Short-lived Daughters Research Articles

Characterisation of radioactive decay series by digital autoradiography, part 1: A theoretical approach using time and space coincidence (TSC) analysis

The three natural decay chains have short-lived daughter elements, and the existence of these radioelements makes it possible for alpha and beta particle emissions to be generated at the same place and the same time. We show theoretically that such time and space coincidences (TSCs) can be detected efficiently by suitable autoradiographic systems using an algorithm that is six times more efficient than an approach based on the classical slicing of space-time. Two types of TSC coexist: true TSCs, resulting from the decay of short-lived daughter elements, and random TSCs. True TSCs are predictable and their numbers vary linearly with activity; the prediction of true α/α and α/α/α TSCs of the 235U chain is presented. Random coincidences are also predictable using Poisson's law. They vary quadratically as a function of activity. Examination of the case of an uranium ore at secular equilibrium shows that the observed α/α coincidences result from the sum of random and true TSCs. For high uranium contents, random coincidences predominate. For uranium at secular equilibrium, the theoretical calculation shows that true TSCs predominate for contents below ∼5000 ppm.

DNA damage response in a 2D-culture model by diffusing alpha-emitters radiation therapy (Alpha-DaRT)

Diffusing alpha-emitters radiation therapy (Alpha-DaRT) is a unique method, in which interstitial sources carrying 224Ra release a chain of short-lived daughter atoms from their surface. Although DNA damage response (DDR) is crucial to inducing cell death after irradiation, how the DDR occurs during Alpha-DaRT treatment has not yet been explored. In this study, we temporo-spatially characterized DDR such as kinetics of DNA double-strand breaks (DSBs) and cell cycle, in two-dimensional (2D) culture conditions qualitatively mimicking Alpha-DaRT treatments, by employing HeLa cells expressing the Fucci cell cycle-visualizing system. The distribution of the alpha-particle pits detected by a plastic nuclear track detector, CR-39, strongly correlated with γH2AX staining, a marker of DSBs, around the 224Ra source, but the area of G2 arrested cells was more widely spread 24 h from the start of the exposure. Thereafter, close time-lapse observation revealed varying cell cycle kinetics, depending on the distance from the source. A medium containing daughter nuclides prepared from 224Ra sources allowed us to estimate the radiation dose after 24 h of exposure, and determine surviving fractions. The present experimental model revealed for the first time temporo-spatial information of DDR occurring around the source in its early stages.

Radon, Thoron and Polonium Concentrations Estimated in Building Materials Samples Collected from Al-Shatra, Dhi-Qar, Iraq

Radon, Thoron and their short-lived daughters have a high contribution to background radiation, as long-term exposure causes the risk of lung cancer. In current study, five types of building materials with a total 55 samples in Al-Shatra City, Dhi-Qar Governorate, Iraq collected to measure the radon and thoron concentration by using CR-39 solid state nuclear track detector. The results showed that the average radon concentrations in all samples were (103.53±55.94) Bqm−3, while the average thoron concentration was (53.20±44.69) Bqm−3. On the other hand, the annual effective dose of radon ranged between (0.85-6.46) msvy−1, with an average of 2.61msvy−1. While, for thoron concentration was ranged between (0.12-3.28) msvy−1, with an average of 1.49 msvy−1. The annual effective dose was found acceptable limit (3-10 msvy−1) recommended by the International Commission on Radiological Protection (ICRP). On the other side, the average Polonium concentrations (218Po, 214Po) have been found to be 2.053 KBqm−3, 0.866 KBqm−3, respectively.

First measurements of radon-220 diffusion in mice tumors, towards treatment planning in diffusing alpha-emitters radiation therapy.

