Atomic Energy Research Articles

Fixed-node errors in real space quantum Monte Carlo at high densities: Closed-shell atomic correlation energies

We consider non-relativistic electron correlation energies of heavy noble gas atoms including the superheavy element Og. The corresponding data enables us to quantify fixed-node errors in real space quantum Monte Carlo methods as a function of the atomic number Z. We confirm that single-reference trial function nodes lead to an overall trend of mild decrease in recovered correlation energy with the increasing Z. This agrees with our previous study that has shown increasing fixed-node biases with the increasing electron density. We also estimate the value of the linear term in the asymptotic expansion of the atomic correlation energy.

Computational simulation of primary damage in silicon carbide under ions irradiation

Silicon carbide (SiC) and its composites are promising structural materials for advanced nuclear energy applications. Due to the lack of advanced nuclear energy devices, ion beam irradiation is widely used to emulate reactor neutron irradiation. At the same time, different types of ion beam irradiation could produce different primary knock-on atom (PKA) energy spectra. PKA energy determines cascade damage sizes and defect clustering distributions, which may influence the irradiated materials’ long-term microstructural evolution and mechanical properties. This work used SRIM and Geant4 software to investigate the PKA characteristic produced by 1 MeV different noble gas ions and neutrons in the silicon carbide. The PKA energy spectra and weighted energy spectra of C and Si are calculated, respectively. The simulation results show that the PKA energy spectra calculated by the two kinds of software have obvious differences, but the weighted average PKA energies are close to each other. Simulation results verified that the weighted average PKA energy of Kr and Xe ion irradiation is close to that weighted average PKA energy spectrum for neutron irradiation of advanced reactors. The simulation results provide scientific references for understanding the difference in irradiation effects of different types of ions and also provide fundamental bases for the simulation of primary defect damage and long-term defect evolution in irradiated SiC.

Total alpha radioactivity in fertilizers used in the Indian state of West Bengal using CR-39 SSNTDs: Presentation of a comparative view for different types of fertilizers

Use of fertilizers in agriculture soils is a worldwide practice to increase the yield of agricultural products. Fertilizers may contain radioactive elements may be present along with plant’s nutrients in fertilizers. Migrated radioactive elements from the fertilized soils can find their entry into the environment and human body through several ways, which may lead to induce a potential radiological risk to human health. In the present study, total alpha radioactivity concentration in 68 samples of 18 different types of organic and inorganic fertilizers which are commonly used for cultivation in West Bengal and other states of India has been measured using a track-etch technique. Calibration of the CR-39 track detectors used in this measurement has been done using a distributed alpha-radioactive reference source material of IAEA-448 soil, obtained from Reference Materials Group of International Atomic Energy Commission (IAEA). The obtained source mass dependent calibration factors of CR-39 detectors have been used to estimate the alpha radioactivity of the fertilizer samples eliminating the self-absorption of alpha-particles in the sample. The estimated alpha radioactivity values have been found to vary from 29.4 Bq.kg-1 to 114.2 Bq.kg-1, 2.2 Bq.kg-1 to 13.1 Bq.kg-1 and 485.0 Bq.kg-1 to 1125.8 Bq.kg-1 respectively for organic, non-phosphatic and phosphatic fertilizers. The highest alpha radioactivity is exhibited by phosphatic fertilizers and lowest alpha radioactivity is exhibited by non-phosphatic fertilizers. Alpha radioactivity is found to be strongly correlated with phosphate content of the fertilizers. The alpha radioactivity values obtained in our study are consistent with the studies reported worldwide with few exceptions. Considering radiological as well as other aspects, farmers should be encouraged to use non-phosphatic fertilizers in combination and try to avoid phosphatic fertilizers as far as practicable.

