1. NAME AND TITLE

TIRION-4: A Program for Calculating Consequences of a Release of Radioactive Material to the Atmosphere.

TIRION-4 is part of the series of programs collectively known as TIRION which were written to fulfill the need to calculate the consequences of releasing radioactive material to the atmosphere.

2. CONTRIBUTOR

Safety and Reliability Directorate, United Kingdom Atomic Energy Authority, Warrington, England.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 3033.

4. NATURE OF PROBLEM SOLVED

For a release of radioactive material to the atmosphere, which can take place on a time scale of minutes to hours, TIRION-4 models the subsequent atmospheric dispersion of the radioactive material out to 100 km in a time-invariant manner. The internal dose from inhaled activity, the external dose from the radioactive cloud and from deposited activity are calculated for a number of downwind distances and the biological effects on the population surrounding the release point are predicted. In addition, contamination of the ground by actinides and gamma-emitters, as well as the milk ingestion pathway, are considered. To enable the FN line for a series of releases to be constructed, the cumulative probability that a given number of casualties will be exceeded is also calculated.

5. METHOD OF SOLUTION

TIRION-4 uses the Gaussian model of atmospheric dispersion modified to take into account radioactive decay, dry and wet deposition, plume rise (where applicable) and building wake effects (where applicable). A grid between which the concentrations of the various nuclides can be interpolated quadratically forms the basis of an approximate method for dealing with deposition and decay.

Whole body gamma-ray doses from the passing cloud and from the deposited activity are calculated numerically using a nested Simpson's routine. Inhalation factors based on the ICRP lung model and standard dose-risk relationships are used in the prediction of the biological effects. The number of casualties is obtained by integrating numerically over a simplified population distribution (typically, 12 sectors and 17 annuli).

6. RESTRICTIONS OR LIMITATIONS

TIRION-4 can consider no more than 70 nuclides to be released and no more than 14 consequences.

The user must supply the plotting package.

7. TYPICAL RUNNING TIME

A typical run of TIRION-4 takes approximately 30 seconds on the IBM 3033.

8. COMPUTER HARDWARE REQUIREMENTS

The code is operable on the IBM 3033 computer. It requires 390 K bytes of storage without graph plotting and system routines.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required. MVS and SE operating systems are used.

10. REFERENCES

P. J. Cooper, "Addendum to SRD R 120," (February 1980).

L. S. Fryer, "A Guide to TIRION 4 A Computer Code for Calculating the Consequences of Releasing Radioactive Material to the Atmosphere," SRD R 120 (December 1978).

L. S. Fryer and G. D. Kaiser, "TIRION-4 A Computer Program for Use in Nuclear Safety Studies," SRD R134 (November 1978).

G. D. Kaiser, "A Description of the Mathematical and Physical Models Incorporated in TIRION 2 - A Computer Program That Calculates the Consequences of a Release of Radioactive Material to the Atmosphere and an Example of Its Use," SRD R63 (October 1976).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

February 1982.

KEYWORDS: RADIOACTIVITY RELEASE; AIRBORNE; RADIOLOGICAL SAFETY; GAUSSIAN PLUME MODEL; ENVIRONMENTAL DOSE; KERNEL; NUCLIDE TRANSPORT; INTERNAL DOSE