**1. NAME AND TITLE**

TRIDENT-CTR: Two-Dimensional x-y and r-z Geometry Multigroup Transport Code System
for Large Toroidal Reactors.

TRIDENT-CTR is a modification of CCC-293/TRIDENT for fusion reactors.

**2. CONTRIBUTOR**

Los Alamos National Laboratory, Los Alamos, New Mexico.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; CDC.

**4. NATURE OF PROBLEM SOLVED**

Although TRIDENT-CTR is a follow-on code to TRIDENT, it has incorporated several features that make it significantly different. It can handle a wide range of irregular geometric domains in both x-y and r-z geometries. However, it was principally designed to solve shielding and blanket problems for large toroidal reactors.

TRIDENT-CTR is a two-dimensional, x-y and r-z geometry, multigroup, neutral particle transport
code. The use of triangular finite elements gives it the geometric flexibility to cope with the
nonorthogonal shapes of many toroidal designs. The code is capable of handling a wide variety of
problems having irregular domains in both x-y and r-z geometries.

**5. METHOD OF SOLUTION**

Spatial discretization is accomplished in TRIDENT-CTR by using triangular finite elements and discontinuous linear trial functions. The use of triangles in r-z geometry allows a user to accurately follow curved or irregularly-shaped boundaries and material interfaces of toroidal shapes.

The code solves, with suitable approximations, both inhomogeneous and homogeneous transport
equations. It uses the following standard approximations used in CCC-222/TWOTRAN,
CCC-319/DOT, TRIDENT, and other 2-D transport codes: (a) energy: multigroup approximations,
(b) angle: discrete ordinates approximation, and (c) scattering transfer: Legendre polynomial
expansion.

**6. RESTRICTIONS OR LIMITATIONS**

TRIDENT required that all the information needed to solve the entire spatial mesh for one group
be held in Small Core Memory (SCM, approximately 60,000 words). This limited the allowable
problem size to approximately 3,000 triangles in a P_{0} calculation. This restriction would not allow
solution of large toroidal problems with an adequate spatial mesh.

To allow for larger problem sizes (a spatial mesh with a greater number of triangles), TRIDENT-CTR was designed to require only the information to solve one band of triangles for one group to be
in SCM at one time. The problem size is now constrained by Large Core Memory (LCM,
approximately 400,000 words). Rough estimates of typical problem sizes that TRIDENT-CTR can
accommodate on a CDC-7600 are 36,000 triangles for a P_{0} calculation, 12,000 triangles for a P1
calculation, and 3,600 triangles for a P_{3} calculation. TRIDENT-CTR has the same energy-group
blocking and overflow to disk as TRIDENT, and any practical number of energy groups may be used.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for TRIDENT-CTR.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code is designed to operate on the CDC computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCE**

T. J. Seed, "TRIDENT-CTR User's Manual," LA-7835-M (May 1979).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and sample problem input.

**12. DATE OF ABSTRACT**

February 1982; reviewed June 1982.

**KEYWORDS: ** TWO-DIMENSIONS; MULTIGROUP; DISCRETE ORDINATES; NEUTRON;
GAMMA-RAY; TOROIDAL GEOMETRY; FINITE ELEMENT METHOD