Alpha Decay Research Articles

Water quality management program for IPR-R1 TRIGA® research reactor

The IPR-R1 Triga nuclear research reactor of the Nuclear Technology Development Center (CDTN) is one of the oldest reactors in operation in the world. It is a compact and inherently safe reactor that operates at a continuous power level of 100 kW with a solid homogeneous General Atomic (GA) fuel element of zirconium hydride moderator homogeneously combined with 20% enriched uranium. The reactor core is at the bottom of a tank under approximately 6.0 meters of shielding water. The long operation time of the reactor, 63 years, and the contact of the water with the core, can induce corrosive processes in the IPR-R1 reactor and affect its safe operation. To keep the water quality according to the chemical-physical recommended standards, a quality management program, as recommended by the International Atomic Energy Agency (IAEA), was implemented. The water quality management program is a guideline of good practices applied to nuclear reactors, targeting to keep their water coolants at specified physical-chemical standard. The main aim of the present work is to introduce IPR-R1 Triga’s water chemistry program results from the second half of 2022 till the first half of 2023, when the installation returned to its regular activities after the Covid-19 pandemic. The physical-chemical parameters evaluated (e.g.: pH, alpha and beta radiation, electrical conductivity and gamma emitters) shows that the IPR-R1 reactor operates within recommended safety standards.

Abnormal high stability halide perovskite thin films and solar cells to alpha and gamma irradiations with varying fluence

Solar cells (SCs) and thin films made of methylammonium lead tri-iodide (MAPbI3) have demonstrated remarkable robustness when irradiated with alpha (He2+) and gamma radiations from americium-241. This study investigates changes in the structure, absorption, and surface morphology of perovskite thin films, as well as the photoelectronic properties of MAPbI3 SCs, with and without irradiation with He2+. According to the XRD analysis, tetragonal MAPbI3 showed increased crystallinity and a decrease in compression micro-strain with an increased flux of He2+. UV–Vis absorption remained unchanged until the flux exceeded 7.36 x 1012 He2+ cm−2. The bandgaps for irradiated films decreased similarly to pristine films up to a dose of 3.07 x 1012 He2+cm−2, with significant differences observed beyond this point. Digital images showed significant changes in thin films irradiated at fluences exceeding 3.07 x 1012 He2+ cm−2, with pits forming in grains responsible for the changes, confirmed by scanning electron microscopy. In conclusion, this study found that MAPbI3 thin films and SCs can withstand doses of He2+ up to 3.07 x 1012 He2+ cm−2 in a He2+ radiation environment.

The low-LET radiation contribution to the tumor dose in diffusing alpha-emitters radiation therapy.

Diffusing alpha-emitters Radiation Therapy ("Alpha DaRT") is a new technique that enables the use of alpha particles for the treatment of solid tumors. Alpha DaRT employs interstitial sources carrying a few Ci of Ra below their surface, designed to release a chain of short-lived atoms (progeny of Ra) which emit alpha particles, along with beta, Auger, and conversion electrons, x- and gamma rays. These atoms diffuse around the source and create-primarily through their alpha decays-a lethal high-dose region measuring a few millimeters indiameter. While previous studies focused on the dose from the alpha emissions alone, this work addresses the electron and photon dose contributed by the diffusing atoms and by the atoms remaining on the source surface, for both a single Alpha DaRT source and multi-source lattices. This allows to evaluate the low-LET contribution to the tumor dose and tumor cell survival, and demonstrate the sparing of surrounding healthytissue. The low-LET dose is calculated using the EGSnrc and FLUKA Monte Carlo (MC) codes. We compare the results of a simple line-source approximation with no diffusion to those of a full simulation, which implements a realistic source geometry and the spread of diffusing atoms. We consider two opposite scenarios: one with low diffusion and high Pb leakage, and the other with high diffusion and low leakage. The low-LET dose in source lattices is calculated by superposition of single-source contributions. Its effect on cell survival is estimated with the linear quadratic model in the limit of low doserate. For sources carrying 3 Ci/cm Ra arranged in a hexagonal lattice with 4mm spacing, the minimal low-LET dose between sources is Gy for the two test cases and is dominated by the beta contribution. The low-LET dose drops below 5Gy mm away from the outermost source in the lattice with an effective maximal dose rate of Gy/h. The accuracy of the line-source/no-diffusion approximation is for the total low-LET dose over clinically relevant distances (2-4mm). The low-LET dose reduces tumor cell survival by a factor of . The low-LET dose in Alpha DaRT can be modeled by conventional MC techniques with appropriate leakage corrections to the source activity. For 3 Ci/cm Ra sources, the contribution of the low-LET dose can reduce cell survival inside the tumor by up to two orders of magnitude. The low-LET dose to surrounding healthy tissue is negligible. Increasing source activities by a factor of 5 can bring the low-LET dose itself to therapeutic levels, in addition to the high-LET dose contributed by alpha particles, leading to a "self-boosted" Alpha DaRT configuration, and potentially allowing to increase the latticespacing.

