Parent Radionuclides 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.

Radionuclide characterization and handling strategy of irradiated Fission Product Material (FPM) capsule waste from molybdenum-99 production

Abstract Irradiated FPM Capsule waste is one of the types of radioactive waste generated from Molybdenum-99 (99Mo) production. This 99Mo is a 99mTc parent radionuclide that is used for the diagnosis of human organ disorders. In its production, the capsule is used for the emplacement of uranium target for irradiation in the GA Siwabessy Reactor. Since the beginning of production until now, the irradiated FPM capsules waste are still being stored in the hot cells because no data on their characteristics and handling systems that are necessary for their treatment. However, long-term storage of the FPM capsules waste in the hot cells shall be avoided because it can disrupt the production process of 99Mo and pose radiation risk to workers. The objectives of this research are to characterize radionuclides composition in the FPM capsule waste and identify its appropriate handling system. The radionuclides characterization was carried out using ORIGEN 2.1 software whereas the selection of the handling system was based on the suitability or modification of the available facilities at Radioactive Waste Management Installation (RWMI)-BRIN. The characterization results show that up to a decay time of 50 years, an FPM capsule waste contains activation product radionuclides such as 55Fe, 59Ni, and 63Ni with a total specific activity of 7.11x106 Bq/g. Three FPM capsule waste handling systems were identified that can be implemented at the RWMI facility, namely by using a 350 -liter concrete shell and then storing in an interim storage for low and intermediate-level waste, using a 60-liter stainless-steel canister which is then stored in the interim storage pit for high-level waste, or by modifying the interim storage pit for high-level waste. Radionuclide characterization and appropriate handling systems are required for the safe management of irradiated FPM capsule waste. This FPM capsule waste management is important for human and environmental protection.

Development of 225Ac-doped biocompatible nanoparticles for targeted alpha therapy

Targeted alpha therapy (TAT) relies on chemical affinity or active targeting using radioimmunoconjugates as strategies to deliver α-emitting radionuclides to cancerous tissue. These strategies can be affected by transmetalation of the parent radionuclide by competing ions in vivo and the bond-breaking recoil energy of decay daughters. The retention of α-emitting radionuclides and the dose delivered to cancer cells are influenced by these processes. Encapsulating α-emitting radionuclides within nanoparticles can help overcome many of these challenges. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles are a biodegradable and biocompatible delivery platform that has been used for drug delivery. In this study, PLGA nanoparticles are utilized for encapsulation and retention of actinium-225 ([225Ac]Ac3+). Encapsulation of [225Ac]Ac3+ within PLGA nanoparticles (Zave = 155.3 nm) was achieved by adapting a double-emulsion solvent evaporation method. The encapsulation efficiency was affected by both the solvent conditions and the chelation of [225Ac]Ac3+. Chelation of [225Ac]Ac3+ to a lipophilic 2,9-bis-lactam-1,10-phenanthroline ligand ([225Ac]AcBLPhen) significantly decreased its release (< 2%) and that of its decay daughters (< 50%) from PLGA nanoparticles. PLGA nanoparticles encapsulating [225Ac]AcBLPhen significantly increased the delivery of [225Ac]Ac3+ to murine (E0771) and human (MCF-7 and MDA-MB-231) breast cancer cells with a concomitant increase in cell death over free [225Ac]Ac3+ in solution. These results demonstrate that PLGA nanoparticles have potential as radionuclide delivery platforms for TAT to advance precision radiotherapy for cancer. In addition, this technology offers an alternative use for ligands with poor aqueous solubility, low stability, or low affinity, allowing them to be repurposed for TAT by encapsulation within PLGA nanoparticles.Graphical

Preparation of Medical 228Th-224Ra Radionuclide Generator Based on SiO2@TiO2 Microspheres.

