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Gamma spectrometry in deep sea water
Jose Busto CPPM /
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Anthropogenic Radionuclides
Concentrations of Natural Radionuclides in the sea Radionuclide Half – life Activity ( dpm / l) 40 K yr 87Rb yr 129I yr 238U yr ~3 – 0.2 … ,226Ra, 214Bi, 210Pb … 206Pb 232Th yr ..., 228Ac,212Pb, 208Tl … 208Pb 3H yr 7Be d 14C yr 137Cs, 60Co, 90 Sr, 3H, …. Single Long Lived U and Th Chains Cosmogenic Anthropogenic Radionuclides
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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. => …
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+ - 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 ( -> < g/g in 238U ) - No continuous evaluation of radioactivity
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Towed detector systems
Mapping large area Control time of measurement Gamma spectrometry (NaI)
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Autonomous in situ detectors
Very high statistic time Evolution of radioactivity Gamma spectrometry (NaI, Ge)
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Measure the radioactivity of the water continuously in the ANTARES site
The case of 40K 40Ca + e- + ne 40Ar + b- (89.3 %) 40K ---> e+ + ne ne b+ (0.03 %) EC (10.67 %) (10.7 %) g spectrometry (NaI, Ge) (89.3 %) 40K Cerenkov light (ANTARES) 10.67 % EC 1460 keV 1312 keV b- 40Ca 40Ar
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13.0 ± 0.5 Hz observed => 12 ± 4 Hz expected
40K continuous measurement with ANTARES -2400 m 13.0 ± 0.5 Hz observed => 12 ± 4 Hz expected 40Ca 40K Cerenkov Anti-neutrino b-
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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 )
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226Ra spectrum 226Ra 214Pb 214Pb 214Pb 214Bi 214Bi 214Bi
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40K spectrum 226Ra 214Pb 40 K 214Bi
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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
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A dream ? Gamma spectrometry with Ge detectors 226Ra Ge spectrum
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Not a dream Canberra 4 h operation with a single battery
Existing project in India cost for a continuous Ge 500 m deep
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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 ).
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Radioactivity from Salt
Fraud control
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