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17-Cl- 37 ORNL EVAL-OCT03 R.SAYER,K.GUBER,L.LEAL,N.LARSON
DIST-JAN09 20090105
----JEFF-311 MATERIAL 1731
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
*************************** JEFF-3.1.1 *************************
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** Original data taken from: JEFF-3.1 **
** **
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***************************** JEFF-3.1 *************************
** **
** Original data taken from: Pre-ENDF/B-VII **
** **
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ORNL Resonance Parameter Evaluation, October, 2003.
R. O. Sayer, K. H. Guber, L. C. Leal, N. M. Larson, T. Rauscher
Our resonance parameter evaluation is described below. File 3
total [MT 1], elastic [MT 2], and capture [MT 102] cross section
values for T=0K for were computed from the resonance parameter
representation. For the energy range 0.00001 eV to 1.2 MeV, the
pointwise File 3 cross sections are based on the resonance
parameter files. Above 1.2 MeV, the current (February 2000) ENDF
cross sections are used. The CL35 file also contains (n,p) [MT
103,600] cross sections for T = 0K. For the energy range 0.00001
eV to 121 keV, the pointwise cross sections are based on the
resonance parameter file. Above 121 keV, the current (February
2000) ENDF cross sections are used. The last resonance with
non-zero proton width is at 103.5 keV.
We performed an evaluation [1] of Cl neutron cross sections in
the resolved resonance region with the multilevel Reich-Moore
R-matrix formalism. Resonance analyses were carried out with the
computer code SAMMY [3], which utilizes Bayes' method, a
generalized least squares technique. A recent modification of
SAMMY enabled us to calculate charged particle penetrabilities
for the proton exit channel. Our evaluation takes advantage of
recent high-resolution capture and transmission measurements at
the Oak Ridge Electron Linear Accelerator (ORELA) to extend the
resolved resonance energy range to 1.2 MeV with much more
accurate representation of the data than previous evaluations.
The total cross section data include measurements by Guber, et
al. [2] and Good, et al. [4], on the 80-m flight path at ORELA;
Cierjacks, et al. [5], on a 57-m flight path at the Karlsruhe
Isochronous Cyclotron; Singh, et al. [6] on the 200-m flight
path at the Columbia synchrocyclotron; Brugger, et al. [7], who
utilized a crystal spectrometer and also the MTR fast chopper
with a flight path of 45 m; Kiehn, et al. [8], with the
Rockefeller generator; and Newson, et al. [9], at the Duke Van
de Graaff facility.
Also included in the evaluation were the high resolution capture
cross section data (0.1 < En < 500 keV) of Guber, et al. [2] and
the older, low resolution capture data (0.02 < En < 1.0 keV) of
Kashukeev, et al. [10]. The 35Cl(n,p)35S cross section data of
Koehler [11] and Druyts, et al. [12] were also fit. The proton
widths are significant fractions of the total widths for
resonances at 398 and 4251 eV.
In order to give a proper treatment for charged particles in an
exit channel, an algorithm to calculate charged particle
penetrabilities (CPP) and shifts was incorporated in the SAMMY
code. The methodology for CPP computation has been given
previously [13]. Routines based on the CPP algorithm have been
developed and incorporated in a development version of the
nuclear data processing code NJOY [14] for use in preparing data
for criticality safety benchmark calculations. The nuclear
radii used for penetrabilities and shifts were computed
according to R = 1.23A**0.33333 + 0.8 fm, where A is the
nuclide mass. These values were 4.8222 and 4.8974 fm for 35Cl
and 37Cl, respectively. In the SAMMY analysis the radii used to
compute hard sphere phase shifts were allowed to vary, and
different radii were allowed for s- and p-waves. Final values
for 35Cl were R(L=0,1) = 3.6680, 4.8888 fm; final values for 37Cl
were R(L=0,1) = 3.3651,3.9565 fm.
Capture Cross Section Analysis
------------------------------
Guber, et al. [2] measured the neutron capture of chlorine up to
500 keV using a natural LiCl sample of thickness 0.09812 atoms/b
and the ORELA capture system, which had been re-engineered [20]
to minimize the amount of structural material surrounding the
sample and detectors. To calculate accurate correction factors
for experimental effects of the neutron capture data, reliable
neutron widths are needed since the sample was fairly thick.
Initial neutron widths were obtained by fitting the
transmission data; using these newly determined values,
corrections for self-shielding and multiple scattering were
calculated with SAMMY and used to determine capture widths.