224Ra (T1/2 = 3.63 d), an α-emitting radionuclide, holds significant promise in cancer endoradiotherapy. Current 224Ra-related therapy is still scarce because of the lack of reliable radionuclide supply. The 228Th-224Ra radionuclide generator can undoubtedly introduce continuous and sustainable availability of 224Ra for advanced nuclear medicine. However, conventional metal oxides for such radionuclide generators manifest suboptimal adsorption capacities for the parent nuclide, primarily attributable to their limited surface area. In this work, core-shell SiO2@TiO2 microspheres were proposed to develop as column materials for the construction of a 228Th-224Ra generator. SiO2@TiO2 microspheres were well prepared and systematically characterized, which has also been demonstrated to have good adsorption capacity to 228Th and very weak binding affinity toward 224Ra via simulated chemical separation. Upon introducing 228Th-containing solution onto the SiO2@TiO2 functional column, a 228Th-224Ra generator with excellent retention of the parent radionuclide and ideal elution efficiency of daughter radionuclide was obtained. The prepared 228Th-224Ra generator can produce 224Ra with high purity and medical usability in good elution efficiency (98.72%) even over five cycles. To the best of our knowledge, this is the first time that the core-shell mesoporous materials have been applied in a radionuclide generator, which can offer valuable insights for materials chemistry, radiochemical separation, and biological medicine.

Advances in heavy alkaline earth chemistry provide insight into complexation of weakly polarizing Ra2+, Ba2+, and Sr2+ cations.

Numerous technologies-with catalytic, therapeutic, and diagnostic applications-would benefit from improved chelation strategies for heavy alkaline earth elements: Ra2+, Ba2+, and Sr2+. Unfortunately, chelating these metals is challenging because of their large size and weak polarizing power. We found 18-crown-6-tetracarboxylic acid (H4COCO) bound Ra2+, Ba2+, and Sr2+ to form M(HxCOCO)x-2. Upon isolating radioactive 223Ra from its parent radionuclides (227Ac and 227Th), 223Ra2+ reacted with the fully deprotonated COCO4- chelator to generate Ra(COCO)2-(aq) (log KRa(COCO)2- = 5.97 ± 0.01), a rare example of a molecular radium complex. Comparative analyses with Sr2+ and Ba2+ congeners informed on what attributes engendered success in heavy alkaline earth complexation. Chelators with high negative charge [-4 for Ra(COCO)2-(aq)] and many donor atoms [≥11 in Ra(COCO)2-(aq)] provided a framework for stable complex formation. These conditions achieved steric saturation and overcame the weak polarization powers associated with these large dicationic metals.

Characterizing 226Ra and its daughters in coastal zone groundwater of a typical human-activity affected bay: occurrence, safety, and source evaluation.

Due to their extremely toxic properties, 226Ra and it daughters (222Rn, 210Pb, and 210Po) in drinking groundwater require monitoring. Recent studies have reported exceptionally high levels of natural 210Po (up to 10,000Bq/m3), 226Ra, and 222Rn isotopes in groundwater. This study aims to provide background data on 226Ra and its daughter radionuclides in the typical agricultural-industrial Dongshan Bay (DSB) before the construction of Zhangzhou Nuclear Power Plant (Zhangzhou NPP). The measurement results indicate that no abnormally high activities of 210Po and 210Pb were detected in the investigated wells. Strong positive correlations between 210Pb and 210Po, as well as between 222Rn and 210Pb activities, suggest that the origins of 210Pb and 210Po in groundwater are strongly influenced by the decay of the parent radionuclides 222Rn and 210Pb, respectively. In the DSB coastal zone groundwater, significant deficiencies of 210Po relative to 210Pb and 210Pb relative to 222Rn were observed, providing further evidence that 210Po and 210Pb are also effectively scavenged due to their geochemical properties (specifically particle affinity) within the groundwater-aquifer system. A systematic comparison among all relevant water bodies in the DSB revealed that the activity concentrations of 210Pb and 210Po in groundwater were the highest, except for rainwater. Based on the evaluation of 210Pb sources, the results imply that submarine groundwater discharge (SGD) is an important pathway for transferring radionuclides (such as 210Pb) from land to the nearshore marine environment, even though the study area has a lower 210Pb background groundwater. By considering all the 210Pb's sources in the DSB, we found low 210Pb background groundwater discharge still needs to be taken into account for small-scale bays. This is because SGD was calculated to be one of the most important 210Pb sources in the bay during observation season. Regardless of whether the system is in a normal state or a nuclear accident emergency state, greater attention should be paid to the groundwater discharge of radionuclides into the ocean.

Dissolution of Molybdenum in Hydrogen Peroxide: A Thermodynamic, Kinetic and Microscopic Study of a Green Process for 99mTc Production.

