February Newsletter

Radiation Safety Information Computational Newsletter

Oak Ridge National Laboratory
Post Office Box 2008 Oak Ridge, Tennessee 37831-6362
managed by Lockheed Martin Energy Research Corp.
for the U.S. Department of Energy
Phone No. 423-574-6176
FAX 423-574-6182
Internet: PDC@ORNL.GOV
WWW: http://epicws.epm.ornl.gov

No. 387	                                                    February 1997

Labor is discovered to be the grand conqueror, enriching and building up nations more surely than the proudest battles.---Channing

CHANGES TO THE COMPUTER CODE COLLECTION Three changes were made to the computer code collection during the month. One new code package was packaged and added to the collection, one existing code package was repackaged to accommodate our users, and the documentation for an existing code package is now available on the internet.
CCC-547/DANTSYS 3.0
OP SYS: Unix
Language: C, Fortran 77
Computers: Cray, WS
Format: tar

Los Alamos National Laboratory informed us that the DANTSYS documentation is now available electronically through the LANL World Wide Web pages at http://www-xdiv.lanl.gov/XTM. Select "Our Services and Products," then "DANTSYS," then "LA12969-M On line." It is also available from the RSICC WWW pages at http://www-rsicc.ornl.gov, click on RSICC, then on Software, then On-line Documentation.
DANTSYS is a one-, two-, and three-dimensional, multigroup, discrete-ordinates transport code system, which includes five major codes: ONEDANT, TWODANT, TWOHEX, THREEDANT, and TWODANT-GQ. DANTSYS runs on the following platforms: CRAY-YMP, Sun SparcStation IPX, IBM RS/6000, HP, and Silicon Graphics under Unix-based operating systems. A Fortran 77 compiler, a C-language preprocessor (cpp), a C-compiler, and GMAKE (GnuMake from Free Software Foundation) are required to install the package which is distributed on 1 DC 6150 (150 MB) cartridge, 4-mm or 8-mm tape in compressed tar format. Reference: LA-12969-M (June 1995). Fortran 77 and C; Cray and workstations (C00547/MFMWS/00).
CCC-601/GENII 1.485
OP SYS: DOS
Language: Fortran 77, Basic
Computers: PC
Format: DOS

This environmental radiation dosimetry software system was repackaged to replace the ZOO archive files with self-extracting DOS files compressed with the PKZIP utility from Pkware, Inc. Some users encountered problems when reading the ZOO files. No changes were made to the files in the package.
GENII, which was developed at Pacific Northwest Laboratory in Richland, Washington, is a coupled system of seven programs and associated data libraries that comprise the Hanford Dosimetry System (Generation II) to estimate potential radiation doses to individuals or populations from both routine and accidental releases of radionuclides to air or water and residual contamination from spills or decontamination operations.
GENII runs on IBM PC's or compatible computers equipped with an 80287 math coprocessor or better and 640 Kbytes of random access memory. Executables included in the package were created with the Lahey F77L and Microsoft QuickBASIC 3.0 compilers under DOS 3.1. The GENII programs also run under Windows95. APPRENTICE requires the proprietary Komputerwerk FINALLY! Modules library. The package is transmitted on 5 DS/HD 3.5-in. (1.44 MB) diskettes in self-extracting compressed DOS files. References: PNL-6584 (Dec. 1988) and WHC-SD-WM-TI-596 (Nov. 1993). Fortran 77 and Basic; IBM PC (C00601/IBMPC/02).
CCC-649/DIF3D
OP SYS: AIX, UNICOS
Language: Fortran 77, C
Computers: workstation, mainframe
Format: tar