Several iterations of fitting the transmission and capture data
were performed to obtain final resonance parameters for 0.1 < En
< 500 keV. From their resonance parameters, Guber, et al. [2],
calculated average cross sections that were rather different
from ENDF/B-VI. This difference is very likely the result of
underestimated neutron sensitivity in the older measurements as
well as an improved calculation of the weighting function.
In nuclides where the (n,gamma) cross section is small, the
direct capture (DC) is often a significant fraction of the cross
section. Guber, et al. [2] describe in detail the DC
calculations they performed for 35Cl and 37Cl using the code
TEDCA [21, 22]. They calculated that the effect of the DC
component was very small for 35Cl where the thermal capture
cross section is 43.6 b. However, for 37Cl approximately 0.31 b
of the thermal capture cross section of 0.433 b is due to direct
capture. We have deduced a set of resonance parameters,
including the external level parameters, that reproduce the
resonant part of the capture cross section. To this resonant
part, one must add the DC contribution to obtain the overall
capture cross section. The thermal value of the DC cross section
is 0.16 +- 0.05 b for 35Cl and 0.31 +- 0.16 b for 37Cl.
Thermal and Integral Quantities
-------------------------------
The following table gives a comparison of our elastic, capture,
(n,p), and total cross sections for En = 0.0253 eV and T = 0K
with the corresponding ENDF/B-VI quantities, which are based
principally on the compilation of Mughabghab [15]. The capture
cross section values include the DC contribution. Also given is
the resonance capture integral, I-gamma.
Cl Thermal Cross Sections and Resonance Integrals for T = 0K
Nuclide Quantity ENDF/B-VI (b) Present Evaluation (b)
------- ------- -------------- ----------------------
35Cl total 64.70 +- 0.50 64.75
elastic 20.60 +- 0.30 20.67
capture 43.60 +- 0.40 43.60
(n,p) 0.48 +- 0.14 0.480
I-gamma 17.80 +- 2.00 18.19
37Cl total 1.583 +- 0.050 1.581
elastic 1.150 +- 0.050 1.148
capture 0.433 +- 0.006 0.433
I-gamma 0.204 +- 0.040 0.198
The new ORELA measurements and the older KFK measurements enabled
us to extend the resonance parameter representation to 1.2 MeV;
the ENDF/B-VI representation above 226 keV, based on calculations
utilizing Hauser-Feshbach statistical theory, is inadequate.
SUMMARY AND CONCLUSIONS
-----------------------
The Cl data used in this evaluation include recent ORELA
high-resolution capture and transmission measurements as well as
several older data sets. Since the 35Cl(n,p)35S reaction yields
a significant contribution to the total cross section from
thermal energies up to about 10 keV, the 35Cl(n,p) data of
Koehler [11] and Druyts, et al. [12] were fit to obtain proton
width values for several resonances. The proton widths are
significant fractions of the total widths for resonances at 398
and 4251 eV. When uncertainties are considered, there is good
agreement between our resonance parameter calculations and
experiment for natCl total cross sections up to 1200 keV, for
35Cl(n,p) cross sections up to 100 keV, and for natCl capture
cross sections up to 500 keV. Our thermal elastic, capture,
(n,p), and total cross sections are in good agreement with the
corresponding ENDF/B-VI quantities, which are based primarily on
the compilation of Mughabghab [15].
Our evaluation fits the data much better than does ENDF/B-VI.
This new representation should be particularly applicable to
improvement of the reliability of criticality safety
calculations for systems where Cl is present.
The present ENDF format does not allow for a resonance parameter
representation of charged particle cross sections. A proposal is
in preparation for a new ENDF format which will permit the full
generality of the Reich-Moore theory, including charged particle
penetrabilities. The parametric representation (File 2) will be
made available when the new ENDF format is approved.
REFERENCES
----------
[1] R. O. Sayer, K. H. Guber, L. C. Leal, N. M. Larson,
and T. Rauscher, ORNL/TM-2003/50, March, 2003.
[2] K. H. Guber, R. O. Sayer, T. E. Valentine, L. C. Leal,
R. R. Spencer, J. A. Harvey, P. E. Koehler, and T. Rauscher,
Phys. Rev. C65, 058801 (2002).
[3] N. M. Larson, ORNL/TM-9179/R5 (2000).
[4] W. M. Good, J. A. Harvey, and N. W. Hill, ORNL-4937,
p. 198 (1973); J. A. Harvey, private communication.
[5] S. Cierjacks, P.Forti, D. Kopsch, L. Kropp, J. Nebe, and H.
