Medical Isotope Production Research Articles

A Magnet Design of an Advanced High-Field Superconducting Cyclotron for Medical Isotope Production

A Magnet Design of an Advanced High-Field Superconducting Cyclotron for Medical Isotope Production

Precision in medical isotope production: Nuclear model calculations using artificial neural networks

In this groundbreaking study, artificial neural networks (ANNs) are employed to predict the production cross-sections of crucial radioisotopes, namely 18O, 209Bi, 232Th, and 68Zn, via the (p,n) reaction. We employed a comparative approach to validate the ANN model's predictions by comparing them to outputs generated by established nuclear reaction codes (TALYS 1.9, EMPIRE-3.2 (Malta)) and data from the authoritative source, the Experimental Nuclear Reaction Data (EXFOR).Motivated by the increasing demand for radioisotopes in precise medical diagnostics and successful therapies, this study focuses on investigating methods and new techniques for determining production cross-sections with high accuracy, which are crucial for the consistent supply of vital radioisotopes. In line with this objective, the ANN model demonstrated exceptional performance, achieving remarkably high correlation coefficients, exceeding 0.999 for training and all data, and reaching 0.98665 for testing. Supportive of this, the high correlation coefficients indicate that the ANN estimations effectively match experimental data. Significantly, our findings illustrate the potential of ANNs as a promising alternative for estimating the production cross-sections of 18O, 209Bi, 232Th, and 68Zn, with the possibility of extending this application to other medically relevant radioisotopes.

Measurement of production cross-sections of natTi(p,x)43K,43,44m,44g,46g,47,48Sc,48V reactions up to 50 MeV

The cross-sections of natTi(p,x) reactions were measured up to 50 MeV by using off-line γ-ray spectrometry and stacked-foil activation technique. The activation experiment was conducted using 57 MeV proton beams from the proton accelerator at the Korea Multi-purpose Accelerator Complex (KOMAC). The natNi(p,x)57Ni reaction was employed to monitor the proton beam flux. The activity of irradiated sample was measured using a high purity germanium (HPGe) detector, and the measured cross-sections were compared with literature data and the TENDL-2023 library. The present work generally matched well with the literature data. The cross-sections for 43,44,47Sc produced through the natTi(p,x) reactions can be used for medical isotopes production, while natTi(p,x)48V reaction can be utilized for proton monitoring reaction.

Convection driven by a nonuniform radiative internal heat source in a cavity: Example of medical isotope production in liquid targets

In the present study we use two-dimensional direct numerical simulations (DNS) to understand the coupled heat transfer to fluid flow in a liquid target for the production of nuclear medicines. Fluid motion is driven by buoyancy created by heat generated by a proton beam. The internal heat source has a gaussian distribution in the vertical direction and a rapidly growing intensity in the horizontal direction until it reaches a range at the Bragg peak where the heating drops to zero. The structure of the heating imposes two convective cells, separated at the location of the range. We solve the governing fluid flow and energy equations in a square cavity subject to highly nonuniform internal heating generated by the energy deposition of a proton beam. While most studies of convection driven by an internal heat source in a fluid layer have been focused on a uniform heating of the fluid, our study shows that the nonuniformity in the heat source has important implications for the temperature and flow fields, the boundary heat fluxes, and the growth of convective instabilities in the flow. Interestingly, the scalings of the maximum and averaged temperatures with the Rayleigh number compare similarly to previously found power laws for uniformly heated fluid layers. At higher power levels, the layer of fluid near the top cold boundary becomes convectively unstable via Rayleigh–Taylor instabilities. By comparing the rate of growth of these instabilities to their rate of advection to the boundaries of the cavity, a model is developed that predicts the instability of the convective cells for different values of the range of the beam and the Rayleigh number. Crucially, we demonstrate that the disturbances in the production of isotopes due to convective instabilities and the design of the cooling system is dependent on the location of the Bragg peak and must be considered in design of future generation of this class of target.

