1. Demonstration and review of a Mobile Unit for Site Characterization in Environmental Remediation Projects
23-27 July 2012, Gabon

2. 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

3. Instruments: Model Detector type Capability Data (discarded) PGIS 21,
Envinet S.A.
NaI(Tl)
(3 x 3 “).
Dose rate
eU, eTh, K
Spectrometry
32929
(0)
High throughput
Reliable dose rate calibration and GPS coordinates
Heavy, but easy to carry

4. Instruments: Model Detector type Capability Data (discarded) AT6101C,
Atomtex
NaI(Tl)
(2.5 x 2.5 “).
+ Neutron He detector
Dose rate
eU, eTh, K
Spectrometry
5604
(0)
High throughput
Reliable dose rate calibration and GPS coordinates
Heavy

5. Instruments: Model Detector type Capability Data (discarded) Stride
ThermoScientific
NaI(Tl)
(2 x 2 “).
Dose rate
Spectrometry
35338
(8.9%)
FH40G from APVL
Ionization chamber
(23.8 %)
High throughput
Reliable dose rate calibration (NaI)
Partial loses of GPS coordinates
Not so easy to carry
Out of calibration readings (Ioniz.Ch)

6. Instruments: Model Detector type Capability Data (discarded) RS-125,
Radiation solutions
NaI(Tl)
(2 x 2 “).
Dose rate
Spectrometry
1853
(0)
Light weight, reliable GPS readings
Dose rate readings require long accumulation time (~ 10 seconds)
Biased results below 400 nSv/h

7. Instruments: Model Detector type Capability Data (discarded)
Victoreen 451P
Fluke
Ionization chamber
Dose rate
38441
(4 %)
Dose rate readings and
GPS readings very reliable
High throughput
Fraction of readings transmitted out of scale
No spectrometry

8. Instruments: Model Detector type Capability Data (discarded)
RadEye B20 from Thermo Scientific
Geiger Muller
Exposure rate
Dose rate (calibrated)
For calibration
Light weight
Accuracy (calibrated)

9. Instruments: Model Detector type Capability Data (discarded)
Niton XLt-Goldd
SDD
Elemental composition
Selected spots
Fast measurement time (60 s)
Light weight
Relative Accuracy (10 – 20 %)

10. Instruments: Model Detector type Capability Data (discarded)
Gamma Surveyor II,
GF-Instruments
BGO
(1.3 x 1.3 “).
Dose rate
eU, eTh, K
Spectrometry
100 % Discarded
Dose rate readings only reliable with long accumulation time (> 20 seconds)
Not quantitative results in scan mode (1 s)

11. Comparison of Dose rate readings

12. Comparison of GPS readings
Deviations
<
Decimal
Degrees
~ 5.5 m

13. Strategy followed Gathering background information
Measurements around the areas (waypoints)
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)

14. The site: Original Map

15. The site: modified map

16. Eyebird view

17. Waypoint readings 114 165 measurements 2 ½ days of measurements
Dose rate
(nSv/h)
Number
(%)
61 267
56.7
24 771
22.9
11 660
10.8
5 283
4.9
5 036
4.7

18. Interpretation of readings
Identification of hot spots

19. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

20. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

21. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

22. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

23. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

24. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

25. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

26. Correlation with the features of the area
Interpolation based on Natural Neighbor
Correlation with the features of the area

27. 1) Analysis of variance of data in space
Interpolation by Kriging
1) Analysis of variance of data in space
 Model definition

28. 2) Using the model for the interpolation
Interpolation by Kriging
2) Using the model for the interpolation

29. 3) Probability of exceeding a given level
Interpolation by Kriging
3) Probability of exceeding a given level
> 300 nSv/h

30. Identification of source of activity
Gamma Spectrometry analysis
Identification of source of activity

31. Identification of source of activity
Gamma Spectrometry analysis
Identification of source of activity
214Bi
Pressed Wood
Remediation Site

32. XRF Spectrometry analysis
Identification of materials based on elemental composition

33. Participants:
Horst
Didier
Marcos
Rean
Eugene
Roman

34. Conclusions
The mission allowed producing maps of radiological status of most of the areas of interest in the Mounana site, as requested by the counterpart
The use of the Mobile is a cost-effective approach for the assessment of surface dose rate distribution and the identification of radiation sources

35. Thanks for your attention