Unseld, "High Resolution Total Neutron Cross Sections for Na,
Cl, K, V, MN and Co between 0.5 and 30 MEV",
KFK-1000, (1969).
[6] U. N. Singh, H. I. Liou, G. Hacken, M. Slagowitz, F. Rahn,
J. Rainwater, W. Makofske, and J. Garg, "Neutron Resonance
Spectroscopy: Chlorine", Phys. Rev. C10, 2138 (1974).
[7] R. M. Brugger, et al., Phys. Rev. 104, 1054 (1956).
[8] R. M. Kiehn, et al., Phys. Rev. 91, 66 (1953).
[9] H. W. Newson, et al., Phys. Rev. 105, 198 (1957).
[10] N. T. Kashukeev, Yu. P. Popov, and F. L. Shapiro,
J. Nucl. Energy 14, 76 (1961).
[11] P. E. Koehler, Phys. Rev. C44, 1675 (1991).
[12] S. Druyts, C. Wagemans, and P. Geltenbort,
Nucl. Phys. A574, 291 (1994).
[13] R. O. Sayer, ORNL/TM-2000/212 (2000).
[14] R. E. MacFarlane and D. W. Muir, LA-12740-M (1994).
[15] S. F. Mughabghab, M. Divadeenam, N. E. Holden, Neutron Cross
Sections, Vol. 1, Part A, Academic Press, Inc. (1981).
[16] G. H. E. Sims and D. G. Juhnke, Phys. Rev. 165, 1184 (1968).
[17] I. G. Schroder, M. McKeown, and G. Schar -Goldhaber,
J. Inorg. Nucl. Chem. 31, 3721 (1969).
[18] Y. M. Gledenov, V. I. Salatski, P. V. Sedyshev, P. J.
Szalanski, J. Andrzejewski, and A. Zak, Proc. Int. Conf. on
Nuclear Data for Science and Technology,
Trieste, p. 511 (1997).
[19] Y. M. Gledenov, L. B. Mitsina, M. Mitukov, Y. P. Popov, J.
Rigol, V. I. Salatski, and F. Van Zuan, Joint Institute for
Nuclear Research, Communications P3-89-351,
Dubna, USSR (1989).
[20] P. E. Koehler, et al., Phys. Rev. C54, 1463 (1996).
[21] H. Krauss, K. Grun, T. Rauscher, and H. Oberhummer, 1992,
TU Wien (Vienna, Austria), code TEDCA (unpublished).
[22] T. Rauscher, R. Bieber, H. Oberhummer, K.-L. Kratz,
J. Dobaczewski, P. Moller, and M. M. Sharma,
Phys.Rev. C57, 2031 (1998).
[23] R. L. Macklin, Phys. Rev. C29, 1996 (1984).
[24] C. E. Porter and R. G. Thomas, Phys. Rev. 104, 483 (1956).
[25] E. P. Wigner, Can. Math. Congr. Proc., Toronto,
p 174 (1957); Ann. Math 67, 325 (1958).
****************************************************************
ENDF/B-VI MOD 1 Evaluation, February 2000, P.G. Young,
R.E. MacFarlane, L.C. Liu (LANL)
NEUTRON ENERGIES BELOW 202 keV ----------------------------------
The resolved resonance parameter data of the JENDL3.2
evaluation by Watanabe (Wa94) was adopted. The description of
those data in the JENDL3.2 evaluation is repeated below.
MF=2 RESONANCE PARAMETERS(BELOW 202.0KEV)
MT=151 RESOLVED RESONANCE PARAMETERS
Resolved resonance parameters for MLBW formula with varying
scattering radius. Negative energy level data were adjusted
to reproduce 2200m/s cross sections.
Evaluation was mainly based on macklin's data [1] and
Mughabghab's compilation [2].
Calculated 2200-m/s cross section and res. integrals (barns)
2200 m/s Res. Integ.
Total 1.583 -
Elastic 1.15 -
Capture 0.433 0.204
MF=12 PHOTON MULTIPLICITIES
The spectrum of gamma rays from radiative capture is based
upon a new evaluation by A. Adams and S.C. Frankle [Ad98].
NEUTRON ENERGIES ABOVE 202 keV ----------------------------------
SUMMARY
This evaluation is based primarily on a theoretical analysis
between neutron energies of 100 keV and 20 MeV that is optimized
to the somewhat limited available experimental data. Elastic
and inelastic scattering angular distributions (through MT=76)
and the radiative capture cross section (MF=3, MT=102)
are taken from the JENDL3.2 evaluation [Wa94].
