92-U -236
92-U -236 TIM Eval-Mar88 T.Yoshida
DIST-MAR02 REV3-MAR00 20000728
----JENDL-3.3 MATERIAL 9231
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
HISTORY
79-03 New evaluation for JENDL-2 was made by T.Yoshida(NAIG).
86-12 JENDL-2 data were critically reviewed.
88-03 JENDL-2 data were revised to make JENDL-3 on the basis of
the 86-12 review. New Russian measurements (1982- 1986)
were fully adopted, resultantly leading to a nearly 30
per-cent reduction of capture cross-section above 1.5 keV.
Sub-threshold fission curve was introduced between 1.5 keV
and 700 keV. Unknown gamma-f was assumed to be 0.354
milli-eV.
Data were compiled by T.Nakagawa (JAERI).
90-07 FP yield data were modified.
90-10 MF=5, MT=16,17,91: Spectra at threshold energies were
modified.
93-12 JENDL-3.2.
Modified by T.Nakagawa (NDC/JAERI)
00-03 JENDL-3.3.
Modified by T.Yoshida (Tech. Inst. Musashi) and compiled by
T.Nakagawa (NDC/JAERI).
***** Modified parts from JENDL-3.2 ********************
(1,455) decay constants
(3,2), (3,102) Direct/Semi-direct process included.
(5,16), (5,17), (5,91), (5,455)
***********************************************************
MF=1 General Information
MT=451 Descriptive data and dictionary
MT=452 Number of neutrons per fission
Sum of MT's 455 and 456.
MT=455 Delayed neutrons per fission
Six group decay constants were adopted from Brady and England
/1/. Nu-d below 6 MeV was adopted from Gudkov et al./2/, and
that above 7 MeV from Bobkov et al./3/, respectively.
MT=456 Prompt neutrons per fission
Taken from Malinovskii's paper /4/. Above 5.9 MeV, their
recommendation was extrapolated.
MF=2 MT=151 Resonance parameters
Resolved resonances for MLBW formula : 1.0E-5 eV to 1.5 keV
Res. energies and Gam-n(for Gam-n greater than 0.1*Gam-g)
: Carraro /5/
Gam-n (for Gam-n smaller than 0.1*Gam-g) : Mewissen /6/
Gam-g : Mewissen /6/, when not given, mean value was taken.
Gam-f : Theobald /7/.
Average Gam-g = 23.0 milli-eV
Average Gam-f = 0.354 milli-eV
A negative resonance was introduced to reproduce the 2200-
m/s capture cross section of (5.11+-0.21) barns recommended
in BNL-325 4th edition.
Unresolved resonances : 1.5 keV to 40 keV
Parameters were determined to reproduce total and capture
cross sections calculated with CASTHY and evaluated fission
cross section. Obtained parameters are:
S0 = 0.906E-4, S1 = energy dependent (1.8E-4 - 2.7E-4)
Gam-g = 0.023 eV, Gam-f = energy dependent
R = 9.36 fm, D-obs = energy dependent (14.66 - 13.57 eV)
Calculated 2200-m/s cross sections and res. integrals
2200-m/sec Res. Integ.
total 13.69 b -
elastic 8.337 b -
fission 0.0613 b 7.77 b
capture 5.295 b 346. b
MF=3 Neutron Cross Sections
Below 1.5 keV, all background cross sections are zero.
In the energy range from 1.5 to 40 keV, unresolved resonance
parameters were evaluated and background cross section was given
to elastic scattering.
Above 40 keV, data were evaluated as follow:
MT=1,2,4,51-79,91,102 Sig-t,Sig-el,Sig-in,Sig-c
Coupled channel and statistical model calculations were made
with ECIS /8/ and CASTHY codes /9/, respectively.
The deformed optical potential parameters after Haouat and
Lagrange /10/:
Vr =49.8 - 16*sy - 0.3*En (MeV),
Ws = 5.3 - 8*sy + 0.4*En (En .LT. 10 MeV) (MeV),
= 9.3 - 8*sy (En .GE. 10 MeV) (MeV),
Vso= 6.2 (MeV),
where sy=(N-Z)/A
r=1.26, rs=1.26, rso=1.12 (fm),
a=0.63, as=0.52, aso=0.47 (fm).
