1. NAME AND TITLE
MILDOS: Calculation of Radiation Doses from Uranium Recovery Operations.
2. CONTRIBUTORS
U.S. Nuclear Regulatory Commission, Washington, D. C.
Pacific Northwest Laboratory, Richland, Washington.
3. CODING LANGUAGE AND COMPUTER
Fortran IV; CDC.
4. NATURE OF PROBLEM SOLVED
MILDOS estimates impacts from radioactive emissions from uranium milling facilities. These impacts are presented as dose commitments to individuals and the regional population within an 80 km radius of the facility. Only airborne releases of radioactive materials are considered: releases to surface water and to groundwater are not addressed in MILDOS. This is a multi-purpose code system, within the range of its proper application, and can be used to evaluate population doses for NEPA assessments, maximum individual doses for predictive 40 CFR 190 compliance evaluations, or maximum offsite air concentrations for predictive evaluations of 10 CFR 20 compliance.
The MILDOS package includes models for both point sources (stacks, vents) and area sources (ore pads, tailings areas). Gaseous releases are limited to consideration of 222Rn plus ingrowth of daughters. Exposure pathways of concern are assumed to be inhalation of airborne radioactive material, ingestion of vegetables, meat, and milk contaminated via deposition, and external exposure to radiation emitted by airborne activity and activity deposited on ground surfaces. Liquid exposure pathways are not treated by MILDOS.
5. METHOD OF SOLUTION
Emissions of radioactive materials from fixed point source locations and from area sources are modeled using a sector-averaged Gaussian plume dispersion model which utilizes user-provided wind frequency data. Mechanisms such as deposition of particulates, resuspension, radioactive decay and ingrowth of daughter radionuclides are included in the transport model. Annual average air concentrations are computed, from which subsequent impacts to humans through various pathways are computed. Ground surface concentrations are estimated from deposition buildup and ingrowth of radioactive daughters. The surface concentrations are modified by radioactive decay, weathering, and other environmental processes. MILDOS allows the user to vary the emission sources as a step function of time by adjusting the emission rates; this can include shutting them off completely. Thus, the results of a computer run can be made to reflect changing processes throughout the facility's operational lifetime.
6. RESTRICTIONS OR LIMITATIONS
A maximum of 20 sources can be used in a single run.
7. TYPICAL RUNNING TIME
No study has been made by RSIC of typical running times for MILDOS.
8. COMPUTER HARDWARE REQUIREMENTS
MILDOS is operable on the CDC computers.
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran IV compiler is required.
10. REFERENCES
G. Gnugnoli, "Suggested Revision in the use of the MILDOS Code," Memorandum (October 1980).
G. N. Gnugnoli and D. E. Martin, "MILDOS Computer Code User's Manual," Preliminary document (May 1980).
D. L. Strenge and T. J. Bander, "MILDOS A Computer Program for Calculating Environmental Radiation Doses from Uranium Recovery Operations," NUREG/CR-2011/PNL-3767 (April 1981).
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.
12. DATE OF ABSTRACT
February 1982; revised February 1983.
KEYWORDS: ENVIRONMENTAL DOSE; RADIOACTIVITY; AIRBORNE; INTERNAL DOSE; AIR-GROUND INTERFACE; GAUSSIAN PLUME MODEL