New Mini Neutron Tubes with Multiple Applications

Recent experimental investigations have demonstrated that a substantial amount of H−/D− ions can be formed by thermal desorption processes. Based on these new findings, new mini axial and coaxial-type neutron tubes have been developed for the production of high or low-energy neutrons via the d-d, d-10B, d-7Li or p-7Li nuclear reactions. By operating these mini neutron tubes with a high frequency AC high-voltage supply, short pulses of high intensity neutron beams can be generated. Multiple applications, such as carbon and well logging, neutron imaging, cancer therapy, medical isotope production, fission reactor start-up, fusion reactor material evaluation, homeland security and space exploration can be performed with the subcompact neutron generator system. It is shown that the performance of these new mini neutron tubes can exceed those of the conventional plasma-based neutron sources.

Tailoring Triuranium Octoxide into Multidimensional Uranyl Fluoride Micromaterials.

Uranium microstructured materials with controlled size and shape are relevant to the nuclear industry and have found applications as targets for medical isotope production, fuels for nuclear reactors, standards for nuclear forensics, and energy sources for space exploration. Until now, most studies at the microscale have focused on uranium microspheres (oxides, nitrides, carbides, and fluorides), while micromaterials of uranium halides, carbides, and pnictides with other morphologies are largely unknown. A promising method to shape the morphology of uranium micromaterials is the replacement of O by F atoms in oxide materials using a solid-gas reaction. Here, with the aim to elaborate unexplored uranium fluoride micromaterials, the fluorination of uranium oxide (U3O8 and UO2) microspheres (ms), microrods (mr), and microplates (mp) in an autoclave at 250 °C with HF(g) (produced from the thermal decomposition of silver bifluoride (SBF)) and with ammonium bifluoride (ABF) was evaluated. We show that the reactions between U3O8 mr and U3O8 mp and SBF provided the most efficient way to elaborate mr and mp UO2F2 micromaterials in a high yield (∼90%). The resulting UO2F2 mr (length: 3-20 μm) and UO2F2 mp (width: 1-7.5 μm) exhibited a well-defined geometry that was identical to that of the U3O8 precursors. Agglomerated (NH4)3UO2F5 and UO2F2 ms (2-3.5 μm) were prepared from the reaction of U3O8 ms with ABF. It is noted that the reaction of UO2 ms with SBF and ABF did not provide any uranium fluoride micromaterials. The successful preparation of uranium fluoride microstructures (ms, mr, and mp) developed here opens the way to novel actinide fluoride micromaterials.

USING THE IAEA MEDICAL ISOTOPE BROWSER FOR SIMULATION THE PRODUCTION OF IODINE-123

The paper presents the results of modeling the production of a medical isotope using the medical isotope browser of the International Atomic Energy Agency. A web application for the production of medical isotopes allows you to obtain the necessary data on a nuclear reaction based on user data: target radionuclide, irradiating particle or irradiating radiation, energy range, irradiation and cooling time. Tabular values and illustrated graphs of the cross section of the nuclear reaction are obtained based on modeling the production of the isotope iodine-123 from tellurium-124; The isotope decay products are presented. The simulation results were compared with the data recommended by the IAEA for this nuclear reaction for the gamma-emitting radionuclide iodine-123. It is shown that gamma-emitting radionuclide iodine-123 is one of the most convenient radionuclides for single-photon emission computed tomography. When experimental methods are not available, modern technologies in the field of computer modeling allow specialists in a narrow profile to use the achievements of world science to solve problems, in this case, for the production of medical isotopes. Modeling approaches for the production of iodine-123 are recommended for the production of other medical isotopes.

Research on the Formation Conditions and Preventive Measures of Uranium Precipitates during the Service Process of Medical Isotope Production Reactors.

