ABSTRACT
The calibration of an underwater spectrometer, consisting of a CeBr3 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.
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 21â¯km2.
ABSTRACT
The FLUKA code was implemented to simulate pulse-height spectra of a NaI(Tl) detector (excluding its resolution), considering radioactive sources of naturally occurring and artificial radionuclides present in the marine environment. For this purpose, a user-defined routine was developed for the proper simulation of the emitted γ-rays. The results were compared with simulations performed using the MCNP-CP code. The comparison of the recorded counts in the full-energy peaks, for the high intensity (emission probability >15%) emitted γ-rays for each radionuclide, yielded a satisfactory agreement (calculated ratios from 0.93 ± 0.05 to 1.07 ± 0.02) in all the studied cases.
Subject(s)
Radiation Monitoring/methods , Water Pollutants, Radioactive/analysis , Iodides/chemistry , Radioisotopes/analysis , Sodium/chemistry , Spectrometry, Gamma , Thallium/chemistryABSTRACT
A new approach for calibrating an in situ detection system for measurements in marine sediments has been developed. The efficiency calibration was deduced on full spectral range by Monte Carlo simulations (MCNP5 code) considering a close detector-seabed geometry set-up. Moreover, the influence of the detection efficiency with respect to the variations of the sediment geological characteristics was studied through Monte Carlo simulations. The results of the theoretical approach were compared with experimental calculations in two different real test cases, yielding a satisfactory agreement (up to 10% and 20% for sites 1 and 2 respectively) in the energy range from 351 keV to 2614 keV. For the experimental measurements, the in situ detection system KATERINA was deployed both in the seawater and on the seabed in two different marine environments. The experimental determinations of the detection efficiency were performed by utilizing the acquired data of the deployments, along with additional necessary laboratory measurements. The adopted approach and the obtained results are discussed.
Subject(s)
Computer Simulation , Monte Carlo Method , Radiation Monitoring/methods , Geologic Sediments/analysis , Seawater/analysis , Spectrometry, GammaABSTRACT
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.
Subject(s)
Radioisotopes/analysis , Spectrometry, Gamma/methods , Water Pollutants, Radioactive/analysis , Algorithms , Calibration , Computer Simulation , Cyprus , Greece , Humans , Monte Carlo Method , Radiation Monitoring/methods , Seawater/analysisABSTRACT
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
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 (40)K), between the two methods.
Subject(s)
Radiation Monitoring/methods , Spectrometry, Gamma/methods , Water Pollutants, Radioactive/analysis , Calibration , Computer Simulation , Greece , Humans , Limit of Detection , Monte Carlo Method , Radiation Monitoring/instrumentation , Radiation Monitoring/statistics & numerical data , Radioisotopes/analysis , Seawater/analysis , Spectrometry, Gamma/instrumentation , Spectrometry, Gamma/statistics & numerical dataABSTRACT
The 63Ni(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from kT=5-100 keV with uncertainties around 20%. Stellar model calculations for a 25Mâ star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.
ABSTRACT
Monte Carlo simulations were performed using the GEANT4 code for the investigation of gamma-ray absorption in water in different spherical geometries and of the efficiency of a NaI(Tl) detector for different radionuclides in the aquatic environment. In order to test the reliability of these simulations, experimental values of the NaI(Tl) detector efficiency were deduced and seem to be in good agreement with the simulated ones. In addition, using the simulated efficiency, an algorithm was developed to determine the minimum detectable activity in becquerels per cubic meter in situ as a function of energy for typical freshwater and seawater spectra.
Subject(s)
Environmental Monitoring/methods , Gamma Rays , Monte Carlo Method , Radiation Monitoring/methods , Seawater/analysis , Water Pollutants, Radioactive/analysis , Computer Simulation , Environmental Monitoring/instrumentation , Greece , HumansABSTRACT
The GEANT4 Monte Carlo code has been used to simulate gamma-ray spectra of natural radionuclides collected by a NaI scintillation detector immersed in seawater. The gamma-rays emitted from the decay of (40)K, and the series of (232)Th and (238)U, were used to describe the radioactive water source around the NaI crystal. The simulated gamma-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 gamma-ray spectra and discussed in comparison with results from the literature.
Subject(s)
Gamma Rays , Iodates , Radiation Monitoring/methods , Radioisotopes/analysis , Seawater/chemistry , Computer Simulation , Monte Carlo Method , Spectrometry, Gamma , Spectrum AnalysisABSTRACT
The production of alpha particles in the 6Li+28Si reaction was studied at near-barrier energies. Angular distributions were performed at four bombarding energies, namely, 7.5, 9, 11, and 13 MeV. The distributions were characterized by a Gaussian shape, which was integrated in order to obtain alpha-particle cross sections. Our results were compared with previous data of 6Li scattering on various heavier targets and found to exhibit a universal behavior. Present continuum-discretized-coupled-channel calculations support the obtained data. The consequences of the systematic behavior of the alpha-particle production on the unusual behavior of the imaginary potential observed previously in elastic scattering of weakly bound systems is discussed.