NESC1092 FIRAC.

1. NAME OR DESIGNATION OF PROGRAM:  FIRAC.

3. DESCRIPTION OF PROGRAM OR FUNCTION

FIRAC predicts fire-induced flows, thermal and material transport, and radioactive and non- radioactive source terms in a ventilation system. It is designed to  predict the radioactive and nonradioactive source terms that lead to gas dynamic, material transport, and heat transfer transients. FIRAC's capabilities are directed toward nuclear fuel cycle facilities and the primary release pathway - the ventilation system. However, it is applicable to other facilities and can be used to model other airflow pathways within a structure. The basic material  transport capability of FIRAC includes estimates of entrainment, convection, deposition, and filtration of material. The interrelated effects of filter plugging, heat transfer, and gas dynamics are also simulated. A ventilation system model includes elements such as filters, dampers, ducts, and blowers connected at nodal points to form networks. A zone-type compartment fire model is incorporated to simulate fire-induced transients within a facility.

4. METHOD OF SOLUTION

FIRAC solves one-dimensional, lumped-parameter, compressible flow equations by an implicit numerical scheme. The lumped-parameter method is the basic formulation that describes the  gas dynamics system. No spatial distribution of parameters is considered in this approach, but an effect of spatial distribution can be approximated by noding.
Network theory, using the lumped-parameter method, includes a number of system elements, called branches, joined at certain points, called nodes. Ventilation system components that exhibit flow resistance and inertia, such as dampers, ducts, valves, and filters, and those that exhibit flow potential, such as blowers, are located within the branches of the system. The connection points of  branches are nodes for components that have finite volumes, such as  rooms, gloveboxes, and plenums, and for boundaries where the volume  is practically infinite. All internal nodes, therefore, possess some finite volume where fluid mass and energy storage are accounted for. The conservation of mass equation is applied at each internal node.  The steady-state flow rate in incompressible flow is determined by the pressure drop. The usual one-dimensional approximation is assumed to treat the quasi-steady compressible flow inside a constant area duct. An iterative implicit numerical scheme is used to solve for pressure and density corrections at each node until the system is balanced.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of -
   100 nodes
   100 rooms
   100 control dampers
   100 branches
    40 blowers
    25 plot frames with 4 curves per plot
    20 special filter types
    20 radioactive source terms that can be tracked
    15 blower characteristic functions
    10 boundary nodes
     5 particulate species
     5 gaseous species
     5 time functions of each type

6. TYPICAL RUNNING TIME

NESC executed the sample problem in approximately 30 CP minutes on a CDC CYBER170/875.

NEA-DB ran the test case included in this pakcage on a
CRAY-XMP/2800 computer in 4.5 minutes of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

FIRAC is one in a family of codes designed to provide improved safety analysis methods for the nuclear industry. Other family members include TORAC (NESC 1093) and EXPAC.  FIRAC includes the capabilities of the zone-type compartment fire model, FIRIN, developed at Battelle Pacific Northwest Laboratories.  The two codes were coupled to allow an improved simulation of a fire-induced transient within a facility.

10. REFERENCES

- R.W. Andrae, R.A. Martin, and P.K. Tang, ans W.S. Gregory,
  TORAC User's Manual: A Computer Code for Analysis of Tornado-
  Induced Flow and Material Transport in Nuclear Facilities,
  NUREG/CR-4260 (LA-10435-M), May 1985.
- M.K. Chan, M.Y. Ballinger, P.C. Owczarski, and S.L. Sutter,
  User's Manual for FIRINI: A Computer Code to Characterize
Accidental Fire and Radioactive Source Terms in Nuclear Fuel Cycle    Facilities,
  NUREG/CR-3037 (PNL-4532), December 1982.

- B.D. Nichols and W.S. Gregory:
  FIRAC User's Manual: A Computer Code to Simulate Fire Accidents in
  Nuclear Facilities,
  NUREG/CR-4561 (April 1986)
- L. Reed:
  NESC Note 87-105 (September 30, 1987)
- L. Reed:
  NESC Note 91-28  (December 14, 1990)

11. MACHINE REQUIREMENTS

Approximately 305,000 (octal) words are required to run the sample problem on a CDC CYBER170/875.

267,776 words of main storage n CRAY-XMP/2800.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  CTSS (Cray1), NOS 2.4 (CDC CYBER170).

COS 1.17 WITH compiler CFT 1.14 (CRAY-XMP/2800).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Memory  must be set to zero prior to running FIRAC. The LTSS-specific postprocessor graphics programs GOPLOT and FOPLOT are not supplied.

15. NAME AND ESTABLISHMENT OF AUTHORS

          B.D. Nichols and W.S. Gregory
          Los Alamos National Laboratory

File name	File description	Records
NESC1092_01.001	Information file	63
NESC1092_01.002	FIRAC Fortran source	11253
NESC1092_01.003	FIRAC Sample input	163
NESC1092_01.004	FIRAC Sample output (FT06)	35486
NESC1092_01.005	FIRAC Sample output(FT15,FT16,FT17,FT12,FT08	1751
NESC1092_01.006	JCL used at Data Bank (print out of FT06)	17
NESC1092_01.007	JCL used at Data Bank (print out of FT15...	30