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7. CALCULATION OF SCATTERING LAW DATA S(α,β,T) IN ENDF-6 FORMAT AND FURTHER PROCESSING In Fig. 34 the scheme of generating thermal neutron cross section data sets for a MCNP(X) data library is shown based on the ENDF-6 format and the nuclear data processing system NJOY. Static structure factor S(κ) Frequency distribution ρ(ω) ENDF/B-VI.5 or JEF-2.2 Evaluated Nuclear Data File Figure 34. Neutron Cross Section Processing SCATHD LEAPR NJOY-99.67+ Nuclear Data Processing System Codes solving the Fourier transformation of the intermediate scattering function for the system neutron-scattering nucleus are LEAPR (solution with the so-called phonon expansion) or GASKET2 (solving by direct integration). In the previous chapters the necessary physical input to these codes as e.g. the generalised frequency distribution ρ(ω) for solid and liquid moderators was given in detail. These codes allow to treat frequency distributions composed of free or hindered translations or diffusive motion, a continuous part of a broad band of frequencies (e.g. for hindered rotations) and discrete Einstein δ-oscillators. LEAPR (a module of NJOY) which is from numerical aspects superior to GASKET2, is used to generate the thermal data sets for water and methane as Scattering Law data files S(α,β,T) and in addition the elastic scattering part for the solid moderators. These parts are stored in file MF=7 and section MT=4 or MT=2 in the evaluated data file of thermal neutron scattering in moderators. 38 . S(α,β,T) + elastic XS ENDF/B-6 Format RECONR, BROADR + THERMR ACER Fast and thermal data sets for MCNP(X)
For fcc Al the incoherent inelastic data set was generated with LEAPR. The coherent elastic file was prepared by our code FCCALPB which was written by Käfer /36/ and then linked with the LEAPR result to the complete ENDF-6 format. For hydrogen with its free rotations of the molecules both codes are not applicable. At IKE we developed the code SCATHD to handle H2 or D2 for solid, liquid or gaseous phases regarding the spin dependent modifications ortho and para. For the liquid phase the static structure factor S(κ) considering the intermolecular interference scattering is input for SCATHD. The coherent neutron scattering is handled according to the Vineyard approximation With the module THERMR of NJOY thermal scattering cross sections as a function of energy and temperature as well as differential data can be calculated based on the corresponding evaluated thermal neutron scattering file in ENDF/B-6 format. Modifications of the modules LEAPR and THERMR to guarantee a correct processing were necessary and are done at IKE. The generation of cross section data sets for MCNP(X) from the pointwise files was done by the module ACER. Two processes are allowed in the S(α,β,T) treatment in MCNP(X): 1. inelastic scattering with cross section σ (inelastic) and a coupled energy-angle representation derived from the S(α,β,T) Scattering Law data in ENDF-6 format 2. elastic scattering with no change in outgoing neutron energy for solids with cross section σ (elastic) and an angular treatment derived from lattice parameters. For inelastic scattering, the secondary energy distributions are represented by a set of equally probable final energies (64) for each member of a grid of initial energies (57) from an upper limit of ∼4 eV down to 0.00001 eV along with a set of angular data for each initial and final energy. 8. CONCLUSIONS For light water for the solid and liquid phases and for hydrogen for the liquid and gaseous phases as well as for solid methane we have derived realistic models to describe the neutron scattering dynamics as a function of energy transfer, impulse change and moderator temperature. The corresponding generalised frequency distributions ρ(ω) were taken to generate Scattering Law data files in ENDF-6 format for the individual moderator phases for specified temperatures. The code LEAPR of the NJOY code package was used for calculation of S(α,β,T) by the so-called phonon expansion method solving the intermediate scattering function. LEAPR was taken to generate the solid and liquid water and methane data sets. The hydrogen data sets were generated with the IKE program SCATHD. For validating of the scattering dynamics models and the calculated Scattering Law data sets S(α,β,T) measured differential and integral neutron cross sections were compared with the corresponding calculated ones. It could be shown that the overall agreement of calculated and measured cross sections for all investigated moderators in its different phases generally was very satisfactory. In addition to the IKE evaluations for the different cold moderators in its special phases we considered other published model assumptions for the neutron-scattering nucleus interaction, took the resulting phonon spectra ρ(ω) to prepare S(α,β,T) files and showed the consequences for calculated neutron scattering cross sections (see e.g. liquid water and solid methane). For calculation of neutron thermalisation and transport in cold moderators data sets for the neutron transport code MCNP were generated. The data sets can be used with the MCNP versions 4C and X. The content of the prepared MCNP(X) library is described in appendix B. 39
Page 1 and 2: ACoM - 6 6th 6 International Worksh
Page 3 and 4: Forschungszentrum Jülich GmbH Inst
Page 5: Preface These are the Proceedings o
Page 8 and 9: List of participants, cont’d. Kü
Page 10 and 11: Pepe M. 43 Petriw S. 43 Picton D.J.
