Fundamental Concepts and Quantities
Shaheen A. Dewji, Nolan E. Hertel in Advanced Radiation Protection Dosimetry, 2019
Following radioactive decay, the nucleus may be left in an excited energy state—see the discussion on nuclear shell models from Section 2.2.5 and Figure 2.2. When undergoes alpha decay to 210Pb (which is itself unstable), photons are emitted from the nucleus. These photons are referred to as gamma emissions since they originate in the nucleus, whereas X-rays originate in the electron orbital shells. The alpha energies and intensities for 214Po decay are listed in Table 2.7 along with the three most intense photon emissions that accompany the alpha emissions (Hubbell and Seltzer 1995). The listed decay energy was determined from the observed alpha particle energy and conservation of momentum. If the 7834 keV decay energy represents the transition to the ground state of the nucleus, then the difference between the 7034 keV and the 7834 keV decays (~800 keV) should appear as an emitted photon energy (Krane1988; Eisberg and Resnick 1985). Similarly, the difference in the next two decay energies (6736 keV and 7034 keV) is 298 keV, and this photon energy is also observed. Other photon energies represent transitions between various nuclear energy states. Since the gamma emissions are characteristic of the shell structure of the nucleus, each atom will decay with specific energies. These characteristic emission energies are routinely used to identify the radioactive nucleus via gamma spectroscopy.
Reactor-Produced Radionuclides
Frank Helus, Lelio G. Colombetti in Radionuclides Production, 2019
This is generally carried out by gamma spectrometry using either NaI(Tl) or Ge(Li) crystal detectors or by beta ray absorption measurements and beta ray scintillation spectrometry. In a few cases, specific chemical separation of the radionuclide, followed by assay is employed. For example, traces of 24Na impurity present in 42K can be evaluated by NaI(Tl) gamma spectrometry; the 2.754 MeV gamma photopeak of 24Na can be measured to estimate the percentage of the impurity. Traces of 60Co impurity in 58Co can be evaluated by gamma spectrometry using a Ge(Li) detector; the 1.17 MeV gamma photopeak of 60Co can be measured to estimate the percentage of the impurity. Beta ray absorption measurements can be used to determine 32P impurity in 35S. Traces of fission product impurities such as 1311, 103Ru, and 90Sr as well as alpha emitting impurities are estimated in fission produced 99Mo by selective extraction of the bulk of 99Mo after adding molybdate carrier and hold-back carriers of sodium iodide and strontium nitrate. For extraction, molybdenum can be converted to silico molybdate heteropolyacid from acid nitrate solutions and then extracted with butanol.38
Use of Computers in Radiotracer Studies
Lelio G. Colombetti in Principles of Radiopharmacology, 2019
Computers are useful in gamma spectroscopy for several applications. The first application is to digitize and store the spectrum. The computer uses an ADC to digitize the pulses, then the pulses are stored in the computer memory as a spectrum. The spectrum is also written to magnetic disk for later numerical analysis. A computer is particularly useful for analyzing the spectrum of a Ge(Li) detector. The peaks are only about 1.0 keV wide. If the spectrum is recorded between 0 keV and 2000 keV, then if 2000 channels of digitization are recorded, each peak will be only one channel wide. A frequently used spectrum approach is to use 8000 channels of digitization, so that a spectrum taken between 0 keV and 1000 keV will have the peaks about 8 channels wide. Another frequently used calibration scheme is to put the 60 Co peak of 1332 keV in a particular channel, so that the peaks will be 4 to 8 channels wide. Therefore, several thousand channels of data are involved with each spectrum.
