1. NAME AND TITLE

MILDOS-AREA: Calculation of Radiation Dose from Uranium Recovery Operations for Large-Area Sources.

MILDOS-AREA is a revision of the CCC-398/MILDOS code, incorporating enhanced capabilities for handling large area source dispersion and updated dosimetry calculations.

2. CONTRIBUTOR

Argonne National Laboratory, Argonne, Illinois under sponsorship of DOE-EM through DOE Energy Science and Technology Software Center, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; IBM PC, PC 386, PC 486.

4. NATURE OF PROBLEM SOLVED

MILDOS-AREA estimates the radiological impacts of airborne emissions from uranium mining and milling facilities or any other large-area source involving emissions of radioisotopes of the uranium-238 series. Wind frequency data are provided by the user. The transport model includes the mechanisms of dry deposition of particulates, resuspension, radioactive decay and progeny ingrowth, and plume reflection. Deposition buildup and ingrowth of radioactive progeny are considered in estimating surface concentrations, which are modified by radioactive transformation, weathering, and other environmental processes. MILDOS-AREA allows the user to vary the emission rates of the sources as a step-function of time. Impacts to humans through such pathways as inhalation, external exposure, and ingestion are estimated based on calculated annual average air concentrations of nuclides. Individual, total individual, annual population, and environmental dose commitments are calculated with conversion factors derived from recommendations of the International Commission on Radiological Protection (ICRP) and Oak Ridge National Laboratory. Age-specific dose factors are calculated.

A validation study of MILDOS-AREA was conducted using measured Rn-222 concentration and flux data from the Monticello, Utah uranium mill tailings impoundment. The results of this study demonstrated that use of MILDOS-AREA can result in generally good agreement between model-generated and measured Rn-222 concentrations.

5. METHOD OF SOLUTION

A sector-average Gaussian plume-dispersion model is used to compute concentrations of radioactive materials from fixed-point sources. Area sources are calculated either with the original MILDOS virtual-point method or a finite-element integration method. A choice of vertical-dispersion coefficients is available; the Briggs dispersion coefficients are most appropriate for a tall source, such as a uranium mill plant stack, while the Martin-Tickvart coefficients provide a more realistic representation for near-ground level sources, such as a mill tailings pond.

6. RESTRICTIONS OR LIMITATIONS

Maxima of 300 nodes, 48 individual receptors, 10 sources (point or area) and 10 time steps. The current version is applicable only to uranium-238 series nuclides.

7. TYPICAL RUNNING TIME

Two to 10 minutes are required on an IBM PS/2 Model 80. On a PC 486 (33 Mhz), SAMPLE.DAT ran in about 16 seconds.

8. COMPUTER HARDWARE REQUIREMENTS

An IBM PC or compatible computer with 500 Kbytes of memory, math coprocessor, and a hard disk. A printer capable of producing 132-column output is needed.

9. COMPUTER SOFTWARE REQUIREMENTS

Lahey Fortran 77 v3.0 under MS DOS 3.1 was used to create the executable file included in the package.

10. REFERENCE

Y. C. Yuan, J. H. C. Wang, and A. Zielen, "MILDOS-AREA: An Enhanced Version of MILDOS for Large-Area Sources," ANL/ES-161 (June 1989).

11. CONTENTS OF CODE PACKAGE

Included is one DS/HD (1.2MB) diskette, including the source code, executable file and sample cases.

12. DATE OF ABSTRACT

June 1992.