Fission Product Yield Data for the Transmutation of Minor Actinide ...

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FIG. 4.4.4. Fragment mass distributions from 236 U fission induced by 235 U+n reaction (points are experimental data [4.4.22]; lines are our calculations); energies of neutrons are shown in the figure. 161
FIG. 4.4.5. Dependence of model parameters on excitation energy for fissioning nuclides 236 U, 239 Pu and 240 Pu formed in reactions with various particles (points are experimental data; lines are our calculations using Eqs ((4.4.6)– (4.4.11)). up to 30 MeV and from the spontaneous fission of 240 Pu [4.4.5]. Results from the analysis show that the most probable mass of heavy fragments for the standard I fission mode of 239 Pu and 240 Pu has a value similar to that for 236 U (A H I = 134.0). The critical value ( cr ) for the angular momentum above which the asymmetric fission channel standard I is converted into the symmetric channel (super long mode) is equal to 8ћ. The most probable mass of heavy fragments for the standard II fission mode is A H II = 140.0 for 239 Pu and 240 Pu fission, up to an excitation energy of 30 MeV. The dependence of the remaining parameters (s AI , s AII , W II) on the excitation energy is shown in Fig. 4.4.5, where they are compared to similar parameters obtained from fission reactions of monochromatic neutrons [4.4.22] (light triangles) and a particles [4.4.23] (dark triangles) with 236 U (solid lines represent calculations using Eqs (4.4.7)–(4.4.11)). At excitation energies above 15 MeV, the calculated energy dependence of the parameters differs significantly from the experimental data for fissioning nuclei 239 Pu and 240 Pu (Fig. 4.4.5), but shows good agreement with the equivalent data for 236 U. 162 Apparently this situation is due to the emissive fission contribution that has to be accounted for more correctly in the case of the fission of actinides by a particles. Experimental data and the results of calculations are given in Figs 4.4.6 and 4.4.7 for fragment mass distributions from 239 Pu and 240 Pu fission by neutrons, g quanta and a particles at excitation energies up to 30 MeV, and also for spontaneous fission of 240 Pu. These figures show satisfactory agreement between the experimental data and calculations. Thus an adequate description of the fragment mass distributions is achieved for fissioning nuclei 239 Pu and 240 Pu formed in reactions with various particles and excitation energies up to 30 MeV by taking into account only two fission modes, namely standard I and standard II. 4.4.4. Fragment mass distributions for photofission The dependence of the fragment mass distributions on excitation energy at a constant value of the angular momentum transferred to the fissioning nucleus can be studied by analysing the experimental data for the photofission of 232 Th, 235 U, 238 U and 239 Pu [4.4.26] at Bremsstrahlung endpoint energies up to 50 MeV. Photofission is one of the most powerful tools for studying the fission process because of the well known spin selectivity of the excitation and the absence of the Coulomb barrier. The main experimental problem in photofission studies is the lack of intense sources of monochromatic photon beams. Therefore, all photofission mass distributions have been measured in bremsstrahlung spectra with a continuous energy distribution, and hence the excitation energy is not well defined. Symmetric fission components have been observed in all photofission experiments but analysed in different ways so that the results are difficult to compare. The systematic investigations of mass fragment distributions in the photofission of nuclei in the mass region 232 £ A £ 239 and Bremsstrahlung endpoint energies between 15 and 55 MeV are presented in Ref. [4.4.26]. Due to the exponential increase of the symmetric fission probability with excitation energy, the symmetric to asymmetric fission yield ratio (Y S /Y A ) is a rather sensitive qualitative measure for the excitation energy of the fissioning nucleus. At low excitation energies and small transferred angular momentum ( £ 7ћ) the fission
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Fission Product Yield Data for the
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AFGHANISTAN ALBANIA ALGERIA ANGOLA
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COPYRIGHT NOTICE All IAEA scientifi
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CONTRIBUTING AUTHORS Denschlag, J.-
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3.2.1. Introduction . . . . . . . .
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6. BENCHMARK EXERCISE . . . . . . .
