Çelik, Necati

True coincidence summing (TCS) effects in gamma-ray spectrometry introduce significant systematic uncertainties in activity determinations, particularly for radionuclides with complex decay schemes such as 214Bi. This study presents a comprehensive Monte Carlo investigation of TCS correction factors (CFs) for seven major gamma-ray lines of 214Bi. The primary contribution of this study is the systematic decoupling of detector geometry effects: nine distinct HPGe detector configurations were simulated with varying crystal dimensions, dead layers, and hole geometries, followed by an isolated analysis of crystal radius versus crystal length contributions for both point and extended source geometries. The decay scheme of 214Bi was meticulously modeled using Nucleide 2000 data, incorporating all beta branches, gamma transitions, internal conversion coefficients, and cascade probabilities to ensure high-fidelity representation of the decay scheme. Results demonstrate that crystal radius exerts a substantially stronger influence on TCS CFs than crystal length, with point source values at 609.3 keV increasing by 18.2% across the radius range of 2.1–4.5 cm, compared to only 3.7% variation across the length range of 3–11 cm. Extended source geometries reduce TCS CFs by 5%–11% compared to point sources across all configurations, highlighting the mitigating effect of distributed sources. Energy-dependent behavior is also evident: the 609.3 keV line exhibits strong summing-in (CF > 1.3 for large detectors), while the 1377.7 keV line shows dominant summing-out (CF < 0.86). These findings provide gamma-ray spectrometrists with insight into the relative importance of detector dimensions for TCS effects, suggesting that crystal radius is the primary geometric parameter influencing coincidence summing corrections. The observed trends illustrate how TCS corrections vary with detector dimensions, offering spectrometrists a basis for understanding the relative sensitivity of these corrections to different geometric parameters.

Düzgün, İbrahim; Çelik, Necati; Kaya, Selim

The increasing use of ionizing radiation in medical, industrial, and nuclear applications necessitates the development of advanced and environmentally friendly shielding materials. In this study, the gamma-ray shielding performance of BaO-modified magnesium borophosphate glasses with compositions xBaO–30MgO–10P2O5–(50−x)B2O3–10Na2O (x = 0–35 mol%) was theoretically investigated. The radiation attenuation properties were evaluated over a wide photon energy range (59.54–2000 keV) using the WinXCOM database and Monte Carlo simulations based on the EGS4 code. Key shielding parameters, including mass attenuation coefficient (μ/ρ), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), radiation protection efficiency (RPE), and gamma-ray kerma coefficients, were determined. The results indicate that increasing BaO content enhances the attenuation capability of the glass system, particularly in the low and medium photon energy regions, due to increased density and effective atomic number. A good agreement between WinXCOM and EGS4 results confirms the reliability of the applied theoretical approaches. These findings suggest that BaO-modified magnesium borophosphate glasses are promising candidates for radiation shielding applications.

Doğruer, Musa; Kaya, Selim

The gamma-ray attenuation behavior of europium (Eu)-doped Bi-2223 ceramic superconductors has been investigated in detail in this work in the photon energy range of 59.54 to 1332 keV. The WinXcom database was used to rigorously estimate the mass attenuation coefficients (μ/ρ), which are the main quantifiers of the probability of photon–matter interaction. Stochastic modeling based on the EGS4 Monte Carlo transport technique was then used to confirm the results. Key shielding metrics such as the mean free path (MFP), radiation protection efficiency (RPE), half-value layer (HVL), and gamma-ray kerma coefficients (kγ) are derived from these coefficients and offer information about the material’s inherent ability to dissipate or attenuate incident photon flux. Additionally, the effective atomic number (Zeff) was established to elucidate the role of compositional heterogeneity and atomic cross-section weighting in regulating photon absorption and scattering probabilities. Concurrently, the macroscopic fast neutron removal cross-sections (ΣR) were computed to measure the dual shielding capacity of the ceramics being studied against electromagnetic radiation and neutrons. The findings showed that although Eu doping led to a minor increase in the effective atomic number and μ/ρ values at lower photon energy, it also resulted in greater HVL and MFP values, particularly at higher energies. The total shielding performance decreases due to the decrease in bulk density, even though the addition of Eu results in better mass attenuation coefficients. The μ/ρ values of Eu-doped Bi-2223 ceramics exhibit high agreement and increase from 2.753 to 3.212 cm2 g−1 at 59.54 keV with increasing Eu content. These values were produced using EGS4 simulations and verified using WinXCOM in the 59.54–1332 keV energy range. This suggests that europium’s higher atomic number enhances photon absorption at lower energies. The study also demonstrates that the Eu-0 sample has the strongest neutron shielding capabilities and the highest radiation protection efficiency (RPE).