96-Cm-246 JAEA+ EVAL-JAN10 O.Iwamoto,T.Nakagawa,T.Ohsawa,+
DIST-MAY10 20100318
----JENDL-4.0 MATERIAL 9643
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
History
06-01 Fission cross section was evaluated with GMA.
06-05 Resonance parameters were modified.
06-11 New calculation was made with CCONE code.
07-03 Fission spectra were evaluated.
07-05 Re-calculation with CCONE code.
08-03 Interpolation of (5,18) was changed.
Data were compiled as JENDL/AC-2008/1/.
09-08 (MF1,MT458) was evaluated.
09-11 New calculation was made with CCONE code.
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
(same as JENDL-3.3)
Evaluated by Maslov et al./2/
* NUMBER OF NEUTRONS PER FISSION FROM TUTTLE'S SYSTEMATICS/3/.
MT=456 Number of prompt neutrons per fission
The experimental data of Zhuravlev et al./4/ was adopted.
An energy dependent term was based on the systematics derived
by Ohsawa/5/.
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/6/. 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 2000/7/ does
not include average neutron energy values, the average values
were calculated using the formula shown in the report by
T.R. England/8/. The fractions of prompt energy were
calculated using the fractions of Sher's evaluation/9/ 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 (MLBW: 1.0E-5 - 400 eV)
The resonance parameters adopted in JENDL-3.3 were evaluated
by Maslov et al./2/ They took the data of Berreth et al./10/,
Benjamin et ak./11/, Belanova et al./12/, Cote et al./13/
into account, and adjusted the parameters to the fission cross
section of Moore and Keyworth/14/ and Maguire et al./15,16/
and gave background data to the fission.
In the present work, the parameters of 4.3-eV resonance and
background cross sections were modified.
The thermal cross sections to be reproduced:
Fission = 0.044 +- 0.022 b
Benjamin et al./10/, Zhuravlev et al./17/,
Serot et al./18/
Capture = 1.15 +- 0.27 b
Halperin et al./19/, Gavrilov et al./20/
Unresolved resonance parameters (400 eV - 140 keV)
Parameters were determined with ASREP code/21/ so as to
reproduce the cross sections. They are used only for self-
shielding calculations.
Thermal cross sections and resonance integrals (at 300K)
-------------------------------------------------------
0.0253 eV reson. integ.(*)
(barns) (barns)
-------------------------------------------------------
total 10.445
elastic 9.222
fission 0.044 7.60
capture 1.179 113
-------------------------------------------------------
(*) 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 elastic scattering (MT=2) and fission cross sections (MT=18,
19, 20, 21, 38) were calculated with CCONE code/22/.
MT= 1 Total cross section
The cross section was calculated with CC OMP of Soukhovitskii
et al./23/
MT= 2 Elastic scattering cross section
Calculated as total - non-elastic scattering cross sections.
MT=18 Fission cross section
The following experimental data were analyzed with the GMA
code/24/:
Authors Energy range Data points Reference
Moore+ 400eV - 2.83MeV 753 /14/
Fomushkin+ 0.3 - 4.5MeV 18 /25/
Maguire+ 0.13eV - 80keV 58 /15/
Fomushkin+ 14.1MeV 1 /26/
Fursov+ 0.164 - 6.8MeV 45 /27/(*1)
Ivanin+ 0.637 - 11.37MeV 25 /28/
(*1) Ratio to Pu-239 fission. JENDL-3.3 data was used to
convert them into the cross section.
Above 7 MeV, an eye-guided cross section curve was adopted.
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 /29/ with modified
Madland-Nix formula considering multi-mode fission processes
(standard-1, standard-2, superlong).
Above 7 MeV, calculated with CCONE code/22/.
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./30/ 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 15% was assumed below 5 MeV and above 5 MeV,
respectively.
MT=456
Covariance was obtained by fitting a linear function to the
data at the thermal energy /4/ and 5 MeV (derived from
systematics) with uncertainties of about 4% and 5%,
respectively.
MF=32 Covariances of resonance parameters
Format of LCOMP=0 was adopted.
Standard deviations were adopted from the data of Moore and
Keyworth/14/, Belanova et al./12/, and others.
For the parameters having no information on uncertainties,
the following errors were assumed:
0.1% to resonance energies
10% to neutron and fission widths
20% to capture widths
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 400 eV), uncertainty of 10 %
was added.
MT=18 Fission cross section
In the resonance region, standard deviation of 50 % was
added.
Above the resonance region, cross section was evaluated with
GMA code/24/. Standard deviations obtained were multiplied
by a factor of 1.5. Above 7 MeV, they were assumed to be 20%.
