95-Am-242MJAEA+ EVAL-JAN10 O.Iwamoto,T.Nakagawa,T.Ohsawa,+
DIST-MAY10 20100318
----JENDL-4.0 MATERIAL 9547
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
History
06-03 Fission cross section was evaluated with GMA code.
06-05 Resonance parameters were revised.
07-03 Fission spectra were evaluated (below 6 MeV).
07-05 Theoretical calculation was made with CCONE code.
Resonance parameters were modified.
07-08 Theoretical calculation was made with CCONE code.
07-11 Theoretical calculation was made with CCONE code.
08-03 Interpolation of (5,18) was changed.
Data were compiled as JENDL/AC-2008/1/.
09-03 (MF1,MT452) and (MF1,MT455) were revised.
09-08 (MF1,MT458) was evaluated.
10-01 Data of prompt gamma rays due to fission were given.
10-03 Covariance data were given.
MF= 1 General information
MT=452 Number of Neutrons per fission
Sum of MT's=455 and 456.
MT=455 Delayed neutron data
Determined from nu-d of the following three nuclides and
partial fission cross sections calculated with CCONE code/2/.
Am-243 = 0.006659 *1)
Am-242 = 0.0049 measured by Saleh et al./3/
Am-241 = 0.003154 *1)
*1) an average of systematics by Tuttle/4/,
Benedetti et al./5/ and Waldo et al./6/
Decay constants calculated by Brady and England./7/ were
adopted.
MT=456 Number of prompt neutrons per fission
(same as JENDL-3.3)
Maslov's evaluation/8/ was adopted.
* MADLAND-NIX MODEL CALCULATIONS /9/ FITTED TO THE MEASURED
DATA OF HOWE ET AL./10/ ABOVE EMISSIVE FISSION THRESHOLD
SUPERPOSITION OF NEUTRON EMISSION IN (N,XNF) REACTIONS /11/
AND PROMPT FISSION NEUTRONS IS EMPLOYED.
MT=458 Components of energy release due to fission
Total energy and prompt energy were calculated from mass
balance using JENDL-4 fission yields data and mass excess
evaluation. Mass excess values were from Audi's 2009
evaluation/12/. Delayed energy values were calculated from
the energy release for infinite irradiation using JENDL FP
Decay Data File 2000 and JENDL-4 yields data. For delayed
neutron energy, as the JENDL FP Decay Data File 2000/13/ does
not include average neutron energy values, the average values
were calculated using the formula shown in the report by
T.R. England/14/. The fractions of prompt energy were
calculated using the fractions of Sher's evaluation/15/ when
they were provided. When the fractions were not given by Sher,
averaged fractions were used.
MF= 2 Resonance parameters
MT=151
Resolved resonance parameters (below 43eV)
Resonance parameters given in JENDL-3.3 were evaluated by
Maslov et al./8/
For the current version, JENDL-3.3 parameters of 0.178eV
resonance were modified so as to reproduce the thermal cross
sections:
fission = 6401+-134b /16,17,18,19, etc./
capture = 1147+-114b /19/
Unresolved resonance parameters (43eV - 20keV)
Parameters were determined with ASREP code/20/ so as to
reproduce the evaluated cross sections in the energy range
from 43 eV to 20keV. They are used only for self-shielding
calculations.
Thermal cross sections and resonance integrals (at 300K)
-------------------------------------------------------
0.0253 eV reson. integ.(*)
(barns) (barns)
-------------------------------------------------------
total 7547.8
elastic 5.24
fission 6401.2 1550
capture 1141.4 236
-------------------------------------------------------
(*) In the energy range from 0.5 eV to 10 MeV.
MF= 3 Neutron cross sections
Cross sections above the resolved resonance region except for
the total (MT=1), elastic scattering (MT=2) and fission cross
sections (MT=18, 19, 20, 21, 38) were calculated with CCONE
code/2/.
MT=1 Total cross section
From 43 eV to 10 keV, the total cross section was calculated
as a sum of partial cross sections. Above 10 keV, the results
of CCONE calculation were adopted. The calculation was made
with CC OMP of Soukhovitskii et al./21/ The OMP was adjusted
by Am-241(n,tot) cross section/22/.
MT=2 Elastic scattering cross section
From 43 eV to 10 keV, calculated with CCONE code.
Above 10 keV, calculated as the total - non-elastic scattering
cross sections.
MT=51 (n,n') to 1st level
Calculated with CCONE code. Below 1 eV, 1/v shape was
assumed.
MT=18 Fission cross section (Above 43eV)
The following experimental data were analyzed with the GMA
code /23/:
Aleksandrov+/24/, Fomushkin+/25/, Dabbs+/16/, Browne+/17/,
Shigin+/26/, Fursov+/27/, Kai+/18/
Above 14MeV, the cross section was determined by eye-guiding.
