Alpha Dose Research Articles

Investigation of radon and thoron exhalation rates in soils: Manali-Leh Highway region of Himalayas

This study analyses the natural radionuclides concentration (226Ra and 232Th) along with the radon and thoron exhalation rates in 50 soil samples collected from the Manali-Leh Highway region of the Himalayas. The specific activity of 226Ra and 232Th radionuclides was determined using a NaI(Tl) detector, revealing that the concentration values of these radionuclides are lower than the global average. The radon and thoron exhalation rates in the soil samples were measured utilizing a SMART RnDuo detector. The radon mass exhalation rates range from 6 to 87 mBq kg−1 h−1, with average values of 25 mBq kg−1 h−1. The thoron surface exhalation rates vary from 110 to 757 Bq m−2 h−1, with a mean value of 385 Bq m−2 h−1. Additionally, the emanation coefficient and alpha dose equivalent for radon were calculated and the correlation between parent and daughter radionuclides was also explored.

A Comprehensive Review of Diffusing Alpha-Emitters Radiation Therapy (DaRT): From Dosimetry to Its Biological Effectiveness

Diffusing alpha-emitters radiation therapy (DaRT) represents a groundbreaking development in cancer therapy, offering a solution to the limitations of conventional radiation therapy. By deploying <sup>224</sup>Ra embedded seeds, DaRT achieves targeted delivery of high-dose alpha particles directly to tumor sites, showing considerable efficacy in tumor control and minimal damage to adjacent healthy tissues. This comprehensive review analyzes the published literature regarding mechanisms, seed production, dose calculation, measurement, and biological experiments related to DaRT. It includes in-depth discussions on mathematical models, Monte Carlo simulations for dose distribution, real-time <i>in vivo</i> dosimetry developments, and biological experiments both in vitro and <i>in vivo</i>. Clinical trial outcomes are also examined to evaluate the therapy’s effectiveness in various cancer types. DaRT utilizes <sup>224</sup>Ra-labeled seeds, using the decay chain of <sup>224</sup>Ra to deliver alpha particles effectively within a tumor. Several asymptotic diffusion-leakage models were developed to calculate the alpha dose distribution of DaRT. <i>In vivo</i> dosimetry techniques have been developed for real-time monitoring. Biological experiments demonstrated the cytotoxic effects of DaRT across various cancer cells, with varying radiosensitivity. Additionally, the enhanced effects of combined therapy with chemotherapy and immunotherapy were suggested by many <i>in vivo</i> studies. Clinical trials have shown high complete response rate in squamous cell carcinoma, with minimal side effects, suggesting DaRT’s feasibility and safety. DaRT emerges as a highly localized cancer treatment method with minimal side effects compared to traditional radiation therapy. It directly ablates tumors and potentially enhances immune responses, indicating a significant advance in cancer therapy. Future research and ongoing clinical trials will further elucidate its efficacy across different cancer types and in combination with other treatments.

Thermoluminescence and optically stimulated luminescence studies of Gypsum for retrospective dosimetry

This study examines the use of gypsum for radiation dosimetry using Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) techniques. It is observed that gypsum preserves the information of radiation dose despite the loss of water upon heating in a laboratory. Deconvolution of the thermoluminescence glow curve suggests thermoluminescence glow peaks at 125, 150, 280, 320, and 440 °C. The glow peak at 440 °C has a minimum detectable dose of 200 mGy, and it bleaches to approximately 50% with 300 min of daylight exposure. The Blue Light Stimulated Luminescence (BLSL) comprises a slow component and is correlated to 255 °C TL glow peak. The alpha efficiency of luminescence production per unit Gy of alpha dose with respect to the beta dose for the TL glow peaks at 440 °C is calculated at 0.18 ± 0.01. For BLSL, the value is calculated at 0.15 ± 0.01. A measurement protocol for the use of gypsum for retrospective dosimetry is also presented.

