Independent Verification Survey of the Clean Coral Storage Pile at the Johnston Atoll Plutonium-Contaminated Soil Remediation Project
The Oak Ridge National Laboratory (ORNL) Environmental Technology Section conducted an independent verification (IV) survey of the clean storage pile at the Johnston Atoll Plutonium Contaminated Soil Remediation Project (JAPCSRP) from January 18-25, 1999. The goal of the JAPCSRP is to restore a 24-acre area that was contaminated with plutonium oxide particles during nuclear testing in the 1960s. The selected remedy was a soil sorting operation that combined radiological measurements and mining processes to identify and sequester plutonium-contaminated soil. The soil sorter operated from about 1990 to 1998. The remaining clean soil is stored on-site for planned beneficial use on Johnston Island. The clean storage pile currently consists of approximately 120,000 m{sup 3} of coral. ORNL conducted the survey according to a Sampling and Analysis Plan, which proposed to provide an IV of the clean pile by collecting a minimum number (99) of samples. The goal was to ascertain with 95% confidence whether 97% of the processed soil is less than or equal to the accepted guideline (500-Bq/kg or 13.5-pCi/g) total transuranic (TRU) activity. In previous IV tasks, ORNL has (1) evaluated and tested the soil sorter system software and hardware and (2) evaluated the quality control (QC) program used at the soil sorter plant. The IV has found that the soil sorter decontamination was effective and significantly reduced plutonium contamination in the soil processed at the JA site. The Field Command Defense Threat Reduction Agency currently plans to re-use soil from the clean pile as a cover to remaining contamination in portions of the radiological control area. Therefore, ORNL was requested to provide an IV. The survey team collected samples from 103 random locations within the top 4 ft of the clean storage pile. The samples were analyzed in the on-site radioanalytical counting laboratory with an American Nuclear Systems (ANS) field instrument used for the detection of low-energy radiation. Nine results exceeded the JA soil screening guideline for distributed contamination of 13.5 pCi/g for total TRUs, ranging from 13.7 to 125.9 pCi/g. Because of these results, the goal of showing with 95% confidence that 97% of the processed soil is less than or equal to 13.5 pCi/g-TRU activity cannot be met. The value of 13.5 pCi/g represents the 88th percentile rather than the 95th percentile in a nonparametric one-sided upper 90% confidence limit. Therefore, at the 95% confidence level, 88% of the clean pile is projected to be below the 13.5-pCi/g goal. The Multi-Agency Radiation Survey and Site Investigation Manual recommends use of a nonparametric statistical ''Sign Test'' to demonstrate compliance with release criteria for TRU. Although this survey was not designed to use the sign test, the data herein would demonstrate that the median (50%) of the clean storage pile is below the l3.5-pCi/g derived concentration guideline level. In other words, with the caveat that additional investigation of elevated concentrations was not performed, the data pass the sign test at the 13.5-pCi/g level. Additionally, the lateral extent of the pile was gridded, and 10% of the grid blocks was scanned with field instruments for the detection of low-energy radiation coupled to ratemeter/scalers to screen for the presence of hot particles. No hot particles were detected in the top 1 cm of the grid blocks surveyed.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 814414
- Report Number(s):
- ORNL/TM-2000/260; TRN: US200317%%219
- Resource Relation:
- Other Information: PBD: 7 Dec 2000
- Country of Publication:
- United States
- Language:
- English
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