99mTc-based radiopharmaceuticals are the most commonly used medical radioactive tracers in nuclear medicine for diagnostic imaging. Due to the expected global shortage of 99Mo, the parent radionuclide from which 99mTc is produced, new production methods should be developed. The SORGENTINA-RF (SRF) project aims at developing a prototypical medium-intensity D-T 14-MeV fusion neutron source specifically designed for production of medical radioisotopes with a focus on 99Mo. The scope of this work was to develop an efficient, cost-effective and green procedure for dissolution of solid molybdenum in hydrogen peroxide solutions compatible for 99mTc production via the SRF neutron source. The dissolution process was extensively studied for two different target geometries: pellets and powder. The first showed better characteristics and properties for the dissolution procedure, and up to 100 g of pellets were successfully dissolved in 250-280 min. The dissolution mechanism on the pellets was investigated by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. After the procedure, sodium molybdate crystals were characterized via X-ray diffraction, Raman and infrared spectroscopy and the high purity of the compound was established by means of inductively coupled plasma mass spectroscopy. The study confirmed the feasibility of the procedure for production of 99mTc in SRF as it is very cost-effective, with minimal consumption of peroxide and controlled low temperature.

Динамика формирования поглощённых доз в крови лабораторных животных от альфа-излучающих радионуклидов с последовательными распадами

Since the beginning of the XXI century, active research has begun on the development of fundamentally new radiopharmaceutical drugs based on alpha-emitting maternal radionuclides for radionuclide therapy of micro-tumors and metastases. The main difficulty in assessing the absorbed doses of internal irradiation of such drugs is to take into account the radiation loads from all daughter radionuclides of sequential decay with alpha and beta transformations. The aim of the work is to develop a methodology for calculating the accumulated and total absorbed doses in the blood of laboratory animals from alpha-emitting radionuclides with successive decays within the framework of the compartment modeling method. To test the developed methodology and calculate the dosimetric characteristics, the free isotope Ac-225, injected into the blood as part of its chloride Ac-225Cl3, and the osteotropic preparation Ac-225-KHEDP (monokalium salt of hydroxyethylidendiphosphonic acid) labeled with it were selected. Quantitative data on the bio-distribution of Ac-225-KHEDP and Ac-225Cl3 in the body of intact mice were used to identify the necessary parameters. Calculations of the dosimetric characteristics of two Ac-225-labeled drugs in the blood of intact mice showed that the values of accumulated absorbed doses monotonically increase from the moment of drug administration, reaching their limit values equal to the total absorbed doses by about 300 hours. Alpha-emitting parent and daughter radionuclides make the main contribution to the values of total absorbed doses. The contribution of daughter beta-emitting radionuclides is significantly less, therefore, they can be ignored when preliminary estimates of the total absorbed doses are made. When using Ac-225-KHEDP, all radiation loads on the blood are approximately 2.5 times less compared to Ac-225Cl3, which is explained by the higher blood clearance value for Ac-225-KHEDP. The results obtained indicate the prospects for further studies of 225Ac-KHEDP and the possibility of its clinical application for the treatment of skeletal metastases.

Radon Level and Effects in Public and Residential Places in Nigeria

Reports from the World Health Organization (WHO) regarding radon as human lung carcinogen has generated a lot of research interest on the impacts of radon exposure to people all over the world. Radon concentration of different building types such as glass house, bricks and basement house structures at different locations geographically were reviewed to evaluate sustainable radon level as a strategic pathway for environmental sustainability in Nigeria. Volumes of expertises in research domain and their respective views were crystallized to forge status of Nigerians on the risk scale. Average mean radon concentration from cumulative survey suggested that dwelling and residential houses are within the recommended limit suggested by standard international and local organizations with little variations owing to several contributory factors. Research also shows that some buildings materials containing relative parent radionuclides of radon and its progenies can also contribute to indoor radon concentration, nevertheless, soil gas containing radon found in soils overlying basement rocks constitute the main source for indoor radon concentration within dwelling places. It is wholly to write that the delineated radon map will serve as a useful tool for determination of new building sites in Nigeria and as a guide for future radon remediation and monitory plan for the safest life in our dear Nation Nigeria.