A finite volume approach to dosimetric calculations in diffusing alpha-emitters radiation therapy

Objective.In diffusing alpha-emitters radiation therapy ('Alpha DaRT'), the diffusion-leakage (DL) model is used to determine the spatial distributions of the emitters and the corresponding alpha dose, critical for a successful treatment. This work first introduces a finite volume (FV) approach to develop numerical schemes to simulate the DL model in one, two and three dimensions then presents how variations over realistic ranges of the DL model parameters related to desorption, diffusion and leakage processes affect the alpha dose distribution and the position of the clinically significant alpha particle10Gy isodose. This work also presents the effects of three modeling approximations: two source geometry approximations (solid cylinder instead of hollow, pixelized cross section instead of circular), and one dosimetric approximation (single-source dose superposition instead of multiple-sources direct dose calculation).Approach.The introduced FV approach was used to obtain spatial distributions of the emitters, from which the corresponding alpha dose distributions were calculated under the assumption of a local deposition of the alpha particles' energies. Variation ranges of the DL model parameters were based on previously published data. For each modeling approximation studied, the error and relative error on the alpha dose distribution were calculated and the displacement of the10Gy isodose was evaluated.Main results.Over realistic ranges, the desorption probabilities, diffusion lengths, and leakage probabilities affect the position of the alpha particle10Gy isodose by∼0.1mm,∼1.5mm and∼0.5mm, respectively. The three modeling approximations studied have a negligible effect on the alpha particle10Gy isodose position, with displacements⩽0.01mm.Significance.This work quantitatively evaluates the relative importance of different parameters and approximations in Alpha-DaRT alpha dose calculations based on their impact not only on the dose variation at a given distance from the source but also on the displacement of clinically significant isodoses.

Incidence risk of hepatobiliary malignant neoplasms in the cohort of workers chronically exposed to ionizing radiation

The increased risk of liver malignancies was found in workers of the first Russian nuclear production facility, Mayak Production Association, who had been chronically exposed to gamma rays externally and to alpha particles internally due to plutonium inhalation. In the present study, we updated the radiogenic risk estimates of the hepatobiliary malignancies using the extended follow-up period (1948–2018) of the Mayak worker cohort and the improved «Mayak worker dosimetry system–2013». The cohort comprised 22,377 workers hired at the Mayak PA between 1948 and 1982. The analysis considered 62 liver malignancies (32 hepatocellular carcinomas, 13 intrahepatic cholangiocarcinomas, 16 angiosarcomas, and 1 anaplastic cancer) and 33 gallbladder adenocarcinomas. The analysis proved the positive significant association of the liver malignancy risk (the total of histological types, hepatocellular carcinoma) with the liver absorbed alpha dose from internal exposure. The excess relative risk per Gy (95% confidence interval) of alpha dose (the linear model) was 7.56 (3.44; 17.63) for the total of histological types and 3.85 (0.95; 13.30) for hepatocellular carcinoma. Indications of non-linearity were observed in the dose–response for internal exposure to alpha radiation. No impact of external gamma-ray exposure on the liver malignancy incidence was found. In the study cohort, the number of angiosarcomas among various types of liver malignancies was very high (25.8%), and most of these tumors (73.3%) were registered in individuals internally exposed to alpha radiation at doses ranging between 6.0 and 21.0 Gy. No association with chronic occupational radiation exposure was observed for the incidence of gallbladder malignancies.

Physico-chemical, technological and radiological characteristics of kaolinized granite from northwestern Serbia

