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

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