PET in vivo generators 134Ce and 140Nd on an internalizing monoclonal antibody probe

The in vivo-generator radionuclides 140Nd (t1/2 = 3.4 d) and 134Ce (t1/2 = 3.2 d) were used to trace a urokinase-type plasminogen activator (uPA)-targeting mouse monoclonal antibody, ATN-291, in U87 MG xenograft tumor-bearing mice. ATN-291 is known to internalize on the uPA/uPA-receptor pair, making it an appropriate targeting vector for investigating the fate of in vivo generator daughters on internalizing probes. Ante-mortem and post-mortem PET imaging at 120 h post-injection gave no indication of redistribution of the positron emitting daughter nuclides 134La and 140Pr from tumor tissue (p > 0.5). The lack of redistribution indicates that the parent radionuclides 134Ce and 140Nd could be considered as long-lived PET-diagnostic matches to therapeutic radionuclides like 177Lu, 161Tb and 225Ac when internalizing bioconjugates are employed.

212Pb: Production Approaches and Targeted Therapy Applications.

Over the last decade, targeted alpha therapy has demonstrated its high effectiveness in treating various oncological diseases. Lead-212, with a convenient half-life of 10.64 h, and daughter alpha-emitter short-lived 212Bi (T1/2 = 1 h), provides the possibility for the synthesis and purification of complex radiopharmaceuticals with minimum loss of radioactivity during preparation. As a benefit for clinical implementation, it can be milked from a radionuclide generator in different ways. The main approaches applied for these purposes are considered and described in this review, including chromatographic, solution, and other techniques to isolate 212Pb from its parent radionuclide. Furthermore, molecules used for lead’s binding and radiochemical features of preparation and stability of compounds labeled with 212Pb are discussed. The results of preclinical studies with an estimation of therapeutic and tolerant doses as well as recently initiated clinical trials of targeted radiopharmaceuticals are presented.

Preparation of 191Os–phytate, an in-vivo radionuclide generator, for radiosynovectomy application

191Os is a parent radionuclide with a 15.4 d half-life. It decays by beta emission to 191mIr, which is a radionuclidewith a 4.96s half-life. It decays by the isomeric transition to stable 191Ir, emitting a 129-keV gamma photon. In thisstudy, 191Os–phytate was developed into an in-vivo radionuclide generator for simultaneous radiosynovectomy and imaging. 191Os-hexachloroosmate was used to prepare 191Os–phytate (100 μCi/50 μl) using reaction condition optimization followed by an intraarticular injection to rat knee joints. Also, its distribution and stability were assessed. The imaging of 191Os cation and 191Os–phytate was performed by SPCET. The 191Os–phytate complex was obtained at pH=5.5 with normal saline at room temperature. Radio-TLC showed an overall radiochemical yield of 95-98%. The complex was injected into the rats’ knees, and the whole injected dose remained at the injection site even three days after injection. Due to the stability and retention of the complex in joints approved by biodistribution and imaging studies, the complex is a potential in vivo generator for cavital radiosynovectomy of minor joints.

IDAC-ALPHA: AN ALPHA DOSIMETRY SOFTWARE FOR NORMAL ORGANS AND TISSUES.

Radiopharmaceuticals have been used for the treatment of various forms of cancer since the 1940s. In recent years, the advantages of alpha emitting radionuclides have emerged as a favourable treatment option. However, most alpha emitting radionuclides have long decay chains with long-lived daughter radionuclides. This leads to uncertainties in the dosimetry for normal organs and tissues, when established dosimetry models are employed. The aim of this project is to assign each progeny its own biokinetic behaviour. The novel dosimetry model was applied to 223Ra-dichloride, frequently used for the treatment of patients with metastatic bone disease from castration-resistant prostate cancer. In this dosimetry model, individual biokinetics for each daughter radionuclide was included. This resulted in a decrease in absorbed dose to bone surfaces and red marrow and increased absorbed dose to liver and kidney, when compared with dosimetry models assuming that the daughter nuclides follow the biokinetics of the parent radionuclide.

Impact of Technologically Enhanced Naturally Occurring Radioactive Materials (TE-NORM) In oil and gas industry On Environment

Naturally-occurring radioactive material (NORM) is the term used to describe materials containing radionuclides that exist in the natural environment. The radionuclides of interest include long-lived radionuclides such as uranium-238 (238U), uranium-235 (235U) and thorium-232 (232Th) and their radioactive decay products (such as isotopes of radium, radon, polonium, bismuth and lead), and individual long-lived radionuclides such aspotassium-40 (40K), rubidium-87 (87Rb) and indium-115 (115In). The parent radionuclides have decay times (half-lives) which are comparable with or larger than the age of the earth, so they have always been present in the earth’s crust and within the tissues of all living species. Where materials contain radionuclides from the naturally occurring decay chains (238U, 235U, 232Th), the large number of radionuclides in each chain, and the resulting large range of physical and chemical properties of the individual radionuclides, means that there can be a highly variable degree of secular equilibrium between the individual members of the chains