In the ceramic industry, the quality of the final ceramic tile as well as the possibility of its use depends on the quality and characteristics of the starting raw materials. One of the potential raw materials that can be used in the production of ceramic tiles is kaolinized granite, and it is necessary to examine its characteristics. In this research, the kaolinized granite of the Jadar block, northwestern Serbia, from the Beli Majdan surface mine, Jadranska Lešnica, was examined. Chemical analysis, X-ray diffraction analysis (XRD), and differential thermal analysis (DTA) were carried out. Ignition tests of the prepared composites were also conducted at three selected temperatures (1000, 1100, and 1250 °C), where total linear shrinkage and water absorption were determined. The activity concentrations of natural radionuclides and the artificial radionuclide 137Cs were determined using the gamma spectrometry method, and then the radiation risk for the external exposure of workers when working with this raw material was assessed. For the samples with the highest content of 226Ra, radon exhalation measurements were performed with the RAD7 device, and the values of the radon emanation coefficient were determined, as well as the values of alpha dose equivalents, which quantified the potential internal exposure of workers. The results of the chemical analysis showed that the content of Al2O3 in the examined composites ranged from 19.11 to 21.00%, and the content of Fe2O3 from 1.53 to 1.72%. Additionally, the K2O content in the tested composites ranges from 4.01 to 5.46%, which indicates the presence of K-feldspar and muscovite, and the Na2O content from 1.82 to 2.61%. Based on XRD analysis, it was established that the mineral composition of kaolinized granite includes quartz, feldspar, mica, calcite/dolomite, and kaolinite minerals. DTA analysis indicates the occurrence of minor endothermic processes at 488.05 °C and 558.12 °C, as well as an exothermic process at 980.8 °C. The color of the ignition is brick red to dark brown red. A trend of increasing linear shrinkage and decreasing water absorption with increasing ignition temperature was observed with the normal appearance of the samples. The average activity concentration of natural radionuclides are around and below the average values for building materials, expect for 40K. The values for 137Cs are below the values measured in soil. Annual effective doses estimated for external exposure are below 1 mSv y−1, which indicates that there is no increased radiation risk when working with this raw material. The values of the radon mass exhalation rate are in the range of 61–113 mBq kg−1 h−1, and the values of the radon emanation coefficient are 6.3–8.4%. The average value of the alpha dose equivalent is 1mSvy−1, which indicates a potential exposure to radon below 100 Bq m−3. Based on the obtained results, it can be concluded that kaolinized granite is a high-quality and radiologically safe raw material for making ceramic composites in the production of ceramic tiles. It has all the necessary characteristics to partially or completely replace feldspar in ceramic composites.

Effect of alpha irradiation on the saturation characteristics of fine-grained quartz OSL

A negative relationship has been reported for the characteristic saturation dose (D0) of the quartz optically stimulated luminescence (OSL) signal and the quartz grain size, of which the mechanism is still not understood. Here, the natural coarse-grained quartz samples (63–90 μm, 90–125 μm) are artificially ground into fine grains and the effect of alpha irradiation on the D0 values of the ground fine grains is investigated. The ground fine grains (4–11, 11–45, 45–63 μm) have similar D0 values as the coarse grains. Laboratory alpha irradiation is administered on the artificial 4–11 μm quartz fraction. The D0 shows an increasing trend with the amount of alpha irradiation; meanwhile, the proportion of the fast OSL component decreases and the proportions of the medium and slow components increase with alpha irradiation. The higher D0 after alpha irradiation may be a result of the higher proportion of electron traps related to the medium component. However, the increasing trend of D0 stops when the alpha dose reaches a certain amount, and the degree of D0 increase induced by alpha irradiation cannot fully account for the much higher D0 values of the fine quartz grains in nature.

Connecting visual metamictization to radiation damage to expand applications of zircon (U-Th)/He thermochronometry