Diffusing alpha-emitters radiation therapy ("Alpha-DaRT") is a new method for treating solid tumors with alpha particles, relying on the release of the short-lived alpha-emitting daughter atoms of radium-224 from interstitial sources inserted into the tumor. Alpha-DaRT tumor dosimetry is governed by the spread of radium's progeny around the source, as described by an approximate framework called the "diffusion-leakage model". The most important model parameters are the diffusion lengths of radon-220 and lead-212, and their estimation is therefore essential for treatmentplanning. Previous works have provided initial estimates for the dominant diffusion length, by measuring the activity spread inside mice-borne tumors several days after the insertion of an Alpha-DaRT source. The measurements, taken when lead-212 was in secular equilibrium with radium-224, were interpreted as representing the lead-212 diffusion length. The aim of this work is to provide first experimental estimates for the diffusion length of radon-220, using a newmethodology. The diffusion length of radon-220 was estimated from autoradiography measurements of histological sectionstaken from 24 mice-borne subcutaneous tumors of five different types. Unlike previous studies, the source dwell time inside the tumor was limited to 30 min, to prevent the buildup of lead-212. To investigate the contribution of potential non-diffusive processes, experiments were done in two sets: fourteen in vivo tumors, where during the treatment the tumors were still carried by the mice with active blood supply, and 10 ex-vivo tumors, where the tumors were excised before source insertion and kept in a medium at with the sourceinside. The measured diffusion lengths of radon-220, extracted by fitting the recorded activity pattern up to 1.5mm from the source, lie in the range , with no significant difference between the average values measured in in-vivo and ex-vivo tumors: versus . However, in-vivo tumors display an enhanced spread of activity 2-3mm away from the source. This effect is not explained by the current model and is much less pronounced in ex-vivotumors. The average measured radon-220 diffusion lengths in both in-vivo and ex-vivo tumors are consistent with published data on the diffusion length of radon in water and lie close to the upper limit of the previously estimated range of . The observation that close to the source there is no apparent difference between in-vivo and ex-vivo tumors, and the good agreement with the theoretical model in this region suggest that the spread of radon-220 is predominantly diffusive in this region. The departure from the model prediction in in-vivo tumors at large radial distances may hint at potential vascular contribution, which will be the subject of futureworks.

Contribution of the Photonic Component to the Ionization of the Atmosphere by Earth Crust Nuclides and Radioactive Emanations

Abstract—We investigate the contribution of gamma radiation of natural radionuclides constituting the Earth crust, radioactive emanations, and their decay product in the ground to the intensity of production of ion pairs in the atmosphere against the background of ionization of the atmosphere by radioactive gases flowing to the atmosphere from the ground and propagating together with their short-lived daughter products. The density of the radon flux to the atmosphere is estimated by three methods: the reservoir method, the integration of altitude profiles of volume activity of radon, based on gamma spectroscopic observation and diffusion model. The distribution of the gamma dose rate dose from the earth radionuclides in the soil and in the atmosphere is calculated using Gleant4 software. The propagation of the radon isotopes and their decay products in the atmosphere is calculated using large eddy simulations supplemented with kinematic simulations of the subgrid transport of a passive scalar. It is shown that depending on the specific activity of nuclides in the ground and the turbulent regime of the atmosphere, the total contribution of the γ-radiation to the ion pair production rate in the atmospheric boundary layer is approximately from 1% to 20% and increases upon a decrease in the penetrability of the upper ground layer for radioactive emanations.

Радионуклидный состав твердых радиоактивных отходов конверсионного производства

The paper overviews the study on the radionuclide composition of solid radioactive waste (RW) held in a near-surface storage facility at a conversion production site. The total α- and β-activity of the waste ranges from 1.2 to 1,250 kBq/kg and from 1.1 to 560 kBq/kg respectively. Three radioactive waste categories have been identified: those with the predominance of 226Ra in combination with short-lived daughter decay products (specific activity of up to 100 kBq/kg); waste with a predominant content of 238U in equilibrium with 234Th, 234Pa (specific activity of up to 30 kBq/kg); waste with a predominance of 210Pb in equilibrium with 210Bi and 210Po (specific activity of 70 kBq/kg). The increased total alpha activity level is explained by 230Th found in the waste. At low 226Ra activities, one can focus on the total alpha activity levels to identify areas with possible high 210Po and 230Th activities. Most of the waste inventory contains uranium with its isotopic composition being similar to the natural one.

A new approach to measure radon by Thick Gas Electron Multiplier

In this article, a novel approach to the use of the Micro Pattern Gas Detector (MPGD) to detect the radon gas contamination in air is presented. It consists in operating the Thick Gas Electron Multiplier (THGEM) in Self-Quenched Streamer (SQS) mode. This detector works based on counting alpha particles emitted from radon and its short-lived daughters, Po-218 and Po-214. If this detector is compared to a scintillation detector, its THGEM can be considered as a scintillator and conventional light sensors as photomultipliers or sensitive photodiodes. A laboratory layout of the recommended system was designed to measure radon concentration in air based on measuring the alpha emitted of radon and its short-lived daughters. One of the advantages of this detector over the scintillation and semiconductor detectors is a vast sensitive surface (5*5 cm2) uninfluenced by noises and background rays. The practical results show that this recommended detector uninfluenced by background rays has a very low limit of detection about zero. Consequently, this detector can measure very low radon gas concentrations in the air.