CONCENTRATION OF RADON IN SPRINGS OF KELBAJAR REGION, REGULARITIES OF ADSORBTION OF RADIONUCLIDES FROM SOLUTIONS ON ADSORBENTS

Higher values of the total radiation and the intensity of alpha radiation were observed in soil areas around thermal and cold springs on the mountain slopes of the Kelbajar region of Azerbaijan. The concentration of radioactive radon in the water of the thermal springs of the “Istisu” sanatorium, located at an altitude (2203 m), is below the directive indicator. However, the concentration of radon in the water of springs, located at an altitude of 2385 m, exceeds the directive indicator by 100 times. Soil samples taken from areas around springs contain uranium isotopes in similar proportions found in natural uranium deposits. Regularities of sorption of uranium isotopes from aqueous solutions on some adsorbents have been studied. It has been established that weak Van der Waals forces exist between the absorbed isotopes and the adsorbents.

Abstract A146: FPI-2068: A novel anti-EGFR/cMET, alpha-particle emitting, radioimmunoconjugate for cancer therapy

Abstract Introduction: FPI-2068, a targeted alpha therapeutic (TAT), consists of a humanized EGFR and cMET targeting bispecific antibody (FPI-2053) radiolabeled with actinium-225 [225Ac]. FPI-2068 leverages the EGFR/cMET co-expression in cancer (high vs. low in normal tissues) and internalizing nature of the receptors to deliver radionuclides into tumor cells. The primary tumoricidal mechanism of FPI-2068 is double-strand DNA breaks (DSB) induced by alpha radiation, which lead to cell death. Methods: FPI-2068 consists of FPI-2053 conjugated with a DOTA-chelate and radiolabeled with [225Ac]. FPI-2071 is the lutetium-177 analogue. The binding and internalization of FPI-2071 was studied in vitro using cancer cell lines (HT29 colorectal and H292, H441, H1975, HCC827 lung cancers). In vivo studies were performed in corresponding xenograft models. For biodistribution studies FPI-2071 was injected intravenously into mice and tumor/organ radioactivity was quantified ex vivo at selected timepoints. For therapeutic studies, a single dose of FPI-2068 was administered to groups of mice over a range from 92.5 to 740 kBq/kg. Explanted HT29 and H441 tumors from FPI-2068 treated mice were analyzed by immunoblotting to detect activation of DDR and cell death pathways. Results: FPI-2071 demonstrated in vitro binding to all cell lines tested, followed by internalization and retention of the radioisotope into target cells. The biodistribution profile of FPI-2071 showed low normal organ uptake in all xenograft models tested, while tumor uptake varied. The peak tumor uptake in each model was: H292 (~73 %ID/g), H441 (~38 %ID/g), HT29 (~30 %ID/g), HCC827 (~25 %ID/g) and H1975 (20 %ID/g). Delivery of FPI-2068 to target xenografts resulted in anti-tumor efficacy; treatment was well-tolerated by animals. Sustained tumor regression (>28 days) was generally observed at doses of 370 kBq/kg and 740 kBq/kg across models. Lower doses were tumor growth suppressive. FPI-2068 treatment resulted in a dose-dependent increase in pATM and pRad50 expression indicating activation of DDR pathways in HT29 and H441 xenografts. Formation of DSB (pH2AX) and the induction of apoptosis (cleaved caspase 3) was also observed, consistent with the proposed primary mechanism of action. Conclusions: FPI-2068 demonstrated its anti-tumor efficacy in colorectal and lung tumor xenograft mouse models. Single-dose administration of FPI-2068 led to prolonged tumor regression. FPI-2068 caused activation of the DDR pathway as well as apoptosis, suggesting an inability of the cellular machinery to repair the DNA damage induced by the alpha radiation. These data support initiation of clinical trials in patients with solid tumors. Citation Format: Sadaf Aghevlian, Sean Collens, Julie Metcalf, Natalie Grinshtein, John Forbes, Frank Comer, Darshan Dalal, Puja Sapra, Eric Burak. FPI-2068: A novel anti-EGFR/cMET, alpha-particle emitting, radioimmunoconjugate for cancer therapy [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A146.