The results of GMA were used to determine the parameters in
the CCONE calculation.
MT=19, 20, 21, 38 Multi-chance fission cross sections
Calculated with CCONE code, and renormalized to the total
fission cross section (MT=18).
MF= 4 Angular distributions of secondary neutrons
MT=2 Elastic scattering
Calculated with CCONE code.
MT=18 Fission
Isotropic distributions in the laboratory system were assumed.
MF= 5 Energy distributions of secondary neutrons
MT=18 Fission neutron spectra
Below 6 MeV, calculated by Ohsawa/28/ with modified Madland-
Nix formula considering multi-mode fission processes
(standard-1, standard-2, superlong).
Above 7 MeV, calculated with CCONE code.
MT=455 Delayed neutron spectra
Summation calculation by Brady and England /7/ was adopted.
MF= 6 Energy-angle distributions
Calculated with CCONE code.
Distributions from fission (MT=18) are not included.
MF=12 Photon production multiplicities
MT=18 Fission
Calculated from the total energy released by the prompt
gamma-rays due to fission given in MF=1/MT=458 and the
average energy of gamma-rays.
MF=14 Photon angular distributions
MT=18 Fission
Isotoropic distributions were assumed.
MF=15 Continuous photon energy spectra
MT=18 Fission
Experimental data measured by Verbinski et al./29/ for
Pu-239 thermal fission were adopted.
MF=31 Covariances of average number of neutrons per fission
MT=452 Number of neutrons per fission
Combination of covariances for MT=455 and MT=456.
MT=455
Error of 20% was assumed.
MT=456
Experimental data of Howe et al./10/ were fitted with a
straight line and covariance data were obtained.
MF=32 Covariances of resonance parameters
Format of LCOMP=0 was adopted.
Covarinaces of JENDL-3.3 /30/ were adopted.
MF=33 Covariances of neutron cross sections
Covariances were given to all the cross sections by using
KALMAN code/31/ and the covariances of model parameters
used in the theoretical calculations.
For the following cross sections, covariances were determined
by different methods.
MT=1, 2 Total and elastic scattering cross sections
In the resonance region (below 1 keV), uncertainty of 10 %
was added.
MT=18 Fission cross section
Above the resonance region cross section was evaluated with
GMA code/23/. The following uncertainties were addeded to
the GMA results.
43 eV to 1 keV 10 %
1 keV to 100 keV 5 %
0.1 MeV to 1 MeV 3 %
MT=102 Capture cross section
In the resonance region, the following uncertainties were
added.
1 to 5 eV 5 %
5 to 10 eV 10 %
10 to 43 eV 15 %
Above 43 keV, covariance matrix was obtained with CCONE and
KALMAN codes/31/.
MF=34 Covariances for Angular Distributions
MT=2 Elastic scattering
Covariances were given only to P1 components.
MF=35 Covariances for Energy Distributions
MT=18 Fission spectra
Below 6 MeV, covarinaces of Pu239 fission spectra given in
JENDL-3.3 were adopted after multiplying a factor of 9.
Above 6 MeV, estimated with CCONE and KALMAN codes.
*****************************************************************
Calculation with CCONE code
*****************************************************************
Models and parameters used in the CCONE/2/ calculation
1) Coupled channel optical model
Levels in the rotational band were included. Optical model
potential and coupled levels are shown in Table 1.
2) Two-component exciton model/32/
* Global parametrization of Koning-Duijvestijn/33/
was used.
* Gamma emission channel/34/ was added to simulate direct
and semi-direct capture reaction.
3) Hauser-Feshbach statistical model
* Moldauer width fluctuation correction/35/ was included.
* Neutron, gamma and fission decay channel were included.
* Transmission coefficients of neutrons were taken from
coupled channel calculation in Table 1.
* The level scheme of the target is shown in Table 2.
* Level density formula of constant temperature and Fermi-gas
model were used with shell energy correction and collective
enhancement factor. Parameters are shown in Table 3.
* Fission channel:
Double humped fission barriers were assumed.
Fission barrier penetrabilities were calculated with
Hill-Wheler formula/36/. Fission barrier parameters were
shown in Table 4. Transition state model was used and
continuum levels are assumed above the saddles. The level
density parameters for inner and outer saddles are shown in
Tables 5 and 6, respectively.
* Gamma-ray strength function of Kopecky et al/37/,/38/
was used. The prameters are shown in Table 7.