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However, this CRP entered an entire
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‘Provisional masses’ are determ
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Three scientists were invited to pa
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8 (d) Prompt or delayed neutron emi
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[2.1.40] ITKIS, M.G., OGANESSIAN, Y
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[2.1.96] PATE, B.D., et al., Distri
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[2.1.152] JACOBS, E., et al., Produ
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16 2.2. MEASUREMENTS OF THE ENERGY
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FIG. 2.2.3. 94 Sr: best experimenta
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FIG. 2.2.15. 132 Te: best experimen
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FIG. 2.2.27. 146 Ba: best experimen
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3. EVALUATIONS 3.1. ACTINIDE NUCLEO
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3.1.2. Statistical model At least t
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J Â K=-J 2 2 2 ^ sym Krot ( U, J)
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nuclei with N > 144. However, for h
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neutron number. The observed fissio
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FIG. 3.1.6. 235 U(n,f) fission cros
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FIG. 3.1.10. 237 Np(n,f) fission cr
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from higher fission chances [3.1.43
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[3.1.48] DUSHIN, V.N., et al., Stat
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where Y S is our new standard, and
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TABLE 3.2.2. EVALUATED REFERENCE FI
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TABLE 3.2.2. EVALUATED REFERENCE FI
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TABLE 3.2.3. EVALUATED REFERENCE YI
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TABLE 3.2.3. EVALUATED REFERENCE YI
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The comparisons of our evaluated da
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TABLE 3.2.4. COMPARISON OF RECOMMEN
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TABLE 3.2.8. COMPARISON OF THE UNCE
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REFERENCES TO SECTION 3.2 [3.2.1] I
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where N C , N U are the modified an
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activities were recorded with a pro
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3.3.4. Results and discussion The r
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FIG. 3.3.10. Li Ze et al. data: com
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96 Annex 3.3.1 EVALUATED EXPERIMENT
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Li Ze et al. [3.3.8] Thierens et al
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100 Annex 3.3.3 EVALUATED DATA SET
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The range of target nuclides availa
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condensation of cross-sections by t
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(h) REFERENCE (C,80KIEV,171,1980) i
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uncertainties of the calculation. T
Page 122 and 123: 4. SYSTEMATICS AND MODELS FOR THE P
Page 124 and 125: FIG. 4.1.2. 235 U total cross-secti
Page 126 and 127: FIG. 4.1.9. Total and mode separate
Page 128 and 129: 4.2. SYSTEMATICS OF FISSION PRODUCT
Page 130 and 131: A - = (PA - NT)/2 (4.2.1b) 4.2.2.3.
Page 132 and 133: FIG. 4.2.4(a). 238 U + 5.5 MeV n, L
Page 134 and 135: FIG. 4.2.8(a). U238 + 300 MeV p, LS
Page 136 and 137: TABLE 4.2.1. EQUATIONS FOR SYSTEMAT
Page 138 and 139: values (points) and the derived fun
Page 140 and 141: distributions. Values of N(A) seldo
Page 142 and 143: FIG. 4.2.19. Systematic Z P paramet
Page 144 and 145: FIG. 4.2.21. Systematic Z P paramet
Page 146 and 147: FIG. 4.2.23. Nuclear charge displac
Page 148 and 149: FIG. 4.2.24. Number of protons emit
Page 150 and 151: epresenting model values and thus s
Page 152 and 153: FIG. 4.2.36. n T(A) for CF249T. FIG
Page 154 and 155: FIG. 4.2.41. U235T, line: model; po
Page 156 and 157: The FAST subroutine in the CYFP pro
Page 158 and 159: [4.2.28] BELHAFAF, D., et al., Kine
Page 160 and 161: 4.3. FIVE GAUSSIAN SYSTEMATICS FOR
Page 162 and 163: Derived from measured data Fitted r
Page 164 and 165: FIG. 4.3.7. Mass distribution of 23
Page 166 and 167: FFIG. 4.3.12. Mass distribution of
Page 168 and 169: 4.4. PHENOMENOLOGICAL MODEL FOR FRA
Page 170 and 171: where = 2mE is the wavelength, E
Page 174 and 175: FIG. 4.4.6. Fragment mass distribut
Page 176 and 177: fragment mass distributions are des
Page 178 and 179: FIG. 4.4.9. Fragment mass distribut
Page 180 and 181: FIG. 4.4.10. Fragment mass distribu
Page 182 and 183: P LD È Ê * E - 44. 7ˆ ˘ = Í1 +
Page 184 and 185: FIG. 4.4.13. Pre-neutron emission m
Page 186 and 187: FIG. 4.4.15. Post-neutron emission
Page 188 and 189: FIG. 4.4.17. Post-neutron emission
Page 190 and 191: fragment mass and charge distributi
Page 192 and 193: of the energy dependence of the fus
Page 194 and 195: 4.5. MODAL APPROACH TO THE DESCRIPT
Page 196 and 197: This information was used for the p
Page 198 and 199: two neighbouring isotopes at differ
Page 200 and 201: FIG.4.5.2. Experimental relative ma
Page 202 and 203: Frequently, the yields Y i (M) are
Page 204 and 205: the nine optimum description parame
Page 206 and 207: TABLE 4.5.6. RELATIVE CONTRIBUTIONS
Page 208 and 209: TABLE 4.5.8. RELATIVE CONTRIBUTIONS
