resonance added
at --20 keV to reproduce the thermal capture cross section of 3 mb
(Table 2) from BNL-325 (1981). No unresolved region. Computed resonance
integral 23 mb.

***CENDL-3:*** Resolved resonance region up to 639.2 keV; resonance
parameters taken from JENDL-3.2 except those of the resonances at
624.38, 626.14, 631.35 keV and out-of range (background) resonances at
641.2, 643.65, 648.04 keV, which radiative widths increased up to 4.5 eV
compared to ***JENDL-3*** values of 0.5 eV. This causes difference
between JENDL and CENDL capture cross sections in the region from 600 to
640 keV. No unresolved region. Computed resonance integral 23 mb.

**Note on the resonance region**: The thermal capture capture cross
section of ***ENDF/B-VI (JEF-2)*** is 20 times higher the recommended
***(JENDL-3, CENDL-3)*** cross section of 3 mb. Similar trend continues
up to 4 keV and accounts for the discrepancy in the one-group capture
cross section (1E-5 eV - 20 MeV) over fast-reactor weighting spectrum
(<http://www.nndc.bnl.gov/sg21/nucl/acs/accs.htm>). No EXFOR data on
measured resonance integrals. ***JENDL-3 (CENDL-3)*** generally agrees
with the EXFOR (n,g) data of Walter (1984). The upper boundary of 13 keV
for the resonance region of ***ENDF/B-VI (JEF-2)*** is too low compared
to the ***JENDL-3 (CENDL-3)*** value of 640 keV.

**Recommendation/Conclusion**: ***JENDL-3*** (***CENDL-3***) recommended
in the resonance region up to 640 keV.

######## **[Fast neutron region]{.underline}**

-   Methodology

***ENDF/B-VI:*** Spherical OM code ABACUS for MT=1 and MT=2; statistical
model code CERBERO for MT=4, 51-64, 91, 102, 103; MT=16, 17, 104, 105
from FASCRO code; no preeq corrections; Legendre coefficients from CHAD
code to get anisotropic angular distribution for MF=4, MT=2 in CM
system. Account taken of MT=1, 2, 4, 16, 17, 51-64, 91, 102, 103, 104,
105.

***JEF-2:*** The same as ***ENDF/B-VI*** with the addition (1989
revision) of the charge particle production data MT=106, 107, 111
included from REAC-ECN-4 Library.

***JENDL-3:*** Spherical OM and statistical model code CASTHY for MT=1,
4, 51-91, 102 by taking into account competing reactions MT=16, 17, 103,
107, etc, which were calculated with the preeq and multi-step
evaporation model code PEGASUS. The gamma-ray strength function adjusted
to measured capture cross section at 100 keV. Direct and semi-direct
capture estimated; 10 levels up to 3.96 MeV adopted for the inelastic
scattering. MT=103 and MT=107 normalized to recommended by Forrest
(1986) values at 14.5 MeV; elastic calculated as (MT1 -- sum of partial
cross sections); Legendre coefficients from CASTHY to get anisotropic
angular distribution for MF=4, MT=2 in CM system. MT=1, 2, 4, 16, 17,
22, 28, 51-60, 91, 102, 103, 104, 105, 107.

***CENDL-3:*** Spherical OM and unified preeq-statistical model code
SUNF; 4 levels up to 2.72 MeV adopted for the inelastic scattering; DWBA
code DWUCK4 to calculate the direct inelastic scattering contribution.
Legendre coefficients obtained to present anisotropic angular
distribution for MF=4, MT=2 in CM system. MT=1, 2, 4, 16, 17, 22, 28,
51-54, 91, 102, 103, 104, 105, 107.

-   MT=1

***ENDF/B-VI, JEF-2:*** Unrealistic shape of the total cross section,
which follows the structure of the inelastic cross section in the region
of several MeV.

***JENDL-3*** and ***CENDL-3*** are reasonable as can be seen from the
experimental (EXFOR) data of Carlton (1988) and Raman (1983) as well as
from comparison of the evaluated files for 86Kr(n,tot) with experimental
(EXFOR) data for KrNat(n,tot).

-   MT=2

***JENDL-3*** and ***CENDL-3*** are almost the same up to 3 MeV.
***CENDL-3*** is about 0.5-0.6 b lower than ***JENDL-3*** from 4 to 20
MeV. This difference is 'compensated' in MT=1 by higher ***CENDL-3***
values for (n,n') above 3 MeV, and for (n,2n) above 12 MeV.

 

-   MT=4

***ENDF/B-VI, JEF-2:*** Show rather peaked shape at \~5 MeV.

***JENDL-3, CENDL-3:*** Show reasonable shape. ***CENDL-3*** is about
0.1-0.5 b higher than ***JENDL-3*** about 3 MeV. The number of levels
considered in ***CENDL-3*** is 4 compared to 10 in ***JENDL-3***.

-   MT=16

All evaluations show reasonable shape. ***CENDL-3*** is about 0.2-0.4 b
higher than ***JENDL-3*** above 12 MeV.

-   MT=102

***ENDF/B-VI, JEF-2:*** Do not take account of the direct (semi-direct)
capture, and are too low at high energies.

-   MT=103

***JENDL-3:*** The quantitative systematics \[1\] for the 86Kr(n,p)
cross section gives the prediction of 8.85(-1.19,+1.35) mb at 14.7(2)
MeV which agrees very well with the ***JENDL-*3** value of 9.0 mb
compared to CENDL-3 and JEF-2 values of 2.75 and 0.25 mb respectively.