Argonne National Laboratory, Argonne, Illinois, contributed the DIF3D 7.0 code system for solving finite-difference diffusion theory problems. DIF3D's nodal option solves the multigroup steady state neutron diffusion equation in two- and three-dimensional hexagonal and Cartesian geometries and solves the transport equation in two- and three-dimensional Cartesian geometries. One-, two- and three-dimensional orthogonal (rectangular and cylindrical) and triangular geometry diffusion theory problems are solved by DIF3D's finite difference option. Eigenvalue, adjoint, fixed source and criticality (concentration) search problems are permitted as are anisotropic diffusion coefficients. Flux and power density maps by mesh cell and region-wise balance integrals are provided. Although primarily designed for fast reactor problems, upscattering and (for finite difference option only) internal black boundary conditions are also treated.
The neutron diffusion equation is solved using a nodal scheme with one mesh cell (node) per hexagonal assembly. The nodal equations are derived using higher order polynomial approximations to the spatial dependence of the flux within the hexagonal or Cartesian node. The final equations, which are cast in response matrix form, involve spatial moments of the node-interior flux distribution plus surface-averaged partial currents across the faces of the node. These equations are solved using a fission source iteration with coarse-mesh rebalance acceleration. Equivalence Theory parameters are permitted with hexagonal nodal models. Mesh-centered finite-difference equations are solved by optimized iteration methods. A variant of the Chebyshev semi-iterative acceleration technique is applied to outer fission source iterations, and an optimized block-successive overrelaxation method is applied to the within-group iterations.
DIF3D is written in FORTRAN 77. Dynamic memory allocation and timing routines are written in "C". It runs under SunOS 4.1.3x and SOLARIS 2.5 on Sun, AIX 3.2.5 and AIX 4.2.0 on the IBM RS6000, and UNICOS on Cray XMP. It is transmitted on either CD-ROM or cartridge tape in a compressed UNIX tar file. References: ANL-83-1 (1983) and ANL-82-64 (1984). Unix Workstations (Sun SparcStation, IBM RS6000), CRAY X-MP (C00649/MFMWS/00).

CHANGE TO THE DATA LIBRARY COLLECTION
As a result of a contribution from Japan one data library was added to the data library collection.
DLC-190/FSX96
OP SYS: all
Language:
Computers: all
Format:

Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken, Japan, contributed this collection of continuous energy cross section libraries for MCNP based on JENDL-3.2. This collection includes FSXLIB-J3R2 based on JENDL-3.2 released in 1994, the FSXLIB-JFF library based on the JENDL Fusion File, and the FSXDOS-J3 library based on the JENDL Dosimetry File. Both FSXLIB-J3R2 and FSXLIB-JFF are to be used for coupled neutron-photon transport calculations while FSXDOS-J3 is for calculation of dosimetry reaction rates with the CCC-200/MCNP4 code system. A modified version of the NJOY 83/6 processing code was used to produce ACE type cross section data, and all 340 nuclides from JENDL-3 Revision-2 were processed for inclusion in FSXLIB-J3R2. The format conforms to the continuous energy neutron cross section table as defined in the MCNP4 manual. Gamma-ray production data are supplied for 66 nuclides in the expanded photon production format. The processing temperature of cross section is 300 K. The energy range for neutron is 10-11 eV to 20 MeV. All 82 nuclides in the JENDL Fusion File were processed with NJOY91.108/FNS to produce ACE type data for FSXLIB-JFF. Gamma-ray production data are supplied for 35 nuclides. The pointwise processing of the JENDL Dosimetry File was done with LINEAR and SIGMA1 from PREPRO, then the MACROS code was used to produce the FSXDOS-J3 library. MAKXSF, which is distributed with CCC-200/MCNP4A, is the program used to convert MCNP Type 1 data to Type 2 (binary). FSXLIB is transmitted on CD-ROM or cartridge tape in a compressed UNIX tar file.
References: Paper presentations (November 1996, April 1996, and November 1995) and JAERI-Data/Code 94-020 (Dec. 1994). BCD card images; any computer (D00190/ALLCP/00).

PERSONAL ITEMS

In serving a specialized area of scientific endeavor, it seems important that we note significant events or changes in the activities of people concerned with radiation protection, transport, and shielding in the nuclear industry. We, therefore, continue to carry personal items as they are brought to our attention.

Alan J. Blotcky Dies New Year's Day

It is with sadness that RSICC notes the death of a participant with our center. On January 1, 1997, Alan J. Blotcky died after a long struggle with cancer. He retired in December 1996 as director of the Medical Research Nuclear Reactor Facility at Omaha, Nebraska, Veterans Affairs Medical Center, a position he held for about 35 years. He had a long association with the American Nuclear Society as a member and participant in the Isotopes and Radiation Division (IRD) and at the time of his death was a member of the IRD Executive Committee. He organized a technical group on biology and medicine which later became the Biology and Medicine Division and over the years held every elected office to the division.