Page 210 and 211: Extracted values of s 2 M,S demonst
Page 212 and 213: FIG. 4.5.10. Fission fragment charg
Page 214 and 215: FIG. 4.5.12. Unchanged charge densi
Page 216 and 217: FIG. 4.5.16. Mass yield variance fo
Page 218 and 219: FIG. 4.5.20. Experimental mass yiel
Page 220 and 221: [4.5.24] GOVERDOVSKII, A.A., MITROF
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TABLE 4.6.1. FISSION PRODUCT YIELD
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TABLE 4.6.2. FIT PARAMETER VALUES O
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FIG. 4.6.2. Charge distributions fo
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model which is elucidated elsewhere
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the agreement is better. The observ
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inner barrier is much lower than th
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e determined in a self-consistent m
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FIG. 4.6.11. Overview of the coupli
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cross-section also has to be incorp
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FIG. 4.6.16. Same as Fig. 4.6.15, b
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FIG. 4.6.20. Pre-neutron emission m
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present have a reasonable contribut
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TABLE 4.6.5. ACCURACIES OBTAINED FR
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[4.6.7] BEIJERS, J.P.M., et al., Se
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5. NEW MODELS AND SYSTEMATICS: DEFI
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therefore his benchmark calculation
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mass distributions and practically
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5.2. BENCHMARK EXERCISE 5.2.1. Benc
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thorough and detailed analysis of t
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the fissioning nucleus and the numb
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should be undertaken — such a stu
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experimental method in order to der
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256 Valley heights and peak-to-vall
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FIG. 6.2.3. Benchmark exercise, par
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260 Wahl uncert. margins Wahl uncer
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264 Wahl uncert. margins (adj. Wahl
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Wahl (1.6-160 MeV): Distributions a
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TABLE 6.2.2. 238 U PRE-NEUTRON EMIS
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as most features are very similar t
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FIG. 6.2.14. Benchmark exercise, pa
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278 REFERENCES TO SECTION 6 [6.1] B
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As mentioned above, the mass distri
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I.3.2.6. Liu Conggui et al. [I.8] M
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after prompt-neutron emission, and
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286 Zöller (1995) 89-110 MeV, post
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(1) Data were linearly interpolated
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1. 290 Annex to Appendix I RECOMMEN
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1.2. E n = 5.5 MeV 292 Nagy et al.
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1.3. E n ª 8 MeV 294 Chapman (1978
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1.5. E n = 14-15 MeV 296 Daroczy et
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1.7. E n = 27.5 (22-33) MeV, Zölle
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1.9. E n = 99.5 (89-110) MeV, Zöll
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3. 302 239 Pu NEUTRON INDUCED FISSI
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Appendix II DATA ADJUSTMENT FOR MAS
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Vivès [II.8], Zöller [II.7] and
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Annex 1 to Appendix II ADJUSTED DAT
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Zöller (1995) [II.7] E n = 13 (11.
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E n = 50 (45-55) MeV Post-neutron e
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Äystö et al. (1998) [II.9] E p =
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E n = 1.60 MeV Pre-neutron emission
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E n = 27.5 (22-33) MeV Post-neutron
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E n = 99.5 (89-110) MeV Post-neutro
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Appendix III FISSION YIELD SYSTEMAT
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FIG. III.6. Dependence of chain yie
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TABLE III.2. Ln(y)-LINEAR(E) FIT CO
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FIG. III.14. Dependence of paramete
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FIG. III.26. Comparison of the mass
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FIG. III.38. Comparison of the mass
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TABLE III.3. QUADRATIC FUNCTION FIT
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Uncertainty ratio or uncertainty Ad
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CONTENTS OF THE CD-ROM The attached
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This publication reports on a coord
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