-   MT=107

***ENDF/B-VI:*** No (n,) in File 3, assumed to be zero.

All available evaluations do not contradict the experimental
([EXFOR11884](http://www.nndc.bnl.gov/htbin/csisrs.cgi?AccNum=11884&DatType=H&RetType=byAccNum&ReDo=N)
010) data of Kondaiah (1968) for 86Kr(n,)83Se-g cross section at 14.4
MeV. The quantitative systematics \[2\] for the 86Kr(n,) cross section
gives the prediction of 1.97(-.51,+0.68) mb at 14.7(2) MeV which also
agrees with all evaluations. The systematics \[3\] is in favor of
***JEF-*2** with the prediction of 2.40(-.39,+.46), since the JEF value
is 2.5 mb compared to the JENDL and CENDL values of 1.5 and 1.6 mb
respectively.

**Recommendation/Conclusion**: ***JENDL-3*** and ***CENDL-3***
recommended in fast energy region 640 keV - 20 MeV; ***JENDL-3*** is the
only reasonable evaluation for MT=103. ***JEF-2*** looks preferable for
the 14.7-MeV value of (n,) cross section.

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

**[Table 1]{.underline}.** Summary for Resolved and Unresolved Resonance
Region: Kr-86

+---------+---+---------+-------+----+-------------------------------+
| Library | Y | First   | RRR   | U  | Remarks                       |
|         | e | Authors |       | RR |                               |
|         | a |         |       |    |                               |
|         | r |         |       |    |                               |
+---------+---+---------+-------+----+-------------------------------+
| EN      | 1 | A.      | 13.0  | \- | Single (s-wave) resonance at  |
| DF/B-VI | 9 | Prince  | keV\  |    | 2.73 keV with GN=34 eV and    |
|         | 7 | (BNL)   | \     |    | GG=168 meV based on           |
|         | 2 |         | SLBW  |    | experimental data (Mann       |
|         |   |         |       |    | 1959); scattering radius 7.47 |
|         |   |         |       |    | fm. Computed resonance        |
|         |   |         |       |    | integral 141 mb.              |
+---------+---+---------+-------+----+-------------------------------+
| JEF-2   | 1 | Sci     | 13.0  | \- | RR parameters taken from      |
|         | 9 | entific | keV\  |    | ENDF/B-V. Flag changed to     |
|         | 8 |         | \     |    | MLBW. Computed resonance      |
|         | 2 | Co-ord  | MLBW  |    | integral 141 mb.              |
|         |   | ination |       |    |                               |
|         |   |         |       |    |                               |
|         |   | Group   |       |    |                               |
+---------+---+---------+-------+----+-------------------------------+
| JENDL-3 | 1 | JNDC FP | 640   | \- | RR parameters based on        |
|         | 9 | Nuclear | keV\  |    | experimental data (Carlton    |
|         | 9 | Data    | \     |    | 1988, Raman 1983); scattering |
|         | 0 | Working | MLBW  |    | radius 7.5 fm from BNL-325    |
|         |   | Group   |       |    | (1981); a negative resonance  |
|         |   |         |       |    | added at --20 keV to          |
|         |   |         |       |    | reproduce the thermal capture |
|         |   |         |       |    | cross section of 3 mb from    |
|         |   |         |       |    | BNL-325 (1981). Computed      |
|         |   |         |       |    | resonance integral 23 mb.     |
+---------+---+---------+-------+----+-------------------------------+
| CENDL-3 | 2 | Z.      | 639.2 | \- | Resonance parameters taken    |
|         | 0 | J.Zhang | keV\  |    | from JENDL-3.2 except the     |
|         | 0 | (NWU),  | \     |    | radiative widths of the       |
|         | 1 |         | MLBW  |    | resonances at 624.38, 626.14, |
|         |   | C.H.    |       |    | 631.35 keV and out-of range   |
|         |   | Cai     |       |    | (background) resonances at    |
|         |   | (NKU),\ |       |    | 641.2, 643.65, 648.04 keV,    |
|         |   | Y.X.    |       |    | which increased to 4.5 eV     |
|         |   | Zhuang  |       |    | compared to JENDL-3 values of |
|         |   | (CNDC)  |       |    | 0.5 eV. Computed resonance    |
|         |   |         |       |    | integral 23 mb.               |
+---------+---+---------+-------+----+-------------------------------+

**[Table 2]{.underline}.** Thermal Cross Sections for Kr-86

+--------------------------------+------------+------------+----------+
| Library / Experiment           | Total      | Capture    | Elastic  |
+--------------------------------+------------+------------+----------+
| ENDF/B-VI                      | 6.10904 b  | 61.47 mb   | 6.04757  |
|                                |            |            | b        |
+--------------------------------+------------+------------+----------+
| JEF-2                          | 6.10904 b  | 61.47 mb   | 6.04757  |
|                                |            |            | b        |
+--------------------------------+------------+------------+----------+
| JENDL-3                        | 6.18949 b  | 3.00 mb    | 6.18649  |
|                                |            |            | b        |
+--------------------------------+------------+------------+----------+
| CENDL-3                        | 6.18957 b  | 3.08 mb    | 6.18648  |
|                                |            |            | b        |
+--------------------------------+------------+------------+----------+
| BNL-325 (1981)                 |            | 3(2) mb    |          |
+--------------------------------+------------+------------+----------+
| S.F.Mughabghab, INDC(NDS)-     |            | 3(2) mb    |          |
|                                |            |            |          |
| 424, p.69 (2001)               |            |            |          |
+--------------------------------+------------+------------+----------+

**References:**

**1.** R.Doczi et al., INDC(HUN)-032, Distr. L, IAEA (1997).

**2.** J.Csikai et al., Fusion Engineering and Design **37**, 65 (1997).

**3.** A.Majdeddin et al., INDC(HUN)-031, Distr. L, IAEA (1997).