This study focuses on the Medical Isotope Production Reactor (MIPR), an aqueous homogeneous reactor utilized for synthesizing medical isotopes like 99Mo. A pivotal aspect of MIPR's functionality involves the fuel solution's complex chemical interactions, particularly during reactor operation. These interactions result in the formation of precipitates, notably water filamentous uranium ore and columnar uranium ore, which can impact reactor performance. The research presented here delves into the reactions between liquid fuel uranyl nitrate and key radiolytic products, employing simulation calculations complemented by experimental validation. This approach facilitates the identification of uranium precipitate types and their formation conditions under operational reactor settings. Additionally, the article explores strategies to mitigate the formation of specific uranium precipitates, thereby contributing to the efficient and stable operation of MIPR.

Shape-Selective Supramolecular Capsules for Actinide Precipitation and Separation.

Improving actinide separations is key to reducing barriers to medical and industrial actinide isotope production and to addressing the challenges associated with the reprocessing of spent nuclear fuel. Here, we report the first example of a supramolecular anion recognition process that can achieve this goal. We have designed a preorganized triamidoarene receptor that induces quantitative precipitation of the early actinides Th(IV), Np(IV), and Pu(IV) from industrially relevant conditions through the formation of self-assembled hydrogen-bonded capsules. Selectivity over the later An(III) elements is shown through modulation of the nitric acid concentration, and no precipitation of actinyl or transition-metal ions occurs. The Np, Pu, and Am precipitates were characterized structurally by single-crystal X-ray diffraction and reveal shape specificity of the internal hydrogen-bonding array for the encapsulated hexanitratometalates. This work complements ion-exchange resins for 5f-element separations and illustrates the significant potential of supramolecular separation methods that target anionic actinide species.

Predicting Critical Heat Flux in Rectangular Channels: Which Correlation to Trust?

The PALLAS-reactor is an advanced nuclear reactor dedicated to the production of medical isotopes and (medical) nuclear technological research currently under construction in The Netherlands RELAP5 is the primary tool used for modeling the accident scenarios relevant for licensing the PALLAS-reactor. The Groeneveld Look-Up Tables (LUT) are the main Critical Heat Flux (CHF) model of RELAP5. These have been extensively validated against experiments with round tubes. However, literature suggests that the LUT over-predict CHF inside the narrow, rectangular fuel channels of research reactors such as the PALLAS-reactor. As literature abounds with CHF correlations of limited applicability and low degrees of validation and confidence, correlations that can accurately predict CHF in rectangular channels are needed. The goal of this work is twofold. First, it aims at selecting a number of promising CHF correlations and to assess these against experiments representative of the PALLAS-reactor design. Secondly, this work ascertains whether the LUT are indeed optimistic with respect to CHF in rectangular channels. To this purpose, a literature review has short-listed the Sudo-Kaminaga (S-K), the Kim-modified S-K, and the Hall–Mudawar (H-M) correlations. These correlations are implemented in the SPECTRA code developed at NRG and assessed against two experiments in rectangular channels. The Kim-modified S-K correlation fits the experiments better than the original S-K scheme for high mass fluxes, while predicting higher CHF values at low flow rates. Interestingly, the H-M correlation predicts the experiments accurately, although the correlation was developed from round tubes data. At high mass fluxes, the LUT predictions converge towards the experiments, thereby suggesting that the effect of the channel geometry becomes less important at high flow rates. At low mass fluxes, on the other hand, the LUT markedly fail to match the experiments. This work contributes to accurately estimating CHF in narrow rectangular channels, which is crucial for licensing research reactors such as the PALLAS-reactor, thus assisting in the betterment of many people’s lives.