MT=102 Capture cross section
In the resonance region, addtional error of 15 % was given.
Above 400 eV, 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/22/ 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 = 0,1,2,3,4 (see Table 2)
* optical potential parameters /23/
Volume:
V_0 = 49.97 MeV
lambda_HF = 0.01004 1/MeV
C_viso = 15.9 MeV
A_v = 12.04 MeV
B_v = 81.36 MeV
E_a = 385 MeV
r_v = 1.2568 fm
a_v = 0.633 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 = 1.1803 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 = 0.2
beta_4 = 0.055
beta_6 = 0.0015
* Calculated strength function
S0= 0.81e-4 S1= 3.33e-4 R'= 9.06 fm (En=1 keV)
--------------------------------------------------
Table 2. Level Scheme of Cm-246
-------------------
No. Ex(MeV) J PI
-------------------
0 0.00000 0 + *
1 0.04285 2 + *
2 0.14201 4 + *
3 0.29490 6 + *
4 0.49980 8 + *
5 0.84168 2 -
6 0.87645 3 -
7 0.92331 4 -
8 0.98100 5 -
9 1.05110 6 -
10 1.05900 5 +
11 1.07885 1 -
12 1.10486 2 -
13 1.12428 2 +
14 1.12802 3 -
15 1.12880 7 -
16 1.16549 3 +
17 1.17474 0 +
18 1.17860 8 -
19 1.21053 2 +
20 1.21998 4 +
21 1.22100 3 +
22 1.24977 1 -
23 1.28930 0 +
24 1.30045 3 -
25 1.31757 2 +
26 1.34020 3 -
27 1.34886 1 -
28 1.36663 2 -
29 1.37923 4 +
30 1.39700 5 -
-------------------
*) Coupled levels in CC calculation
Table 3. Level density parameters
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Cm-247 18.3955 0.7635 1.7794 0.3734 -0.6804 2.7533
Cm-246 18.8984 1.5302 1.7310 0.3608 0.1621 3.4286
Cm-245 18.8322 0.7667 1.4601 0.3623 -0.5771 2.6382
Cm-244 19.1414 1.5364 1.5347 0.3530 0.2436 3.3454
Cm-243 18.3259 0.7698 1.3577 0.3635 -0.5169 2.5698
--------------------------------------------------------
Table 4. Fission barrier parameters
----------------------------------------
Nuclide V_A hw_A V_B hw_B
MeV MeV MeV MeV
----------------------------------------
Cm-247 5.400 0.800 5.650 0.650
Cm-246 6.300 1.040 5.100 0.600
Cm-245 6.050 0.500 5.700 0.420
Cm-244 6.100 0.900 5.100 0.600
Cm-243 6.150 0.600 5.800 0.400
----------------------------------------
Table 5. Level density above inner saddle
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Cm-247 20.8609 0.8908 2.6000 0.3256 -1.5320 2.8908
Cm-246 20.7882 1.6500 2.6000 0.3263 -0.7728 3.6500
Cm-245 20.7155 0.8944 2.6000 0.3342 -1.6357 2.9944
Cm-244 20.6427 1.7925 2.6000 0.3275 -0.6303 3.7925
Cm-243 20.5699 0.8981 2.6000 0.3281 -1.5248 2.8981
--------------------------------------------------------
Table 6. Level density above outer saddle
--------------------------------------------------------
Nuclide a* Pair Eshell T E0 Ematch
1/MeV MeV MeV MeV MeV MeV
--------------------------------------------------------
Cm-247 20.8609 0.8908 0.8200 0.3573 -0.8210 2.8908
Cm-246 20.7882 1.7852 0.7800 0.3658 -0.0107 3.8852
Cm-245 20.7155 0.8944 0.7400 0.3596 -0.8163 2.8944
Cm-244 20.6427 1.7925 0.7000 0.3455 0.2502 3.5925
Cm-243 20.5699 0.8981 0.6600 0.3619 -0.8115 2.8981
--------------------------------------------------------
Table 7. Gamma-ray strength function for Cm-247
--------------------------------------------------------
* E1: ER = 11.41 (MeV) EG = 2.72 (MeV) SIG = 330.04 (mb)
ER = 14.31 (MeV) EG = 4.19 (MeV) SIG = 427.95 (mb)
* M1: ER = 6.53 (MeV) EG = 4.00 (MeV) SIG = 1.47 (mb)
* E2: ER = 10.04 (MeV) EG = 3.15 (MeV) SIG = 7.06 (mb)
--------------------------------------------------------
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