Bismuth-210, its parent, and daughter and their use as particle tracers in aquatic systems

Disequilibrium between 210Pb (t½: 22.3 years) and its granddaughter 210Po (t½: 138.4 days) has been used to infer organic particle removal rates from the surface ocean on a timescale of weeks to months; however, the behavior of the short-lived intermediary daughter 210Bi (t½: 5.01 days) is not well known. Here, timeseries measurements of 210Pb, 210Bi, and 210Po in the Milwaukee Inner Harbor on Lake Michigan showed respective particle distribution (Kd) coefficients of 7.1 (± 0.4) × 105, 9.3 (± 1.7) × 105, and 10.2 (± 0.6) × 105 L kg −1, giving Kd ratios, or fractionation factors (F), of FBi/Pb = 1.3 ± 0.3, FPo/Bi = 1.1 ± 0.2, and FPo/Pb of 1.4 ± 0.1. After a large rain event, total 210Pb, 210Bi, and 210Po activities in the harbor water column decreased over a course of 12 days from 347 to 105 dpm 210Pb m−3, 397 to 88 dpm 210Bi m−3, and 144 to 58 dpm 210Po m−3. This is the first observation of a total 210Bi/210Po activity ratio of <1 in an aquatic system. A 1-D non-steady-state model of nuclide fluxes suggested that 92% of the reduction in 210Bi activity was due to removal from the water column, with the remainder accounted for by net in situ decay. The potential for using 210Bi as a tracer of high and variable particle scavenging rates in lakes and shallow marine systems is supported.

Hygienic assessment of personnel working conditions in underground uranium mining

The aim of the study is to assess the main radiation-hazardous factors that determine the effective dose of personnel during underground uranium mining at the Priargunsky Industrial Mining and Chemical Association, and to summarize the data of the radiation control of the enterprise for 2016-2020. The main factors that create personnel dose loads are: the volume activity of short-lived daughter products of radon decay in the air, the dose rate of external gamma radiation, and the volume activity of long-lived alpha-emitting radionuclides of the uranium-radium series in industrial dust. Information on the structure and values of individual effective doses of workers is presented. Recommendations for improving the radiation monitoring system are given.

Multi-curie production of gallium-68 on a biomedical cyclotron and automated radiolabelling of PSMA-11 and DOTATATE

BackgroundWith increasing clinical demand for gallium-68, commercial germanium-68/gallium-68 ([68Ge]Ge/[68Ga]Ga) generators are incapable of supplying sufficient amounts of the short-lived daughter isotope. In this study, we demonstrate a high-yield, automated method for producing multi-Curie levels of [68Ga]GaCl3 from solid zinc-68 targets and subsequent labelling to produce clinical-grade [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTATATE.ResultsEnriched zinc-68 targets were irradiated at up to 80 µA with 13 MeV protons for 120 min; repeatedly producing up to 194 GBq (5.24 Ci) of purified gallium-68 in the form of [68Ga]GaCl3 at the end of purification (EOP) from an expected > 370 GBq (> 10 Ci) at end of bombardment. A fully automated dissolution/separation process was completed in 35 min. Isolated product was analysed according to the Ph. Eur. monograph for accelerator produced [68Ga]GaCl3 and found to comply with all specifications. In every instance, the radiochemical purity exceeded 99.9% and importantly, the radionuclidic purity was sufficient to allow for a shelf-life of up to 7 h based on this metric alone. Fully automated production of up to 72.2 GBq [68Ga]Ga-PSMA-11 was performed, providing a product with high radiochemical purity (> 98.2%) and very high apparent molar activities of up to 722 MBq/nmol. Further, manual radiolabelling of up to 3.2 GBq DOTATATE was performed in high yields (> 95%) and with apparent molar activities (9–25 MBq/nmol) sufficient for clinical use.ConclusionsWe have developed a high-yielding, automated method for the production of very high amounts of [68Ga]GaCl3, sufficient to supply proximal radiopharmacies. The reported method led to record-high purified gallium-68 activities (194 GBq at end of purification) and subsequent labelling of PSMA-11 and DOTATATE. The process was highly automated from irradiation through to formulation of the product, and as such comprised a high level of radiation protection. The quality control results obtained for both [68Ga]GaCl3 for radiolabelling and [68Ga]Ga-PSMA-11 are promising for clinical use.

