**
1. NAME AND TITLE**

MARIA SYSTEM: Code System to Calculate Cross Sections for PWR Fuel Assembly Calculations.

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2. CONTRIBUTOR**

Junta de Energia Nuclear and Universidad Politecnica de Madrid, Madrid, Spain through the NEA Data Bank, Issy-les-Moulineaux, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran 77; DEC VAX. (P00359/D6000/00)

**4. NATURE OF PROBLEM SOLVED**

The MARIA System calculates cross sections for PWR fuel assembly calculations. It generates the cross sections library for the diffusion calculations with burnup and feedback effects (CARMEN System, NEA 0649 and RSIC CCC-487) and the k(infinite) and M**2 parameters for the nodal calculations (SIMULA, NEA 0768). MARIA includes three modules. PRELIM generates the input data for the fuel assembly calculation module, for all fuel assembly types in the core and at any condition of power rate and temperature. WIMS-TRACA is a modified version of the fuel assembly calculation program WIMS-D/4 (NEA 0329 and RSIC CCC-576), which generates the collapsed cross sections versus burn up needed by the CARMEN code (reference cell, boron, xenon, samarium, and light water). POSWIM calculates the transport corrections to the diffusion constant of the absorber materials generated by WIMS-TRACA, to be used directly in the diffusion code when rods or burnable absorber rods are present.

**5. METHOD OF SOLUTION**

PRELIM models the PWR assembly as a cluster of rods, taking into account all the physical effects (Dancoff factor per fuel pin dependent on position, real fuel cells and absorber cells volume ratio, fuel pin spectrum in 69 groups independent of fuel assembly type, etc.)

WIMS-TRACA performs the cluster calculation in two steps. First the theory of collision probabilities is used in 69 energy groups, then a Sn transport calculation is performed in few energy groups with detailed geometry. WIMS-TRACA provides the collapsed cross sections in two groups for every cluster region. Special treatment is made in the condensation of the microscopic transport cross section for light water.

POSWIM corrects the diffusion constants for the absorber or control materials fitting the leakages in the diffusion theory calculation to those of the transport calculation.

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6. RESTRICTIONS OR LIMITATIONS**

PRELIM has some dimension restrictions which can be changed.

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7. TYPICAL RUNNING TIME**

The approximate run time for the 11 sample problems was 20 minutes on a VAX 6000-420.

**8. COMPUTER HARDWARE REQUIREMENTS**

The MARIA System was tested at on a VAX 6000-420 running VMS 5.5, and the code is portable to other platforms.

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9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran compiler is required if you want to compile the source files, but the VMS executables are included.

**10. REFERENCES**

E. Sartori, NEA Data Bank Memo (May 17, 1988).

C. Ahnert, J. M. Aragones, "MARIA System: A Code Block for PWR Fuel Assembly Calculations," JEN 543, ISBN 84-500-8823-2 (1983).

**
11. CONTENTS OF CODE PACKAGE**

The referenced document and two DS/HD 3.5-inch (1.44 MB) diskettes are included written in self-extracting compressed DOS files. The code package contains sample input and output, the author's executables, and the MARIA source files.

**
12. DATE OF ABSTRACT**

December 1995.

**KEYWORDS:** PWR; BURNUP; CROSS SECTION PROCESSING; DIFFUSION THEORY; WIMS
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