JANUARY ACCESSION OF LITERATURE

The following literature cited has been ordered for review, and that selected as suitable will be placed in the RSICC Information Storage and Retrieval Information System (SARIS). This early announcement is made as a service to the shielding community. Copies of the literature are not distributed by RSICC. They may generally be obtained from the author or from a documentation center such as the National Technical Information Service (NTIS), Department of Commerce, Springfield, Virginia 22161. For literature listed as available from INIS contact INIS Clearinghouse, International Atomic Energy Agency, P.O. Box 100, A-1400 Vienna.

RSICC maintains a microfiche file of the literature entered into SARIS, and duplicate copies of out-of-print reports may be available on request. Naturally, we cannot fill requests for literature which is copyrighted (such as books or journal articles) or whose distribution is restricted.

This literature is on order. It is not in our system. Please order from NTIS or other available source as indicated.

Radiation Shielding Literature

KEK-PROC-95-9 . . . Proceedings of the Fifth EGS4 Users' Meeting in Japan. . . . Hirayama, H.; Namito, Y.; Ban, S. (eds.) . . . November 1995 . . . National Laboratory for High Energy Physics, Tsukuba, Ibaraki, Japan. . . . INIS (mf only).

Health Phys., 72, 10-18 . . . Measurement and Application of Uranium Isotopes for Human and Environmental Monitoring. . . . Goldstein, S.J.; Rodriguez, J.M.; Lujan, N. . . . January 1997 . . . Los Alamos National Laboratory, Los Alamos, NM.

Health Phys., 72, 34-41 . . . Influence of Measurement Geometry on the Estimate of 131I Activity in the Thyroid: Monte Carlo Simulation of a Detector and a Phantom. . . . Ulanovsky, A.V.; Minenko, V.F.; Korneev, S.V. . . . January 1997 . . . Research Institute of Radiation Medicine, Minsk, Belarus.

Health Phys., 72, 56-59 . . . Analysis of Long-Lived Radionuclidic Impurities in Short-Lived Radiopharmaceutical Waste Using Gamma Spectrometry. . . . Salako, Q.; DeNardo, S.J. . . . January 1997 . . . Molecular Cancer Institute, University of California, Davis, Sacramento, CA.

Health Phys., 72, 92-96 . . . Gamma Doses From Phospho-Gypsum Plaster-Board. . . . O'Brien, R.S. . . . January 1997 . . . Australian Radiation Laboratory, Victoria, Australia.

Nucl. Technol., 112, 63-78 . . . A Route-Specific System for Risk Assessment of Radioactive Materials Transportation Accidents. . . . Moore, J.E.; Sandquist, G.M. Slaughter, D.M. . . . October 1995 . . . E. R. Johnson Associates, Fairfax, VA; University of Utah, Salt Lake City, UT.

Nucl. Technol., 112, 79-88 . . . Thermal and Thermomechanical Analyses for Disposal in Drifts of a Repository in Rock Salt. . . . Pudewills, A.; Muller-Hoeppe, N.; Papp, R. . . . October 1995 . . .Inst. f. Nukleare, Entsorgungstechnik, Karlsruhe, Germany; Deutsche Gesellschaft zum Bau und Betrieb von Endlagern f. Abfallstoffe mbH, Peine, Germany; Projekttragerschaft Entsorgung, Karlsruhe, Germany.

Nucl. Technol., 112, 89-98 . . . Fast Multiple-Path Model To Calculate Radionuclide Release from the Near Field of A Repository. . . . Romero, L.; Moreno, L.; Neretnieks . . . October 1995 . . . Royal Institute of Technology, Stockholm, Sweden.

Nucl. Technol., 112, 99-107 . . . The Fast Multiple-Path Nuctran Model-Calculating the Radionuclide Release from a Repository. . . . . . . October 1995 . . . Royal Institute of Technology, Stockholm, Sweden.

Nucl. Technol., 112, 132-141 . . . Calculated Shielding Characteristics of Eight Materials for Neutrons and Secondary Photons Produced by Monoenergetic Source Neutrons with Energies Less Than 400 MeV . . . Nakanishi, N.; Shikata, T.; Fujita, S.; Kosako, T. . . . October 1995 . . . Riken, Saitama, Japan; University of Tokyo, Tokyo, Japan.

Nucl. Technol., 112, 142-153 . . . Improved Neutronics Model of the High Flux Isotope Reactor. . . . Goluoglu, S.; Dodds, H.L. . . . October 1995 . . . University of Tennessee, Knoxville, TN.