Zircon (U-Th)/He (ZHe) thermochronometry quantifies the timing and tempo of low-temperature processes and is used to deconvolve tectonic and erosional histories. Accumulation and annealing of radiation damage impacts He diffusion in zircon and resulting ZHe dates. Resolving complex histories requires building relationships between ZHe date, effective U (eU), and radiation damage in grains sharing a common thermal history. Prior work demonstrated that purposefully selecting grains with a spectrum of visual metamictization yields a broad range of intrasample eU values (Ault et al., 2018), but it remained unclear if visual metamictization tracks effective radiation damage. Here we evaluate relationships between visual metamictization, effective damage calculated from Raman spectroscopy, and ZHe dates from a new suite of grains from some of the same Precambrian samples investigated in Ault et al. (2018) and Phanerozoic detrital grains from Armstrong et al. (2022). New ZHe analyses (n = 21) confirm increasing visual metamictization corresponds with increasing eU concentration and dates fall along previously reported ZHe date-eU trends for each sample, despite grain selection by different analysts in different sessions. Raman-based alpha dose calculations from multiple spot analyses from transects across the surface and interior of each grain (n = 480 total analyses) range from 3.19 × 1016 to 1.52 × 1019 α/g across the whole dataset. Alpha dose increases in samples characterized by a clear increase in visual metamictization from different types of ZHe date-eU patterns, supporting that visual metamictization reflects effective radiation damage in these samples. Complexities in visual metamictization-damage trends are due to damage zonation observed in cathodoluminescence, comparative internal and external spot analyses, and 2-D Raman maps, as well as limited spread in intrasample visual metamictization and user grain selection bias. Overall, visual metamictization provides a qualitative estimate of effective damage and should be leveraged when selecting grains for traditional ZHe analyses to build ZHe date-eU-damage patterns.

Geochronological and geochemical effects of zircon chemical abrasion: insights from single-crystal stepwise dissolution experiments

Abstract. Chemical abrasion in hydrofluoric acid (HF) is routinely applied to zircon grains prior to U–Pb dating by isotope dilution thermal ionization mass spectrometry (ID-TIMS) to remove radiation-damaged portions of grains affected by Pb loss. Still, many chemically abraded datasets exhibit evidence of residual Pb loss. Here we test how the temperature and duration of chemical abrasion affect zircon U–Pb and trace element systematics in a series of 4 h, single-crystal stepwise dissolution experiments at 180 and 210 ∘C. Microtextural data for the zircon samples studied are presented in a companion paper by McKanna et al. (2023). We find that stepwise dissolution at 210 ∘C is more effective at eliminating material affected by open-system behavior and enriched in U, common Pb (Pbc), and light rare earth elements (LREEs); reduces the presence of leaching-induced artifacts that manifest as reverse discordance; and produces more consistent and concordant results in zircon from the three rocks studied. We estimate that stepwise dissolution in three 4 h steps is roughly equivalent to a single ∼ 8 h leaching step due to the insulating properties of the PTFE sleeve in the Parr pressure dissolution vessel, whereas traditionally labs utilize a single 12 h leaching step. We conclude that a single 8 h leaching step at 210 ∘C should remove Pb loss effects in the majority of zircon and that this can be used as an effective approach for routine analysis. Further, we calculate time-integrated alpha doses for leachates and residues from measured radionuclide concentrations to investigate (1) the alpha dose of the material dissolved under the two leaching conditions and (2) the apparent minimum alpha dose required for Pb loss susceptibility: ≥ 6×1017 α g−1.

Using femtosecond laser pulses to explore the nonlinear optical properties of a CR-39 polymer after being exposed to alpha particles

The effect of alpha particle radiation on nonlinear optical properties of poly(allyl diglycol carbonate) (CR-39) polymer has been investigated using the Z-scan technique. CR-39 polymers were exposed to alpha particles at different doses: 23.7 and 47.5 Gy. Alpha particles cause significant optical and chemical changes in the polymer CR-39. Data from UV-visible spectrometers revealed that when alpha particle doses increased, the absorption edge of polymer redshifted and the energy band gap decreased. Fourier transform infrared absorption spectra of alpha irradiation samples show a change in intensity and bond breakage in the chemical groups constituting the CR-39 polymer compared to the pristine one. With 100 fs laser pulses and 80 MHz repetition rate, the nonlinear absorption coefficient and nonlinear refractive index are measured for a pristine and irradiated polymer with different alpha doses at different excitation wavelengths and laser peak power. The samples displayed a negative nonlinear refractive index and reverse saturable absorption behavior with three photons absorption. The results reveal that the nonlinear optical properties of CR-39 were enhanced by alpha particle radiation.