The theoretical calculations utilize Hauser-Feshbach
statistical theory with corrections for width fluctuations,
preequilibrium and direct reaction processes. Spherical optical
model calculations are used to obtain the neutron total cross
section and neutron, proton, deuteron, triton, and alpha
transmission coefficients.
Cross sections and spectra for individual reactions are
included for exiting neutron, proton, deuteron, alpha, and
gamma-ray reactions. Multiplicities, angular distributions, and
emission energy spectra are given for gamma rays, particles, and
recoil nuclei emitted in the dominant reactions, utilizing File
6 of the ENDF/B-6 format [Ro91]. Energy-angle-correlated
spectra are given for all outgoing particles and photons, and
residual nuclei energy distributions are included.
THEORY
HAUSER-FESHBACH STATISTICAL THEORY CALCULATIONS. The GNASH
code [Yo92] was used for all Hauser-Feshbach statistical theory
calculations. Preequilibrium corrections were performed in the
course of the GNASH calculations using the exciton model of
Kalbach [Ka77,Ka85]. Discrete level data from nuclear data
sheets were matched to continuum level densities using the
formulation of Gilbert and Cameron [Gi65] and pairing and shell
parameters from the Cook [Co67] analysis. Neutron and charged-
particle transmission coefficients were obtained from the
optical potentials, as discussed below. Gamma-ray transmission
coefficients were calculated using the Kopecky-Uhl model [Ko90].
Calculations were performed for all significant reactions
producing neutrons, protons, deuterons, alpha particles, and
gamma rays for incident neutrons between 100 keV and 20 MeV.
The angular distribution systematics by Kalbach [Ka88] were
used to describe the angular distributions for all continuum
particles.
OPTICAL MODEL POTENTIALS. For incident and exiting neutrons,
a phenomenological optical model potential by Arthur and Young
[Ar80], based on an analysis of n + Fe and p + Fe reactions, was
utilized for the neutron transmission coefficients, whereas the
potential of Watanabe [Wa94] was used to calculate the neutron
total cross section. The two differenct potentials were used
because on the one hand the Watanabe potential agreed well with
total cross section measurements, whereas the Arthur potential
appears to give a better reaction cross section, which is very
important for Hauser-Feshbach calculations. The SCAT2 optical
model code [Be92] was used for all calculations.
To obtain transmission coefficients for charged particle
reactions, the Beccetti-Greenlees potential [Be71] was used for
protons, the Perey and Perey [Pe63] potential for deuterons, the
Beccetti-Greenlees potential [Be69] for tritons,and the potential
of MacFadden [Mc66] was used for alpha particles.
DIRECT REACTIONS: Energy-dependent cross sections of
inelastic neutrons from 37Cl(n,n') direct reactions were
obtained using DWUCK calculations and deformation parameters
estimated from systematics using the compilations of Raman et
al. [Ra89] and Spear [Sp89].
EVALUATED DATA
CALCULATIONAL RESULTS. The MF=3 cross sections and MF=6
energy/angle distributions that are based completely on
calculations are:
MT = 16: (n,2n) Reaction
MT = 17: (n,3n) Reaction
MT = 22: (n,nalpha) Reaction
MT = 28: (n,np) Reaction
MT = 32: (n,nd) Reaction
MT = 51-80: (n,n') Discrete Level Reactions
MT = 91: (n,n') Continuum Reaction
MT = 103: (n,p) Reaction
MT = 104: (n,d) Reaction
MT = 105: (n,t) Reaction
MT = 107: (n,alpha) Reaction
MT = 649: (n,p) Continuum Reaction
MT = 650-669: (n,d) Discrete Level Reactions
MT = 699: (n,d) Continuum Reaction
MT = 700-730: (n,t) Discrete Level Reactions
MT = 749: (n,t) Continuum Reaction
MT = 800-824: (n,alpha) Discrete Level Reactions
MT = 849: (n,alpha) Continuum Reaction
Additionally, (n,gamma) cross sections (multiplicities)
included in MF=12 and energy distributions in MF=15 are taken
from the GNASH calculations. In addition to the usual Hauser-
Feshbach cross section component obtained using the Kopecky-Uhl
gamma-ray strength function, a semidirect component is included
in GNASH that enhances the cross section and hardens the
spectrum near En = 10-18 MeV.
Discrete (n,n') cross sections and angular distributions were
calculated using a combination of the GNASH and COMNUC [Du70]
codes for compound nucleus reactions. Preequilibrium components
were included in the (n,n') reactions at higher energies to
approximate direct reaction effects (in an average manner) for
discrete states not included in the DWUCK calculations. Cross
sections for a total of 30 excited states are included for 37Cl.
