1. NAME AND TITLE

PRESTO-II: Code System for Low-Level Waste Environmental Transport and Risk Assessment.

AUXILIARY ROUTINES

PRESTO-PREP: Data preprocessor for PRESTO-II accesses radionuclide data bases to prepare a radionuclide data set.

RADFMT: Converts RADRISK.BCD data file to unformatted records for use by PRESTO-II.

DATA LIBRARY

RADRISK.BCD: 1981 version of dose and risk factors for radionuclides written by CCC-422/RADRISK for use with the DARTAB Calculation in PRESTO-II.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran 66; IBM 360/370. PRESTO-PREP runs on the PDP-10. Informal instructions are provided for VAX/VMS Fortran 77 implementation.

4. NATURE OF PROBLEM SOLVED

The U.S. Environmental Protection Agency is responsible for developing a generally-applicable environmental standard for the disposal of low-level radioactive waste. PRESTO-EPA was developed in 1983 to assist in assessing potential human health impacts from such operations and is under continuing development. The PRESTO-II methodology, which differs from the EPA code in several respects, was developed for general release and application to a wider range of problems than its EPA predecessors.

PRESTO-II evaluates possible health effects from shallow-land and waste-disposal trenches. The model is intended to serve as a non-site-specific screening model for assessing radionuclide transport, ensuing exposure, and health impacts to a static local population for a 1000-year period following the end of disposal operations. Human exposure scenarios considered include normal releases (including leaching and operational spillage), human intrusion, and limited site farming or reclamation. Pathways and processes of transit from the trench to an individual or population include ground-water transport, overland flow, erosion, surface water dilution, suspension, atmospheric transport, deposition, inhalation, external exposure, and ingestion of contaminated beef, milk, crops, and water. Both population doses and individual doses, as well as doses to the intruder and farmer, may be calculated. Cumulative health effects in terms of cancer deaths are calculated for the population over the 1000-year period using a life-table approach developed by EPA [CCC-422/RADRISK]. The DARTAB model is used in modified form to generate human health risk estimates from radionuclide concentrations and intake values.

5. METHOD OF SOLUTION

PRESTO-II tracks radionuclide transport through surface and subsurface pathways and human exposures through external exposure, inhalation, and ingestion with a resolution of 1y. The methodology is mechanistic, and physical transport processes are modeled separately and in detail. PRESTO-II computes infiltration through the trench cap from experimentally determined permeability and hourly precipitation values. Watershed infiltration is determined using a parametric evapotranspiration equation requiring input values for several site variables. A finite element approach is used to compute trench water balance.

6. RESTRICTIONS OR LIMITATIONS

The PRESTO-II model is most appropriately used as a screening model, and site specific codes should be considered in cases where PRESTO-II numerical results fall close to reference values used for decision making. Some release and transport scenarios, such as those necessary to consider major meteorological changes, mining of the trench contents, in-situ combustion of trench wastes, and intrusion and radionuclide transport by burrowing animals or plant roots are not considered in the PRESTO-II model and code.

It should be noted that PRESTO-PREP runs only on the PDP-10.

7. TYPICAL RUNNING TIME

The sample case compiled, linked and executed on the IBM 3033 in less than 1.5 cpu minutes.

8. COMPUTER HARDWARE REQUIREMENTS

PRESTO-II is operable on the IBM 3033. PRESTO-PREP runs on the PDP-10.

9. COMPUTER SOFTWARE REQUIREMENTS

PRESTO-II compiled under OS/VS2 using the IBM VS compiler and language level 66 option.

10. REFERENCES

a. Included in documentation:

D. E. Fields, C. J. Emerson, R. O. Chester, C. A. Little, G. Hiromoto, "PRESTO-II: A Low-Level Waste Environmental Transport and Risk Assessment Code," ORNL-5970 (April 1986).

M. A. Bell, C. J. Emerson, and D. E. Fields, "PRESTO-PREP: A Data Preprocessor for the PRESTO-II Code," ORNL-5981 (July 1984).

J. L. King and J. E. Horwedel, "Modifications to PRESTO-II for VAX/VMS Fortran 77," Informal Memo (August 1987).

b. Background information:

C. L. Begovich, K. F. Eckerman, E. C. Schlatter, S. Y. Ohr, R. O. Chester, "DARTAB, A Program to Combine Airborne Radionuclide Environmental Exposure Data with Dosimetric and Health Effects Data to Generate Tabulations of Predicted Health Impacts," ORNL-5692 (August 1981).

D. E. Dunning, Jr., R. W. Leggett, M. G. Yalcintas, "A Combined Methodology for Estimating Dose Rates and Health Effects from Exposure to Radioactive Pollutants," ORNL/TM-7105 (December 1980).

11. CONTENTS OF CODE PACKAGE

Included are the documents in 10.a. and a DS/HD 5.25 (1.2MB) DOS diskette which contains the source codes and data library plus output from the sample problem.

12. DATE OF ABSTRACT

June 1987; November 1987.