Strategic Approach for the Elaboration of a Safety Design Basis for Nonreactor Nuclear Facilities in Brazil

A nonreactor nuclear facility (NRNF) for maritime activities is being designed as part of the Brazilian naval nuclear propulsion program. The absence of national regulations for the design and licensing of naval NRNFs presents a challenge that must be addressed. This study aims to present an initial proposal for developing a safety design basis for NRNFs in Brazil. This proposal is based on the collection and analysis of national and international standards (documentary research), as well as articles, dissertations, and theses (bibliographic research) that discuss the criteria and safety requirements relevant to the licensing and design of NRNFs. This research develops a strategy for applying U.S. Department of Energy (DOE) regulations derived from the U.S. Code of Federal Regulations, Title 10, “Energy,” Part 830, “Nuclear Safety Management,” in conjunction with CNEN (National Nuclear Energy Commission, Brazil) regulation NE 1.04, “Licensing of Nuclear Installations,” aligned with International Atomic Energy Agency requirements to develop a safety design basis for naval NRNFs. The first step of the proposed strategy involves categorizing facility hazards conducted in accordance with DOE-STD-1027. The process continues for facilities categorized as hazard categories 1, 2, and 3. The directive DOE O 420.1C, “Facility Safety,” and the invoked standards serve as foundational elements for developing the safety design basis. The results of this research demonstrate that the DOE regulatory framework for NRNFs is a suitable alternative to address the national regulatory gap and improve the national licensing process by incorporating the safety-in-design concept.

Levels of naturally occurring radionuclides in foods from the first German total diet study.

Although natural radionuclides are always present in foods, information about the levels is scarce. The diet-related exposure to radiation is, however, dependent on the radionuclide content of respective food items. In this study, the levels of the naturally occurring radionuclides lead-210 (Pb-210), uranium-234 (U-234), uranium-238 (U-238), radium-226 (Ra-226) and radium-228 (Ra-228) were investigated in over 200 foods as part of the first German total diet study. Radioanalytical techniques and measurements were applied for determination. The natural radionuclide activity concentrations obtained were generally low compared to international data compilations. Together, Ra-228 and Ra-226 mostly dominated the levels of activity concentrations. Of all Ra-226, Ra-228 and Pb-210 results, between 1% and 19% exceeded the International Atomic Energy Agency (IAEA) guidance level for food products of 0.1Bq/kg or 1Bq/kg. The received activity levels for both U-234 and U-238 were found to be below the suggested IAEA guidance level of 10Bq/kg. The radionuclide activity ratios of Ra-226/Ra-228, U-234/U-238 and Pb-210/Ra-226 of the foods were examined as well. In particular, it was found that the average Ra-226/Ra-228 ratio in all main food groups was substantially lower than the average Ra-226/Ra-228 ratio in soils. An isotope dependent transfer of Ra-226 and Ra-228 from soil to plants and foods is suggested to explain the difference. The obtained data set will be a valuable contribution to international data collections and thus help to a better understanding of the public exposure to natural radionuclides from the food consumption in the future.

Atomic Adsorption Energies Prediction on Bimetallic Transition Metal Surfaces Using an Interpretable Machine Learning-Accelerated Density Functional Theory Approach.

In this study, we identified features with the largest contributions and property trends in predicting the adsorption energies of carbon, hydrogen, and oxygen adsorbates on transition metal (TM) surfaces by performing Density Functional Theory (DFT)-based calculations and Machine Learning (ML) regression models. From 26 monometallic and 400 bimetallic fcc(111) TM surfaces obtained from Catalysis-hub.org, three datasets consisting of fourteen elemental, electronic, and structural properties were generated using DFT calculations, site calculations, and online databases. The number of features was reduced using feature selection and then finely-tuned random forest regression (RFR), gaussian process regression (GPR), and artificial neural network (ANN) algorithms were implemented for adsorption energy prediction. Finally, model-agnostic interpretation methods such as permutation feature importance (PFI) and shapely additive explanations (SHAP) provided rankings of feature contributions and directional trends. For all datasets, RFR and GPR demonstrated the highest prediction accuracies. In addition, interpretation methods demonstrated that the largest contributing features and directional trends in the regression models were consistent with structure-property-performance relationships of TMs like the d-band model, the Friedel model, and higher-fold adsorption sites. Overall, this interpretable ML-DFT approach can be applied to TMs and their derivatives for atomic adsorption energy prediction and model explainability.

Alchemical harmonic approximation based potential for iso-electronic diatomics: Foundational baseline for Δ-machine learning.

