GPS based gamma survey for decommissioning …...GPS gamma survey data Method for gathering soil...
Transcript of GPS based gamma survey for decommissioning …...GPS gamma survey data Method for gathering soil...
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GPS based gamma survey for decommissioning NORM sitesE. Ruedig, PhD, CHP
T. Alecksen
M. Schierman, CHP
24 September 2019
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True distribution of
soil contaminationInvestigation grid
+ =OR
ERG Note: figure after Lively, J. The Art and Power of Data Imaging. ICEM2013.
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GPS gamma survey data➢ Method for gathering soil concentration data for gamma emitting NORM over large areas
Critical assumption: a stable correlation between soil concentrations and gamma count rate
➢ Cost effective compared to traditional soil sampling
➢Survey parameters can be optimized based upon study goals: obtain more quantitative survey data, with a commensurate response on survey cost, or perform a survey that is less quantitative in nature (scoping only – high uncertainties).
➢ Sensitive to all gamma-emitting radionuclides, including NORM, so the set of nuclides that contribute to ambient gamma must be understood at some phase of the project.
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Overview –Ambrosia Lake West Facility
ERGAverage Ra-226 Concentration (Bq g-1)
Colorado
New Mexico
Me
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p < 0.001
Adj R2 = 0.24
Grey bands represent the 95 prediction limits
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Improving gamma survey data quality
Physical parameters:
• Scan more slowly
• Position the detector closer to the ground
• Survey tighter transects
• Use a shield
Detector parameters
• Use newer, digital electronics
• Avoid algorithmic processing of data
Environmental parameters
• Control for ambient radon
• To the detector, radon in the ground is the same as radon in the air!
Grey bands = 8am to 5pmERG
Date
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Results: radium-226/gamma correlation
p < 1E-7
Adj R2 = 0.63
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Mean Ra-226 Concentration (Bq g-1)Mean Ra-226 Concentration (Bq g-1)
p = 0.117
Adj R2 = 0.053
Me
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s-1
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Grey bands represent the 95 prediction limitsGrey bands represent the 95 prediction limits2019 Survey2016 Survey
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2019 Survey 2016 Survey
Note: histograms are log/log plots.Note: color bins in both figures generated using 10 geometric intervals with the same color ramp.
65m 65m
LOG - Normalized gamma count rate
LO
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(Grey) 2019 Survey
(Outlines) 2016 Survey
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The authors wish to gratefully acknowledge:
BHP, for funding this work, and especially BHP’s site staff:Kent Applegate, Theresa Ballaine,
Michaella Gorospe, and Sandra Ross
Our field crew:Tom Bottomly, Jake Halstead,
Patrick Hendrickson, Sam Paterniti
Acknowledgements
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