Nucl. Technol., 116, 261-269 . . . Analysis of Ya-21u Thermionic Fuel Elements. . . . Paramonov, D.V.; El-Genk, M.S. . . . December 1996 . . . University of New Mexico, Albuquerque, NM.

Nucl. Technol., 116, 373-377 . . . Epithermal Neutron Beam Upgrade with a Fission Plate Converter at the Brookhaven Medical Research Reactor. . . . Liu, H.B.; Patti, F.J. . . . December 1996 . . . Brookhaven National Laboratory, Upton, NY.

Nucl. Technol., 117, 40-48 . . . How the Code Analyst Can Influence the Calculation and Use Good Practices to Minimize Pitfalls. . . . Shotkin, L.M. . . . January 1997 . . . U.S. Nuclear Regulatory Commission, Washington, DC.

Nucl. Technol., 117, 184-194 . . . Boiling Water Reactor Benchmark Calculations. . . . Rahnema, F.; Ilas, D.; Sitaraman, S. . . . February 1997 . . . Georgia Institute of Technology, Atlanta, GA; George Woodruff School of Mechanical Engineering, Atlanta, GA; General Electric Nuclear Energy, San Jose, CA.

Nucl. Technol., 117, 206-222 . . . Evaluation of Shielding Analysis Methods in Spent-Fuel Cask Environments. . . . Broadhead, B.L.; Tang, J.S.; Childs, R.L.; Parks, C.V.; Taniuchi, H. . . . February 1997 . . . Oak Ridge National Laboratory, Oak Ridge, TN.

Nucl. Technol., 117, 223-233 . . . Radionuclide Transport in Fractured Porous Media - Analytical Solutions for a System of Parallel Fractures with a Flux-Type Boundary Condition. . . . Chu-Tien Chen; Shih-Hai Li . . . February 1997 . . . National Tsing Hua University of Taiwan, Hsinchu, Taiwan.

Nucl. Technol., 117, 255-266 . . . Virtual Radiation Fields - A Virtual Environment Tool for Radiological Analysis and Simulation. . . . Knight, T.W.; Dalton, G.R.; Tulenko, J.S. . . . February 1997 . . . University of Florida, Gainesville, FL.

ANL/APS/TM-16 . . . Atomic Physics with Hard X-Rays from High Brilliance Synchrotron Light Sources. . . . . . . August 1996 . . . Argonne National Laboratory, Argonne, IL . . . NTIS; OSTI . . . Proceedings of a Workshop held at Argonne National Laboratory, May 20 and 21, 1996.

IAEA-NDS-7 . . . Index of Nuclear Data Libraries (available from the IAEA Nuclear Data Section). . . . Lemmel, H.D. . . . November 1996 . . . IAEA, Vienna, Austria . . . IAEA.

J. Radiat. Res. Radiat. Proces., 14, 134-142 . . . Comparative Study on Attenuation and Scattering of Gamma-Rays Through Sedimentary and Igneous Rocks. . . . Mahmoud, H.M.; Hok, A.S.; Armia, E.; Eltaher, A.M. . . . August 1996 . . . South Valley University, Egypt.

JINR No. 3, 47-54 . . . Absorbed Dose in Scintillators of Zero Degree Calorimeter at Irradiation by PB Nuclei with 157.7 GeV/Nucleon Energy. . . . Astapov, A.A.; Maximov, A.N.; Vodopianov, A.S.; Zaitsev, L.N. . . . 1996.

JINR, 3, 55-64 . . . Track Finding with Neural Networks in ALICE ITS. . . . Batyunya, B.V.; Belikov, Y.A.; Fedunov, A.G.; Zinchenko, A.I. . . . 1996.

ORNL-6889 . . . Preliminary Calculational Analysis of the Actinide Samples from FP-4 Exposed in the Dounreay Prototype Fast Reactor. . . . Murphy, B.D.; Newton, T.D.; Raman, S. . . . December 1996 . . . Oak Ridge National Laboratory, Oak Ridge, TN.

Computer Codes Literature CDTN, 716-721. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IDENT
Prototype of an Expert System to Help Nuclide Identification in Gamma Spectrum Analysis. . . . Jayanthi, K.A.; Corcuera, R.P.; Oliveira, G.M.B. . . . 08/95 . . . Centro Tecnico Aerospacial, Sao Jose dos Campos, Brazil . . . Library of Comissao Nacional de Energia Nuclear, RJ Brazil.

