GNOMER Program Description

GNOMER is a program which solves the multigroup neutron diffusion equation in 1D, 2D and 3D cartesian geometry. It uses the highly efficient Green's function nodal method. Best performance is obtained for coarse mesh calculations (for example, one node per assembly in the radial direction of a PWR-type reactor core).

The program is designed to calculate the global core power distributions, as well as power distributions and homogenized cross sections over a fuel assembly. Core symmetries can be considered and include reflective quadrant symmetry, cyclic quadrant symmetry and octant symmetry.

For global core power distribution calculations the program includes a rather simple thermohydraulics module to calculate the temperature distributions. When the reactivity coefficient library RCFlib is available, a correction to the cross sections is made by the reactivity coefficient method, to compensate for feedback effects. Such corrections are valid when the core conditions at which the cross sections are calculated do not differ significantly from the actual core conditions. For global core calculations, two-group cross sections are usually adequate.

To calculate homogenized cross sections over a fuel assembly a number of options are available, ranging from the simple flux-volume weighting, criticality search, to the more refined EDH method. For the assembly calculations it is recommended to use 6 to 10 energy groups.

Package Distribution

The package is distributed by the NEA Data Bank with the designation
   IAEA 1271/03

and the Radiation Shielding Information Center (RSIC) with the designation

CORD-2 Program Description

CORD-2 system is intended for core design applications of pressurised water reactors. The main objective was to assemble a core design system which could be used for simple calculations (such as frequently required for fuel management) as well as for accurate calculations (for example, core design after refuelling).

Package Distribution

The package is distributed by the NEA Data Bank with the designation

   IAEA 1226/03

The package contains four Fortran source fules: CORD2.FUL containing the main programs sources, CORLIB.FUL with routines common to many utility programs, PCLIB.FUL with specific interface programs for DOS and EILIBE.FUL which is a selection of relevant routines from the public domain EISPACK and BLAS libraries.


The links below refer to:
- Core design manuals and input instructions
- Articles from the literature describing the methods
- Supplementary documents
- Updates for program GNOMER and CORD2

The manuals provide the technical details for setting-up the system, maintain CORD-2 libraries and run design calculations. The articles provide theoretical basis and validation of the methods used. Supplementary information is included in documents to which the test cases refer to.


  CORD-2 Core Design System for PWR Type Reactors
  CORD-2 Package Users' Guide

  GNOMER Program Manual


 TRKOV, Andrej, NAJŽER, Mitja, ŠKERGET, Leopold. Variant of Green's funtion nodal method for neutron diffusion. J. Nucl. Sci. Technol., 1990, vol. 27, str. 766-777. [COBISS.SI-ID 14166567]

 TRKOV, Andrej, RAVNIK, Matjaž. Effective diffusion homogenisation of cross sections for pressurized water reactor core calculations. Nucl. sci. eng., 1994, vol. 116, str. 86-95. [COBISS.SI-ID 8198439]

 TRKOV, Andrej, RAVNIK, Matjaž. CORD-2 package for PWR nuclear core design calculations. V: RONEN, Yigal (ur.), ELIAS, Ezra (ur.). International Conference on Reactor Physics and Reactor Computations, Tel-Aviv1994. Reactor physics and reactor computations : proceedings. Tel-Aviv: Ben-Gurion University of the Negev Press, 1994, 1994, str. 371-378. [COBISS.SI-ID 8203559]

 TRKOV, Andrej, KROMAR, Marjan. Recent improvement to the GNOMER code for reactor calculations.  4th Regional Meeting Nuclear Energy in Central Europe, Bled, Slovenia, 7-10 September 1997. Proceedings. Ljubljana: Nuclear Society of Slovenia, 1997, 1997, str. 362-266. [COBISS.SI-ID 12892967]

 KROMAR, Marjan, TRKOV, Andrej. Application of the reactivity coefficient method for the nuclear design calculations.  Nuclear energy in Central Europe '98 : proceedings, Terme Čatež, Slovenia, 7 to 10 September, 1998. Ljubljana: Društvo jedrskih strokovnjakov Slovenije: = Nuclear Society of Slovenia, 1998, str. 133-138. [COBISS.SI-ID 13649447]

 KROMAR, Marjan, TRKOV, Andrej. Generation of the reactivity coefficient library in the CORD-2 system. 4th Regional Meeting Nuclear Energy in Central Europe, Bled, Slovenia, 7-10 September 1997. Proceedings. Ljubljana: Nuclear Society of Slovenia, 1997, 1997, str. 367-372. [COBISS.SI-ID 12893479]

 KROMAR, Marjan, TRKOV, Andrej. Simulation of the power feedback effects with the reactivity coefficient method. V: PHYSOR 2000. Pittsburgh: American Nuclear Society, 2000, 2000. [COBISS.SI-ID 15071271]


Since the release of the latest version, a few minor changes were made to the code. They can be found in the form of Update directives on the file GNOMER.UPN and are compatible in format with the CDC system Update or an emulator such as UPD.

For program GNOMER:

The changes introduced from the previous version to generate the latest one can be found on the file GNOMOLD.UPN in Update format. Normally the user does not need to consider these updates.


For program CORD-2:

The updates for the CORD2 source are found on the UPA. file. The updates for the CORLIB source are found on the UPB. file. At present, there are no updates for the PCLIB source. The EILIBE routines are public domain software. To update these, the user should follow the instructions in the comments of the main source and download them through the network.