Examining the potential for detecting simultaneous noble gas and aerosol samples in the international monitoring system radionuclide network

The purpose of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is to establish a legally binding ban on nuclear weapon test explosions or any other nuclear explosions. The Preparatory Commission for the CTBT Organization (CTBTO PrepCom) is developing the International Monitoring System (IMS) that includes a global network of 80 stations to monitor for airborne radionuclides upon entry into force of the CTBT. All 80 radionuclide stations will monitor for particulate radionuclides and at least half of the stations will monitor for radioxenon. The airborne radionuclide monitoring is an important verification technology both for the detection of a radionuclide release and in the determination of whether the release event originates from a nuclear explosion as opposed to an industrial use of nuclear materials.Nuclear power plants and many medical isotope production facilities release radioxenon into the atmosphere. Low levels of a few particulate isotopes, such as iodine, may also be released. Detections of multiple isotopes are useful for screening the radionuclide samples for relevance to the Treaty. This paper examines the anticipated joint detections in the IMS of noble gas and particulate isotopes from underground nuclear explosions where breaches in the underground containment vents from low levels to up to 1% of the radionuclide inventory of the resulting fission products to the atmosphere. Detection probabilities are based on 844 simulated release events spaced out at 17 release locations and one year in time. Six different release (venting) scenarios, including two fractionated scenarios, were analyzed.When ranked by detection probability, 11 particulate isotopes and one noble gas isotope (133Xe) appear in the top 20 isotopes for all six release scenarios. Using the 11 particulate isotopes and the one noble gas isotope, the IMS has nearly the same detection probability as when 45 particulate and 4 noble gas isotopes are used. Thus, a limited list of relevant radionuclides may be sufficient for treaty verification purposes. The probability that at least one particulate and at least one radioxenon isotope would be detected in the IMS from the release events ranged from 0.15 to 0.86 depending on the release scenario.

Irradiation performance of a U-7Mo in Al-Si matrix dispersion full-size fuel plate assembly

The Korea Atomic Energy Research Institute (KAERI) is leading the Ki-Jang Research Reactor (KJRR) project with the intent to develop a new reactor for medical isotope production and other nuclear research purposes. The KJRR core is designed to use high density fuel system where uranium alloyed with 7 wt% molybdenum (U-7Mo) particles are dispersed in a matrix of aluminum alloyed with 5 wt% silicon (Al-5Si) and clad in aluminum alloy 6061 (Al-6061) to form fuel plates. KAERI developed a fabrication facility to construct KJRR fuel assemblies and partnered with the Idaho National Laboratory (INL) to irradiate a full-size fuel assembly, with 21 total fuel plates, in the Advanced Test Reactor (ATR). Irradiation testing and subsequent Post Irradiation Exam (PIE) campaigns were performed successfully over a multi-year project. Monte Carlo neutronic calculations, coupling with a depletion code, were performed based on ATR’s as-run power history which showed that the highest power plate (plate 20) reached 83.1 % end-of-life (EOL) local burnup based on initial 235U content. Finite element thermal modeling was performed based as-run power history which showed a beginning-of-life (BOL) peak local heat flux of 184 W/cm2. No anomalous fuel performance was observed during the irradiation and target test conditions were achieved. PIE showed favorable performance of the fuel assembly regarding all important phenomena. This paper describes the KJRR fuel assembly irradiation conditions and PIE data to support the conclusion that it performed well, without evidence of unexpected or problematic fuel performance, within an irradiation test designed to bound the KJRR design environment.

Short-lived noble gas effluent trends from a research reactor

An understanding of anthropogenic sources of radioactive noble gases in the atmosphere is needed to enhance the discrimination ability of the International Monitoring System's sensors. These sources include commercial and research nuclear reactors and medical isotope production facilities. While abiding by local environmental ordinances these facilities all emit noble gas radioisotopes through normal operation. This research presents measurements and analysis of noble gas isotopes (41Ar, 135Xe, 135mXe, 137Xe, 138Xe, 87Kr, 88Kr, and 89Kr) made directly at the stack of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. The Xe and Kr noble gases are concurrently observed with 41Ar, a neutron activation product, when the reactor is operational. The magnitude of the Xe and Kr noble gases released is not constant over the HFIR cycle, but they temporally match the 41Ar trend. An isotope activity ratio analysis of these shorter lived isotopes combined with the observation of the cycle's temporal trend helps understand the noble gas production mechanism at the HFIR. Isotopes with short half-lives are not useful for long-range environmental monitoring. However, these measurements could potentially be combined with atmospheric modeling to predict the background source term of the longer-lived Xe ratios at a monitoring station.