Page 12 and 13: Experimental background, results an
Page 14 and 15: • Light water ice as H(H2O) at T
Page 16 and 17: In Table 2 a survey is given about
Page 18 and 19: sigma-T in barns/molecule Figure 4.
Page 20 and 21: 2.3 Liquid water Compared to the so
Page 22 and 23: presented. The corresponding experi
Page 24 and 25: 3.2 Gaseous hydrogen and deuterium
Page 26 and 27: Rho(Omega) normalised 160 140 120 1
Page 28 and 29: elatively free and can also suffer
Page 30 and 31: Figure 16. Heat Capacity for Solid
Page 32 and 33: o-D2 and p-H2 at 5K for an ucn ener
Page 34 and 35: Figure 22. UCN Upscattering Rates i
Page 36 and 37: ho(omega) normalised 40 35 30 25 20
Page 38 and 39: derived from Walker [52]. The neutr
Page 40 and 41: Since there is only a small gain of
Page 44 and 45: For the validation of these data se
Page 46 and 47: [36] Nielsen, M.: Phonons in Solid
Page 48 and 49: 2. THE CASE OF MOLECULAR SOLIDS An
Page 50 and 51: γ r ( 0) ≅ 2 2 2 T erf e ( ) / 2
Page 52 and 53: 4. PRELIMINARY APPLICATION Solid Me
Page 54 and 55: [5] Meeting on Moderator Concepts a
Page 56 and 57: state. Conversely, the monatomic hy
Page 58 and 59: Note that the equilibrium trihydrog
Page 60 and 61: para hydrogen system under irradiat
Page 62 and 63: [12] T. E. Fessler and J. W. Blue,
Page 64 and 65: tion of neutron intensities, partic
Page 66 and 67: varied between calculations but the
Page 68 and 69: 5. THE OPTIMISATION OF MULTIPLY GRO
Page 70 and 71: Figure 7. A comparison of time dist
Page 72 and 73: 4.8 cm hydrogen slab in front of a
Page 75 and 76: ACoM - 6 6 th Meeting of the Collab
Page 77 and 78: the moderator is annealed every 12
Page 79 and 80: The method requires two additional
Page 81 and 82: ABSTRACT ACoM - 6 6 th Meeting of t
Page 83 and 84: Heat transfer processes across phas
Page 85 and 86: 3. TWO-PHASE FLOW PATTERN IN THE MO
Page 87 and 88: continuous phase dominating, and a
Page 89 and 90: Also the velocity pattern has chang
Page 91 and 92: Figure 8. Methane pellets concentra
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ACoM - 6 6 th Meeting of the Collab
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sample volume and the nominal densi
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The results presented in this paper
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Table 10. Summary of energy transfe
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2. EXPERIMENTAL Methane hydrate was
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Figure 4. Energy levels of methane
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102
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phase transitions from phase II to
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After melting phase I in the cryost
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4. SOLID PHASES OF MESITYLENE-D0 AN
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G(ν) [a.u.] 8 6 4 2 Phase II Phase
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112
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A not quite as perfect cold spectru
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2.2 Inelastic neutron scattering Th
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Figure 4. Inelastic spectra at the
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3.2 Moderator performance The resul
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122
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Figure 2. The methane pelletizer, m
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Figure 5. The cryogenic hopper fill
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128
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ture
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The charging device scheme could be
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Table 1. Data of irradiation of met
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5. METHODS OF PROCESSING OF RAW EXP
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of radicals, that is, before a burp
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6.2 Condition for thermally stimula
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Table 4. Estimated values of an ene
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• Nine spontaneous burps were obs
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APPENDIX Some useful relations and
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APPENDIX. Graphs of burps. 148
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150
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152
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154
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2. EXPERIMENTAL SETUP Fig. 1 will g
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All these parameters are kept const
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4. CONCLUSIONS We demonstrated that
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JESSICA (Juelich Experimental Spall
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The moderator system consists of th
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to change the temperatures and to p
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168
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supplied from the high pressure bom
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10 9 10 8 10 7 10 6 Para35%[Experim
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174
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2. TIME OF FLIGHT SPECTRA AND ENERG
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When applying this transformation t
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data were analyzed in more detail.
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182
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First of all, we should conclude th
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The equation (a) may also describe
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Even at h=0.01 mm which is too smal
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model and some consequences of its
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methane and 0.7-1.5% for water ice
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case: the sample of infinite size.
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200
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Phase Diagram of the CH4-H20 system
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Reaction Chamber for Hydrate Produc
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Analysis: X-ray diffraction pattern
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Comparison with non-hydrate forming
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Mechanical Tests: Apparatus 220
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Morphology of Indium Jacket 222
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Schriften des Forschungszentrums J
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Schriften des Forschungszentrums J
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