100-Fm-255 JAEA+ EVAL-JAN10 O.Iwamoto, T.Nakagawa, et al. DIST-MAY10 20100304 ----JENDL-4.0 MATERIAL 9936 -----INCIDENT NEUTRON DATA ------ENDF-6 FORMAT History 07-09 Theoretical calculation was performed with CCONE code. 07-11 Data were compiled as JENDL/AC-2008/1/ 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 (Same as JENDL-3.3) Estimated from systematics by Tuttle/2/, Benedetti et al./3/ and Waldo et al./4/ Decay constants were evaluated by Brady and England/5/. MT=456 Number of prompt neutrons per fission A value of 4.0 measured by Flynn et al./6/ was adopted at the thermal energy. A coefficient of energy dependent term was estimated from Howerton's systematics/7/. 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/8/. 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 2000/9/ does not include average neutron energy values, the average values were calculated using the formula shown in the report by T.R. England/10/. The fractions of prompt energy were calculated using the fractions of Sher's evaluation/11/ when they were provided. When the fractions were not given by Sher, averaged fractions were used. MF= 2 Resonance parameters MT=151 No resonance parameters are given. Thermal cross sections and resonance integrals (at 300K) ------------------------------------------------------- 0.0253 eV reson. integ.(*) (barns) (barns) ------------------------------------------------------- total 3641.4 elastic 9.319 fission 3361.6 1460 capture 270.1 116 ------------------------------------------------------- (*) In the energy range from 0.5 eV to 10 MeV. MF= 3 Neutron cross sections Below 0.45 eV: * Elastic scattering cross section is 9.3 b calculated from scattering radius of 8.62 fm/12/. * Fission cross section is in the 1/v shape. 3360+-150 b at 0.0253 eV/13,6/. * Capture cross section is in the 1/v shape. 270 b at 0.0253 eV which was estimated from the ratio of capture and fission cross sections calculated with CCONE code/12/ at 1 eV and the thermal fission cross section. Above 0.45 eV: Cross sections were calculated with CCONE code/12/. MT= 1 Total cross section The cross section was calculated with CC OMP of Soukhovitskii et al./14/ MF= 4 Angular distributions of secondary neutrons MT=2 Elastic scattering Calculated with CCONE code/12/. MT=18 Fission Isotropic distributions in the laboratory system were assumed. MF= 5 Energy distributions of secondary neutrons MT=18 Prompt netrons Calculated with CCONE code/12/. MT=455 Delayed neutrons Calculated by Brady and England/5/. MF= 6 Energy-angle distributions Calculated with CCONE code/12/. 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./15/ for Pu-239 thermal fission were adopted. MF=31 Covariances of average number of neutrons per fission MT=452 Number of neutrons per fission Sum of covariances for MT=455 and MT=456. MT=455 Error of 15% was assumed. MT=456 Covariance was obtained by fitting a linear function to the at 0.0 and 5.0 MeV with uncertainties of 12.5% and 10%, respectively. MF=33 Covariances of neutron cross sections Covariances were given to all the cross sections by using KALMAN code/16/ and the covariances of model parameters used in the cross-section calculations. For the following cross sections, standard deviations in the energy region below 0.45 eV were assumed as follows: Total 46 % Elastic scattering 50 % Fission 50 % estimated from experimental data Capture 50 % 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 Estimated with CCONE and KALMAN codes. ***************************************************************** Calculation with CCONE code ***************************************************************** Models and parameters used in the CCONE/12/ 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/17/ * Global parametrization of Koning-Duijvestijn/18/ was used. * Gamma emission channel/19/ was added to simulate direct and semi-direct capture reaction. 3) Hauser-Feshbach statistical model * Moldauer width fluctuation correction/20/ 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/21/. 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/22/,/23/ was used. The prameters are shown in Table 7. ------------------------------------------------------------------ Tables ------------------------------------------------------------------ Table 1. Coupled channel calculation -------------------------------------------------- * rigid rotor model was applied * coupled levels = 0,1,3 (see Table 2) * optical potential parameters /14/ 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 = 0.213 beta_4 = 0.066 beta_6 = 0.0015 * Calculated strength function S0= 1.34e-4 S1= 3.34e-4 R'= 8.62 fm (En=1 keV) -------------------------------------------------- Table 2. Level Scheme of Fm-255 ------------------- No. Ex(MeV) J PI ------------------- 0 0.00000 7/2 + * 1 0.06000 9/2 + * 2 0.08400 11/2 - 3 0.13300 11/2 + * 4 0.16500 13/2 - 5 0.23800 15/2 - 6 0.27200 9/2 + 7 0.31800 11/2 + ------------------- *) Coupled levels in CC calculation Table 3. Level density parameters -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Fm-256 19.5580 1.5000 1.5985 0.3543 0.1323 3.3878 Fm-255 19.4922 0.7515 1.2018 0.3532 -0.5536 2.5647 Fm-254 19.4263 1.5059 0.8560 0.3723 0.0580 3.5059 Fm-253 19.3604 0.7544 0.3502 0.3909 -0.8123 2.9141 Fm-252 19.2945 1.5119 0.1288 0.3822 0.0732 3.5119 -------------------------------------------------------- Table 4. Fission barrier parameters ---------------------------------------- Nuclide V_A hw_A V_B hw_B MeV MeV MeV MeV ---------------------------------------- Fm-256 6.000 1.040 5.000 0.600 Fm-255 6.500 1.000 5.500 0.800 Fm-254 6.500 1.040 5.500 0.600 Fm-253 6.500 1.000 5.500 0.800 Fm-252 6.500 1.040 5.500 0.600 ---------------------------------------- Table 5. Level density above inner saddle -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Fm-256 21.9050 1.7500 2.3000 0.3196 -0.6668 3.7500 Fm-255 21.8312 0.8767 2.3000 0.3201 -1.5401 2.8767 Fm-254 21.7575 1.7569 2.3000 0.3207 -0.6600 3.7569 Fm-253 21.6837 0.8802 2.3000 0.3213 -1.5368 2.8802 Fm-252 21.6098 1.7638 2.3000 0.3219 -0.6531 3.7638 -------------------------------------------------------- Table 6. Level density above outer saddle -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Fm-256 21.9050 1.7500 1.1200 0.3442 0.0370 3.7500 Fm-255 21.8312 0.8767 1.0800 0.3453 -0.8358 2.8767 Fm-254 21.7575 1.7569 1.0400 0.3464 0.0450 3.7569 Fm-253 21.6837 0.8802 1.0000 0.3474 -0.8312 2.8802 Fm-252 21.6098 1.7638 0.9600 0.3485 0.0531 3.7638 -------------------------------------------------------- Table 7. Gamma-ray strength function for Fm-256 -------------------------------------------------------- K0 = 1.500 E0 = 4.500 (MeV) * E1: ER = 11.36 (MeV) EG = 2.70 (MeV) SIG = 263.70 (mb) ER = 14.15 (MeV) EG = 4.10 (MeV) SIG = 527.39 (mb) * M1: ER = 6.46 (MeV) EG = 4.00 (MeV) SIG = 1.89 (mb) * E2: ER = 9.92 (MeV) EG = 3.04 (MeV) SIG = 7.65 (mb) -------------------------------------------------------- References 1) O.Iwamoto et al.: J. Nucl. Sci. 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