Los 5-5Version 3.0 iii 16-19Version 3.0 ix Table 5.2: Table 6.1: Table 6.2: Table 7.1: Table 7.2: -. The DANTSYS code package includes the following transport codes: ONEDANT, TWODANT, TWODANT/GQ, TWOHEX, and THREEDANT. This document is the central user, methods and programming documentation for the system of codes. LIST OF FIGURES LIST OF FIGURESThe DANTSYS code package is a modular computer program package designed to solve the time-independent, multigroup discrete ordinates form of the Boltzmann transport equation in several different geometries. The modular construction of the package separates the input processing, the transport equation solving, and the post processing (or edit) functions into distinct code modules: the Input Module, one or more Solver Modules, and the Edit Module, respectively. The Input and Edit Modules are very general in nature and are common to all the Solver Modules. The ONEDANT Solver Module contains a one-dimensional (slab, cylinder, and sphere), time-independent transport equation solver using the standard diamond-differencing method for space/angle discretization. It was previously documented in Ref.1. Also included in the package are Solver Modules named TWODANT, TWODANT/GQ, THREEDANT, and TWOHEX. The TWODANT Solver Module solves the time-independent two-dimensional transport equation using the diamond-differencing method for space/angle discretization and was previously documented in Ref. 2. We have also introduced an adaptive weighted diamond differencing (AWDD) method for the spatial and angular discretization into TWODANT as an option. The TWOHEX Solver Module solves the time-independent two-dimensional transport equation on an equilateral triangle spatial mesh. The user's guide for TWOHEX was previously documented in Ref. The THREEDANT SolverModule solves the time independent, three-dimensional transport equation for XYZ and RZO symmetries using both diamond differencing with set-to-zero fixup and the AWDD method. The TWODANT/GQ Solver Module solves the two-dimensional transport equation in X Y and RZ symmetries using a spatial mesh of arbitrary quadrilaterals. The spatial differencing method is based upon the diamond differencing method with set-tozero fixup with changes to accommodate the generalized spatial meshing.This manual describes the standardized Input and Edit Modules together with each of the Solvers in the package. Throughout this manual we will refer to this package as the DANTSYS code package.Some of the major features included in the DANTSYS code package are: a free-field format ASCII text input capability;standardized, data-and file-management techniques as defined and developed by the Module solves the time independent, three-dimensional transport equation for XYZ and RZO symmetries using both diamond differencing with set-to-zero fixup and the AWDD method. The TWODANTIGQ Solver Module solves the two-dimensional transport equation in X Y and RZ symmetries using a spatial mesh of arbitrary quadrilaterals. The spatial differencing meth...

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The one-dimensional diffusion accelerated neutral-particle transport (ONEDANT) code is augmented to explore the effects of gravity on neutron flux spectra near planetary surfaces. The lifetime of the neutron is also explicitly accounted for. The results show a qualitatively new feature in planetary neutron leakage spectra in the form of a component of returning neutro,ns having kinetic energies less than the gravitational binding energy (0.132 eV for Mars). The net effect is an enhancement in flux at the lowest energies that is largest at and above the outermost layer of planetary matter. This effect diminishes with increasing depth. Fluxes for kinetic energies larger than the gravitational binding potential are minimally changed by gravity. All energy spectra can be well characterized by a model consisting of the superposition of relatively simple thermal and epithermal functions that are completely specified .by four parameters; the thermal and epithermal amplitudes, • and/g, respectively; the thermal temperature, T•; and the epithermal power law exponent, p. Instrumental parameters for the initial version of the neutron mode of the Mars observer gamma ray spectrometer are used to demonstrate the ability to use measured, count rates to determine thermal and epithermal amplitudes. 1. thickness of the CO 2 polar caps up to thicknesses of about 250 g/cm 2. Information provided by both measurements is essential to understand processes that determine the nature and evolution of the Martian surface and atmosphere as well as the Martian climate. Pioneering calculations of neutron leakage spectra were made exclusively for the Earth and the Moon [e.g., Hess et al., 1961; Lin•7enfelter et al., 1961; Armstrong7 et al., 1973]. Monte Carlo and multigroup diffusion codes coupled with an appropriate cross-section library were used for this purpose. However, these calculations did not include effects of a possible nonuniform stratigraphy and a rigorous account of the influence of gravity on the orbits of low-energy neutrons escaping outward. Gravitational and lifetime effects are explored for the planet Mars in this paper. The effects of general composition and stratigraphy are surveyed by Drake et al. [1988]. A recent treatment at the Sun's surface of solar flare neutron production and transport including gravity has been given by Hua and Lin•7enfelter [ 1987]. Neutron moderation in both the Drake et al. [1988] and present papers is modeled using the one-dimensional diffusion accelerated neutral-particle transport (ONEDANT) code Paper number 88JB03341. 0148-0227/89/88J B-03341 $05.00 513 [O'Dell et al., 1982] coupled with a multigroup cross-section library tailored specifically for Mars. Because details of the code and its operation are given elsewhere [O'Dell et al., 1982; Drake et al., 1988], they will not be repeated here. Only those special effects that depend significantly on planetary gravity will be considered. The technique of modifying ONEDANT to include gravity is detailed in section 2, and a survey of the nature an...

