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Radioactive releases from nuclear facilities may contribute to radiation exposure through a number of pathways: external exposures by direct radiation from plumes or deposited radionuclides; internal exposures from inhalation or ingestion of radioactive material. The Radiological Safety Analysis Computer Program (RSAC) calculates the consequences of a release of radionuclides to the atmosphere. Using a personal computer, a user can generate a fission product inventory; calculate inventory decay and ingrowth; the inventory during transport through processes, facilities, and the environment; model the downwind dispersion of the activity; and calculate doses to downwind individuals.

History of RSAC

RSAC was originally developed and written in assembly language (MAP) for the IBM 7044/44 in 1966 by R. L. Coates and N. R. Horton (Coates and Horton 1966). In 1968, a FORTRAN version of the program was prepared by L. C. Richardson (Richardson 1968). Since 1968, RSAC has undergone substantial revision.

In 1973, RSAC-2 was issued by D. R. Wenzel (Wenzel 1973) to:

• add input and output options
• change the inhalation dose calculations (lung and gastro-intestinal tract)
• change the numerical integration methods for cloud gamma dose calculations
• change the gamma-ray buildup factor model
• revise radionuclide yields and half-lives in the standard library
• refine output format for ease of reading
• reduce computer memory requirements

In 1982, RSAC-3 was issued (Wenzel 1982) to:

• add a fifty-mile population dose calculations
• use the U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.109 (NRC 1977a) for ingestion dose calculations
• use the International Commission for Radiological Protection (ICRP) Lung Dynamics Model for inhalation dose calculations
• use the Dolphin and Eve Gastro-intestinal Tract Model
• improve error detection

After undergoing an extensive verification and validation, RSAC-4 (Wenzel 1990) was enhanced and issued in 1990 to:

• convert the program FORTRAN 77
• execute RSAC-4 on a personal computer
• use internal dose conversion factors from DOE/EH-0071 and external dose-rate conversion factors from DOE/EH-0070
• add dose summary tables
• add an ingestion dose model for an acute release
• increase the number of organs in the dose calculations
• include water immersion dose calculations
• program calculated plume rise for either jet or buoyant plume
• revise fission yields and half-lives
• add radionuclides to the standard library
• update the photon data library
• enhance error diagnostics
• include validation and verification necessary to meet the additional requirements for software imposed by ASME-NQA-1, "Quality Assurance Program Requirements for Nuclear Facilities" (ASME 1989).

In 1994, RSAC-5 was issued (Wenzel 1994) to:

• add an option to calculate cloud-gamma doses expressed in external dose equivalent
• add a variable particle size option for inhalation dose calculations
• resolve the over depletion for ground level releases during stable meteorology that was observed in earlier versions of RSAC
• add a reflective meteorological model to better model diffusion below the mixing depth
• include additional radionuclides to more accurately model the U-235 fission chain
• add a dose summing option
• incorporate a simplified notation for radionuclide identification
• include a capability to read radionuclide inventories from external files
• correct errors observed in earlier versions of RSAC for the finite-plume model integration for cloud-gamma dose calculations and large plumes
• add meteorological diffusion using Pasquill-Gifford parameters
• include an option to simulate the release of fission products from an operating reactor
• update forage and vegetation yields
• include an option to read ingestion transfer parameters from an external file
• refine the model for ingestion dose calculations from an acute release
• add a companion program, RSAC+, that assists the user in preparing an input file for RSAC-6.

The sixth and current version, RSAC-6, is a major revision to the program. Numerous areas were:

• add additional radionuclides to the program library
• use internal dose conversion factors from Federal Guidance Report No. 11 (Eckerman 1988) and external dose-rate
• conversion factors from Federal Guidance Report No. 12 (Eckerman 1993)
• provision to calculate doses at distances of less than 100 m
• correction of minor errors identified in the program
• printout of radionuclides in a logical order
• add of default lung clearance classes to provide the maximum dose based on each element
• entry of radionuclide input in either upper or lower case characters
• elimination of a discontinuity in the leakage function
• addition of an option to allow the user to enter a respirable fraction for inhalation dose calculations
• addition of an option to allow the user to enter an occupancy factor for ground surface dose calculations
• incorporation of editorial changes in program output
• enhanced method for estimation of the building wake effect
• evaluate the instantaneous release to a room
• evaluate the resuspension of particulate activity
• enhanced method for evaluation of dry deposition
• perform calculation of an effective sy and sz when C/Q is directly input