Instrument maintenance and management laboratory

The instrument maintenance and management laboratory of the oceanic physics department is responsible for hosting, servicing and managing all equipment used for field deployments and operations. The main field equipment of the laboratory consists of (amongst others):

• SeaBird Electronics SBE911plus CTD unit + 24 & 12 Niskin bottles carousels. The CTD unit is fully equipped with pressure, temperature, conductivity, oxygen, fluorescence and optical sensors.
• SeaBird Electronics SBE19plus portable CTDs
• SeaBird Electronics SBE37 microCATs
• Aanderaa current meters (RCM9, RCM11, Seaguard)
• RDI Workhorse LADCPs and ADCPs
• IXSEA acoustic releasers

The laboratory is also equipped with a Guildline 8410A salinometer for precise salinity measurements and inter-calibration.

The highly experienced engineers and technicians that man the laboratory, provide their services to all other departments of the IO, regarding field operations and instrument deployment in the marine environment.

MARINE ENVIRONMENTAL RADIOACTIVITY LABORATORY (MERL)

The HpGe detection system

A laboratory broad energy Germanium detector is set up at HCMR since 2007 for measuring radioactivity is various marine matrices (water, seawater, sediment, beach sand biota). The detector is calibrated using reference sources for its efficiency and energy resolution along with gamma ray energy. The system provides execution of quantitative analysis (using the software package SPECTRW) of gamma-radiation spectra for low levels of activity of each natural radionuclides (NORM and TENORM), including ^134,137Cs, ⁶⁰Co, ²⁴¹Am, ⁵⁴Mn, ¹³¹I, ¹⁴⁰Ba, ²⁴Na, ⁴⁰K, ⁷Be. The detection system was used in many marine areas for radioprotection, gas monitoring, seawater mass transfer, seabed characterisation in contaminated areas, mapping, sedimentation rate and rainfall.

The in-situ KATERINA II (low resolution)

The Hellenic Centre for Marine Research (HCMR) has developed (since 2004) an autonomous subsea gamma spectrometer KATERINA II for marine applications (like radioprotection, submarine groundwater discharge, submarine volcanos/faults and rainfall studies). KATERINA consists of a detector unit and a power unit shielded by an aluminium and polyester pressure tube. The detector unit is a 3”x3” NaI detection crystal with built in photomultiplier tube, preamplifier, an analog-digital converter, a high voltage controller and electronic modules for autonomous data acquisition and data storage. Qualitatively the radionuclides are characterised from its emission energy and quantitatively from the peak area. The simulation code GEANT4 was used to calculate the marine efficiency of the system and the minimum detectable activity for specific measuring time for all emission energies. The set-up of KATERINA II together with the underwater battery package has been used for various deployments at Mediterranean Sea. The operational depth is 4500m while the current deployments were at depths of 3000m.

The in-situ GeoMAREA (medium resolution)

GeoMAREA consists of a detector unit and a power unit shielded by an aluminium and polyester pressure tube. The detector unit is a 2”x2” CeBr₃ crystal with built in photomultiplier tube, preamplifier, appropriate digital electronics, a high voltage controller and electronic modules for autonomous data acquisition and data storage. A key application of the GeoMAREA system is to support mapping activities and site characterization in areas that potential radioactive leaks may appear. GeoMAREA is an optimized detection system, cost effective with small dimensions and low consumption and it provides assured results in a continuous basis to the operational center. GeoMAREA is characterized by the capability to offer free‐of‐error continuous functionality down to 400 m water depth, it is pluggable with a watertight cabling system for real time data transmission in case of operation at a buoy and it has high efficiency due to the minimum gamma‐ray absorption in the surrounding materials. GeoMAREA is capable of performing measurements for different applications in the marine environment exhibiting the capability of the separating ^134,137Cs isotopes as artificial tracers after a nuclear accident for dating purposes.

Areas of APPLICATION / SERVICES

The area of applications is related to the radioprotection/radioecology and marine studies using radionuclides as tracers in the aquatic systems. A lot of effort is given the last years to use the laboratory also to provide services for industrial applications (oil, cement, phosphate, bauxite and mining). More details are given below:

Radio-tracing applications:

• Seawater movement and identification of water masses (¹³⁷Cs)
• Sedimentation rate and dating (²¹⁰Pb, ¹³⁷Cs, ^228,226Ra)
• Localization of Submarine Groundwater sources (^222,220Rn progenies), esidence time (^224,226Ra) and quantitative estimation of the water flow (radium isotopes)
• Earthquakes and Mud Volcanoes study (Radon emanation).
• Tracing rainfall

Radioprotection/Radioecology:

• ERICA Assessment Tool (NORMs and artificial radionuclides)
• Dating of artificial pollution after an accident (^134,137Cs)