RSICC CODE PACKAGE PSR-459

1. NAME AND TITLE

TORAC: Code System to Calculate Tornado-Induced Flow Material Transport.

2. CONTRIBUTORS

Los Alamos National Laboratory, Los Alamos, New Mexico through the Energy Science and Technology Software Center, Oak Ridge, Tennessee and the NEA Data Bank, Issy-les-Moulineaux, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN; CDC CYBER170 and CRAY1 (P00459C017000).

4. NATURE OF PROBLEM SOLVED

TORAC models tornado-induced flows, pressures, and material transport within structures. Its use is directed toward nuclear fuel cycle facilities and their primary release pathway, the ventilation system. However, it is applicable to other structures and can model other airflow pathways within a facility. In a nuclear facility, this network system could include process cells, canyons, laboratory offices, corridors, and offgas systems. TORAC predicts flow through a network system that also includes ventilation system components such as filters, dampers, ducts, and blowers. These ventilation system components are connected to the rooms and corridors of the facility to form a complete network for moving air through the structure and, perhaps, maintaining pressure levels in certain areas. The material transport capability in TORAC is very basic and includes convection, depletion, entrainment, and filtration of material.

5. METHOD OF SOLUTION

The lumped-parameter method, network theory includes a number of system elements called branches, joined at certain points, called nodes. Ventilation system components that exhibit resistance or potential are located within the branches. Components that have larger volumes are located at nodal points. The gas dynamics governing equations require that the continuity equation be satisfied at every node and that a pressure-flow equation be satisfied for each element or branch. Variations in the node equations depend on whether the node represents a finite volume. This variation also exists for branches, depending on whether the branch is simply a duct or contains a filter, blower, or damper. Material concentrations and material mass flow rates can be calculated at any location in the network as a function of time. The basic mechanisms considered are transport initiation, convective transport, and transport deletion. The user must identify the type, quantity, and location of material at risk. If the material is a solid or liquid aerosol, a characteristic size and density must be specified. TORAC gives the user two options for transport initiation: specification of mass injection rate versus time and calculated aerodynamic entrainment. For each time-step of a calculation, the gas dynamics problem is solved first for the entire network. Then the gas dynamics module calls the convective transport module to solve the mass conservation equation and advance the material transport calculation by one time-step. Two-phase flow is allowed in the sense that normal ventilation gas is one phase and a pneumatically transportable contaminant material is the other phase. The calculation of aerosol depletion is based on quasi-steady-state settling with the terminal settling velocity corrected by the Cunningham slip factor.

6. RESTRICTIONS OR LIMITATIONS

The transport deletion module is restricted to gravitational settling and filtration.

7. TYPICAL RUNNING TIME

NEA-DB executed the sample problem in 15 CP seconds on a CDC CYBER170/875. NESC executed the sample problem in 15 CP seconds on a CDC CYBER170/875. The sample problem was also executed on a Cray-V-MP in approximately 4 CPU seconds.

8. COMPUTER HARDWARE REQUIREMENTS

Approximately 126,200 octal words are required to run the sample problem on a CDC CYBER170/875.

9. COMPUTER SOFTWARE REQUIREMENTS

TORAC executed under NOS 2.4 (CDC CYBER 170), CTSS(CRAY1), or UNICOS5.0(Cray Y-MP) operating systems and requires a FORTRAN compiler.

10. REFERENCES

A) Included in document:

R.W. Andrae, P.K. Tang, R.A. Martin, and W.S. Gregory, "TORAC User's Manual A Computer Code for Analyzing Tornado-Induced Flow and Material Transport in Nuclear Facilities," NUREG/CR-4260 (LA-10435-M) (May 1985).

K.H. Duerre, R.W. Andrae, and W.S. Gregory, "TVENT A Computer Program for Analysis of Tornado-Induced Transients in Ventilation Systems," LA-7397-M (July 1978), with Errata (April 1979).

B) Background Information provided by NEA-DB:

B.D. Nichols and W.S. Gregory, "FIRAC User's Manual: A Computer Code to Simulate Fire Accidents in Nuclear Facilities," NUREG/CR-4561, LA-10678-M (April 1986) (PSR-444).

11. CONTENTS OF CODE PACKAGE

Included in the package are the referenced documents in (10.a) and one 3.5" diskette on which the FORTRAN source, test case input and output are written in DOS format.

12. DATE OF ABSTRACT

November 1999.

KEYWORDS: HEAT TRANSFER; REACTOR ACCIDENTS