NDA SYSTEM RESPONSE MODELING AND ITS APPLICATION
The Portsmouth gaseous diffusion plant (PORTS) is a uranium enrichment facility that was historically used to enrich uranium to levels that range from 2% to greater than 97%. The feed material for PORTS was obtained from the Paducah Gaseous Diffusion Plant (PGDP) that produced uranium in the form of UF6 that was enriched to about 1 to 2%. The enrichment process involves a multistage process by which gaseous UF{sub 6} passed through a diffusion barrier in each stage. The porous diffusion barrier in each stage retards the rate of the diffusion of the heavier {sup 238}U atoms relative to the diffusion of the lighter {sup 235}U atoms. By this process the product stream is slightly enriched by each stage of the process. Each stage consists of a compressor, converter and a motor. There are more than 4000 stages that are linked together with piping of various diameters to form the PORTS cascade. The cascade spans three interconnected buildings and comprises miles of piping, thousands of seals, converters, valves, motors, and compressors. During operation, PORTS process equipment contained UF{sub 6} gas with uranium enrichment that increased in the process stream from the first to the last stage in a known manner. Gaseous UF{sub 6} moving through the PORTS process equipment had potential to form deposits within the process equipment by several mechanisms, including solidification due to incorrect temperature and pressure conditions during the process, inleakage of atmospheric moisture that chemically reacts with UF{sub 6} to form hydrated uranyl fluoride solids, reduction reactions of UF{sub 6} with cascade metals, and UF{sub 6} condensation on the internal equipment surfaces. As a result, the process equipment of the PORTS contains a variable and unknown quantity of uranium with variable enrichment that has been deposited within the equipment during plant operations. The exact chemical form of this uranium is variable, although it is expected that the bulk of the material is of the form of uranyl fluoride that will become hydrated on exposure to moisture in air when the systems are no longer buffered. The deposit geometry and thickness is uncertain and variable. However, a reasonable assessment of the level of material holdup in this equipment is necessary to support decommissioning efforts. The assessment of nuclear material holdup in process equipment is a complex process that requires integration of process knowledge, nondestructive assay (NDA) measurements, and computer modeling to maximize capabilities and minimize uncertainty. The current report is focused on the use of computer modeling and simulation of NDA measurements.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC09-08SR22470
- OSTI ID:
- 974330
- Report Number(s):
- SRNL-TR-2010-00058; TRN: US1002709
- Country of Publication:
- United States
- Language:
- English
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