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

**36-Kr-85 Review**

I. Sirakov, INRNE, February 14, 2003

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

***ENDF/B-VI:*** Year of origin 1974, 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:*** No resonance parameters given (Table 1);
scattering radius 5.30 fm. The capture cross section below 708.62 eV is
in the form of 1/v, with 1.66 b at 0.0253 eV taken from BNL-325 (1973).
The elastic scattering cross section at T=0 K is a constant value.
Computed resonance integral 1.667 b.

***JENDL-3:*** No resolved resonance parameters; scattering radius 7.06
fm in MF=2 (6.7 fm assumed in MF=3); Capture and elastic cross sections
below 1 keV assumed to be \~1/v (1.66 b at 0.0253 eV) and a constant
(R=6.7 fm) respectively. Unresolved region 1- 100 keV; strength
functions calculated with CASTHY; Level spacing determined to reproduce
the capture cross section from CASTHY; the scattering radius fitted to
the calculated MT=1 at 100 keV. Computed resonance integral 1.82 b,
according to MF=1.

***CENDL-3:*** Resonance parameters and pointwise cross sections taken
from JENDL-3.2. Computed resonance integral 1.553 b, according to MF=1.

**Note on the resonance region**: The values of the one-group capture
cross section over fast-reactor weighting spectrum in the energy range
1E-5 eV - 20 MeV (<http://www.nndc.bnl.gov/sg21/nucl/acs/accs.htm>)
represent the discrepancies of the evaluations above 708.62 eV and
predominantly up to 100 keV. For ***ENDF/B-VI***, ***JEF-2***,
***JENDL-3*** and ***CENDL-3***, the above averages are 4.3674E-2,
4.3576E-2, 5.9805E-2 and 6.0008E-2 b respectively. The discrepancy
between the computed resonance integrals according to MF=1 of JENDL and
CENDL evaluations is not reasonable. The computations should give almost
the same results. The resonance integral data of 1.8(10) b measured by
Bemis (1972) have too large uncertainty in order to be used for
recommendation. Comparison of the evaluated files for 85Kr(n,tot) with
EXFOR data for KrNat(n,tot), in the keV region and above, gives
preference to ***JENDL-3*** and ***CENDL-3***.

**Recommendation/Conclusion**: ***JENDL-3*** (***CENDL-3***) recommended
in the resonance region up to 100 keV.

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

-   Methodology

***ENDF/B-VI:*** The optical potential of Moldauer used for MT=1;
inelastic cross sections (MF=3, MT=4, 51, 91) from COMNUC-3 code, no
preeq corrections; MT=102 from NCAP code; elastic cross section obtained
as (MT1-MT102-MT4); no threshold reaction cross sections are given.
Isotropic angular distribution assumed for MF=4, MT=2 in CM system. One
discrete level considered for the inelastic scattering. Evaporation
spectrum (NCAP code) presented in MF=5 for the continuum inelastic
scattering. Account taken of MT=1, 2, 4, 51, 91, 102.

***JEF-2:*** The same as ***ENDF/B-VI*** with the addition (1989
revision) of the charge particle production data MT=103, 104, 105, 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. Gamma-ray strength function determined
from systematics of radiation width and level spacing. Direct and
semi-direct capture estimated; 12 levels up to 2.46 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, 32, 51-62, 91, 102, 103, 104, 105, 107.

***CENDL-3:*** Spherical OM and unified preeq-statistical model code
SUNF; 3 levels up to 1.14 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,
51-53, 91, 102, 103, 104, 105, 106, 107.

-   MT=1

Since no experimental data are available for the Kr-85 total cross
section, the comparison with the experimental (EXFOR) data for natural
Kr shows that ***JENDL-3*** and ***CENDL-3*** are better than the others
and ***JENDL-3*** is preferable.

-   MT=2

***ENDF/B-VI, JEF-2:*** Too high above 11 MeV since (n,2n) reaction is
neglected.

***JENDL-3*** is \~0.5 b higher than ***CENDL-3*** around 3 MeV, and
above 11 MeV. ***CENDL-3*** curve has the advantage of being smooth.

-   MT=4

***ENDF/B-VI, JEF-2:*** Unrealistic trend of (n,n\') cross section;
(n,2n) reaction neglected.

***CENDL-3:*** The number of levels considered in CENDL-3 for the
inelastic scattering is too small. Compared to ***JENDL-3***, the
(n,n\') cross section of ***CENDL-3*** is enhanced around 3 MeV and
above 11 MeV at the expense of (n,el); and from 7 MeV to 11 MeV at the
expense mainly of (n,2n).

-   MT=16

***ENDF/B-VI, JEF-2:*** No (n,2n) in File 3, assumed to be zero.

***CENDL-3:*** Compared to ***JENDL-3***, the (n,2n) cross section of
***CENDL-3*** is suppressed below 11 MeV at the expense of (n,n'), and
enhanced above 13 MeV at the expense of (n,el).

-   MT=102

The evaluations are relatively close and are below 30 mb. It is
difficult to say which evaluation is the best.

