Historical Site Assessments

Historical Site Assessments for Decommissioning Radiological Sites

RSCS performs Historical Site Assessments (HSAs) for nuclear plants decommissioning. The HSA documents a comprehensive investigation that identifies and evaluates historical information pertaining to events and conditions that may have resulted in contamination during the operating history of the site. Contaminants of interest include both radiological and non-radiological materials that may have impacted systems, structures or components of the plant or environmental media within the site boundary. The information compiled in the HSA differentiates impacted from non-impacted areas of the site.


HSAs involve a thorough review of spill reports, radiological incident files, special survey and operational survey records, records of contamination incidents in compliance with 10 CFR 50.75(g), Radioactive Effluent Release Reports, Annual Radiological Environmental Monitoring Reports and other documents related to radioactive material handling and contamination.  In addition to reviewing records, HSAs involve personnel interviews to capture the historical use of buildings for activities that may have resulted in contamination that may not be documented otherwise.  Long term employees, particularly those employed during plant construction and early operation, are particularly important sources of historical information.  This is because spill reporting and documentation of contamination incidents early on may not have been as complete as they have become more recently. For example, federal regulation 10 CFR 50.75(g), which requires record management of contamination incidents that may have significance during decommissioning, did not exist prior to 1988. Therefore, incidents that occurred prior to 1988 may have been documented but those records may not appear in the 10 CFR 50.75(g) file and may not be easily found. Employee interviews are very time sensitive in that workforce reductions can result in lost opportunities to obtain valuable information on site operations and incidents throughout the decades.

The HSA is the first step in a process described in NUREG -1575, “Multi-Agency Radiation Survey and Site Investigation Manual” (MARSSIM).  The completed HSA is eventually provided to the Nuclear Regulatory Commission (NRC) as a document to support the plant’s License Termination Plan (LTP). The HSA and LTP represent key documents that are needed in order to release a nuclear plant from its NRC license, which is a pre-requisite to sell the property or use it for other purposes. RSCS developed two NRC approved License Termination Plans for the Connecticut Yankee Decommissioning Site and the Yankee Rowe Decommissioning Site.  These LTPs relied upon HSAs that were performed by RSCS and Millennium Services, whom RSCS acquired in 2014.