Addressing the quantification of meteorological uncertainties in the atmospheric transport simulations of the 133Xe industrial background

The French National Data Center (NDC) uses an automated simulation of the 133Xe worldwide atmospheric background as one of the means to categorize the radionuclide measurements of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System (IMS). These simulations take into account 133Xe releases from the known or assumed major industrial emitters in the world and global-scale meteorological data. However, a quantification of the simulation uncertainties in this operational set up is yet to be addressed. This work discusses the benefits of meteorological ensemble data as available from National Centers for Environmental Prediction (NCEP) for that purpose. For this study, the daily dispersion of releases from the Institute for Radio Elements (IRE), a medical isotope production facility located in Fleurus (Belgium), was calculated over one year with emissions measured in-site and ensemble meteorological data. The ensemble contains 31 members, which resulted in as many predictions of activity concentration for any given time and place. The resulting distribution statistics (mean, median and spread), and the control run, were confronted to the deterministic run and to measurements at one IMS-like station near Paris (France) and one IMS station in Freiburg (Germany). Overall, the ensemble results have decreased the simulation performance, as expected given the use of meteorological analyses only. However, contrasting patterns were found with a detailed analysis of daily activity concentration over two one-month-and-a-half periods. Noticeably, outlier results were found to carry the best forecast in some significant detections, proving their relevance for the measurement categorization, despite their isolated character. Importantly, the ensemble has allowed the quantification of meteorological uncertainties, which was beneficial in all cases. It either has improved the confidence of IMS data categorization or has pointed to low confidence predictions. A criterion to identify the latter is suggested, based on information provided by the ensemble distributions. In addition, maps of probability of detections and of relative spread are suggested to show additional benefits of ensemble meteorology.

Determination of detection efficiency on HPGe detector for point-like and volumetric samples based on Geant4 simulations

Production of medical isotopes has recently been developed at the Institute of Modern Physics (IMP) in China and many aqueous samples containing produced radioisotopes at wide range of volume were generated. Evaluation of radionuclidic purity and quantification of radioactivity for these samples are of significant importance, especially for medical purpose. High purity germanium (HPGe) detectors and gamma spectrometry are widely used in radionuclidic purity evaluation due to the high energy resolution. However, radionuclidic purity assessment and determination of radioactivity cannot be accurately conducted by using the HPGe detector installed at Laboratory of Nuclear Chemistry in IMP due to the lack of competent calibration standard sources. Therefore, an efficient method based on Geant4 simulation was proposed to calculate the detection efficiency curve for samples with different geometry, composition and source-to-detector distance. A set of efficiency data measured with a point-like standard source containing multi-radionuclides was used to determine the dimension of germanium crystal and thickness of dead layers. Afterwards, a point-like and 3 volumetric standard sources (5 ml, 10 ml and 20 ml, respectively) containing 152Eu were measured at 5–50 cm source-to-detector distances. The EFFTRAN code was applied to calculate the correction factor of coincidence summing for all measurements. The full energy peak (FEP) efficiencies with energy range of 121–1408 keV were calculated and compared with the values obtained from simulations. The simulated FEP efficiency values were in good agreement with experimental results, which illustrated a satisfactory precision of the Geant4 simulations. The feasibility of obtaining detection efficiency for point-like and volumetric samples by means of Geant4 simulations was confirmed. This method can be applied to address the efficiency problem caused by sample geometry and composition.

