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Historical Site Assessments for Decommissioning Plants
Posted on March 3rd, 2016

Several operating nuclear power plants have come off line in the past two years or have indicated their intent to do so.  The decommissioning schedules for these plants vary, with some making preparation to decommission in the near term while others are being placed into an extended dormant period (SAFESTOR) to allow their decommissioning funds to grow to cover decommissioning costs.  Regardless of the short or long-term decommissioning plans, these sites are performing Historical Site Assessments (HSAs) to ensure that the institutional knowledge of the current workforce is captured for future reference. 

RSCS has been contracted to perform the HSAs for several of the plants planning for 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.  As the plants planning for decommissioning have been in operation for 40-50 years, the records review alone is a significant effort. 

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). Once approved by the NRC, the LTP becomes the guidance document for the entire decommissioning project. The LTP specifies all decommissioning activities, from initial characterization surveys, to D&D activities, to waste disposal and final status surveys to release the site. The HSA is instrumental for developing all initial scoping surveys and deriving the site’s derived concentration guideline levels, or DCGLs for each radionuclide that may be present.

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.

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