Characterization of Rocky Flats Environmental Technology Site through Paint Sampling and Rapid Gamma Spectroscopy

Scope:

• The work was performed at Rocky Flats Environmental Technology Site (RFETS) in USA.
• The goal was to distinguish between naturally occurring radionuclides and transuranics/uranium which had originated from the site operations.
• A CANBERRA™ team developed a technique for characterizing paint chippings, using in-situ gamma spectroscopy as part of an on-site mobile laboratory.

Key Drivers:

• Meet the criteria for unrestricted release under the Multi-Agency Radiological Site Survey Investigations Manual (MARSSIM).
• Develop a rapid and costbeneficial approach to perform the paint sampling analysis.
• Unrestricted release criteria are regulated by DOE-O-5400.5, which includes limits of 100 dpm/100 cm² for transuranics and 5,000 dpm/100 cm² for uranium.
• It is not possible to differentiate transuranics from uranium using hand-held probes which are typically used. The measurement challenge requires a new approach.

Instruments & Techniques Used:

1. ISOCS™ Spectroscopy System
2. Genie™ 2000 Gamma Spectroscopy Software

CANBERRA Solution:

• Collaboration between “RISS (Remediation, Industrial D&D & Site Services) Characterization” Subject Matter Experts (SMEs) and CANBERRA gamma spectroscopy SMEs.
• Deployment of CANBERRA In Situ Object Counting System (ISOCS) high purity germanium (HPGe) gamma spectroscopy system capabilities in an on-site laboratory.
• Use of MARSSIM gridding methodologies.
• Pre- and post-sampling radiological surveys (i.e., a smear survey and a total surface activity measurement using standard site alpha- and beta-survey instrumentation) were performed at each paint sample location.

Achievements

• Post-sampling methodology to verify that the facility surfaces behind the paint were less than the DOE-O-5400.5 unrestricted release criteria.
• The analysis was able to quantitatively and qualitatively differentiate uranium from transuranics with a two- to four-hour analysis time per sample, and meet the minimum detectable activity (MDA) requirements specified in MARSSIM.
• A batching method was developed which resulted in only four gamma spectroscopy analysis measurements being required, versus 110 separate sample analysis counts.
• This work at RFETS has brought cost savings (see table), schedule acceleration, helped achieve the site closure goals, and provided legally defensible, quality gamma spectroscopy and activity characterization data.

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