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

Anthropogenic Radionuclides 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

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. => …

+ - 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

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

Autonomous in situ 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 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

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-

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 )

226Ra spectrum 226Ra 214Pb 214Pb 214Pb 214Bi 214Bi 214Bi

40K spectrum 226Ra 214Pb 40 K 214Bi

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

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

Not a dream Canberra 4 h operation with a single battery Existing project in India cost for a continuous Ge spectrometer @ 500 m deep

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