Development of local-power-free, remote α-particle detection using optical fibers.

We demonstrate the application of fluorescence optical fiber coupled to a telecom grade fiber as a sensor for alpha particles using alpha-specific ZnS(Ag) scintillation materials whose wavelength is down-shifted into a low-loss region of the telecom grade fiber transmission band. Telecom-grade fiber optics offer a solution for sensing alpha radiation in deep repositories and cask storage for radioactive materials due to the stability of SiO2 under normal environmental conditions and its relative radiation hardness at low radiation doses. Long-term nuclear waste storage facilities require sensors for the detection of leakage of radioactive materials that are maintenance-free, do not require power and can survive with no 'wear out' mechanisms for decades. By accomplishing the wavelength transformation, we maximize efficiencies in the detection of α-particles and signal transport and can detect alpha scintillation at distances on the order of >1km with a sensor that is ~3% efficient and can be easily scaled as a sensor array. This paper describes the construction and testing of the sensor including manufacture of the controlled thickness films, verification of the wavelength shift from 450to 620nm and optimization of the sensitivity as a function of thickness. We also model the relative sensitivity of the film as a function of film thickness, and we demonstrate a signal-to-noise ratio of 10 at a range of greater than 1km.

Partially depleted operation of 250 μm-thick silicon carbide neutron detectors

Fusion experiments put many challenges on the neutron detection methods, since they require fast neutron counters and spectrometers with good energy resolution capable of operating in harsh environments under a large range of neutron flux intensities. Recently, SiC detectors were proposed for these roles due to their outstanding properties. Among those, the operation of SiC with partial polarization is of interest since it might allow for a fast neutron detector with efficiency tunable online, which would allow a good functionality under a large range of flux intensities.This paper describes the characterization of a series of SiC detectors operated with a fraction of the polarization needed to achieve full depletion. The characterization is performed through I/V measurements, alpha irradiation in vacuum and neutron irradiation. A functionality with excellent detection characteristics is demonstrated, reaching an energy resolution of 1.05 % for 5.5 MeV alphas and 2.05 % for 14 MeV neutrons. Some limitations on the maximum bias will be also discussed, pointing out some challenges for the manufacturing of thick SiCs in the future.