Optimization of γ-Spectrometry Measurements of Radionuclides of Natural Thorium-232 and Uranium-238 Series

The nuclear-physical properties of radionuclides of natural 232Th and 238U series differ significantly; therefore, the problem of selecting particular γ-lines for calculations arises in direct γ-spectrometry measurements in assessing the absolute activities of the parent radionuclides of these series. In the present study, we develop an approach yielding a reliable value of the specific activity of 232Th and 238U by a single measurement of a sample with the smallest deviation from the true value. We used a bottom sediment sample, taken during the 66th cruise of the Akademik Mstislav Keldysh research vessel in the Kara Sea (station coordinates: 72°30.4' N, 80°20.4' E; depth 14 m), as a model sample. When processing the results, only those lines were selected from the entire set of lines belonging to the 232Th natural series, the quantum yield of which exceeded 2% (taking into account branching). When analyzing the natural 238U series, we selected lines that were free from interference with nuclides of the 232Th series and with the quantum yield above 3%.

Dosimetric impact of natural terrestrial radioactivity on residents of lower Himalayas, India.

A comprehensive radio-ecological evaluation of soil samples of Solan and Shimla districts of Himachal Pradesh has been carried out for risk and dose assessment. Twenty-six randomly selected environmental soil samples were analysed for natural radionuclide concentrations (226Ra, 232Th and 40K) using NaI(Tl) scintillator detector. The average concentration of 226Ra, 232Th and 40K was observed as 37, 59 and 430Bqkg-1, respectively, which exceeded the worldwide average of 33, 45 and 412Bqkg-1 reported by UNSCEAR (Sources and effects of ionizing radiation. Report to the general assembly with scientific annexes, New York, 2008). Radium equivalent activity (Raeq), hazard indices (Hex, Hin) and radioactivity level indices (Iϒr, Iα, AUI) and Clark value were checked against their threshold limits, and their mean values were safely below the recommended criteria. This confirms the soil applicability for construction purposes. Indoor and outdoor dose rates (Ḋ), age-dependent annual effective doses (AED), organ-specific doses and lifetime attributable cancer risk (both cancer incidence and cancer mortality) were also computed. Strong positive correlation was established between radon/thoron exhalation rate and their parent radionuclides. Multivariate statistical technique was employed to explore spatial distribution of radionuclides and homogeneity between various radiological parameters.

Biokinetic Method on Simultaneous Intake of Radionuclides from Multiple Intake Scenarios for Application in Internal Exposures.

Biokinetics underlies the basis for assessment of internal exposures. This paper develops a biokinetic method on simultaneous intake of radionuclides from multiple intake scenarios in internal exposures. With numerical techniques that transform the whole biokinetics between the coupled and decoupled representations of the same problem, this method applies to coupled biokinetics with complex structures and has no restrictions of practical importance on the number of intake scenarios, the number of intake parent radionuclides and decay products, and the complexity of decay relationships between parent and progeny nuclides. For illustration, this method is applied to an assumed case of mixed inhalation and ingestion of weapon-grade plutonium material for reference workers that is focused on Pu and Am. Due to coupled biokinetics between the direct intake and ingrowth parts in different intake pathways, the multiple intake results (the contents of lungs, daily excretions, and cumulative contents) display richer behaviors as compared to single intake cases. This method benefits both the prospective and retrospective assessment of internal exposures for complex intake cases in actual applications.

A general probabilistic solution of randomized radioactive decay chain (RDC) model using RVT technique

This article develops a complete solution of the randomized nuclear radioactive decay chain model based on Bateman master equations. A multidimensional version of the random variable transformation technique is adapted to derive a full probabilistic description for this model. To present general and more realistic physical situation, the initial number of the parent radionuclides and the decay parameters are considered to be random variables. The first probability density functions for the solution processes and the time until a given number of parent radionuclides remains in its state before decaying are constructed and used to calculate the mean, the variance and the confidence intervals. To test the efficiency of the theoretical findings, some numerical results are graphically presented and found to be consistent with the observations.

