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Abstract: The GEANT4 Monte Carlo code has been used to simulate γ-ray spectra of natural radionuclides collected by a NaI scintillation detector immersed in seawater. The γ-rays emitted from the decay of 40K, and the series of 232Th and 238U, were used to describe the radioactive water source around the NaI crystal. The simulated γ-ray spectra were compared with real data recorded in situ by a newly constructed NaI spectrometer and were found to be in good agreement. The NaI spectrometer was calibrated in the laboratory in a water tank, before its deployment in seawater. Activity concentrations were deduced from the γ-ray spectra and discussed in comparison with results from the literature. [Copyright &y& Elsevier]

Several cross-section measurements of neutron-induced reactions on Ge found in literature, are performed utilizing natGe targets. The production of the same residual nucleus as the measured one might occur as a result of the unavoidable presence of neighboring isotopes in the same target, acting as a contamination. Corrections must be made based on theoretical calculations and models in order to resolve this problem. The accuracy and limits of a methodology for these "theoretical corrections" are investigated in this work using isotopically enriched targets, which can produce very accurate results without the need for such corrections. Experimental cross-section measurements have been made for the 76Ge(n,2n)75Ge, 72Ge(n, α)69mZn and 72Ge(n,p)72Ga reactions, via the activation technique, with the 27Al(n, α)24Na reaction used as reference, employing both a natGe and isotopically enriched Ge targets. The 3H(d,n)4He (D–T) reaction was used for producing the quasi-monoenergetic neutron beam in the 5.5 MV Tandem Accelerator Laboratory of the National Centre for Scientific Research "Demokritos" in Athens, Greece, at an incident deuteron beam energy of 2.9 MeV. Using HPGe detectors, γ -ray spectroscopy was applied to determine the induced γ -ray activity of the residual nuclei. • Cross section measurements with natural Ge targets need to be corrected for contaminations from neighboring isotopes • A methodology is proposed for the correction of the contribution from parasitic channels • The accuracy and limits of the methodology are investigated with two sets of measurements • Enriched and natural Ge targets were employed for cross-section measurements via the activation technique [ABSTRACT FROM AUTHOR]

Abstract Natural radionuclides, present in mining materials, can exhibit elevated values, thus it is of great interest to study their dispersion in mining areas. Radionuclide spatial variations were determined in coastal surface sediments near the mining area of Ierissos Gulf in northern Greece. 226Ra and 235U measured concentrations were compared with the estimations of ERICA Tool, the dispersion patterns were derived and the affected region around the load-out pier area was calculated to be approximately 21 km2. Highlights • 226Ra and 235U spatial distribution indicated elevated values near Stratoni port. • The 226Ra concentrations at Stratoni port were higher than the soil world median. • The applied dispersion model determined the dispersion pattern. • The affected area due to mining activities was estimated approximately 21 km2. [ABSTRACT FROM AUTHOR]

Abstract The intensities of γ -rays from the 196m2Au decay adopted in 1998 and 2007 ENSDF evaluations differ up to 20%. Gold samples were irradiated in intensive neutron fluxes with energies up to 35 MeV to produce the isotopes 196Au in all isomeric states. The intensities of gammas from the radioactive decay of the isomer 196m2Au were measured by means of the nuclear γ -ray spectrometry (HPGe detectors) and compared to the existing adopted data. [ABSTRACT FROM AUTHOR]

A methodology based on γ-spectrometry measurements of untreated coastal water samples is proposed for the direct estimation of coastal residence time of submarine discharged groundwater. The method was applied to a submarine spring at Stoupa Bay covering all seasons. The estimated residence time exhibited an annual mean of 4.6±1.7 d. An additional measurement using the in situ underwater γ-spectrometry technique was performed, in the same site. The in situ method yielded a value of 2.8±0.2 d that was found consistent with the corresponding value derived using the developed lab-based method (3.4±2.0 d) for the same period. [ABSTRACT FROM AUTHOR]

Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of 226 Ra, 235 U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk. [ABSTRACT FROM AUTHOR]