Impact of nuclear rotation corrections on alpha decay half-lives of superheavy nuclei within 98 ≤ Z ≤ 120

The influence of nuclear rotation on the decay half-lives of superheavy nuclei within the range 98≤Z≤120 is investigated using the axially deformed relativistic Hartree-Bogoliubov theory in the continuum (DRHBc) with the PC-PK1 parameter set. The deduced DRHBc decay energies (with and without the rotation effect) are compared with those calculated from the macroscopic-microscopic WS4 and the available experimental binding energies. Six semi-empirical formulae, such as the Viola-Seaborg formula (VSS), the modified Brown formula (mB1), the semi-empirical relationship based on fission theory (SemFIS2), the Royer formula (R), the Wang formula (Wang) and the modified YQZR formula (MYQZR) are employed to estimate the half-lives of α decay. Among these formulae, the half-live predictions of SemFIS2 are found to gradually deviate from the systematic trend beyond Nd=184, showing that the probability of undergoing spontaneous fission is less feasible beyond this point. A minimum is observed at Nd=184, reflecting its neutron shell closure for the mass region considered on the nuclear chart. The results further indicate that, for 98≤Z≤104, the predictions of all semi-empirical formulae are more closely matched to the available experimental data when the rotation effect is taken into account. However, we have demonstrated that the effect of nuclear rotation gradually reduces as the atomic nucleus becomes heavier.

Comparative of HPHT and CVD diamond: performance and defect analysis for alpha radiation detector

Currently, the high-purity single crystal diamond preparation is still a challenging task, which restricts the application of diamond in electronics. In this paper, the chemical vapor deposition (CVD) IIa type single crystal diamond was prepared on the IIa type high pressure high temperature (HPHT) substrate by combining the chamber design with the plasma purifying technology, and the performance of diamond detectors using both IIa type single crystal diamonds were compared based on the defect analysis. The dislocations in diamonds were directly observed by synchrotron radiation X-ray white-beam topography. The CVD diamond shows the comparatively low dislocation density resulting from the high-quality HPHT diamond substrate. No observable NV impurity could be found in photoluminescence (PL) spectrum. The trace impurity of substitutional nitrogen (Ns) was characterized by electron paramagnetic resonance (EPR). It shows the very low concentration in the CVD diamond (2.1 ppb) compared with the several tens ppb in HPHT diamond. This value is comparable with the electronic-grade diamond reported by Element Six. Furthermore, both of the HPHT and CVD single crystal diamonds were packaged as the α-particle radiation detectors with the typical sandwich structure and used Ni/Al (50 nm/500 nm) as metal electrodes. The energy resolution of HPHT and CVD diamond detectors were 2.04% and 0.86%, respectively. Based on Schottky contact and defect regulation, at 0 voltage, the CVD diamond detector achieved response of α-particle radiation and the charge collection efficiency (CCE) was 10.76%. Under positive voltage, the CCE of HPHT and CVD diamond detectors were 38.11% and 86.65%, respectively. The deep level trapping effect of Ns impurities on charge carriers resulted in low CCE of HPHT diamond detector. The spatial polarization effect caused by defects leaded to the formation of an internal electric field, which was the main reason affecting the transport of charge carriers in CVD diamond.

A systematic study of alpha decay half-lives of isotones in superheavy region

A systematic study of alpha decay half-lives of isotones in superheavy region

Investigation of the Dosimetry Characteristics of the GAFCHROMIC® EBT3 Film Response to Alpha Particle Irradiation

The purpose of this study was to investigate the dosimetric characteristics of the GAFCHROMIC® EBT3 film responding to alpha particle irradiation. Unlaminated GAFCHROMIC® EBT3 film pieces, were irradiated with a 30.055 kBq 241Am alpha source, at eight different dose levels, between 0 and 509 Gy. The irradiations were performed inside an enclosed box. Epson Expression 10000 XL scanner in transmission mode was used to digitize irradiated films 24 hours post-irradiations as 16-bit RGB images in tagged image file format (TIFF). Optical density (OD) values were obtained by following the OD theorem. Raw and normalized pixel values (PVnorm) from the red, green, and blue colour channels were sampled from a 3 × 3 mm2 region of interest. Calibration curves were created for both data sets (OD and PVnorm) and were fit accordingly. Monte Carlo simulations with the Geant4 toolkit were performed to establish a dose rate at the point within the sensitive layer of the film. An alpha dosimetry protocol for EBT3 films was obtained from the Monte Carlo calculated dose rate and dose calibration curves for alpha radiation were created. It is necessary to extend this study for different film types and compare to photon dosimetry calibration curves.