Bioaccumulation of natural radio-nuclides in aquatic, riparian and terrestrial animals along Suez-Azzafrana coastline, Egypt: insights from RESRAD-BIOTA
Published in International Journal of Radiation Biology, 2023
Mohamed Hegazy Mohamed Salama, Mohamed Safwat Mohamed Tawfik
Ten samples of sea water and ten samples of sediments were being collected from different 10 sites at the inshore of the Egyptian Suez bay beach till El-Zafarna as being showed in Figure 1. The study survey showed that investigated area (Suez Bay) is located between longitudes 32° 28\ and 32° 35\E and latitudes 29° 53\ and 29° 57\N. The bay is shallow extension of the Gulf of Suez, roughly elliptic in shape, with its major axis in the NE–SW direction. These samples were taken from the beach surface and subsurface (20 cm–1 m) from the same sites, using GIS tool to draw GIS map of the sampling sites, GIS is employed in accordance with the outcome of measures as a unit supported knowledge analysis as will be showed in Figure 1. The 226Ra (238U) series, 232Th series and 40K specific activities were measured using well-calibrated gamma spectrometry based on hyper-pure germanium (HPGe) detectors. The HPGe detector has a relative efficiency of 40% and full width at half maximum of 1.95 keV for 60Co gamma energy line at 1332 keV. The lower limits of detection at 95% confidence level for 226Ra, 232Th and 40K are 0.28, 0.16 and 1.0 Bq/kg, respectively, for 20 h counting.
The enduring legacy of Marie Curie: impacts of radium in 21st century radiological and medical sciences
Published in International Journal of Radiation Biology, 2022
Rebecca Abergel, John Aris, Wesley E. Bolch, Shaheen A. Dewji, Ashley Golden, David A. Hooper, Dmitri Margot, Carly G. Menker, Tatjana Paunesku, Dörthe Schaue, Gayle E. Woloschak
Radon, thoron and actinon gases decay into solid progeny comprised of radionuclides that emit alpha particles. These progenies deliver >95% of the dose received by the lung airway epithelia. As progeny decay, they form 1 nm clusters, termed the ‘unattached fraction’ alongside larger particles (10 nm to >1 nm), termed the ‘attached fraction’. The difference in concentration between radon gas and solid progeny is given by the ‘equilibrium factor’, its value depends on the radon progeny rather than the radon gas. Radon gas is chemically inert but can be absorbed into the pulmonary, arterial and venous blood. Measurement of the radium radionuclide, typically from gamma spectroscopy of the progeny of the 238U and 232Th series (Figure 1), can be used to calculate the activity concentration and dose coefficient models to determine internalized dose. Effective dose from the inhalation of radon is attributed mostly to lung equivalent doses from the deposition in the respiratory airway of solid aerosol particles (Figure 2), which is dependent on the particle size distribution. Physiologically, breathing rate is additionally a core factor in determining the intake and subsequent lung dose.
Radiological risk assessment of natural radionuclides in the marine ecosystem of the northwest Mediterranean Sea
Published in International Journal of Radiation Biology, 2022
Akbar Abbasi, Hesham M. H. Zakaly, Merfat Algethami, Shams H. Abdel-Hafez
The samples of sediments with a mass of 1 kg from 15 sampling coastline sites were collected. The samples were then dried for 24 hours at 100 °C to eliminate the moisture. To ensure that the daughter products of 226Ra and 232Th are in secular equilibrium with their respective parent radionuclides, the samples were placed in a standard Marinelli beaker, sealed after correctly fastening the top, and left for 30 days before counting by gamma spectrometry. The radionuclides were assumed to be in equilibrium, meaning that each daughter's activity was equal to the initial isotopes of the series (Asgharizadeh et al. 2012). The samples were measured using a gamma spectrometer (SILENA, Milano, Italy) measurement system, based on a coaxial P-type shielded High Purity Germanium detector (HPGe) detector with an energy resolution of 1.80 keV FWHM for the 60Co 1332 keV gamma-ray line and an 80% relative photopeak efficiency (Abbasi 2019a). The mean activity of photopeaks of the daughter nuclides 228Ac (338.40, 911.07, and 968.90 keV) and 212Pb (238.63 keV) was used to calculate 232Th activities. Similarly, 226Ra activities were calculated from the activity of its short-lived daughters 214Bi at 609.3 keV and 214Pb at 295.2 and 351.9 keV (Abbasi 2013; Abbasi and Mirekhtiary 2013).
Related Knowledge Centers
- Compton Scattering
- Gamma Ray
- Germanium
- Photoelectric Effect
- Radionuclide
- Optical Spectrometer
- X-Ray
- Multichannel Analyzer
- Scintillation Counter
- Scintillator