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Gamma spectrometry in deep sea water

Gamma spectrometry in deep sea water. Jose Busto CPPM / 9 -11 - 2010. Concentrations of Natural Radionuclides in the sea. Radionuclide Half – life Activity ( dpm / l). 40 K 1.25 10 9 yr 670

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Gamma spectrometry in deep sea water

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  1. Gamma spectrometry in deep sea water Jose Busto CPPM / 9 -11 - 2010

  2. Concentrations of Natural Radionuclides in the sea Radionuclide Half – life Activity ( dpm / l) 40 K 1.25 109 yr 670 87Rb 4.7 1010 yr 64 129I 1.7 107 yr 0.06 238U 4.9 109 yr ~3 – 0.2 … ,226Ra, 214Bi, 210Pb … 206Pb 232Th 1.4 1010yr 0.005 - 0.05 ..., 228Ac,212Pb, 208Tl … 208Pb 3H 12.26 yr 0.036 7Be 53 d 0.05 14C 5570 yr 0.2 - 0.3 137Cs, 60Co, 90 Sr, 3H, …. Single Long Lived U and Th Chains Cosmogenic Anthropogenic Radionuclides

  3. Radioactivity in the marine environment  1950’s -> Water or sea floor measurements • => mineral exploration • => geological mapping • => sediments transport => discharge and dump of radioactive wastes • => radiation damage to optical fiber telephone cables. • => …

  4. Single sample collection of water or sediments ===> Classical Radioanalytical methods • Preconcentration • Separation • Long-term measurements • Alpha spectrometry • Gamma spectrometry • Neutron Activation Analysis • Mass spectrometry + Access to all radionuclide with very high sensibility ( -> < 10-12 g/g in 238U ) - No continuous evaluation of radioactivity

  5. Towed detector systems • Mapping large area • Control time of measurement • Gamma spectrometry (NaI)

  6. Autonomous in situ detectors • Very high statistic time • Evolution of radioactivity • Gamma spectrometry (NaI, Ge)

  7. Measure the radioactivity of the water continuously in the ANTARES site The case of 40K b- 40Ca + e- + ne 40Ar + (89.3 %) 40K ---> e++ ne ne b+ (0.03 %) EC (10.67 %) (10.7 %) (89.3 %) g spectrometry (NaI, Ge) 40K Cerenkov light (ANTARES) 10.67 % EC 1460 keV 1312 keV b- 40Ca 40Ar

  8. 40K continuous measurement with ANTARES -2400 m 13.0 ± 0.5 Hz observed => 12 ± 4 Hz expected 40Ca 40K Cerenkov b- Anti-neutrino

  9. Project to measure gamma activity in ANTARES site NaI g spectrometer in an standard ANTARES glass sphere USB feed HV + MCA 3’ x 3’ NaI cristal 17’ ANTARES glass sphere 3’ PM FIT PC2 data acquisition ( 6W )

  10. 226Ra spectrum 226Ra 214Pb 214Pb 214Pb 214Bi 214Bi 214Bi

  11. 40K spectrum 226Ra 214Pb 40 K 214Bi

  12. Preliminary tests => Autonomy ~ 15 days •  Autonomy increase => suppression of hard disk • Still to do  inner background => Pb shielding (LSM)  efficiency => MC v.s KCl dilute in water

  13. 226Ra Ge spectrum A dream ? Gamma spectrometry with Ge detectors

  14. Nota dream Canberra 4 h operation with a single battery Existing project in India cost for a continuous Ge spectrometer @ 500 m deep

  15. Conclusion • Many measurements of sea radioactivity. • Long period in situ measurements never done (?). •  Installation of a preliminary continuous NaI gamma • spectrometer in the ANTARES site. • Possibility to perform continuous gamma spectrometry with very high energy resolution ( Ge ).

  16. Radioactivity from Salt  Fraud control

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