GEOCHEMICAL VIEW ON “INOFFENSIVE” DEPLETED URANIUM

The interaction of alpha radiation from UO2 micro- and nanoparticles (uraninite) with the substance was visualized using alpha-autoradiography data on A-2 thick-layer nuclear photographic emulsions. The spherical area of action of alpha particles around UO2 micrograins, up to 100 microns in size, is a deeply transformed substance with a high density of radiation defects. The translation of these results on a living organism leads to the conclusion about the specific type of impact of micro- and nanoparticles of depleted uranium, in which prolonged internal irradiation in small doses of the whole organism is combined with catastrophically high doses of alpha radiation in local zones, near micro- and nanoparticles UO2.

Profound DNA methylomic differences between single- and multi-fraction alpha irradiations of lung fibroblasts

BackgroundAlpha (α)-radiation is a ubiquitous environmental agent with epigenotoxic effects. Human exposure to α-radiation at potentially harmful levels can occur repetitively over the long term via inhalation of naturally occurring radon gas that accumulates in enclosed spaces, or as a result of a single exposure from a nuclear accident. Alterations in epigenetic DNA methylation (DNAm) have been implicated in normal aging and cancer pathogenesis. Nevertheless, the effects of aberrations in the methylome of human lung cells following exposure to single or multiple α-irradiation events on these processes remain unexplored.ResultsWe performed genome-wide DNAm profiling of human embryonic lung fibroblasts from control and irradiated cells using americium-241 α-sources. Cells were α-irradiated in quadruplicates to seven doses using two exposure regimens, a single-fraction (SF) where the total dose was given at once, and a multi-fraction (MF) method, where the total dose was equally distributed over 14 consecutive days. Our results revealed that SF irradiations were prone to a decrease in DNAm levels, while MF irradiations mostly increased DNAm. The analysis also showed that the gene body (i.e., exons and introns) was the region most altered by both the SF hypomethylation and the MF hypermethylation. Additionally, the MF irradiations induced the highest number of differentially methylated regions in genes associated with DNAm biomarkers of aging, carcinogenesis, and cardiovascular disease. The DNAm profile of the oncogenes and tumor suppressor genes suggests that the fibroblasts manifested a defensive response to the MF α-irradiation. Key DNAm events of ionizing radiation exposure, including changes in methylation levels in mitochondria dysfunction-related genes, were mainly identified in the MF groups. However, these alterations were under-represented, indicating that the mitochondria undergo adaptive mechanisms, aside from DNAm, in response to radiation-induced oxidative stress.ConclusionsWe identified a contrasting methylomic profile in the lung fibroblasts α-irradiated to SF compared with MF exposures. These findings demonstrate that the methylome response of the lung cells to α-radiation is highly dependent on both the total dose and the exposure regimen. They also provide novel insights into potential biomarkers of α-radiation, which may contribute to the development of innovative approaches to detect, prevent, and treat α-particle-related diseases.Graphical abstract

Improved calculation of alpha decay half-life by incorporating nuclei deformation shape and proximity potential

Accurate evaluation of alpha decay half-life is essential for understanding nuclear stability, ensuring nuclear safety, optimizing medical treatments, and studying astrophysical processes. Considering the deformed shape of nuclei, we calculated the alpha-decay half-life of 359 nuclei using the proximity potential. In addition, we employed the Wentzel–Kramers–Brillouin approximation to compute the penetration probability through the potential barrier comprising nuclear, Coulomb, and centrifugal potentials. Our calculations revealed that the penetration probability, and hence the alpha-decay half-life, depend on the direction of alpha particle emission relative to the axial symmetry of the nucleus. Furthermore, our results suggested that the dependence of alpha-decay on parent nuclei temperature needs to be reassessed. We tabulated the alpha-decay half-life for various nuclei, and our results showed better agreement with experimental data compared to theoretical data in the literature.