Search for Electron-Capture Delayed Fission in the New Isotope ^{244}Md.

The electron-capture decay followed by a prompt fission process was searched for in the hitherto unknown most neutron-deficient Md isotope with mass number 244. Alpha decay with α-particle energies of 8.73-8.86MeV and with a half-life of 0.30_{-0.09}^{+0.19} s was assigned to ^{244}Md. No fission event with a similar half-life potentially originating from spontaneous fissioning of the short-lived electron-capture decay daughter ^{244}Fm was observed, which results in an upper limit of 0.14 for the electron-capture branching of ^{244}Md. Two groups of fission events with half-lives of 0.9_{-0.3}^{+0.6} ms and 5_{-2}^{+3} ms were observed. The 0.9_{-0.3}^{+0.6} ms activity was assigned to originate from the decay of ^{245}Md. The origin of eight fission events resulting in a half-life of 5_{-2}^{+3} ms could not be unambiguously identified within the present data while the possible explanation has to invoke previously unseen physics cases.

Real-time in-vivo dosimetry for DaRT

Diffusing alpha-emitters radiation therapy (DaRT) is a revolutionary brachytherapy technique used to treat solid tumours. Implant seeds are coated with 224Ra which, along its shortlived daughter atoms, emits alpha particles of high linear energy transfer (LET) and of high relative biological efficiency (RBE), creating a tumour-killing dose distribution a few mm wide. Those alpha particles are of energy between 5.67 and 8.78 MeV. DaRT is under investigation in clinical trials, but there currently is no obvious solution for dosimetry aimed at quality assurance of treatment. This study introduces alpha-RAD, a dosimeter based on a metal-oxide-semiconductor (MOS) sensor technology. Alpha-RAD was characterized with 241Am, which emits alpha particles of energy 5.49 MeV. The results showed that alpha-RAD had good linearity with dose, with the signal increasing linearly in the range from 0 to 6.84 Gy. Also, an external bias in the range between 15 and 60 V, applied on the gate of alpha-RAD during irradiation, would optimize sensitivity to alpha particles of energies typical of DaRT. Alpha-RAD, owing to its compactness, can fit into a brachytherapy needle, to be placed next to 224Ra seed implants in the tumour, for real-time in vivo dosimetry.

Sodium strontium phosphate nonahydrate (NaSrPO4·9H2O) found in Hanford nuclear waste

The Hanford site, near Richland, WA, in the U.S.A., has legacy radioactive waste left over from plutonium production. Strontium-90 and its short-lived daughter Y-90 account for about half of the radioactivity of the waste, yet there has been limited understanding of the speciation of strontium in the waste. The speciation of strontium will drive its behavior during any waste separation or treatment options, and may determine the Sr-90 source term to the environment after tank closure. A strontium-bearing phase containing sodium, phosphorus, and oxygen, was found in Hanford waste using energy dispersive spectroscopy (EDS). Polarized light microscopy determined that this phase was isotropic so had to have a cubic structure. NaSrPO4·9H2O is the only known cubic phase containing these EDS observable elements. These results confirm that NaSrPO4·9H2O is present, so the solubility of this species may drive the behavior of strontium in the waste.

Absorbed Dose Assessment from Short-Lived Radionuclides of Radon (222Rn) Decay Chain in Lung Tissue: A Monte Carlo Study

Introduction: Internal exposure to radon gas progeny can lead to serious biologic damages to the lung tissue. The aim of this study was to evaluate the absorbed dose by lung tissue due to the exposure from short-lived radioactive products of radon (222Rn) decay using Monte Carlo simulation. Material and Methods: A lung equivalent phantom including 64 air sacs was simulated by MCNPX code. Then, the absorbed dose from short-lived radioactive products of radon decay chain including 218Po, 214Po, 214Pb and 214Bi was calculated for both suspended and deposited states of daughter nuclides inside the lung. Results: The results showed that alpha decay has more contribution to the lung absorbed dose in comparison with the beta and gamma decay. Furthermore, the received dose by the lung was higher when the radon progenies were deposited inside the lung so that the maximum received dose to lung was 100 times higher than that of calculated in suspended state. Conclusion: Short-lived daughter radionuclides of radon decay chain, especially alpha emitter products, can be considered as dangerous internal radiation sources. The biological effects of these daughter radionuclides is more severe when are suspended inside the respiratory system.

Radon-222: environmental behavior and impact to (human and non-human) biota.

