**RSIC CODE PACKAGE CCC-378**

**1. NAME AND TITLE**

MURLI: Integral Transport Theory Code System for Thermal Reactor Lattice Cell Calculation.

**2. CONTRIBUTOR**

Bhabha Atomic Research Center, Trombay, Bombay, India.

**3. CODING LANGUAGE AND COMPUTER**

DEC Fortran; PDP-11.

**4. NATURE OF PROBLEM SOLVED**

MURLI solves the multigroup integral transport theory equations in the cylindrical cell of a thermal reactor lattice.

**5. METHOD OF SOLUTION**

The code system uses multigroup integral transport theory to obtain space- and energy-dependent neutron flux distribution in the cylindrical cell of a thermal reactor lattice. It obtains physics parameters such as reactivity reaction rates, etc., for the unit cell of a thermal reactor lattice using the interface currents (J ±) approach to the integral transport theory in multigroup structure. The effective multiplication factor is obtained through the solution of multigroup diffusion theory in the fundamental mode buckling. Depletion equations are solved by the 4th order Runge Kutta method.

MURLI can use either the 27-group MINIWIMS or the 69-group WIMS library for the group cross-sections.

**6. RESTRICTIONS OR LIMITATIONS**

The program normally solves the single rod cell problem. However, clusters could be treated under ring homogenization procedure provided that the effective surface for resonance group cross sections is specified.

Other restrictions include: (1) the number of spatial regions must be 20 or less, (2) the number of elements must be limited to 40 or less and can include 8 resonant and/or 8 fissionable ones, (3) the number of mixtures must be limited to 5 or less.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for MURLI.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code is operable on the PDP-11 computer. One scratch tape or working disc or drum is required to store the microscopic scattering matrices. Another tape is optional for writing the cell-smeared cross-sections.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran compiler is required.

**10. REFERENCES**

**a. Included in document:**

H. C. Huria, "The Calculational Model of Lattice Physics Code MURLI,"Informal Report (1980).

**b. Background information:**

H. C. Huria, "MURLI A Multigroup Code for Thermal Reactor Lattices," BARC/I-262 (1973).

"MURLI A Multigroup Integral Transport Theory Code for Thermal Reactor Lattice
Studies," *Atomkernenergie*, 31 (1978).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document (10.a) and one (1.2MB) DOS diskette which contains the source code and sample problem input and output.

**12. DATE OF ABSTRACT**

February 1982; revised February 1983.

**KEYWORDS: ** MULTIGROUP; INTEGRAL BOLTZMANN EQUATION; CELL
CALCULATION; LWR