The Full Spectrum Analysis approach was applied to obtain activity concentration estimations for in situ measurements in the marine environment. The ‘standard spectra’ were reproduced using the MCNP-CP code. In order to extract the activity concentrations, χ 2 minimization calculations were performed by implementing the MINUIT code. The method was applied to estimate the activity concentrations for measurements in the marine environment in three different test cases. The estimated activity concentrations were in good agreement with the experimentally derived ones within uncertainties. [ABSTRACT FROM AUTHOR]

Activity concentration measurements were carried out on the seabed, by implementing the underwater detection system KATERINA. The efficiency calibration was performed in the energy range 350–2600 keV, using in situ and laboratory measurements. The efficiency results were reproduced and extended in a broadened range of energies from 150 to 2600 keV, by Monte Carlo simulations, using the MCNP5 code. The concentrations of 40 K, 214 Bi and 208 Tl were determined utilizing the present approach. The results were validated by laboratory measurements. [ABSTRACT FROM AUTHOR]

Abstract: The in-situ underwater gamma-ray spectrometry method is validated by inter-comparison with laboratory method. Deployments of the spectrometer KATERINA on a submarine spring and laboratory measurements of water samples with HPGe detector were performed. Efficiency calibrations, Monte Carlo simulations and the Minimum Detectable Activity (MDA) estimations were realized. MDAs varied from 0.19 to 10.4 (lab) and 0.05 to 0.35 (in-situ) Bq/L, while activity concentrations differed from 7% (for radon progenies) up to 10% (for 40K), between the two methods. [Copyright &y& Elsevier]

Abstract: A new detection system named “KATERINA” is developed and applied for measuring marine radioactivity using NaI(Tl) as a crystal. This apparatus is designed for qualitative and quantitative radionuclide detection in the marine environment with maximum depth of deployment 400m. A detailed study for the enclosure of the system and for the electronics development is performed. The system offers volumetric activities in Bq/m3 using the marine efficiency calibration, which is measured by dilution of three reference sources (99mTc, 137Cs, and 40K) in a special tank. The calibration procedures for energy, energy resolution and efficiency were analyzed with particular attention to the factors that affect the calibration parameters. The underwater detector is tested in the field for acquiring radon daughters (214Pb and 214Bi) in a region where submarine groundwater discharge exists in the coastal zone. [Copyright &y& Elsevier]

Abstract: Sediment samples have been collected in the Butrint area, located in the south-west Albania to determine the radioactivity levels of 40K, 137Cs, 212Bi, 212Pb, 214Bi, 214Pb, 226Ra and 228Ac on the bed of the lagoon and adjacent sea, using direct counting gamma spectroscopy. The concentration of 137Cs and 40K varied from 2.8 to 37.5Bq/kg and from 266 to 675Bq/kg dry weight (dw), respectively (central values). The average concentrations of 238U and 232Th daughter products varied from 8 to 27Bq/kg and from 13 to 40Bq/kgdw, respectively. The measured 235U activity ranged from 0.7 to 2.5Bq/kgdw. Samples of different sedimentary properties, studied for the radioactivity concentration, revealed an inversely proportional relation between grain size and a linear combination of measured specific activities of 226Ra, 232Th (228Ac, 212Bi and 212Pb), 40K and 137Cs. [Copyright &y& Elsevier]

The calibration of an underwater spectrometer, consisting of a CeBr 3 crystal, is performed for sediment sample measurements, via experimental data and Monte Carlo simulations. The system was implemented for activity concentration measurements in marine sediment samples in the laboratory. The results were compared with corresponding high resolution measurements and showed that the system provides accurate results, but relatively high uncertainties. Different measurement geometries are theoretically studied via Monte Carlo simulations in order to improve the system performance for such measurements. • Application of a CeBr 3 crystal for measurements in the laboratory and in the field. • Calibration for sediment samples measurements combining experimental and simulation data. • The measurement geometry is optimized using a Marinelli beaker. • A valid MC model is developed for the efficiency estimation in different geometries. [ABSTRACT FROM AUTHOR]