About MILDOS-AREA

MILDOS-AREA History

HISTORY

The MILDOS-AREA computer code has gone through many changes over the years. In 1981 MILDOS (NUREG/CR-2011) was developed from version IV of the Argonne National Laboratory (Argonne) computer program UDAD (Uranium Dispersion and Dosimetry). Version IX of UDAD is documented as NUREG/CR-0553. The models and assumptions on which the MILDOS program was based are described in the U.S. Nuclear Regulatory Commission Draft Regulatory Guide RH 802-4 and portions of the UDAD document. Models were included in MILDOS to consider both point sources (stacks, vents) and area sources (ore pads, tailing areas). Releases of particulates explicitly considered are limited to the radionuclides U-238, Th-230, Ra-226, and Pb-210. Other radionuclides are implicitly accounted for under the secular equilibrium assumption. Gaseous releases were limited to consideration of Rn-222 plus ingrowth of decay products. The dose to exposed individuals is calculated for comparison with requirements of both 40 CFR 190 and 10 CFR Part 20.

The version of MILDOS developed in 1981 allowed the user to define a maximum of 20 source terms, 10 time steps, and 48 individual receptor locations. Ingestion dose conversion factors were based on ICRP Publication 2 and 10 A's ingestion models. Inhalation dose conversion factors were calculated by the UDAD computer code in accordance with the Task Group on Lung Dynamics (TGLM) lung model of the ICRP (ICRP 1966 and 1972), and the external dose conversion factors were directly taken from Hones and Soldat (1977) .

In 1989, Argonne developed the MILDOS-AREA code (ANL/ES-161) by modifying the MILDOS code developed in 1981. The changes were intended to provide enhanced capability to compute doses from large-area sources and to incorporate changes in methods for dosimetry calculations (ICRP 1979). This version of MILDOS-AREA allowed the user to define a maximum of 10 sources (point or area), 48 individual receptors, and 10 time steps. The number of sources was reduced from 20 allowed in the MILDOS code because in the revised code a large-area source is considered as a single source rather than as two or more virtual-point sources. MILDOS-AREA considers the same radionuclides as MILDOS.

While the MILDOS code could only be used on a mainframe computer, MILDOS-AREA was designed for use on an IBM or IBM-compatible personal computer. MILDOS-AREA was easier to use; more flexible in handling the large amount of printer output; and although slower in execution, usually exhibited a better net turnaround time than MILDOS. A validation study of MILDOS-AREA was conducted with measured Rn-222 concentration and flux data from the Monticello, Utah, uranium mill tailings impoundment. The results of that study demonstrated that use of MILDOS-AREA can result in generally good agreement between model-generated and measured Rn-222 concentrations.

The MILDOS-AREA computer code was further updated by Argonne in 1997. The 1989 version of MILDOS-AREA computer code incorporated dose conversion factors derived by the ICRP recommendations of 1978. The annual average air concentrations were compared with the maximum permissible concentrations (MPCs) in the Nuclear Regulatory Commission's Standards for Protection Against Radiation (10 CFR Part 20). On January 1, 1994, a revision to 10 CFR Part 20 (revised Part 20) went into effect. The revised Part 20 updated its dosimetry to the ICRP 1978 recommendations. The dose limit to the general public also changed. The changes led to a revision of the calculated allowable concentrations (ALC) for unrestricted areas, with MPC being replaced by the term "effluent concentrations." In addition, a new method of recovering uranium gained popularity in the late 1980s, and the majority of operating licensees started using the in-situ leach (ISL) method.

The 1997 MILDOS-AREA update had two principal objectives. The first objective was to update the code's data structures and terminology to meet the needs of the revised Part 20; the second objective was to create an example problem for in-situ leach facilities. These two objectives resulted in the creation of a patch program that updated the 1989 version to the 1997 version of MILDOS-AREA.

In 1998, Argonne is again updating MILDOS-AREA. In previous versions, up to the 1997 update, code lacked user-friendly features. To run the code, a user must first separately develop an input file, which is an ASCII file containing all of the pertinent values that are required by the code. The code was then executed to produce the output file, which contains results of the calculations. The latest version of MILDOS-AREA code includes a user-friendly software interface. This graphical user interface (GUI) is simple and easy to use and allows MILDOS-AREA to run under the Windows operating system. The interface contains sufficient information so that the user clearly understands where to input each parameter needed for the calculations. The GUI follows standard Windows 3.x and Windows 95 structures. The GUI allows the creation, retrieval, and editing of MILDOS-AREA input files. In the various editing windows, the GUI provides information to clearly indicate where each parameter value should be input and what units should be used for each parameter. The GUI allows the results of the MILDOS-AREA calculations (the output file) to be viewed, the results file to be saved, the information from the results to be moved into other software applications, and the results files from previous runs to be retrieved.

The GUI is implemented with standard Windows 3.x and Windows 95 usage of menus, windows, buttons, and other Windows functions. All user actions in the GUI are accessible through keystrokes and keystroke combinations, as well as a pointing device (mouse). The GUI contains an online help system that uses Windows-standard protocols and includes information from the user's manual and other basic operating information.

The 1998 GUI version of MILDOS-AREA computer code runs on a baseline PC, configured with a 486/66 MHz CPU, with 8 MB RAM, that uses the Windows 3.x or Windows 95 operating system.