CMPYEL, 4, 176-181. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MULTIPLET
MULTIPLET - A Computer Program for Analysis of Overlapping Peaks. . . . Le Hong Khiem; Nguyen Van Do . . . 1994 . . . National Centre for Sciences and Technology, Hanoi, Viet Nam.

EDF-96-NB-00038. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N3S
A Free Surface Algorithm in the N3S Finite Element Code for Turbulent Flows. . . . Nitrosso, B.; Pot, G.; Abbes, B.; Bidot, T. . . . 08/95 . . . Electricite de France (EDF), Clamart, France . . . INIS (mf only) . . . In French.

EDF-96-NB-00044 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TURBULENT FLUID
Modelling Turbulent Fluid Flows in Nuclear and Fossil-Fired Power Plants. . . . Viollet, P.L. . . . 06/95 . . . Electricite de France (EDF), Clamart, France . . . INIS (mf only) . . . In French.

HDYUEC, 16, 260-263 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MCNP-3B
Development and Improvement for MCNP-3B Interactive Plotter. . . . Gao Yanfeng . . . 07/96 . . . Computer Application Inst. of Nuclear Industry, Beijing, China . . . . . . In Chinese.

IAEA-TECDOC-872. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RELAP5/MOD3
RELAP5/MOD3 Pre-Test Predictions for the SPES-2 1" C.L. Break Test S01613. . . . Alemberti, A.; Frepoli, C.; Graziosi, G. . . . 04/96 . . . ANSALDO Nuclear Div., Genoa, Italy . . . INIS (mf only).

IAEA-TECDOC-872 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TRAP-2
Development and Initial Validation of Fast-Running Simulator of PWRs: TRAP-2. . . . Brega, E.; Lombardi, C.; Ricotti, M.; Sordi, R. . . . 04/96 . . . ENEL-ATN, Milan, Italy . . . INIS (mf only).

JAERI-Data/Code-96-022 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MVP/GMVP; QMDRELP; EQMD; HSABC; CURBAL; STREAM V3.1; TOSCA; EDDYCAL; RELAP5/MOD/C36095; RELAP5/MOD3
Vectorization, Parallelization and Implementation of Nuclear Codes (MVP/GMVP, QMDRELP, EQMD, HSABC, CURBAL, STREAM V3.1, TOSCA, EDDYCAL, RELAP5/MOD2/C36-05, RELAP5/MOD3) on the VPP . . . Nemoto, T.; Watanabe,H.; Fujita, T.; Kawai, W.; Harada, H.; Gorai, K.; Yamasaki, K.; Shoji, M.; Fujii, M. . . . 07/96 . . . Fujitsu Ltd., Tokyo, Japan; JAERI, Japan . . . INIS (mf only) . . . Progress Report 1995 Fiscal Year. In Japanese.

Nucl. Technol, 117, 133-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RETRAN-03
Parallel and Serial Applications of the RETRAN-03 Power Plant Simulation Code Using Domain Decomposition and Krylov Subspace Methods. . . . Downar, T.J.; Jen-Ying Wu; Steill, J.; Janardhan, R. . . . 02/97 . . . Purdue University, West Lafayette, Indiana.

NUREG/CP-0149-V.2; CONF-9510156, v.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . SCDAP/RELAP5
SCDAP/RELAP5 Code Devlopment and Assessment. . . . Allison, C.M.; Hohorst, J.K. . . . 03/96 . . . INEL, Idaho Falls, ID . . . OSTI; NTIS; GPO; INIS (mf only).