Immunohistochemical Analysis of Lung Adenocarcinoma in Russian Mayak Nuclear Workers

Specimens of lung adenocarcinoma (AdCa) from Russian nuclear workers (n = 54) exposed to alpha particles and gamma rays and from individuals non-exposed to radiation (n = 21) were examined using immunohistochemistry. Estimated significant associations with alpha dose were negative for Ki-67 and collagen IV in AdCa. Associations with gamma-ray dose were negative for tissue inhibitor of matrix metalloproteinase 2 and caspase 3 and positive for matrix metalloproteinase 2 and leukemia inhibiting factor in AdCa. The findings provide some evidence supporting alterations in apoptosis, cell proliferation and extracellular matrix in lung tissues affected by chronic radiation exposure that can contribute to radiogenic cancerogenesis.

Radiolytic Evaluation of 3,4,3-LI(1,2-HOPO) in Aqueous Solutions

The octadentate hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) (abbreviated as HOPO) has been identified as a promising candidate for both chelation and f-element separation technologies, two applications that require optimal performance in radiation environments. However, the radiation robustness of HOPO is currently unknown. Here, we employ a combination of time-resolved (electron pulse) and steady-state (alpha self-radiolysis) irradiation techniques to elucidate the basic chemistry of HOPO and its f-element complexes in aqueous radiation environments. Chemical kinetics were measured for the reaction of HOPO and its Nd(III) ion complex ([NdIII(HOPO)]-) with key aqueous radiation-induced radical transients (eaq-, H• atom, and •OH and NO3• radicals). The reaction of HOPO with the eaq- is believed to proceed via reduction of the hydroxypyridinone moiety, while transient adduct spectra indicate that reactions with the H• atom and •OH and NO3• radicals proceeded by addition to HOPO's hydroxypyridinone rings, potentially allowing for the generation of an extensive suite of addition products. Complementary steady-state 241Am(III)-HOPO complex ([241AmIII(HOPO)]-) irradiations showed the gradual release of 241Am(III) ions with increasing alpha dose up to 100 kGy, although complete ligand destruction was not observed.

Alpha dose modeling in diffusing alpha-emitters radiation therapy-Part I: single-seed calculations in one and two dimensions.

Diffusing alpha-emitters Radiation Therapy ("DaRT") is a new method, presently in clinical trials, which allows treating solid tumors by alpha particles. DaRT relies on interstitial seeds carrying μCi-level 224 Ra activity below their surface, which release a chain of short-lived alpha emitters that spread throughout the tumor volume primarily by diffusion. Alpha dose calculations in DaRT are based on describing the transport of alpha emitting atoms, requiring new modelingtechniques. A previous study introduced a simplified framework, the "Diffusion-Leakage (DL) model", for DaRT alpha dose calculations, and employed it to a point source, as a basic building block of arbitrary configurations of line sources. The aim of this work, which is divided into two parts, is to extend the model to realistic seed geometries (in Part I), and to employ single-seed calculations to study the properties of DaRT seed lattices (Part II). Such calculations can serve as a pragmatic guide for treatment planning in future clinicaltrials. We derive a closed-form asymptotic solution for an infinitely long cylindrical source, and extend it to an approximate time-dependent expression that assumes a uniform temporal profile at all radial distances from the source. We then develop a finite-element one-dimensional numerical scheme for a complete time-dependent solution of this geometry and validate it against the closed-form expressions. Finally, we discuss a two-dimensional axisymmetric scheme for a complete time-dependent solution for a seed of finite diameter and length. Different solutions are compared over the relevant parameter space, providing guidelines on their usability and limitations. We show that approximating the seed as a finite line source comprised of point-like segments significantly underestimates the correct alpha dose, as predicted by the full two-dimensional calculation. The time-dependent one-dimensional solution is shown to coincide to sub-percent-level with the two-dimensional calculation in the seed midplane, and maintains an accuracy of a few percent up to ∼2mm from the seed edge. For actual treatment plans, the full two-dimensional solution should be used to generate dose lookup tables, similarly to the TG-43 format employed in conventional brachytherapy. Given the accuracy of the one-dimensional solution up to ∼2mm from the seed edge it can be used for efficient parametric studies of DaRT seedlattices.