Discrete gamma-ray cross sections that exceed 1 mb are included
explicitly in the MF=6 distributions for all reactions. The
elastic angular distributions are included in in MF =4; the
(n,n') angular distributions and (n,n'gamma) multiplicities are
included in MF=6.
Cross sections (MF=3) for approximately 20 or more discrete
states are included for charged-particle reactions. Again,
multiplicities for (n,x gamma) reactions are included in MF=6.
Kalbach systematics (Ka88) are used to specify all continuum
particle angular distributions in MF=6. All continuum photon
angular distributions are assumed isotropic. Residual nucleus
recoil energy spectra are included in MF=6 for all reactions.
USE OF EXPERIMENTAL DATA. The available experimental data for
37Cl is somewhat limited. Data that were useful for the
evaluation are measurements of the neutron total cross section
for natural Cl; measurements of (n,gamma) cross sections for
35Cl and 37Cl at lower energies; and a few measurements above
12 MeV of (n,p) and (n,alpha) cross sections.
The only adjustment made to the calculated cross sections on
the basis of the experimental data was to fine tune the
normalization of the gamma-ray strength function calculations
using the radiative capture measurement. The final
normalization that was determined is approximately a factor of 2
higher than the value we have established from systematics in
other analyses.
****************************************************************
REFERENCES
[Ad98] A. Adams and S.C. Frankle, LANL Group X-CI, personal
communication (1998).
[Ar80] E.D.Arthur and P.G. Young, "Evaluation of Neutron Cross
Sections to 40 MeV for 54,56Fe," Proc. Sym Neutron Cross
Sections from 10 to 50 MeV, BNL, 12-14 May 1980, p. 731.
[Be92] O. Bersillon, "SCAT2 - A Spherical Optical Model Code,"
in Proc. ICTP Workshop on Computation and Analysis of Nuclear
Data Relevant to Nuclear Energy and Safety, 10 February-13
March, 1992, Trieste, Italy, to be published in World
|Scientific Press, and Progress Report of the Nuclear Physics
Division, Bruyeres-le-Chatel 1977, CEA-N-2037 (1978) p.111.
[Be71] F.D. Becchetti, Jr., and G.W. Greenlees in "Polarization
Phenomena in Nuclear Reactions," (Ed: H.H.Barschall and
W.Haeberli, The University of Wisconsin Press, 1971) p.682.
[Co67] J.L. Cook, H. Ferguson, and A.R. Musgrove, Aust.J.Phys.
20, 477 (1967).
[Du70] C.L. Dunford, "A Unified Model for Analysis of Compound
Nucleus Reactions," Atomics International report AI-AEC-12931
(1970).
[Gi65] A. Gilbert and A.G.W. Cameron, Can.J.Phys. 43, 1446
(1965).
[Ka77] C. Kalbach, Z.Phys.A 283, 401 (1977).
[Ka85] C. Kalbach, "PRECO-D2: Program for Calculating
Preequilibrium and Direct Reaction Double Differential Cross
Sections," Los Alamos National Laboratory report LA-10248-MS
(1985).
[Ka88] C.Kalbach, Phys.Rev.C 37, 2350 (1988); see also
C. Kalbach and F. M. Mann, Phys.Rev.C 23, 112 (1981).
[Ko90] J.Kopecky and M.Uhl, Phys.Rev.C 42, 1941 (1990).
[Mc66] L. McFadden and G.R. Satchler, Nucl. Phys. 84, 177 (1966).
[Pe63a] F.G. Perey, Phys. Rev. 131, 745 (1963).
[Pe63b] C.M. Perey and F.G. Perey, Phys. Rev. 132, 755 (1963).
[Pe72] F.G. Perey, et al., Oak Ridge report ORNL-4823 (1972).
[Ra89] S. Raman et al., At.Nucl.Data Tables 42, 1 (1989).
[Ro91] P. Rose, "ENDF-102: Data Formats and Procedures for the
Evaluated Nuclear Data File, ENDF-6," Brookhaven National
Laboratory informal report BNL-NCS-44945 [ENDF-102, Rev. 10/91]
(1991).
[Sp89] R.H. Spear, At.Nucl.Data Tables 42, 55 (1989).
[Wa94] T. Watanabe, JENDL-3.2 Evaluation (1994).
[Yo92] P.G. Young, E.D. Arthur, and M.B. Chadwick, Los Alamos
report LA-12343-MS (1992).
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