waste technology section, nefw nuclear spectrometry and applications laboratory, napc demonstration...
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Waste Technology Section, NEFW Nuclear Spectrometry and Applications Laboratory , NAPC
Demonstration and review of a Mobile Unit for Site Characterization in Environmental Remediation Projects
23-27 July 2012, Gabon
Scope of the mission:
To gather together experienced professionals in designing, constructing and operating Mobile Laboratory Units for environmental measurements of radionuclides to perform a real case exercise of site characterization in areas contaminated by past activities involving NORM
Instruments:
Model Detector type
Capability Data (discarded)
PGIS 21,Envinet S.A.
NaI(Tl) (3 x 3 “).
Dose rateeU, eTh, KSpectrometry
32929(0)
High throughputReliable dose rate calibration and GPS coordinatesHeavy, but easy to carry
Instruments:
Model Detector type
Capability Data (discarded)
AT6101C,Atomtex
NaI(Tl) (2.5 x 2.5 “).+ Neutron He detector
Dose rateeU, eTh, KSpectrometry
5604(0)
High throughputReliable dose rate calibration and GPS coordinatesHeavy
Instruments:
Model Detector type
Capability Data (discarded)
StrideThermoScientific
NaI(Tl) (2 x 2 “).
Dose rateSpectrometry
35338(8.9%)
FH40G from APVL Ionization chamber
Dose rate 35338(23.8 %)
High throughputReliable dose rate calibration (NaI)Partial loses of GPS coordinates Not so easy to carry Out of calibration readings (Ioniz.Ch)
Instruments:
Model Detector type
Capability Data (discarded)
RS-125,Radiation solutions
NaI(Tl) (2 x 2 “).
Dose rateSpectrometry
1853(0)
Light weight, reliable GPS readingsDose rate readings require long accumulation time (~ 10 seconds)Biased results below 400 nSv/h
Instruments:
Model Detector type
Capability Data (discarded)
Victoreen 451PFluke
Ionization chamber
Dose rate 38441(4 %)
Dose rate readings and GPS readings very reliableHigh throughputFraction of readings transmitted out of scaleNo spectrometry
Instruments:
Model Detector type
Capability Data (discarded)
RadEye B20 from Thermo Scientific
Geiger Muller Exposure rateDose rate (calibrated)
For calibration
Light weightAccuracy (calibrated)
Instruments:
Model Detector type
Capability Data (discarded)
Niton XLt-Goldd SDD Elemental composition
Selected spots
Fast measurement time (60 s)Light weightRelative Accuracy (10 – 20 %)
Instruments:
Model Detector type
Capability Data (discarded)
Gamma Surveyor II,GF-Instruments
BGO (1.3 x 1.3 “).
Dose rateeU, eTh, KSpectrometry
100 % Discarded
Dose rate readings only reliable with long accumulation time (> 20 seconds)Not quantitative results in scan mode (1 s)
Comparison of Dose rate readings
0
1
2
3
4
5
6
7
0 500 1000 1500 2000 2500 3000 3500
1 / PGIS21
1 / Atomtex
1 / RS125
1 / Thermo
Comparison of GPS readings
Deviations < 0.00005 DecimalDegrees~ 5.5 m
Strategy followed
o Gathering background informationo Measurements around the areas (waypoints)o Grid measurements in the areas with hot spots
Hot spot: Dose rate values exceeding 10 x 114 nSv/h
114 nSv/h: Internationally accepted level for public exposure(1 mSv/year)
The site: Original Map
The site: modified map
Eyebird view
Waypoint readings
• 114 165 measurements
• 2 ½ days of measurements
Dose rate(nSv/h)
Number (%)
10 - 114 61 267 56.7
114 - 250 24 771 22.9
250 - 500 11 660 10.8
500 - 1140 5 283 4.9
1140 - 10400 5 036 4.7
Interpretation of readings
Identification of hot spots
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area
Interpolation by Kriging
1) Analysis of variance of data in space
Model definition
Interpolation by Kriging
2) Using the model for the interpolation
Interpolation by Kriging
3) Probability of exceeding a given level
> 300 nSv/h
Gamma Spectrometry analysis
Identification of source of activity
Gamma Spectrometry analysis
Identification of source of activity
214Bi
Pressed Wood
Remediation Site
XRF Spectrometry analysis
Identification of materials based on elemental composition
Participants:
HorstDidier
MarcosRean
Eugene
Roman
Conclusions
o The mission allowed producing maps of radiological status of most of the areas of interest in the Mounana site, as requested by the counterpart
o The use of the Mobile is a cost-effective approach for the assessment of surface dose rate distribution and the identification of radiation sources
Thanks for your attention