Alpha dose modeling in diffusing alpha-emitters radiation therapy. Part II: Lattice studies.

Diffusing alpha-emitters radiation therapy ("DaRT") is a new method, presently in clinical trials, which allows treating solid tumors by alpha particles. DaRT relies on interstitial seeds carrying μCi-level 224 Ra activity on their surface, which release a chain of short-lived alpha emitters that spread throughout the tumor volume primarily by diffusion. Alpha dose calculations in DaRT are based on describing the transport of alpha emitting atoms, requiring new modelingtechniques. A previous study introduced a simplified framework, the "diffusion-leakage (DL) model," for DaRT alpha dose calculations, and employed it to a point source, as a basic building block of arbitrary configurations of line sources. The aim of this work, which is divided into two parts, is to extend the model to realistic seed geometries (in Part I), and to employ single-seed calculations to study the properties of DaRT seed lattices (Part II). Such calculations can serve as a pragmatic guide for treatment planning in future clinicaltrials. We employ the superposition of single-seed solutions, developed in Part I, to study the alpha dose in DaRT seed lattices and investigate the sensitivity of the required seed activity and spacing to changes in the DL model parameters and to seed placementerrors. We show that the rapid fall-off of the dose, which guarantees sparing healthy tissue already 2-3 mm away from the tumor, strongly favors a hexagonal, rather than square, seed placement pattern. Realistic variations in the seed manufacturing parameters (224 Ra activity and emission rate of its daughters) are shown to have a negligible effect on the required lattice spacing. On the other hand, tumor parameters (i.e., diffusion lengths and 212 Pb leakage probability), as well as seed placement errors, have a significanteffect. In most cases, hexagonal lattice spacing on the scale of ∼3.5-4.5 mm using seeds carrying a few μCi/cm 224 Ra will enable overcoming realistic uncertainties in measured tumor environment parameters, as well as seed placement errors, and result in therapeutically relevant alpha dose levels.

Proton beam secondary depth-dose calculation with a secondary propagation model

PurposeThis study aimed to construct a proton beam secondary depth-dose calculation model to improve the depth-dose accuracy in proton therapy. MethodsThe secondary dose contributed by secondary particles was investigated in this study. A secondary propagation model (SPM) was constructed to calculate the absolute secondary depth-dose. The transport of secondary particles was considered by introducing a dose propagation function. An approximated linear formula of the propagation function was applied, replacing an accurate but complex Bragg curve function to simplify the calculation process. The primary depth-dose was also calculated using a straight-track approximation model, and the total calculated result (primary plus secondary) was evaluated by gamma analysis referring to the Geant4 simulation result. ResultsProton beams with initial energies of 50, 100, 150, and 200 MeV were calculated and verified. The inelastic secondary proton dose and elastic recoiled proton dose had a similar trend and were close to the simulation result. The inelastic alpha dose deviated between the calculation and simulation at the entrance of the primary beam and decreased along the depth. Under the given gamma tolerance (2% max/1 mm), the calculated and simulated total doses showed an acceptable gamma index below one in the entire beam range. ConclusionThe secondary propagation model improved the depth-dose distribution accuracy. The SPM combined with a primary calculation model will help make more accurate treatment plan calculations.

Incidence risks for subtypes of heart diseases in a Russian cohort of Mayak Production Association nuclear workers.

