1. NAME AND TITLE

ALARM-B2: A Computer Code System for Analysis of a Large Break LOCA of a BWR.

2. CONTRIBUTOR

Japan Atomic Energy Research Institute (JAERI), Tokyo, Japan, through the OECD Nuclear Energy Data Bank, Gif-sur-Yvette, France.

3. CODING LANGUAGE AND COMPUTER

Fortran IV and Assembler; IBM 360/370, 3084.

4. NATURE OF PROBLEM SOLVED

ALARM-B2 is a modified version of ALARM-B1 and is a tool to analyze thermo-hydraulic phenomena of a BWR during a postulated large break LOCA.

5. METHOD OF SOLUTION

ALARM-B1 does not calculate the heat transfer to the coolant during the transient but specifies it by input data. ALARM-B2 provides a one-dimensional heat conduction equation, a heat transfer correlation package, and a point reactor kinetics equation to analyze the heat transfer phenomenon in the core region during a LOCA. It also calculates thermal hydraulics in the pressure vessel and the primary coolant loop during the transient of a large break of the recirculation line.

The system of partial differential equations describing fluid conservation for stream-tube are integrated over a number of control volumes. The resulting set of simultaneous equations that is based on the assumptions of one-dimensional, homogeneous, thermal-equilibrium flow is linearized and advanced for a small time increment by a simple explicit numerical technique. The one-dimensional heat conduction equations describing temperature profiles within solid material are written in finite difference forms which are linearized and solved by the Crank-Nicolson implicit method.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

No study has been made by RSIC of typical running times for ALARM-B2.

8. COMPUTER HARDWARE REQUIREMENTS

ALARM-B2 is operable on the IBM 360/370 and the IBM 3084 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

Fortran IV and Assembler compilers are required.

10. REFERENCE

F. Araya, "ALARM-B2: A Computer Program for Analysis of Large Break LOCA of BWR," JAERI-M 9665 (Revised September 1984).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and two (1.2MB) DOS diskettes which contain the source code and sample problem input.

12. DATE OF ABSTRACT

June 1986.