Back
42-Mo- 95 BNL+KAERI EVAL-OCT03 Lee,Oh,Mughabghab,Oblozinsky
DIST-JAN09 20090105
----JEFF-311 MATERIAL 4234
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
*************************** JEFF-3.1.1 *************************
** **
** Original data taken from: JEFF-3.1 Updated **
** Modification: Correction: Legendre MF6/MT849 **
******************************************************************
***************************** JEFF-3.1 *************************
** **
** Original data taken from: Pre-ENDF/B-VII **
** **
******************************************************************
History
1980 The evaluation was done by R.E.Schenter and F.Schmittroth.
Total cross section was calculated using Moldauer potential.
1999 Jul, ENDF/B-VI MOD 1 Evaluation, J.H. Chang (KAERI) and
S.F. Mughabghab (BNL): Resonance parameters revised.
****************************************************************
ENDF/B-VII MOD 1 Evaluation, December2002, Y.D.Lee(KAERI),
S.Y.Oh(KAERI), P.Oblozinsky(BNL) and S.F.Mughabghab(BNL)
This evaluation is combined result of 2 evaluations produced
under the BNL-KAERI project on neutron cross sections for
fission products:
a) 1999 evaluation in the thermal, resolved resonance and
unresolved resonance regions by Oh and Mughabghab. The
URR upper energy range is 206.26 keV, given as neutron
scattering threshold to the 1-st excited level of 95- Mo
(204.00 keV). This evaluation has already been included into
ENDF/B-VI MOD 1.
b) 2003 evaluation in the fast energy region by Lee
and Oblozinsky
Merging of these 2 evaluations was performed as follows:
- Capture cross sections were adopted from evaluation a) up to
the URR upper energy, from evaluation b) at higher energies.
- Total cross sections were adopted from evaluation a) up to
206.26 keV, from evaluation b) at higher energies, the
experimental data were considered.
****************************************************************
FAST ENERGY REGION, November 2002, Y.D. Lee(KAERI)
and P. Oblozinsky(BNL)
This is entirely new evaluation for 95- Mo in the region of
10 keV - 20 MeV.
EVALUATION PROCEDURES
Adopted procedures are based on careful theoretical analysis
utilizing available experimental data, including optical model
parameter search and nuclear reaction model calculations [Le02].
OM parameter search was performed in one of two different
ways:
- Interactive OM search code ABRXPL was used, based on the
ABAREX code (spherical OM and Hauser-Feshbach with width
fluctuation correction).
Nuclear reaction model calculations were performed with the
code EMPIRE-II by M. Herman [He01, He02]. This is modularized
statistical model code that integrates into a single system a
number of important modules and features:
- Spherical OM (code SCAT2 by O. Bersillone), and deformed OM
including coupled-channels model (code ECIS95 by J. Raynal).
- Hauser-Feshbach statistical model including HRTW width
fluctuation correction.
- Qauntum-mechanical MSD TUL model (codes ORION & TRISTAN by
H.Lenske), and MSC NVWY model.
- Exciton model (code DEGAS by E. Betak). This code represents
good approximation to DSD capture model.
- Complete gamma-ray cascade after emission of each particle,
including realistic treatment of discrete transitions.
- Access to OM segment of the RIPL library [Ri98].
- Built-in input parameter files, such as masses, level density,
discrete levels, OM parameters and gamma strength functions.
- ENDF-6 formatting (utility code EMPEND by A. Trkov), coupled
to grahpical presentation (utility code ZVView by V.Zerkin).
PARAMETERIZATION
Optical model
- SCAT2 code used for spherical OM parameterization.
- For neutrons, spherical OM by Lee's was adopted.
The resulting total cross section was compared with available
EXFOR data and good agreement was found.
- For protons, EMPIRE default OM was used (Becchetti-Greenless).
- For alpha particles, EMPIRE default OM was used (McFadden-
Satchler).
Level densities and discrete levels
- Dynamical approach in densities was used, as parametrized by
the EMPIRE code, after careful matching to low-lying discrete
levels.
- Particle-hole level densities for preequilibrium component
were set to g=A/15 for neutron channel, and g=A/13 for proton
channel.
- Discrete levels were taken from the built-in EMPIRE orsi.liv
file that is based on the 1996 version of the ENSDF database.
Other parameters and tuning
- ECIS95 with DWBA default option was used to account for direct
contribution to low lying discrete levels in (n,n').
- Preequilibrium components were calculated using the following
options: Multistep direct and multistep compound models with
default parameters for neutron channel, exciton model using
the Kalbach parameter K=100 MeV-3 for (n,gamma) and (n,p)
channels.
- Default gamma-ray strength function was used for capture. It
was adjusted by a factor of 0.80 below 5 MeV, and by a factor
of 1.10 at higher energies to reproduce experimental data
[Mu76]
- Fine tuning of parameters was made to reproduce the following
cross sections:
(n,p) activation measurement [Mo97,Qa74]
(n,a) activation measurement.
RESULTS
MF=3 Neutron cross sections
- EMPIRE calculations were adopted (statistical model, including
multistep/preequilibrium decay and direct processes).
MT=1 Total
- Experimental data[Pa88] were taken into account to
adjust cross sections
MT=2 Elastic scattering
- Calculated as (total - sum of partial cross sections).
MT=4, 51-91 Inelastic scattering
- EMPIRE calculations were adopted (statistical model with
multistep direct & multistep compound component, and DWBA
component for low-lying levels).
MT=102 Capture
- EMPIRE calculations were adopted (statistical model with
exciton preequilibrium component as approximation to
direct-semidirect capture with fast neutrons).