We introduce the alchemical harmonic approximation (AHA) of the absolute electronic energy for charge-neutral iso-electronic diatomics at fixed interatomic distance d0. To account for variations in distance, we combine AHA with this ansatz for the electronic binding potential, E(d)=(Eu-Es)Ec-EsEu-Esd/d0+Es, where Eu, Ec, Es correspond to the energies of the united atom, calibration at d0, and the sum of infinitely separated atoms, respectively. Our model covers the two-dimensional electronic potential energy surface spanned by distances of 0.7-2.5Å and differences in nuclear charge from which only one single point (with elements of nuclear charge Z1, Z2, and distance d0) is drawn to calibrate Ec. Using reference data from pbe0/cc-pVDZ, we present numerical evidence for the electronic ground-state of all neutral diatomics with 8, 10, 12, and 14 electrons. We assess the validity of our model by comparison to legacy interatomic potentials (harmonic oscillator, Lennard-Jones, and Morse) within the most relevant range of binding (0.7-2.5Å) and find comparable accuracy if restricted to single diatomics and significantly better predictive power when extrapolating to the entire iso-electronic series. We also investigated Δ-learning of the electronic absolute energy using our model as a baseline. This baseline model results in a systematic improvement, effectively reducing training data needed for reaching chemical accuracy by up to an order of magnitude from ∼1000 to ∼100. By contrast, using AHA+Morse as a baseline hardly leads to any improvement and sometimes even deteriorates the predictive power. Inferring the energy of unseen CO converges to a prediction error of ∼0.1 Ha in direct learning and ∼0.04 Ha with our baseline.

Bimetallic Sulfides Cr0.99V1.8S4 with Loosely Packed Structure: Exploring the Boundary of Conversion and Intercalation Sodium-Ion Storage Mechanism.

Metal sulfide electrodes for sodium-ion batteries face trade-offs among high capacity, fast kinetics, and stability. The challenge lies in breaking and restoring metal-sulfur bonds and allowing rapid ionic transport. Here we explore the boundary of conversion- and intercalation-type metal sulfides to develop ideal sodium-ion storage materials. We focus on sulfides of vanadium and chromium because of their adjacent atomic numbers but different energy storage mechanism. Among various sulfides of vanadium and chromium, a loosely packed bimetallic sulfide, Cr0.99V1.8S4, with cationic vacancies and metallic conductivity (4.28 S m-1), shows optimal sodium-ion storage performance: an initial Coulombic efficiency of 95.6%, a reversible capacity of 551 mAh g-1 at 1.6 C, and maintaining 100% capacity after 600 cycles at a high rate of 16-66 C.

Resisting Static Inertia

This Note analyzes the various approaches that United States courts have taken on the licensing authority of the Nuclear Regulatory Commission as it relates to the private temporary storage of spent nuclear fuel. It seeks to establish a sound statutory basis for the Nuclear Regulatory Commission’s (NRC’s) authority to issue such licenses under the Atomic Energy Act (AEA) by recharacterizing spent nuclear fuel as a “byproduct material” under the meaning of the Act. It then looks to the enumerated uses of byproduct material to establish that the NRC has the authority to issue licenses to the private sector to store spent nuclear fuel. Finally, it will argue that the Nuclear Waste Policy Act (NWPA) could not and should not be interpreted as restricting or superseding the NRC’s existing licensing authority under the AEA. This interpretation of the AEA and NWPA is more reflective of the statutory language and provides for a better nuclear waste policy.

MAJOR ADVERSE CARDIOVASCULAR EVENTS IN PATIENTS PRESENTING WITH ACUTE CORONARY SYNDROME AT PAEC HOSPITAL, ISLAMABAD IN YEAR 2023

Background: Acute Coronary Syndrome (ACS) encompasses a range of serious cardiovascular conditions, including unstable angina, non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI)[ Objective: This study aimed to examine the frequency of major adverse cardiovascular events (MACE) in ACS patients at the Pakistan Atomic Energy Commission (PAEC) Hospital in Islamabad in 2023. Methodology: The study was carried out department of Cardiology, Pakistan Atomic Energy Commission (PAEC), during the period 1st Jan 2023 till 31st December 2023. Male and female patients diagnosed with ACS and received thrombolytic therapy or PCI were enrolled. The patients were followed till hospital discharge and occurrence of MACE during the hospital stay was noted. Results: A total of 215 individuals were registered. Patients were mostly male (65.11%) and with mean age 58.2 years. ST-elevation myocardial infarction (STEMI) was the most common type of ACS, at 40%, followed by NSTEMI at 34.89% and unstable angina at 25.11%. The most common symptom of ACS was chest pain (85.58%), followed by shortness of breath (30.23%). Hypertension, affecting 45.11% of the population, was followed by diabetes, 29.30% were the most prevalent risk factors. Treatment included antiplatelet drugs (90.23%) and beta-blockers (75.81%) for most patients. PCI was performed on 60.47 percent of patients, whereas thrombolysis was given to 20.47 percent. MACE was observed in 16 patients (7.4%). Conclusion: The results support earlier studies and emphasize the disease's substantial burden and the need for ongoing care and monitoring after thrombolysis and PCI.