As an inert radioactive gas, 222Rn could be easily transported to the atmosphere via emanation, migration, or exhalation. Research measurements pointed out that 222Rn activity concentration changes during the winter and summer months, as well as during wet and dry season periods. Changes in radon concentration can affect the atmospheric electric field. At the boundary layer near the ground, short-lived daughters of 222Rn can be used as natural tracers in the atmosphere. In this work, factors controlling 222Rn pathways in the environment and its levels in soil gas and outdoor air are summarized. 222Rn has a short half-life of 3.82days, but the dose rate due to radon and its radioactive progeny could be significant to the living beings. Epidemiological studies on humans pointed out that up to 14% of lung cancers are induced by exposure to low and moderate concentrations of radon. Animals that breed in ground holes have been exposed to the higher doses due to radiation present in soil air. During the years, different dose-effect models are developed for risk assessment on human and non-human biota. In this work are reviewed research results of 222Rn exposure of human and non-human biota.

Diffusing alpha-emitters radiation therapy: approximate modeling of the macroscopic alpha particle dose of a point source

Diffusing alpha-emitters radiation therapy (‘DaRT’) is a new cancer-treatment modality, which enables treating solid tumors by alpha particles. The treatment utilizes implantable seeds embedded with a low activity of radium-224. Each seed continuously emits the short-lived alpha-emitting daughters of radium-224, which spread over several mm around it, creating a ‘kill region’ of high alpha-particle dose. DaRT is presently tested in clinical trials, starting with locally advanced and recurrent squamous cell carcinoma (SCC) of the skin and head and neck, with promising results with respect to both efficacy and safety. This work aims to provide a simple model which can serve as a zero-order approximation for DaRT dosimetry, allowing for calculating the macroscopic alpha particle dose of a point source, as a basis for more realistic source geometries. The model consists of diffusion equations for radon-220, lead-212 and bismuth-212, with the other short-lived daughters in local secular equilibrium. For simplicity, the medium is assumed to be homogeneous, isotropic and time-independent. Vascular effects are accounted for by effective diffusion and clearance terms. To leading order, the alpha particle dose can be described by simple analytic expressions, which shed light on the underlying physics. The calculations demonstrate that, for a reasonable choice of model parameters, therapeutic alpha-particle dose levels are obtained over a region measuring 4–7 mm in diameter for sources carrying a few Ci of radium-224. The model predictions served as the basis for treatment planning in the SCC clinical trial, where treatments employing DaRT seeds carrying 2 Ci of radium-224 and spaced 5 mm apart resulted in ∼ complete response of the treated tumors with no observed radiation-induced toxicity. The promising results of the SCC clinical trial indicate that in spite of its approximate nature, the simple diffusion-based dosimetry model provides a quantitative starting point for DaRT treatment planning.

Stimulated X-rays in resonant atom Majorana mixing

Massive neutrinos demand to ask whether they are Dirac or Majorana particles. Majorana neutrinos are an irrefutable proof of physics beyond the Standard Model. Neutrinoless double electron capture is not a process but a virtual ΔL = 2 mixing between a parent AZ atom and a daughter A(Z — 2) excited atom with two electron holes. As a mixing between two neutral atoms and the observable signal in terms of emitted two-hole X-rays, the strategy, experimental signature and background are different from neutrinoless double beta decay. The mixing is resonantly enhanced for almost degeneracy and, under these conditions, there is no irreducible background from the standard two-neutrino channel. We reconstruct the natural time history of a nominally stable parent atom since its production either by nature or in the laboratory. After the time periods of atom oscillations and the decay of the short-lived daughter atom, at observable times the relevant “stationary” states are the mixed metastable long-lived state and the short-lived excited state, as well as the ground state of the daughter atom. Their natural population inversion is most appropriate for exploiting the bosonic nature of the observed X-rays by means of stimulating X-ray beams. Among different observables of the atom Majorana mixing, we include the enhanced rate of stimulated X-ray emission from the long-lived metastable state by a high-intensity X-ray beam. A gain factor of 100 can be envisaged in a facility like European XFEL.

Actinium Biokinetics and Dosimetry: What is the Impact of Ac-227 in Accelerator-Produced Ac-225?