CHANGES TO THE COMPUTER CODE COLLECTION Three changes were made to the computer code collection during the month. One new code package was packaged and added to the collection, one existing code package was repackaged to accommodate our users, and the documentation for an existing code package is now available on the internet.
CCC-547/DANTSYS 3.0 OP SYS: Unix Language: C, Fortran 77 Computers: Cray, WS Format: tar	Los Alamos National Laboratory informed us that the DANTSYS documentation is now available electronically through the LANL World Wide Web pages at http://www-xdiv.lanl.gov/XTM. Select "Our Services and Products," then "DANTSYS," then "LA12969-M On line." It is also available from the RSICC WWW pages at http://www-rsicc.ornl.gov, click on RSICC, then on Software, then On-line Documentation. DANTSYS is a one-, two-, and three-dimensional, multigroup, discrete-ordinates transport code system, which includes five major codes: ONEDANT, TWODANT, TWOHEX, THREEDANT, and TWODANT-GQ. DANTSYS runs on the following platforms: CRAY-YMP, Sun SparcStation IPX, IBM RS/6000, HP, and Silicon Graphics under Unix-based operating systems. A Fortran 77 compiler, a C-language preprocessor (cpp), a C-compiler, and GMAKE (GnuMake from Free Software Foundation) are required to install the package which is distributed on 1 DC 6150 (150 MB) cartridge, 4-mm or 8-mm tape in compressed tar format. Reference: LA-12969-M (June 1995). Fortran 77 and C; Cray and workstations (C00547/MFMWS/00).
CCC-601/GENII 1.485 OP SYS: DOS Language: Fortran 77, Basic Computers: PC Format: DOS	This environmental radiation dosimetry software system was repackaged to replace the ZOO archive files with self-extracting DOS files compressed with the PKZIP utility from Pkware, Inc. Some users encountered problems when reading the ZOO files. No changes were made to the files in the package. GENII, which was developed at Pacific Northwest Laboratory in Richland, Washington, is a coupled system of seven programs and associated data libraries that comprise the Hanford Dosimetry System (Generation II) to estimate potential radiation doses to individuals or populations from both routine and accidental releases of radionuclides to air or water and residual contamination from spills or decontamination operations. GENII runs on IBM PC's or compatible computers equipped with an 80287 math coprocessor or better and 640 Kbytes of random access memory. Executables included in the package were created with the Lahey F77L and Microsoft QuickBASIC 3.0 compilers under DOS 3.1. The GENII programs also run under Windows95. APPRENTICE requires the proprietary Komputerwerk FINALLY! Modules library. The package is transmitted on 5 DS/HD 3.5-in. (1.44 MB) diskettes in self-extracting compressed DOS files. References: PNL-6584 (Dec. 1988) and WHC-SD-WM-TI-596 (Nov. 1993). Fortran 77 and Basic; IBM PC (C00601/IBMPC/02).
CCC-649/DIF3D OP SYS: AIX, UNICOS Language: Fortran 77, C Computers: workstation, mainframe Format: tar	Argonne National Laboratory, Argonne, Illinois, contributed the DIF3D 7.0 code system for solving finite-difference diffusion theory problems. DIF3D's nodal option solves the multigroup steady state neutron diffusion equation in two- and three-dimensional hexagonal and Cartesian geometries and solves the transport equation in two- and three-dimensional Cartesian geometries. One-, two- and three-dimensional orthogonal (rectangular and cylindrical) and triangular geometry diffusion theory problems are solved by DIF3D's finite difference option. Eigenvalue, adjoint, fixed source and criticality (concentration) search problems are permitted as are anisotropic diffusion coefficients. Flux and power density maps by mesh cell and region-wise balance integrals are provided. Although primarily designed for fast reactor problems, upscattering and (for finite difference option only) internal black boundary conditions are also treated. The neutron diffusion equation is solved using a nodal scheme with one mesh cell (node) per hexagonal assembly. The nodal equations are derived using higher order polynomial approximations to the spatial dependence of the flux within the hexagonal or Cartesian node. The final equations, which are cast in response matrix form, involve spatial moments of the node-interior flux distribution plus surface-averaged partial currents across the faces of the node. These equations are solved using a fission source iteration with coarse-mesh rebalance acceleration. Equivalence Theory parameters are permitted with hexagonal nodal models. Mesh-centered finite-difference equations are solved by optimized iteration methods. A variant of the Chebyshev semi-iterative acceleration technique is applied to outer fission source iterations, and an optimized block-successive overrelaxation method is applied to the within-group iterations. DIF3D is written in FORTRAN 77. Dynamic memory allocation and timing routines are written in "C". It runs under SunOS 4.1.3x and SOLARIS 2.5 on Sun, AIX 3.2.5 and AIX 4.2.0 on the IBM RS6000, and UNICOS on Cray XMP. It is transmitted on either CD-ROM or cartridge tape in a compressed UNIX tar file. References: ANL-83-1 (1983) and ANL-82-64 (1984). Unix Workstations (Sun SparcStation, IBM RS6000), CRAY X-MP (C00649/MFMWS/00).