Modified human respiratory tract model to describe the retention of plutonium in scar tissues.

The Human Respiratory Tract Model described in Publication 130 of the International Commission on Radiological Protection provides some mechanisms to account for retention of material that can be subject to little to no mechanical transport or absorption into the blood. One of these mechanisms is 'binding', which refers to a process by which a fraction ('bound fraction') of the dissolved material chemically binds to the tissue of the airway wall. The value of the bound fraction can have a significant impact on the radiation doses imparted to different parts of the respiratory tract. To properly evaluate-and quantify-bound fraction for an element, one would need information on long-term retention of the element in individual compartments of the respiratory tract. Such data on regional retention of plutonium in the respiratory tract of four workers-who had inhaled materials with solubility ranging from soluble nitrate to very insoluble high-fired oxides-were obtained at the United States Transuranium and Uranium Registries. An assumption of bound fraction alone was found to be inconsistent with this dataset and also with a review of the literature. Several studies show evidence of retention of a large amount of Pu activity in the scar tissues of humans and experimental animals, and accordingly, a model structure with scar-tissue compartments was proposed. The transfer rates to these compartments were determined using Markov Chain Monte Carlo analysis of the bioassay and post-mortem data, considering the uncertainties associated with deposition, dissolution and particle clearance parameters. The models predicted that a significant amount-between 20 and 100% for the cases analyzed-of plutonium retained in the respiratory tract was sequestered in the scar tissues. Unlike chemically-bound Pu that irradiates sensitive epithelial cells, Pu in scar tissues may not be dosimetrically significant because the scar tissues absorb most, if not all, of the energy from alpha emissions.

Environmental Alpha Radiation from the Soil at a Prehispanic Ancient Sacred Site in Lima, Perú

Environmental Alpha Radiation from the Soil at a Prehispanic Ancient Sacred Site in Lima, Perú

Comparison of different nuclear potentials to predict the alpha decay half-lives

Comparison of different nuclear potentials to predict the alpha decay half-lives

Breaking an Electron

An electron is a subatomic particle with a negative charge and is a medium for electricity to travel. An electron, being a stable particle, cannot be broken down; but the results shown in this experiment show otherwise. We can break an isolated electron by bombarding alpha radiation and beta radiation with the help of electricity. We also use photoelectric effect to isolate the electron. But due to no financial aid, we replaced the alpha and beta radiation with electromagnetic radiation.

Neutronic Chain Reactions for Polonium-210 Production

The production of the industrially significant radionuclide polonium-210 from the neutron irradiation of bismuth metal and the subsequent beta decay of bismuth-210 is highly inefficient due to the small neutron capture cross section of bismuth-209. In this paper, we report a previously undescribed self-sustaining nuclear chain reaction involving self-propagating neutron multiplication in bismuth salts that allow for rapid and cost-effective production of polonium-210. The reaction proceeds in a cycle of three alternating elementary steps – the capture of neutrons by bismuth-209 and the subsequent formation of polonium-210, the emission of high-energy alpha particles by polonium-210, and the production of more neutrons from (α, n) and (n,2n) reactions on light element and bismuth-209 nuclei respectively. Furthermore, the high hydrogen density of the compound also confers it intrinsic neutron moderation properties, increasing the neutron capture cross section of bismuth-209 at thermal neutron energies. The chain reaction was proven to have successfully occurred by irradiating a sample of the bismuth salt with a 80 μCi neutron source and monitoring the activity levels of the reaction. It was found that the activity of the reaction increased exponentially after an initial stable period following a derived formula for polonium production trends for the reaction, thus validating the occurrence of the reaction. Furthermore, alpha spectroscopy confirmed that polonium-210 had been produced by characterising the 5.30 MeV alpha emission peak of the reaction in addition to using beta spectroscopy to identify the parent nuclide bismuth-210, further proving that the reaction was successful. Hence, this paper reports the successful initiation and characterisation of a novel nuclear chain reaction, and its potential applications offered by a method of rapidly producing large quantities of polonium-210.

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.