Accounting for ingrowth of radioactive progeny in dose assessments: generic weighting factors for dose coefficients

In this paper, we describe a practical and convenient method to include the contribution of the ingrowth of radioactive progeny in dose assessments of the corresponding parent nuclides. This method modifies the dose coefficients (DCs) of parent nuclides by adding weighted DCs of the corresponding daughter nuclides to them. Based on the decay kinetics of serial nuclear transformations, the progeny weighting factors, with values between 0 and 1, are derived by analysis of the time-integrated activity of each nuclide in the (branched) decay chain headed by a parent nuclide. Using the electronic, nuclear-decay database of Publication 107 of the International Commission on Radiological Protection (ICRP 2008), DC weighting factors for annual dose assessments are calculated for all daughter radionuclides in the decay chains and are tabulated in this paper. Weighting factors based on integration periods other than one year, ranging from 1 h–70 years, are also provided (see the supplementary material). With a priori established weighting factors, dose assessments become significantly simplified by considering the decay kinetics of only the parent nuclides and by applying the modified DCs. This ensures that the ingrowth of progeny is taken into account realistically. In some cases, one requires a conservative estimate of the dose, for instance when dealing with issues of the clearance of materials under regulatory control. Therefore, we adapted the weighting-factor method to derive conservative DC weighting factors for dose evaluations. These values are calculated for various integration periods and compared with those from an existing method adopted by the Euratom Article 31 Group of Experts and by the International Atomic Energy Agency. Identical progeny weighting factors are obtained for long-lived parent radionuclides, whereas for short-lived parent radionuclides, the new method can yield significantly larger values. For example, the weighting factor of I-131 (daughter of parent Te-131) increases from 0.002 to 1.0 based on an integration period of 1 year. The progeny DC weighting factors, derived based on nuclear transformations in exit-only decay chains, may not always be suitable for use in radiological dose evaluations. For instance, when environmental removal pathways are dominant, the application of these weighting factors may have its limitations. This paper, therefore, provides guidance on the proper selection and application of weighting factors.

A Monte Carlo Method for Determining the Response Relationship between Two Commonly Used Detectors to Indirectly Measure Alpha Particle Radiation Activity.

Using targeted ligands to deliver alpha-emitting radionuclides directly to tumor cells has become a promising therapeutic strategy. To calculate the radiation dose to patients, activities of parent and daughter radionuclides must be measured. Scintillation detectors can be used to quantify these activities; however, activities found in pre-clinical and clinical studies can exceed their optimal performance range. Therefore, a method of correcting scintillation detector measurements at higher activities was developed using Monte Carlo modeling. Because there are currently no National Institute of Standards and Technology traceable Actinium-225 (225Ac) standards available, a well-type ionization chamber was used to measure 70.3 ± 7.0, 144.3 ± 14.4, 222.0 ± 22.2, 299.7 ± 30.0, 370.0 ± 37.0, and 447.7 ± 44.7 kBq samples of 225Ac obtained from Oak Ridge National Lab. Samples were then placed in a well-type NaI(Tl) scintillation detector and spectra were obtained. Alpha particle activity for each species was calculated using gamma abundance per alpha decay. MCNP6 Monte Carlo software was used to simulate the 4π-geometry of the NaI(Tl) detector. Using the ionization chamber reading as activity input to the Monte Carlo model, spectra were obtained and compared to NaI(Tl) spectra. Successive simulations of different activities were run until a spectrum minimizing the mean percent difference between the two was identified. This was repeated for each sample activity. Ionization chamber calibration measurements showed increase in error from 3% to 10% as activities decreased, resulting from decreasing detection efficiency. Measurements of 225Ac using both detector types agreed within 7% of Oak Ridge stated activities. Simulated Monte Carlo spectra of 225Ac were successfully generated. Activities obtained from these spectra differed with ionization chamber readings up to 156% at 147.7 kBq. Simulated spectra were then adjusted to correct NaI(Tl) measurements to be within 1%. These were compared to ionization chamber readings and a response relationship was determined between the two instruments. Measurements of 225Ac and daughter activity were conducted using a NaI(Tl) scintillation detector calibrated for energy and efficiency and an ionization chamber calibrated for efficiency using a surrogate calibration reference. Corrections provided by Monte Carlo modeling improve the accuracy of activity quantification for alpha-particle emitting radiopharmaceuticals in pre-clinical and clinical studies.