Heart diseases are one of the main causes of death. The incidence risks were assessed for various types of heart diseases (HDs) in a cohort of Russian nuclear workers of the Mayak Production Association (PA) who had been chronically occupationally exposed to external gamma and/ or internal alpha radiation. The study cohort included all workers (22,377 individuals) who had been hired at the Mayak PA during 1948-1982 and followed up until 31 December 2018. The mean gamma-absorbed dose to the liver (standard deviation) was 0.43 (0.63) Gy, and the mean alpha-absorbed dose to the liver was 0.25 (1.19) Gy. Excess relative risk (ERR) per unit liver-absorbed dose (Gy) was calculated based on maximum likelihood. At the end of the follow-up, 559 chronic rheumatic heart disease (CRHD), 7722 ischemic heart disease (IHD) [including 2185 acute myocardial infarction (AMI) and 3976 angina pectoris (AP)], 4939 heart failure (HF), and 3689 cardiac arrhythmia and conduction disorder (CACD) cases were verified in the study cohort. Linear model fits of the gamma dose response for HDs were best once adjustments for non-radiation factors (sex, attained age, calendar period, smoking status and alcohol consumption) and alpha dose were included. ERR/Gy in males and females was 0.17 (95% confidence intervals: 0.10, 0.26) and 0.23 (0.09, 0.38) for IHD; 0.18 (0.09, 0.29) and 0.26 (0.08, 0.49) for AP; -0.01 (n/a, 0.1) and -0.01 (n/a, 0.27) for AMI; 0.27 (0.16, 0.40) and 0.27 (0.10, 0.49) for HF; 0.32 (0.19, 0.46) and 0.05 (-0.09, 0.22) for CACD; 0.73 (-0.02, 2.40) and -0.12 (-0.50, 0.69) for CRHD, respectively. Sensitivity analyses demonstrated the persistence of a significant dose-response regardless of exclusion/inclusion of adjustments for known potential non-radiation confounders (smoking, alcohol consumption, body mass index, hypertension, diabetes mellitus), and it was only the magnitude of the risk estimate that varied. The risks of HD incidence were not modified with sex (except for the CACD risk). This study provides evidence for a significant association of certain types of HDs with cumulative dose of occupational chronic external exposure to gamma radiation.

Assessment of Alpha Doses Received by Spa Workers Due to the Inhalation of 214 Po and 218 Po Radon Progeny.

In Morocco spas are more and more frequented by bathers for massages, body treatments, and aromatherapy and hair services, among others. Alpha-activities due to 222 Rn, 220 Rn and their progeny have been evaluated inside spa room atmospheres by means of a technique based on using two types of solid-state nuclear track detectors. 222 Rn and 220 Rn concentrations ranged between (67 ± 5 and 103 ± 7) Bq m -3 and (5.5 ± 0.4 and 9.8 ± 0.7) Bq m -3 for the studied spa rooms, respectively. The influence of ventilation rate in spa rooms on 222 Rn and 220 Rn concentrations has been studied. Alpha-activities due to the attached and unattached fractions of 214 Po and 218 Po radon progeny have been evaluated in various compartments of the respiratory system of spa working personnel. It has been shown that the majority of 214 Po and 218 Po radon progeny are attached to aerosols inside the considered spa rooms. Alpha-doses to the respiratory tract tissues of spa working personnel due to the energy loss of the emitted alpha-particles were evaluated. It has been shown that alpha-doses to the respiratory system of spa working personnel are influenced by exposure time of workers, mass of respiratory system target tissues, and radon concentration inside the studied spa rooms. The largest value of alpha-dose due to the 214 Po and 218 Po radon progeny from inhalation of air by female workers working 2,080 hours per year in the studied spa rooms was found equal to 5.16 mSv y -1 .