The spherical optical potential parameters for the statisti-
cal model calculation with CASTHY:
Vr =40.8 - 0.05*En (MeV),
Ws = 6.5 + 0.15*En (MeV),
Vso= 7.0 (MeV),
r=1.32, rs=1.38, rso=1.32 (fm),
a=0.47, as=0.47, aso=0.47 (fm).
Competing processes : fission, (n,2n) and (n,3n)
Level fluctuation was considered.
The gamma-ray strength function was determined so that the
calculated capture cross section reproduced the measured
value of 0.85 barns /11/ around 10 keV. The direct and
semi-direct capture cross section was calculated with DSD
code /12/ and added to the capture cross section calculated
with CASTHY code.
The level scheme taken from Ref. /13/.
No. Energy(MeV) J-Parity No. Energy(MeV) J-Parity
gs 0.0 0 + 1 0.04524 2 +
2 0.14948 4 + 3 0.30979 6 +
4 0.52225 8 + 5 0.68757 1 -
6 0.7442 3 - 7 0.7828 10 +
8 0.8476 5 - 9 0.91916 0 +
10 0.9581 2 + 11 0.9604 2 +
12 0.9670 1 - 13 0.9880 2 -
14 1.0014 3 + 15 1.0020 7 -
16 1.0356 3 - 17 1.0512 4 +
18 1.0529 4 - 19 1.0587 4 +
20 1.0661 3 + 21 1.0700 4 -
22 1.0862 12 + 23 1.0938 2 +
24 1.1044 5 - 25 1.1110 2 -
26 1.1267 5 + 27 1.1470 3 +
28 1.1494 3 - 29 1.1640 6 -
Continuum levels assumed above 1.17 MeV.
The ground state, 1-st and 2-nd excited levels were coupled
in the ECIS calculation.
MT=16,17 (n,2n) and (n,3n)
Calculated with the PEGASUS code /14/.
MT=18 Fission
Evaluated on the basis of measured data of U-236/U-235
/15,16/. To get absolute value Matsunobu's evaluation /17/
for U-235(n,f) was employed.
MF=4 Angular Distributions of Secondary Neutrons
MT=2,51,52
Calculated with ECIS and CASTHY
MT=53-79,91
Calculated with CASTHY.
MT=16,17,18
Isotropic distribution in the lab. system.
MF=5 Energy Distributions of Secondary Neutrons
MT=16,17,91
Calculated with EGNASH /18/.
MT=18
Maxwellian fission spectrum. Temperature was estimated from
Z**2/A values /19/.
MT=455
Summation calculation made by Brady and England /1/ was
adopted.
References
1) M.C. Brady and T.R. England: Nucl. Sci. Eng., 103 (1989) 129.
2) A.N. Gudkov et al.: Atomnaya Energiya, 66 (1989) 100.
3) E.Yu. Bobkov et al.: Atomnaya Energiya, 67 (1989) 408.
4) V.V. Malinovskii et al.: Atomnaya Energiya, 53 (1982) 83.
5) G. Carraro, et al.: Nucl. Phys., A275 (1976) 333.
6) L. Mewissen, et al.: 1975 Washington, 729 (1975).
7) J.P. Theobald: Nucl. Phys.,181 (1972) 637.
8) J. Raynal: IAEA SMR-9/8 (1970).
9) S. Igarasi and T. Fukahori: JAERI 1321(1991).
10) cited by P.G. Young in Proc. Specialists' Mtg on Use of
Optical Model, Paris, NEANDC - 222 U (1986)
11) A.A. Bergman: Atomnaya Energiya, 52 (1982) 409.
O.T. Grudzevich et al.: IAEA INDC(CCP)-220/L (1984)
A.N. Gudkov: Atomnaya Energiya, 61 (1986) 379
12) T. Kawano: private communication (1999).
13) M.R. Schmorak: Nucl. Data Sheets, 20 (1977) 192.
14) S. Iijima et al.: JAERI-M 87-025, 337 (1987).
T. Nakagawa et al.: JAERI-Data/Code 99-031 (1999).
15) J.W. Behrens and C.W. Carlson: Nucl. Sci. Eng., 63 (1977) 250.
16) J.W. Meadows: Nucl. Sci. Eng., 65 (1978) 171.
17) H. Matsunobu: evaluation for JENDL-3 (MAT=3924).
18) N. Yamamuro: JAERI-M 90-006 (1990).
P.G. Young and E.D. Arthur: LA-6947 (1977).
19) A.B. Smith et al.: ANL/NDM-50 (1979).