Among the growing list of alpha-emitting isotopes now available for pharmaceutical development, Ac-225 can act as an in vivo alpha-generator radionuclide and is of great interest for new targeted alpha-therapy applications. To seek further development of Ac-225 bioconjugate therapeutics, ongoing efforts aim at addressing current limitations, including lacking supply of the radioisotope, insufficient understanding of its biodistribution and biodosimetry, poor retention of alpha-emitting daughter products at the target site, as well as inadequate chelation, one of the major drawbacks. The U.S. Department of Energy’s Isotope Program has been exploring new pathways for the production of the radioisotope Ac-225 at accelerator facilities to address a potential increased need for medical applications. However, the presence of co-produced, long-lived Ac-227 (21.8 y half-life) is observed in about 0.15-0.3 activity percent in the accelerator derived product at the end of target bombardment. Up to 0.5 activity percent values due to Ac-227 could be anticipated in a research/clinical setting. One goal of our work is to delineate the biodistribution of Ac-225, its short-lived daughter products, and potential trace contaminants such as Ac-227 that may be co-produced in new larger-scale accelerator derived processes. The biokinetics of unchelated, chelated (with classic macrocyclic structures, amino-polycarboxylic acids, or new hydroxypyridinone ligands under development), and bio-conjugated Ac-225 and Ac-227 were determined in several mouse models. The resulting biodistribution and dosimetry profiles highlight significant differences among isotope and ligand combinations that must be considered and addressed in order to ensure bioconjugated Ac-225 is safe for use in the clinic. Part of the discussed work was supported by the U.S. Department of Energy’s Isotope Program in the Office of Nuclear Physics at the Lawrence Berkeley National Laboratory under Contract DE-AC02-05CH11231.

Measurement of radon, thoron and their daughters in the air of marble factories and resulting alpha-radiation doses to the lung of workers.

Concentrations of radon (222Rn) and thoron (220Rn) were measured in the air of different marble factories by using a nuclear track technique. The influence of the marble dust nature and ventilation on radon and thoron concentrations was investigated. It was observed that measured radon and thoron concentration ranged from 310 to 903Bqm-3 and 6 to 48Bqm-3, respectively. In addition, alpha-activities due to the unattached and attached fractions of 218Po and 214Po radon short-lived progeny were evaluated in the marble factories studied. Committed equivalent doses due to the attached and unattached fractions of 218Po and 214Po nuclei were evaluated in the lung tissues of marble factory workers. The dependence of the resulting committed equivalent dose on the concentration of the attached and unattached fractions of the 218Po and 214Po radionuclides and mass of the tissue was investigated. The resulting annual committed effective doses to the lung of marble factory workers due to the attached and unattached fractions of the 218Po and 214Po radionuclides were calculated. The obtained results show that about 80% of the global committed effective doses received by workers in the studied marble factories are due to the attached fraction of the 218Po and 214Po radon short-lived daughters from the inhalation of polluted air. Male workers spending 8h per day (2080h per year) in a marble factory receive a maximum dose of 34.46mSvy-1 which is higher than the (3-10mSvy-1) dose limit interval given by the ICRP. Good agreement was found between data obtained for the average effective dose gotten by using this method and the UNSCEAR and ICRP conversion dose coefficients.

Comparison of Reactor Production of 229Th vs. Accelerator Production of 229Th at Oak Ridge National Laboratory

Actinium-225 (t1/2 = 10.0 ± 0.1 d) is one of the more effective radioisotopes used in alpha radioimmunotherapy. It has been used to treat many forms of cancer including glioblastoma, acute myeloid leukemia, prostate cancer, and breast cancer. Actinium-225 can be directly applied in vivo or used as a generator of the short-lived daughter product 213Bi (t1/2 = 45.59 ± 0.06 minutes). Actinium-225 can be produced directly via cyclotron through the 226Ra(p,2n)225Ac reaction or by high energy proton spallation (Ep > 90 MeV) of thorium targets. However, because of its ten-day half-life, it is more efficient to create its precursor, 229Th (t1/2 = 7932 ± 28 years). Current supplies of 229Th originate from the decay of 233U [t1/2 = (1.592 ± 0.002) x 105 y], but that supply is insufficient to support the demand for 225Ac and access to 233U is limited. In order to close the gap between supply and demand of 225Ac, work has been initiated at Oak Ridge National Lab to produce 229Th through the irradiation of 226Ra targets in the High Flux Isotope Reactor. This method to produce 229Th will be presented and compared to previous studies performed at ORNL to produce 229Th through the low energy proton bombardment (Ep < 40 MeV) of 232Th at the Holifield Radioactive Ion Beam Facilities Tandem Accelerator.