Aktuální trendy a výzvy v oblasti právní úpravy odpovědnosti za jaderné škody v evropském kontextu

Currently, the legal framework for nuclear liability derives mainly from two major international treaties: The Paris Convention on Third Party Liability in the Field of Nuclear Energy, signed under the auspices of the Organization for European Economic Cooperation (OEEC) in 1960 and the Vienna Convention on Civil Liability for Nuclear Damage, that was signed under the auspices of the International Atomic Energy Agency (IAEA) in 1963. Both the Paris Convention and the Vienna Convention, are governed by identical basic principles. These principles are strict (objective) liability, congruence between liability and coverage, channelling of liability exclusively onto the operator, very restricted exonerations, non-discrimination of victims, and exklusive jurisdiction of the courts of one country. So, if we would like to analyse the situation with nuclear liability in the European Union, we can define this as a “patchwork”. Before 2004 enlargement, the EU member states, with exception of Austria, Ireland and Luxembourg, were parties to the Paris Convention and most of them also to the Brussels Conventions. During the 2004 and 2008 enlargements, mainly Vienna Convention signatories entered the Union. While all of these Vienna Convention states are also parties the 1988 Joint Protocol, only 8 of the Paris Convention states adhere to this instrument which creates a “bridge” between the Paris and the Vienna Conventions. Slovenia originally was a Vienna State but in 2001 signed the Paris Convention and terminated the Vienna Convention.

The occupational hazards of anesthesiologists: A literature review and evidence-based approach to prevention

Background An occupational hazard is any workplace condition that poses a risk to an employee's health. Occupational hazards are ubiquitous in the field of anesthesiology and often go underappreciated. These hazards warrant careful assessment and strategic preventative planning. Objective This narrative literature review examines the occupational hazards encountered by anesthesiologists and discusses evidence-based techniques to mitigate these risks. Facilitating the health and safety of anesthesia professionals protects not only the providers themselves but also enhances patient care by reducing the possibility of medical errors due to occupational fatigue, stress, and injuries. Methods A targeted search of PubMed and other databases (SCOPUS, Web of Science) was used to review the literature. Safety standard handbooks by the International Atomic Energy Agency, The Pan American Health Organization, The World Health Organization, and Food and Agriculture of the United Nations, were also consulted to provide the current guidelines for hazards discussed. Articles and information were included if they provided information about the occupational hazards of anesthesiologists or evidence-based prevention techniques for mitigating the hazards. Results The occupational hazards are classified into physical, chemical, and biological categories. Evidence-based preventive measures are proposed and examined for each category. Conclusion This paper examines the challenges faced by anesthesiologists by categorizing the physical, chemical, and biological occupational hazards. Each identified hazard is accompanied by evidence-based strategies to mitigate its impact. By illuminating these issues, increased awareness among healthcare professionals, policymakers, and the public can foster a collective effort to improve the safety of the work of anesthesia providers.

IPEM code of practice for proton therapy dosimetry based on the NPL primary standard proton calorimeter calibration service.

