1. NAME AND TITLE

ACRA-II: Kernel Integration Code System for Estimation of Radiation Doses Caused by a Hypothetical Reactor Accident.

ACRA-II solves essentially the same problem as CCC-99/PLUME.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV and Assembler language; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

ACRA calculates the internal dose from inhalation of radionuclides in the air and the gamma radiation dose from a passing cloud of finite size. The assumption is made that the radioactive material is released to the atmosphere at ground level or some finite distance above the ground. Subsequently, the material is transported away by the wind and is dispersed to a 3-dimensional normal distribution. The radioactivity of the material is described throughout the space domain as a function of time.

ACRA-II expands the capability of ACRA-I to include the effects of fallout, washout, and ground contamination. The built-in containment model of ACRA-I was eliminated and the emission of nuclides to the atmosphere is described by a step function of time. This was done because the containment models vary depending on the radionuclides, the leakage pathways and the filter mechanisms involved.

5. METHOD OF SOLUTION

ACRA-II computes external dose, internal dose, and ground contamination as a function of location and points in time. The three-dimensional normal distribution is used for dispersion, and the cloud concentration accounts for washout by rain, fallout, and radioactive decay. Fallout is described by Chamberlain's model and assumes that the rate of depletion of a given nuclide "i" in the clouds equals the average concentration times the deposition velocity for the particular nuclide "i"; also the depletion by fallout extends uniformly over the cloud.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

Computer time is approximately 2 seconds per receptor and per time interest for 30 radionuclides on the IBM 360/91 computer. This time is doubled if inversion layers are present. The packaged sample problem ran in 3 minutes on the IBM 360/75 computer.

8. COMPUTER HARDWARE REQUIREMENTS

ACRA-II is operable on the IBM 360/370 computers. Approximately 320 K storage is required.

9. COMPUTER SOFTWARE REQUIREMENTS

FORTRAN IV and Assembler compilers are required. Nonstandard library routines which are essential to execution are included in the package.

10. REFERENCES

F. B. K. Kam, "Informal Notes on ACRA-II" (July 1974).

F. W. Stallmann and F. B. K. Kam, "ACRAA Computer Program for the Estimation of Radiation Doses Caused by a Hypothetical Reactor Accident," ORNL-TM-4082 (April 1973).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

July 1973; updated July 1975; revised September 1982.

KEYWORDS: KERNEL; GAMMA-RAY; AIRBORNE; AIR-GROUND INTERFACE