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

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3.4. EXAMINATION OF POSSIBLE EVALUATION METHODS FOR FUTURE ENERGY DEPENDENT FISSION PRODUCT YIELD DATA SETS REQUIRED FOR MINOR ACTINIDE INCINERATION, AND OTHER CONSIDERATIONS Much work has been done on new methods to predict unmeasured fission product yields outside of the traditional thermal, fast and 14 MeV neutron induced fission. The current use of traditional fission product yield data is initially described. Differences required for the evaluation and usage of the new data are considered and possible solutions proposed. Other contributions are noted, and the current status of the UK fission product yield files is briefly summarized. 3.4.1. Introduction The overall objective of the CRP was to investigate methods for the evaluation of neutron induced fission yields in the energy range 10– 150 MeV, as requested for the transmutation of nuclear waste. These investigations include the studies and further development of both empirical and theoretical models for the calculation of energy dependent fission yields, which were benchmarked against the other codes and experimental data. An examination was initially made of the ways in which the results from other participants could be combined and used in future evaluations to provide the data required to carry out inventory calculations for regulatory required safety assessments. Contributions to the collection of experimental fission yield references and data are described, as well as the adoption of Wahl’s CYFP code to produce postneutron emission data for the benchmark exercise. Finally, related work on the production of a new evaluation file is described (UKFY3.4). 3.4.2. Thoughts on future evaluations utilizing the fission product yield methodologies described by CRP participants Recent studies have determined that the long term radiotoxicity of nuclear waste could be significantly reduced by transmutation of minor actinides and possibly some long lived fission products (e.g. Refs [3.4.1, 3.4.2]). These technologies need to be R.W. Mills British Nuclear Fuels plc, United Kingdom quantitatively assessed in terms of the resultant radiation doses to workers and the general public, and the risks from the use of such technologies. Releases to the environment from storage and possible processing are also important in these calculations. The important properties of nuclear waste (activities, toxic potentials, radiation emission and subsequent radiation doses) are all a direct result of the radionuclide inventory of the waste. Thus, as a prerequisite to such calculations, radionuclide inventories resulting from the use of such technologies need to be determined. These inventory calculations require a wide range of nuclear data. One type of nuclear data required for such calculations that have previously been unavailable in evaluated files are neutron and other particle induced fission product yields as a function of energy, particularly above 10 MeV. Accurate determinations of fission product inventories from accelerator driven minor actinide transmutation scenarios require these yield data to be determined. The recent empirical and theoretical methodologies reported by other CRP participants have, for the first time, permitted the determination of fission product yields for a wide range of particle induced fission reactions as a function of incident particle energy. The possible use of such predictions is discussed below. 3.4.2.1. Fission product yield libraries and their production Current fission product yield libraries (e.g. JEF-2.2 [3.4.3]) consist of independent and CU yields for a range of major and minor actinides. Yields are available for a range of neutron induced and spontaneous fission systems. The data are tabulated for a set of standard neutron spectra selected from thermal, fast and ‘high’ energy (about 14 MeV). The independent and CU yields are given for each product nuclide. 101
The range of target nuclides available in JEF- 2.2 is given in Table 3.4.1. It was felt desirable to base the selection of fission reactions in JEF-2.2 on objective criteria. Consequently, a series of calculations were made with the inventory code FISPIN for both thermal and fast reactors. For the former, initial fuelling by enriched uranium, recycled uranium, mixed plutonium/uranium and thorium/ uranium were individually considered. The ratings and irradiations applied to the calculations were greater than actually achieved in practice at present, but these values were regarded as feasible within the near future. Reactions were regarded as important if they contributed more than 0.1% of the fission rate at any time. Thus, it is thought that the derived list is more than adequate for current reactor designs. This list does depend on the initial fuel compositions and on the assumed capture and fission cross-sections for the higher actinides; it is acknowledged that uncertainties in the latter may be considerable. In addition, the JEF-2.2 file includes fission of 232 Th, 233 U, 235 U and 238 U by ‘high energy’ neutrons (about 14 MeV); these reactions were in the earlier UK libraries for calculations involving breeder blankets around fusion devices. The yields from the spontaneous fission of 242 Cm and 244 Cm were also included, which