-   MT=103

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

***CENDL-*3*:*** The quantitative systematics \[1\] for the 85Kr(n,p)
cross section gives the prediction of 11.85(-1.53,+1.73) mb at 14.7(2)
MeV which agrees very well with the ***CENDL-*3** value of 11.9 mb
compared to JENDL-3 and JEF-2 values of \~6.0 mb.

-   MT=107

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

***JENDL-*3*:*** The quantitative systematics \[2\] for the 85Kr(n,α)
cross section gives the prediction of 2.78(-.69,+.90) mb at 14.7(2) MeV
which agrees with the ***JENDL-*3** value of 2.3 mb compared to CENDL-3
value of 1.5 mb and JEF-2 value of 2 mb. The systematics \[3\] is also
in favor of ***JENDL-*3** with the prediction of 3.41(-.53,+.62).

**Recommendation/Conclusion**: ***JENDL-3*** and ***CENDL-3***
recommended in fast energy region 100 keV - 20 MeV; ***JENDL-3*** is
preferable for MT=1, 107; ***CENDL-3*** is preferable for MT=103.

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

**[Table 1]{.underline}.** Summary for Resolved and Unresolved Resonance
Region: Kr-85

+---------+---+---------+-------+----+-------------------------------+
| Library | Y | First   | RRR   | U  | Remarks                       |
|         | e | Authors |       | RR |                               |
|         | a |         |       |    |                               |
|         | r |         |       |    |                               |
+---------+---+---------+-------+----+-------------------------------+
| EN      | 1 | S       | 7     | \- | No resonance parameters       |
| DF/B-VI | 9 | chenter | 08.62 |    | given. The capture cross      |
|         | 7 | (HEDL)\ | eV\   |    | section below 708.62 eV is in |
|         | 4 | Schm    | \     |    | the form of 1/v with 1.66 b   |
|         |   | ittroth | Point |    | at 0.0253 eV taken from       |
|         |   | (HEDL)  | wise\ |    | BNL-325 (1973). The elastic   |
|         |   |         |       |    | scattering at T=0 K is a      |
|         |   |         |       |    | constant value. Computed      |
|         |   |         |       |    | resonance integral 1.667 b.   |
+---------+---+---------+-------+----+-------------------------------+
| JEF-2   | 1 | Sci     | 7     | \- | Taken from ENDF/B-V. The      |
|         | 9 | entific | 08.62 |    | cross sections are            |
|         | 8 |         | eV\   |    | practically the same as those |
|         | 2 | Co-ord  | \     |    | of ENDF/B-VI. Computed        |
|         |   | ination | Poin  |    | resonance integral 1.667 b.   |
|         |   |         | twise |    |                               |
|         |   | Group   |       |    |                               |
+---------+---+---------+-------+----+-------------------------------+
| JENDL-3 | 1 | JNDC FP | 1     | 1  | No resolved resonance         |
|         | 9 | Nuclear | keV\  | 00 | parameters. Capture and       |
|         | 9 | Data    | \     | k  | elastic cross sections below  |
|         | 0 | Working | Poin  | eV | 1 keV assumed to be 1/v (1.66 |
|         |   | Group   | twise |    | b at 0.0253 eV) and constant  |
|         |   |         |       |    | (R=6.7 fm) respectively.      |
|         |   |         |       |    |                               |
|         |   |         |       |    | URR: S0, S1 and S2 strength   |
|         |   |         |       |    | functions and the effective   |
|         |   |         |       |    | scattering radius determined  |
|         |   |         |       |    | using optical model           |
|         |   |         |       |    | calculations. Level spacing   |
|         |   |         |       |    | determined to reproduce the   |
|         |   |         |       |    | capture cross section from    |
|         |   |         |       |    | CASTHY.                       |
|         |   |         |       |    |                               |
|         |   |         |       |    | Computed resonance integral   |
|         |   |         |       |    | 1.82 b, according to MF=1.    |
+---------+---+---------+-------+----+-------------------------------+
| CENDL-3 | 1 | Yo      | 1     | 1  | Resonance parameters and      |
|         | 9 | u-Xiang | keV\  | 00 | pointwise cross sections      |
|         | 9 | Zhuang  | \     | k  | taken from JENDL-3.2.         |
|         | 9 | (CNDC), | Poin  | eV | Computed resonance integral   |
|         |   |         | twise |    | 1.553 b, according to MF=1.   |
|         |   | Ch      |       |    |                               |
|         |   | ong-Hai |       |    |                               |
|         |   | Cai     |       |    |                               |
|         |   | (NKU)   |       |    |                               |
+---------+---+---------+-------+----+-------------------------------+

**[Table 2]{.underline}.** Thermal Cross Sections for Kr-85

  -------------------------------- ------------- ------------- -----------
  Library / Experiment             Total         Capture       Elastic

  ENDF/B-VI                        5.22 b        1.66 b        3.56 b

  JEF-2                            5.23 b        1.66 b        3.56 b

  JENDL-3                          7.98 b        1.66 b        6.31 b

  CENDL-3                          7.98 b        1.66 b        6.31 b
  -------------------------------- ------------- ------------- -----------

**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).