Microstructure and microchemistry changes at U-10Mo fuel/AA6061 cladding interfaces with varying hot isostatic pressing conditions

Monolithic uranium - 10 wt.% molybdenum (U-10Mo) is a promising high-assay low-enriched uranium fuel system for nuclear reactors used in research, medical isotope production, and remote power applications. During manufacturing, an aluminum alloy (AA6061) cladding is bonded to the U-10Mo fuel plate via hot isostatic pressing, during which diffusion and fuel/cladding chemical interaction occurs at plate edges. The microstructure and microchemistry changes that occur at fuel/cladding interfaces are important to understand as a function of process parameters to develop a reliable fuel fabrication process and to meet the desired specifications. Here, microstructural and microchemical changes are studied using complementary electron microscopy and atom probe tomography for two manufactured fuel plates with varied hot isostatic pressing (HIP) parameters. Results highlight that modifying thermomechanical processing parameters significantly changes the interaction layer thickness between U-10Mo and AA6061 by an order of magnitude. In addition, the distribution and concentration of elements (i.e., Al, Si, Mg) from cladding to fuel are investigated.

Density reduction effects on the production of [11C]CO2 in Nb-body targets on a medical cyclotron

Medical isotope production of 11C is commonly performed in gaseous targets. The power deposition of the proton beam during the irradiation decreases the target density due to thermodynamic mixing and can cause an increase of penetration depth and divergence of the proton beam. In order to investigate the difference how the target-body length influences the operation conditions and the production yield, a 12 cm and a 22 cm Nb-target body containing N2/O2 gas were irradiated using a 13 MeV proton cyclotron. It was found that the density reduction has a large influence on the pressure rise during irradiation and the achievable radioactive yield. The saturation activity of [11C]CO2 for the long target (0.083 Ci/μA) is about 10% higher than in the short target geometry (0.075 Ci/μA).

Synthesis and Morphological Control of UO2F2 Particulates.

Uranium-based microspheres are of interest due to their potential applications as targets for medical isotopes production, as fuel for nuclear reactors, and as standardized materials for nuclear forensics. Here, for the first time, UO2F2 microspheres (1-2 μm) have been prepared from the reaction between UO3 microspheres and AgHF2 in an autoclave. In this preparation, a new fluorination method has been applied, and HF(g)-produced in situ from the thermal decomposition of AgHF2 and NH4HF2-was used as the fluorinating agent. The microspheres were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Diffraction results indicated that the reaction performed with AgHF2 at 200 °C led to anhydrous UO2F2 microspheres, while at 150 °C, hydrated UO2F2 microspheres were obtained. Meanwhile, NH4HF2 led to the formation of contaminated products as driven by the formation of volatile species.

High-power Fixed-Field Accelerators

We report the state of the field of High-Power Fixed-Field Accelerators (with an emphasis on cyclotrons) as discussed by international experts during a three-day workshop of the same name in 2021. The workshop was part of the Snowmass'21 Community Planning Exercise. Here, we take stock of the world inventory of high-power fixed-field accelerators, assess available beam currents and beam powers, and investigate limitations. Furthermore, we evaluate the role of these machines in particle physics, directly used or as injectors to other machines, and in industry, as drivers for (medical) isotope production and, potentially, for accelerator-driven systems and sub-critical reactors. Finally, we discuss novel concepts and cutting-edge developments to push the available current higher at several energy scales, thereby increasing relative power. Highlights include new spiral inflector types, direct RFQ injection, H2 + acceleration, utilizing vortex motion, and self-extraction schemes. We also discuss modern computational frameworks to optimize accelerators more efficiently, and better describe the relevant physical processes in simulations.

Detection of anomalous radioxenon concentrations: A distribution‐free approach

AbstractThe detection of anomalous atmospheric radioxenon concentrations plays a key role in detecting both underground nuclear explosions and radioactive emissions from nuclear power plants and medical isotope production facilities. For this purpose, the CTBTO's International Data Centre uses a procedure based on descriptive thresholds. In order to supplement this procedure with a statistical inference‐based method, we compared several non‐parametric change‐point control charts for detecting shifts above the natural radioxenon background. The results indicate that the proposed methods can provide valuable tools for the institutions responsible for the verification and classification of anomalous radioxenon concentrations.