1. Program Identification: ONEDANT 2. Computer for which Program is Designed: CDC-76OO, but the program has been implemented and run on tht IBM-370/190 and CRAY-I computers. 3. Function: ONEDANT solves the one-dimensional multigroup transport equation in plane, cylindrical, spherical, and two-angle plane geometries. Both regular and adjoint, inhomogeneous and homogeneous (k. and eigenvalue search) problems subject to vacuum, reflective, perioaic, white, albedo, or inhomogeneous boundary flux conditions are solved. General anisotropic scattering is allowed and anisotropic inhomogeneous sources are permitted. 6. Running Time: Running time is directly related to problem size and to cen¬ tral processor and data transfer speeds. On the CDC-7600 a 70 energygroup, S ,, P-scatter, 40 space-point eigenvalue problem requires about A0 sec CPU time. A 42 energy-group, S_, P-scatter, 121 space-point fixed-source problem requires about 30 sec CPU time on the CDC-7600. A 1 energy-group, S,", P scatter, 307 space-point fixed-source problem requires from 2 to 3 sec CPU time on the CDC-7600. Generally, then, on the CDC-7600, the running times for ONEDANT will range from a few seconds to 1 or 2 minutes. 'I. Unvisual Features of the Program: The ONEDANT code package is modularly struc¬ tured in a form that separates the input and the output (or edit) func¬ tions from the main calculational (or solver) section of the code. The code makes use of binary, sequential data files,called interface files, io transmit data between modules and submodules. Standard interface files whose specifications have been defined by the Reactor Physics Committee on Computer Code Coordination are accepted, used, and cheated by the code. A totally new free-field card-image input capability is provided for the user. The code provides the user with considerable flexibility in using both card-image or sequential file input and also in controlling the execution of both modules and submodules. Separate versions of the code exist for short-word and long-word computers. 8. Programming Languages: The program is written in standard FORTRAN-IV language. 10. Material Available: Source deck (about 30 000 card-images), sample problems and this manual have been submitted to the Argonne Code Center and to the Radiation Shielding Information Center. viii I.

This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied. or aSSUmeS any legal liability or responsibility for the accuracy, Conpleteness or usefulness o f any information, apparatus. product or process disclosed, or represents that its *e would not infringe privately owned rights.

Tkla report na prepared •• an account ot Oovcruacnt apDoaorcd vork, Neither Qm Halted States, aor th* ComciulM, nor any pereoa actlag on bekalf ol the Coamlealoo:A. MifcBB any warrsniy or reprefczntaUaa.eipreaKd or implied, with respect ID UU> BCCUrmcr. compteXMtie-i, or uae!uU*ea ol the iajoraatlun contained in tkla rwpor.. or tkal Uw Me ol any laforaaaUon, apporatua, metaod. or proecaa dlKloaed la tkla rapon aujr aot lafrtaf* prlialaljt o«Mi*d rtfAta; or ( B AMunvu «/.y liabultlta will) r«ar««l U> the ur-o of. or lor damagea reavlUaf [row la* UM jf u/ Informtlon. apparatua. mthod. or procna illacUiaad la ikln report.Aa uMd In tfcc abooa, "peracn actla| oa behaU of the Coataalaaioa" Ucliiitl uy ••-pioyr* or rnntractor of the Cosunlaalon. or eaploye* ol such ccMUaclar. to lha eHeiil that aucb enplojrec -ir contractor of the Com ml ••loo. or eat ploy** of rjch contractor prepar*a, dfseaeMnatea. ai provldM acC«M U, any lalorautloo puraaaRt to hla catplormeM or ceatracl •life the Coaaueaim. or hla •npioyawnt •nth uuch contractor.DlSTHlGL'TIuN ul-TIU5> UUt.L.UhM li (Fig. 8) 18 9. Subroutine OUTER (Fig. 9) 18 10. Subroutine INNER (Fig. 10) 20 11. Subroutine SETBC (Fig. 12) 23 12. Subroutine REBAL (Fig. 13 Ordering of S n directions. Finite difference equations are derived for the Boltziaann transport equation in (x,y) rectangular, (r,Q) cylindrical,and (r,z) cylindrical geometries. These equations are shown to be consistent with the analytic forms of the transport equation, and when used with the arithmetic mean difference assumption, to have second-order truncation error. The TWOTRAN program to solve the multigroup approximation to the transport equation using these difference equations is described. The theory of a coarsemesh rebalancing procedure which accelerates all the iterative processes of the program is derived. Detailed input and usage instructions for the program are given, including flow charts of the major subroutines. Functional descriptions of the major sweeps through the space-angle mesh are provided. A sample problem is described.

XIV." Function of TJB'DENT Subroutines 49 XV. Relation of Key Problem Variables to Program Mnemonics 51 XVI. Contents of Blank Common Blocks IA and RIA 52 XVII. Contents of Named Common Block FWBGN1-_____ 59 XVIIi: Contents of Named Common Block FWBGN2 61 XIX.

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