Risk factors of liver malignancies in workers chronically exposed to ionizing radiation

OBJECTIVE: To assess the impact of non-radiation factors and ionizing radiation on the incidence of liver malignant neoplasms in workers of a nuclear facility.
 METHODS: This was a retrospective study that considered a cohort of Mayak PA workers (22,377 individuals hired during 19481982 and followed up until 31.12.2018). The analysis included 60 malignant neoplasms of liver that were histologically confirmed. Hazard ratio (HR) and 95% confidence intervals (CI) were estimated in relation to factors under the study using Poissons regression.
 RESULTS: The risk of total liver malignancies increased with attained age and for individuals with chronic liver diseases HR=3,59 (95%CI 1,57; 7,21), chronic gallbladder and biliary tract diseases HR=1,83 (95%CI 1,07; 3,11), gallstone disease HR=2,45 (95%CI 1,15; 4,77). Viral hepatitis elevated the risk of hepatocellular carcinoma (HCC) HR=7,41 (95%CI 1,20; 24,63). Gallstone disease raised the risk of cholangiocarcinoma (CC) HR=14,69 (95%CI 3,05; 56,18). Risk of hemangiosarcoma (HAS) was increased in individuals with chronic liver diseases HR=7,52 (95%CI 1,68; 24,48), and with diseases of the gallbladder and biliary tract HR=6,01 (95%CI 1,86; 26,88). The risks of total liver malignancies and HAS were found to increase due to external exposure at gamma dose 0,5 Gy and internal exposure at alpha dose of plutonium 1,0 Gy. The risk of HCC increased with alpha dose 4,0 Gy and was not associated with external gamma-ray exposure. The risk of CC increased with gamma-ray exposure at doses 1,0 Gy and was not associated with alpha particle exposure. Among total liver malignancies, the number of HAS was high (26,7%) and among them 68,8% were observed at internal exposure alpha doses 4,0 Gy.
 CONCLUSIONS: Incidence of liver malignancies in Mayak PA workers was associated with ionizing radiation, chronic diseases of hepatobiliary tract and viral hepatitis (in case of HCC). To investigate the risk related to occupational radiation exposure, we need to perform a dose-response analysis that will consider non-radiation factors.

Geometrical aspects of alpha dose rates from UO2 based fuels

Models for calculating dose rates of spherical particles as well as in fuel cracks are important for radionuclide source term estimations. Dose rates from UO2 based fuels were calculated for planar, spherical, and crack geometries. The escape probability for α-particles in spherical UO2 particles was derived as a continuous equation. The dose rate increased with increasing spherical radius due to the decreasing relative volume of the surrounding water layer. The model produced escape probabilities that were closely predicted by the theoretical derivation. It was shown that the dose rate in water filled fuel cracks with width smaller than the range of an α-particle led to dissolution rates that were lower per unit surface area.

Characterization of MOSFET Dosimeters for Alpha Particle Therapy

Alpha particle therapy, such as diffusing alpha-emitters radiation therapy (DaRT) and targeted alpha-particle therapy (TAT), exploits the short range and high linear energy transfer (LET) of alpha particles to destroy cancer cells locally with minimal damage to surrounding healthy cells. Dosimetry for DaRT and TAT is challenging, as their radiation sources produce mixed radiation fields of <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> particles, <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> particles, and <inline-formula> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> rays. There is currently no dosimeter for real-time <b><i>in vivo</i></b> dosimetry of DaRT or TAT. Metal-oxide-semiconductor field-effect transistors (MOSFETs) have features that are ideal for this scenario. They can be read out in real-time nondestructively, store information permanently, and their sensitivity to radiation can be varied by changing the bias on the gate during irradiation. Moreover, owing to their compactness, MOSFETs can fit into fine-gauge needle applicators, such as those used to carry radioactive seeds into the tumor. This study characterized the response of MOSFETs designed at the Centre for Medical and Radiation Physics, University of Wollongong. Irradiations were performed with a mono-energetic helium ion beam (He^2&#x002B;) of 5.5 MeV and an Americium-241 (²⁴¹Am) source, for MOSFETs with three different gate oxide thicknesses (0.55, 0.68, and 1.0 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>). The results showed that the response was linear with alpha dose up to 25 Gy. Also, it was found that a gate bias of between 15 and 60 V would optimize the sensitivity to alpha particles with energy of 5.5 MeV.