1. 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

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: ModelDetector typeCapability 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: ModelDetector typeCapability 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: ModelDetector typeCapability Data (discarded) Stride ThermoScientific NaI(Tl) (2 x 2 “). Dose rate Spectrometry 35338 (8.9%) FH40G from APVLIonization chamber Dose rate35338 (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: ModelDetector typeCapability 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: ModelDetector typeCapability Data (discarded) Victoreen 451P Fluke Ionization chamber Dose rate38441 (4 %) Dose rate readings and GPS readings very reliable High throughput Fraction of readings transmitted out of scale No spectrometry

8. Instruments: ModelDetector typeCapability Data (discarded) RadEye B20 from Thermo Scientific Geiger MullerExposure rate Dose rate (calibrated) For calibration Light weight Accuracy (calibrated)

9. Instruments: ModelDetector typeCapability Data (discarded) Niton XLt-GolddSDDElemental composition Selected spots Fast measurement time (60 s) Light weight Relative Accuracy (10 – 20 %)

10. Instruments: ModelDetector typeCapability 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 < 0.00005 Decimal Degrees ~ 5.5 m

13. Strategy followed oGathering background information oMeasurements around the areas (waypoints) oGrid 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(%) 10 - 11461 26756.7 114 - 25024 77122.9 250 - 50011 66010.8 500 - 11405 2834.9 1140 - 104005 0364.7

18. Interpretation of readings Identification of hot spots

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

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

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

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

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

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

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

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

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

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

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

30. Gamma Spectrometry analysis Identification of source of activity

31. 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 oThe mission allowed producing maps of radiological status of most of the areas of interest in the Mounana site, as requested by the counterpart oThe 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