are important as sources of neutrons in reactors and in fuel handling, and of 252 Cf, which is important as a standard. The reactions considered by the burnup calculations are given as three sub-sets in the three left hand columns of Table 3.4.1. These are distinguished 102 by the value of the maximum fission rate percentage due to the nuclide in question at any time during the irradiation (the range in which the percentage falls is indicated in the column heading). Clearly, the required accuracy of yields is greater if the percentage fission rate is greater; hence the nuclides in the first column need the most careful treatment, followed by those in the second column, and then by those in the third column. The process by which these files were produced is described in Refs [3.4.4–3.4.6]. The main steps can be summarized as: (a) Collect as much relevant data as possible; (b) Analyse data to produce best estimates of measured yields; (c) Produce parameterizations to allow estimation of unmeasured data; (d) Produce complete sets of yields for each required nuclide and neutron energy combination; (e) Adjust results for physical constraints and produce ENDF-6 formatted library. 3.4.2.2. Traditional inventory calculation in reactor fuel All calculations of the nuclides present in irradiated material, whether from a reactor or accelerator driven system, are governed by a set of coupled linear differential equations. The concentration of an individual nuclide can be calculated by integrating all relevant production and destruction TABLE 3.4.1. THIRTY-NINE FISSIONING SYSTEMS IN UKFY2 Maximum fraction of fission rate >10% 1–10% 0.1–1% 233 U TFH 235 U TFH 238 U FH 239 Pu TF 241 Pu TF 240 Pu F 245 Cm TF 232 Th FH 234 U F 236 U F 237 Np TF 238 Np TF 238 Pu TF 242 Pu F 241 Am TF 242m Am TF 243 Am TF 243 Cm TF 244 Cm TF Spontaneous fission 252 Cf S 242 Cm S 244 Cm S T: Thermal fission; F: Fast fission; H: 14-MeV fission; S: Spontaneous 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
Page 62 and 63: TABLE 3.2.3. EVALUATED REFERENCE YI
Page 64 and 65: The comparisons of our evaluated da
Page 66 and 67: TABLE 3.2.4. COMPARISON OF RECOMMEN
Page 94 and 95: TABLE 3.2.8. COMPARISON OF THE UNCE
Page 96: REFERENCES TO SECTION 3.2 [3.2.1] I
Page 99 and 100: where N C , N U are the modified an
Page 101 and 102: activities were recorded with a pro
Page 103 and 104: 3.3.4. Results and discussion The r
Page 105 and 106: FIG. 3.3.10. Li Ze et al. data: com
Page 107 and 108: 96 Annex 3.3.1 EVALUATED EXPERIMENT
Page 109 and 110: Li Ze et al. [3.3.8] Thierens et al
Page 111: 100 Annex 3.3.3 EVALUATED DATA SET
Page 115 and 116: condensation of cross-sections by t
Page 117 and 118: (h) REFERENCE (C,80KIEV,171,1980) i
Page 119 and 120: 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
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Derived from measured data Fitted r
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FIG. 4.3.7. Mass distribution of 23
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FFIG. 4.3.12. Mass distribution of
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4.4. PHENOMENOLOGICAL MODEL FOR FRA
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where = 2mE is the wavelength, E
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FIG. 4.4.4. Fragment mass distribut
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fragment mass distributions are des
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FIG. 4.4.10. Fragment mass distribu
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P LD È Ê * E - 44. 7ˆ ˘ = Í1 +
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FIG. 4.4.13. Pre-neutron emission m
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FIG. 4.4.15. Post-neutron emission
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FIG. 4.4.17. Post-neutron emission
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fragment mass and charge distributi
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of the energy dependence of the fus
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4.5. MODAL APPROACH TO THE DESCRIPT
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This information was used for the p
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two neighbouring isotopes at differ
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FIG.4.5.2. Experimental relative ma
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Frequently, the yields Y i (M) are
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the nine optimum description parame
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TABLE 4.5.6. RELATIVE CONTRIBUTIONS
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TABLE 4.5.8. RELATIVE CONTRIBUTIONS
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Extracted values of s 2 M,S demonst
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FIG. 4.5.10. Fission fragment charg
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FIG. 4.5.12. Unchanged charge densi
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FIG. 4.5.16. Mass yield variance fo
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FIG. 4.5.20. Experimental mass yiel
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[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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