------------------------------------------------------------------
Tables
------------------------------------------------------------------
Table 1. Coupled channel calculation
--------------------------------------------------
* rigid rotor model was applied
* coupled levels = 2,6,10 (see Table 2)
* optical potential parameters /21/
Volume:
V_0 = 48 MeV
lambda_HF = 0.004 1/MeV
C_viso = 15.9 MeV
A_v = 12.04 MeV
B_v = 81.36 MeV
E_a = 385 MeV
r_v = 1.255 fm
a_v = 0.58 fm
Surface:
W_0 = 17.2 MeV
B_s = 11.19 MeV
C_s = 0.01361 1/MeV
C_wiso = 23.5 MeV
r_s = 1.15 fm
a_s = 0.601 fm
Spin-orbit:
V_so = 5.75 MeV
lambda_so = 0.005 1/MeV
W_so = -3.1 MeV
B_so = 160 MeV
r_so = 1.1214 fm
a_so = 0.59 fm
Coulomb:
C_coul = 1.3
r_c = 1.2452 fm
a_c = 0.545 fm
Deformation:
beta_2 = 0.243
beta_4 = 0.08
beta_6 = 0.0015
* Calculated strength function
S0= 1.26e-4 S1= 2.08e-4 R'= 9.60 fm (En=1 keV)
--------------------------------------------------
Table 2. Level Scheme of Am-242
-------------------
No. Ex(MeV) J PI
-------------------
0 0.00000 1 -
1 0.04409 0 -
2 0.04860 5 - *
3 0.05270 3 -
4 0.07582 2 -
5 0.09900 2 +
6 0.11400 6 - *
7 0.14800 5 -
8 0.14969 4 -
9 0.17100 4 -
10 0.19000 7 - *
11 0.19770 3 -
12 0.23053 1 +
13 0.24436 3 -
14 0.26300 6 -
15 0.26990 3 +
16 0.27433 1 -
17 0.28350 7 +
18 0.28901 4 -
19 0.29284 2 -
20 0.29641 2 -
21 0.30700 5 +
22 0.32784 3 -
23 0.33071 3 -
24 0.34158 0 +
25 0.34200 5 -
26 0.35569 2 +
27 0.36470 2 +
28 0.37040 4 +
29 0.37247 4 -
-------------------
*) Coupled levels in CC calculation
Table 3. Level density parameters
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Am-243 17.8584 0.7698 2.0985 0.4029 -0.9548 3.1071
Am-242 18.6337 0.0000 1.6845 0.2795 -0.6541 0.9592
Am-241 18.1961 0.7730 1.7328 0.3819 -0.7226 2.8365
Am-240 18.5012 0.0000 1.3474 0.2883 -0.6831 1.0000
Am-239 18.4349 0.7762 1.5592 0.3648 -0.5528 2.6354
--------------------------------------------------------
Table 4. Fission barrier parameters
----------------------------------------
Nuclide V_A hw_A V_B hw_B
MeV MeV MeV MeV
----------------------------------------
Am-243 6.200 0.800 5.150 0.520
Am-242 6.410 0.600 5.800 0.550
Am-241 6.100 0.800 5.500 0.520
Am-240 6.100 0.650 6.000 0.450
Am-239 6.000 0.800 5.400 0.520
----------------------------------------
Table 5. Level density above inner saddle
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Am-243 21.5049 0.8981 2.6000 0.2555 -0.6419 2.0981
Am-242 20.8697 0.0000 2.6000 0.3254 -2.4113 2.0000
Am-241 21.3526 0.9018 2.6000 0.3213 -1.4929 2.9018
Am-240 21.2764 0.0000 2.6000 0.3219 -2.3947 2.0000
Am-239 21.2001 0.9056 2.6000 0.3225 -1.4891 2.9056
--------------------------------------------------------
Table 6. Level density above outer saddle
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Am-243 21.5049 0.8981 0.6000 0.3532 -0.8019 2.8981
Am-242 21.4288 0.0000 0.5600 0.3688 -1.8681 2.2000
Am-241 21.3526 0.9018 0.5200 0.3556 -0.7969 2.9018
Am-240 21.2764 0.0000 0.4800 0.3567 -1.6981 2.0000
Am-239 21.2001 0.9056 0.4400 0.3579 -0.7919 2.9056
--------------------------------------------------------
Table 7. Gamma-ray strength function for Am-243
--------------------------------------------------------
* E1: ER = 11.52 (MeV) EG = 2.77 (MeV) SIG = 244.72 (mb)
ER = 14.31 (MeV) EG = 4.19 (MeV) SIG = 489.44 (mb)
* M1: ER = 6.57 (MeV) EG = 4.00 (MeV) SIG = 1.28 (mb)
* E2: ER = 10.10 (MeV) EG = 3.19 (MeV) SIG = 6.92 (mb)
--------------------------------------------------------
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