Internationally, reference dosimetry for clinical proton beams largely follows the guidelines published by the International Atomic Energy Agency (IAEA TRS-398 Rev. 1, 2024). This approach yields a relative standard uncertainty of 1.7% (k=1) on the absorbed dose to water determined under reference conditions. The new IPEM code of practice presented here, enables the relative standard uncertainty on the absorbed dose to water measured under reference conditions to be reduced to 1.0% (k=1). This improvement is based on the absorbed dose to water calibration service for proton beams provided by the National Physical Laboratory (NPL), the UK's primary standards laboratory. This significantly reduced uncertainty is achieved through the use of a primary standard level graphite calorimeter to derive absorbed dose to water directly in the clinical department's beam. This eliminates the need for beam quality correction factors (k_(Q,Q_0 )) as required by the IAEA TRS-398 approach. The portable primary standard level graphite calorimeter, developed over a number of years at the NPL, is sufficiently robust to be useable in the proton beams of clinical facilities both in the UK and overseas.
The new code of practice involves performing reference dosimetry measurements directly traceable to the primary standard level graphite calorimeter in a clinical proton beam. Calibration of an ionisation chamber is performed in the centre of a standard test volume (STV) of dose, defined here to be a 10 x 10 x 10 cm volume in water, centred at a depth of 15 cm. Further STVs at reduced and increased depths are also utilised. The designated ionisation chambers are Roos-type plane-parallel chambers.
This article provides all the necessary background material, formalism, and specifications of reference conditions required to implement reference dosimetry according to this new code of practice. The Annexes provide a detailed review of ion recombination and how this should be assessed (Annex A1) and detailed work instructions for creating and delivering the standard test volumes (Annex A2).&#xD.

Pentafluoroorthotellurate Uncovered: Theoretical Perspectives on an Extremely Electronegative Group.

The pentafluoroorthotellurate group (-OTeF5, teflate) exhibits high electron-withdrawing properties. Indeed, it is often used as a bulky substitute for fluoride due to its high chemical stability and larger size, which reduces its tendency to act as a bridging ligand. These characteristics make it a valuable ligand in synthetic chemistry, facilitating the preparation of molecular structures analogous to polymeric fluoride-based compounds. In this study, we explore the electronic structure of the teflate group by using advanced Quantum Chemical Topology (QCT) methods to better understand its bonding nature and compare its group electronegativity with that of the halogens. For that, we examine XOTeF5 systems (X = F, Cl, Br, I) and decompose X-OTeF5 interactions into classical (ionic) and exchange-correlation (covalent) contributions by using interacting quantum atoms (IQA) energy decomposition scheme. We also conduct a detailed analysis of electron distribution by utilizing the statistical framework of electron distribution functions (EDFs) and examine the electron localization function (ELF), electron density, and reduced density gradient scalar functions, as well as delocalization indices and QTAIM charges. The results show that the electron-withdrawing properties of the teflate group are comparable to those of fluorine, albeit slightly lower. Moreover, its internal bonding is primarily ionic. Additionally, we compare -OTeF5 with other O-donor groups, demonstrating that the electron-withdrawing properties within OEF5 (E = S, Se, Te) systems are nearly identical, and these groups show a higher group electronegativity than OCF3, OC(CF3)3, and OC6F5.

Numerical analysis of natural convective heat transfer with porous medium using JUPITER

ABSTRACT Japan Atomic Energy Agency (JAEA) has developed a numerical method with the JUPITER code with a porous medium model to calculate the thermal behavior in primary containment vessels (PCVs) of Fukushima Daiichi nuclear power stations of Tokyo Electric Power Company (1F). In this study, we performed an experiment and numerical simulation of the natural convective heat transfer with the porous medium and compared those results. In comparison of the temperature and velocity distributions between the experiment and simulation, the temperature distribution in the simulation was in good agreement with the distribution in the experiment except the temperature near the top and side surface of the porous medium. The velocity distribution also agreed qualitatively with the experimental result. In addition, we also performed the numerical simulations with various effective thermal conductivity models to discuss the effect of the conductivity based on the internal structure of porous media on the natural convective heat transfer. The result indicated that the temperature distribution in the porous medium and the velocity distribution of the natural convection were significantly different for each model, and the simulation result with the Kunii–Smith model was close to the experimental results.

Analytical and Numerical Solutions of Concentration With Deposition Under Unstable Condition

ABSTRACTIn order to study the analytical and numerical solutions with Adomain decomposition of the pollutant's concentration from point source, wind speed and vertical turbulent eddy diffusivity are taken into account as functions of the vertical height above the surface layer power law. The top of the boundary layer of height has an elevated inversion layer that limits the concentration, and there is dry deposition on the ground surface. The pollutant's degradation distance is also estimated. The outcomes of the analytical and numerical solutions were compared with Iodine‐135 measured data under unstable conditions at the Egyptian Atomic Energy Authority. One finds that there is a better agreement between the predicted and observed concentrations than between the numerical concentrations. This study compares the analytical and numerical solutions of the advection‐diffusion equation and data of Iodine‐135 concentrations observed under unstable conditions.

