Cost Sensitivity to Radiological Soil Release Criteria in Decontamination and Decommissioning Projects

The linear no-threshold (LNT) hypothesis and the ALARA (as low as reasonably achievable) principle are fundamental to setting release criteria for Decontamination and Decommissioning (D&D) projects. The LNT model assumes that any radiation dose, no matter how small, increases health risks, such as cancer, in a linear, proportional manner without a safe threshold. This can lead to selection of release criteria that are more stringent than federal requirements, potentially driving up project costs. This research presents a method to quantify the impact of lower release criteria on the relative cost of soil remediation and final status surveys (FSS).

Using Python scripts, a methodology was developed that uses existing radiological characterization data to calculate total contaminated soil volumes and surface areas for a range of release criteria. Unit cost factors for both soil remediation and FSS were then applied to these calculations. The remediation unit costs were based on a previous license termination plan's ALARA analysis and the FSS unit costs were derived using the MARSSIM methodology and available characterization data.

This methodology was tested on two case studies: the Rocky Flats Plant and the former Hematite fuel fabrication facility. The results show a power-function relationship where costs increase significantly as release criteria are lowered. Costs were normalized to a 0.25 mSv/y release criterion and compared with historical estimates identified in a Government Accountability Office report. The Rocky Flats case study demonstrated a more sensitive, inversely proportional cost response to reductions in the release criterion, consistent with previous estimates for the Nevada Test Site. The Hematite facility showed a less sensitive but still significant cost escalation.

These case studies illustrate a clear, direct relationship between project cost and the selected release criterion. The model developed can serve as a valuable tool for stakeholders to scope the relative costs of soil remediation and FSS for future D&D projects.