MT=16 (n,2n) taken from EMPIRE calculations
MT=17 (n,3n) taken from EMPIRE calculations
MT=22 (n,n'a) taken from EMPIRE calculations
MT=28 (n,n'p) taken from EMPIRE calculations
MT=103 (n,p) taken from EMPIRE calculations
MT=107 (n,a) taken from EMPIRE calculations
MF=4 Angular distributions of secondary neutrons
- EMPIRE calculations (including SCAT2 results for elastic
scattering) were adopted.
MF=6 Energy-angle distributions of reaction products
- EMPIRE calculations were adopted.
---------------------------------------------------------------
REFERENCES
[He01] M. Herman "EMPIRE-II Statistical Model Code for Nuclear
Reaction Calculations", in Nuclear Reaction Data and Nuclear
Reactors, eds. N.Paver, M. Herman and A.Gandini, ICTP
Lecture Notes 5 (ICTP Trieste, 2001) pp.137-230.
[He02] M.Herman, R.Capote, P.Oblozinsky, A.Trkov and V.Zerkin,
"Recent Development and Validation of the Nuclear Reaction
Code EMPIRE", in Proc. Inter. Conf. on Nuclear Data for
Science and Technology, October 7-12, 2001, Tsukuba, Japan,
to be published in J.Nucl.Sci.Tech. (2002).
[Le02] Yong-Deok Lee, Jonghwa Chang and Pavel Oblozinsky,
"Neutron Cross-Section Evaluations of Fission Products in
the Fast Energy Region", in Proc. Inter. Conf. on Nuclear
Data for Science and Technology, October 7-12, 2001, Tsukuba,
Japan, to be published in J.Nucl.Sci.Tech. (2002).
[Mo97] N.I.Molah et al., "Excitation functions of (n,p), (n,a)
and (n,2n) processes on some isotopes of Cl, Cr, Ge, Mo and Ce
in the energy range 13.57 - 14.71 MeV," C, 97TRIEST, 1, 517,1997.
[Mu76] R.Del.Musgrove et al,. "Average Neutron Resonance
Parameters and Radiative Capture Cross Sections for the Isotopes
of Molybdenum," J, NP/A, 270, 108, 1976.
[Pa88] M.V.Pasechnik et al., "Total Neutron Cross-Sections for
Molybdenum and Zyrconium at Low Energies," C, 80KIEV, 1, 304,
1980.
[Qa74] M.Qaim and G.Stoecklin, "Measurement and Systematics of
Cross Sections for Common and Low Yield 14 MeV Neutron Induced
Nuclear Reactions on Structural FR-Material and Transmuted
Species," R, EUR-5182E, 939, 1974.
[Ri98] Handbook for calculations of nuclear reaction data
Reference input parameter library, IAEA-TECDOC-1034, 1998.
******************************************************************
MF=2 has been re-evaluated by S.Y.Oh and S.F.Mughabghab.(May99)
RESOLVED RESONANCES in MLBW
Calculated 2200 m/s cross sections and resonance integral
Cross Section (b) Res. Integral (b)*
Capture 13.6 111
Elastic 6.38
* Integrated from 0.5 eV to 100 keV with 1/E spectrum
Notes:
Resonance parameters were based on BNL compilation[Mu81]. In
addition, 2gGn data from Wynchank[Wy68] were incorporated.
A bound level resonance was invoked to reproduce 2200 m/s
capture cross section that was obtained by weighting
14.0+-0.5[Mu81] and 13.4+-0.3 b of Koester[Ko87].
Parameters that had not been determined from measurements;
radiative width of 150 meV was given to s-wave,
radiative width of 180 meV[Mu76] was given to p-wave,
L was assigned by applying Bayesian approach, and
Effective scattering radius of 7.0 fm was adopted from BNL
compilation[Mu81].
UNRESOLVED RESONANCES in 'all energy-dependent parameters'(LRF=2)
Average parameters:
S (10**4) (eV)* (meV)
s-wave 0.45 69.4 150
p-wave 6.54 34.7 180
d-wave 1.70 23.1 150
* Level spacing at the neutron separation energy of target+n
Notes:
, S0, and S1 were deduced from fittings of reduced widths
of resolved resonances to the Porter-Thomas distribution.
was set to 2*.
Capture cross sections measured by Musgrove[Mu76], which was
corrected later by Allen[Al82], and Kapchigashev[Ka64] were
considered in adjusting S2.
Energy- and J-dependence of level spacing were calculated
according to the Gilbert-Cameron's level density formula with
associated parameters from Mughabghab[Mu98].
REFERENCES
[Al82] Allen,B.J. et al., Nucl.Sci.Eng.,82,230 (1982)
[Ka64] Kapchigashev,S.P. and Popov,Yu.P., Proc.Conf. Neutron
Interactions, p.104, Dubna, 1964.
[Ko87] Koester,L. et al., Z.Phys.A-Atomic Nuclei,326,227 (1987)
[Mu76] Musgrove, A.R.de L. et al., Nucl.Phys. A270,108 (1976)
[Mu81] Mughabghab,S.F. et al., Neutron Cross Sections, Vol.1,
Part A, Academic Press (1981)
[Mu98] Mughabghab,S.F. and Dunford,C.L., Proc.Int.Conf. on Phys.
of Nucl.Sci.Technol., p.784, Long Island, Oct.5-8,1998.
[Wy68] Wynchank,S. et al.,Phys.Rev.,166,1234 (1968)
END OF DESCRIPTION OF NEW EVALUATION ----------------------------
******************************************************************
Back
|