Adaptive Sampling Limit Surface Search Application to Identify Cliff-Edge Effects in Severe Accident Uncertainty Analysis

Severe accident (SA) codes and their core degradation models have to deal with strongly nonlinear and discontinuous phenomena. In the application of uncertainty quantification to SA simulations, the combination of such phenomena may lead to a strong increase in the uncertainty propagated through the simulation, as well as to the chaotic behavior of the output variables. In this framework, the application of the limit surface search method of the RAVEN tool is proposed for a case where cliff-edge effects of SA phenomena determine a bifurcation of an output figure of merit. The algorithm is based on a predictive method making use of a support vector machine model, and it is applied with the aim of separating those input values that lead to different phenomenologies among the uncertainty calculations. The case study is in regard to the uncertainty analysis of the ASTEC code simulation of the QUENCH6 experimental test conducted in the framework of the International Atomic Energy Agency Coordinated Research Project I31033.

Quality Control And Dosimetric Accuracy Assessment Of Cobalt-60 Teletherapy Unit At Ssdl, Bangladesh

External beam radiotherapy, often known as teletherapy, is one of the most efficient ways to treat cancer since it targets harmful cells with radiation. Dosimetric accuracy of a recently installed Cobalt-60 teletherapy unit (Theratron Equinox100#2149, Initial Activity: 12000 Ci) at the Bangladesh Atomic Energy Commission's Secondary Standard Dosimetry Laboratory (SSDL), Savar, Dhaka, has been the main focus of this work. Several measurements are made that are necessary to ensure the accuracy of the Cobalt-60 teletherapy unit in terms of dosimetric level, specifically the accuracy of absolute and relative dosimetry. These measurements include the following dosimetric parameters: absorbed dose to water, percentage depth dose (PDD), beam profile, inter-chamber comparison (to ensure the highest level of dosimetry accuracy), and comparison of absorbed doses using two protocols named IAEA TRS-277 and IAEA TRS-398. The absorbed dose rate at reference field size (10 × 10 cm2) was found to be 1.548 Gy/min with an uncertainty of ±0.020. In the case of the inter-chamber comparison, the maximum deviation among values of absorbed dose to water for four Farmer chambers was 0.27% for Dw(Zref) and 0.26% for Dw(Zmax). The resultant output of this study may contribute to developing the treatment planning system in the realm of cancer treatment. Bangladesh Journal of Physics, 28(1), 1-10, June 2021

Review of: "to bring The surface atoms of nanoparticles are not compensated in terms of energy. In general, the results of nanoparticle energy growth can be expressed as the total energy of atoms on the surface of the particle"

Review of: "to bring The surface atoms of nanoparticles are not compensated in terms of energy. In general, the results of nanoparticle energy growth can be expressed as the total energy of atoms on the surface of the particle"

Beyond the Surface: Evaluating the Impacts of Fukushima Nuclear Wastewater Release

Following the 2011 Fukushima nuclear power plant accident in Japan, managing contaminated water became a long-term challenge. In August 2023, Japan began discharging treated atomic wastewater into the Pacific Ocean, sparking global concern. Since nuclear wastewater discharge involves environmental safety, public health, and international relations, understanding various perspectives and presenting scientific data is crucial for formulating reasonable policies. This study aims to analyse the attitudes of different countries towards the Fukushima nuclear wastewater discharge, assess its scientific basis, and explore its economic impact on Japan's fishing industry. The results show that Japan's wastewater discharge complies with international safety standards, based on an evaluation of publicly available data from the Tokyo Electric Power Company and the International Atomic Energy Agency. The analysis encompassed both safety measures and environmental impacts of this specific nuclear wastewater release. Despite scientific studies confirming that the treated nuclear wastewater meets safety standards, ongoing public concerns and geopolitical tensions have caused significant economic impacts on Japan's fishing industry. Therefore, enhanced scientific dialogue and research are needed to effectively address the potential long-term challenges that nuclear wastewater discharge may pose to marine ecosystems and global food safety