Gamma spectrometry in deep sea water
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Transcript of Gamma spectrometry in deep sea water
Gamma spectrometry in Gamma spectrometry in deep sea waterdeep sea water
Jose BustoJose BustoCPPM / 9 -11 - 2010CPPM / 9 -11 - 2010
Concentrations of Natural Radionuclides in the sea
Radionuclide Half – life Activity ( dpm / l)
40 K 1.25 109 yr 67087Rb 4.7 1010 yr 64129I 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 0.0367Be 53 d 0.0514C 5570 yr 0.2 - 0.3
137Cs, 60Co, 90 Sr, 3H, ….
Single Long Lived
U and ThChains
Anthropogenic Radionuclides
Cosmogenic
Radioactivity in the marine environment Radioactivity in the marine environment 1950’s1950’s
Water or sea floor measurementsWater or sea floor measurements
=> mineral exploration
=> geological mapping
=> sediments transport
=> discharge and dump of radioactive wastes
=> radiation damage to optical fiber telephone cables.
=> …
Classical Radioanalytical methodsClassical 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 )
Single sample collection of water or sedimentsSingle sample collection of water or sediments
No continuous evaluation of radioactivity
Towed detector systemsTowed detector systems
• Mapping large area
• Control time of measurement
• Gamma spectrometry (NaI)
Autonomous Autonomous in situin situ detectors detectors
• Very high statistic time
• Evolution of radioactivity
• Gamma spectrometry (NaI, Ge)
Measure the radioactivity of the water continuously in the ANTARES site
The case of 40K
40K
40Ar
40Ca
1460 keV
(89.3 %)(10.7 %)
1312 keV
10.67 % EC
spectrometry (NaI, Ge)
Cerenkov light (ANTARES)
40K
40Ca + e + e
40Ar +
e+ e
e
EC
(89.3 %)
(10.67 %)
(0.03 %)
Anti-neutrino
40K continuous measurement with ANTARES
Cerenkov
40K
-2400 m
13.0 ± 0.5 Hz observed => 12 ± 4 Hz expected
40Ca
Project to measure gamma activity in ANTARES site
NaI spectrometer in an standard ANTARES glass sphere
3’ x 3’ NaI cristal
3’ PM
HV + MCAUSB feed
FIT PC2 data acquisition ( 6W )
17’ ANTARES glass sphere
214Bi
214Pb
214Pb
214Bi214Bi
214Pb
226Ra
226Ra spectrum
40K spectrum
226Ra
214Pb
214Bi
40 K
• 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
226Ra Ge spectrum
A dream ?A dream ? Gamma spectrometry with Ge detectorsGamma spectrometry with Ge detectors
NotNot a dream a dream
4 h operation with a single battery
Existing project in India cost for a continuous Ge spectrometer @ 500 m deep
Canberra
Conclusion 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 ).
Radioactivity from Salt
Fraud control