Commercial Reactor Research Articles

Comparative Study on the Neutronic Performance of Thermal and Fast Molten Salt Reactors under Once-Through Fuel Cycle

Once-through molten salt reactors have the advantages of easy availability of fuel, nuclear nonproliferation, and low technical difficulty. It is expected to be the earliest commercial molten salt reactor fuel cycle mode. The current research on the neutronic performance of the once-through fuel cycle mainly focuses on the thermal spectrum range, and broader spectrum research needs to be carried out further. In particular, the fuel utilization characteristics of molten salt fast reactors in once-through fuel cycle are not yet clear. In addition, small modular design is one of the trends of molten salt reactor development, and small modular design under thermal and fast spectrum has different advantages and needs further comparative analysis. In this paper, the single lattice, bare reactor, and core with reflector models are used to compare the neutronic performance in once-through fuel cycle from thermal to fast spectrum, which includes burnup, variation of fuel salt composition and volume with burnup, temperature reactivity coefficient, neutron irradiation lifetime, and small modular size. The results show that the burnup increases first, then decreases, and then increases again with the increase of the average lethargy causing fission (EALF). For small-scale molten salt reactors, the difference in fuel utilization under thermal and fast spectra is small. However, for large-scale reactors, the burnup under fast spectrum is significantly higher than that under thermal spectrum. When the EALF is large enough, and the neutron loss ratio is small enough, the breed-and-burn (BNB) fuel cycle mode can be realized, and then, the fuel utilization will be significantly improved. In the fast spectrum reactors, the HN and volume of molten salt change violently because of the longer burnup period. Based on the infinite single lattice model, the temperature reactivity coefficient increases first, then decreases, and increases again with EALF. It is negative over the entire energy spectrum. In addition, the small modular designs are discussed by the bare reactor model, and the neutron irradiation lifetime of the materials is analyzed by the core model with a reflector.

On developing a practical safety culture for the advanced reactor workforce: Experiences of working with sodium

The Versatile Test Reactor is meant to fill a need in the advanced nuclear reactor development community. Accelerated nuclear testing of fuels and materials is needed to allow designs to proceed. To accomplish this, a fast neutron spectrum is needed. To have a fast neutron spectrum, the reactor coolant needs to not only have excellent heat transfer properties to sufficiently cool the reactor core, but also not significantly slow neutrons down following their birth in the fission process. Sodium is an excellent coolant choice that can fulfill these needs and many others. Sodium is the sixth most abundant element in the Earth’s crust and can be acquired easily through simple chemical separation methods. Sodium, however, reacts when in contact with water and air, but with proper precautions, these scenarios can be avoided. Nuclear reactors that utilize molten sodium as a primary heat transfer medium [a.k.a. sodium-cooled fast-neutron reactors, or SFRs, Figure 1 (1)] provide unique challenges in their daily operation, and therefore require focused training for researchers, scientists, staff, and employees alike to understand these unique challenges. Therefore, a comprehensive understanding of sodium properties is needed by all personnel involved in the design, construction, operation, experiment planning and execution of SFRs. Additionally, several commercial advanced reactor designs are under development which will use sodium for the reactor coolant. These advanced reactor designs include the Natrium reactor from TerraPower and GE-Hitachi (2), the ARC-100 reactor from Advanced Reactor Concepts (3), and the Aurora reactor from Oklo (4).

Conversion of CO2 by reverse water gas shift (RWGS) reaction using a hydrogen oxyflame

Climate change concerns demand for drastic measures to mitigate greenhouse gas (GHG) emissions from fossil resources particularly those of CO2. Effective conversion of CO2 into syngas (a mixture of CO and H2) via reverse water gas shift (RWGS) reaction requires high temperatures (> 900 °C) to overcome thermodynamic limitations. Challenges may arise in commercial catalytic reactors in achieving close to equilibrium efficiencies due to physical barriers such as maximum catalyst operating temperature and associated operating costs. Herein, a simple and novel approach is presented to produce syngas from CO2 via RWGS reaction using a high temperature hydrogen oxyflame. Test results from a tubular laboratory reactor show that a CO2 conversion of up to 75 % is achievable in a single pass with a gas residence time of < 0.03 s. Lower than equilibrium CO2 conversions are observed due to non-adiabatic temperatures in the reactor. Heat integration and reactor insulation at industrial scale would help in a closer to equilibrium performance. Systematic analysis of reactor performance supported by empirical modelling revealed that there is an optimum economical point where hydrogen consumption can be minimized (< 1.0 mol H2/mol CO2). A trade-off must be made to identify an optimum operating point depending on required syngas quality. Relatively small effect of reactor wall material (within 10 % in CO2 conversion) may indicate an enhancing effect of hydrogen oxyflame as the main contributor to the reactor performance.

Linear Regression and Machine Learning for Nuclear Forensics of Spent Fuel from Six Types of Nuclear Reactors

The illicit trafficking of radioactive materials, especially weapon-grade uranium or plutonium, is a significant security threat. Nuclear forensics helps trace the illicit trafficking of radioactive materials. The present study develops the methods for the forensics of the possible origins of fuels irradiated in nuclear reactors, which are the most powerful sources producing radioactive materials, including plutonium. Three key factors are significant for irradiated fuel forensics, namely, initial 235U enrichment, burnup, and the type of irradiation nuclear reactors. The methods for the first two are determined based on experimental data of six nuclear-reactor technologies and are further verified using the neutron-transport-depletion coupling simulation of the two major commercial reactor technologies, a pressurized-water reactor (PWR) and a boiling-water reactor (BWR). In addition, three machine-learning techniques are applied to discriminate between a PWR and a BWR, which are quite similar in neutronic properties, with nice accuracy and generalization ability. In summary, the presently determined methods provide a reliable pathway to predict the origins of spent nuclear fuels.3 MoreReceived 18 August 2022Revised 7 November 2022Accepted 1 February 2023DOI:https://doi.org/10.1103/PhysRevApplied.19.034028© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasFissionNeutron physicsNuclear decayNuclear powerRadioactive wasteTheory, design & simulation of reactorsTechniquesNuclear data analysis & compilationNuclear PhysicsEnergy Science & Technology

Modeling of a Two-Bed Reactor for Low-Temperature Removal of Nitrogen Oxides in Nitric Acid Production

In this study, the modeling of the low-temperature catalytic abatement of NOX and N2O from tail gases in a weak nitric acid plant utilizing a single-pressure 0.716 MPa system was performed. A one-reactor concept assumes that in the first bed, NOX is reduced by ammonia on a commercial vanadia–alumina catalyst, and in the second bed, N2O is decomposed on a proprietary nickel–cobalt catalyst. The kinetics of N2O decomposition on a Cs/Ni0.1Co2.9O4 catalyst was experimentally studied in an isothermal flow reactor. The reaction rate constants were determined by varying the residence time and temperature; these data formed the basis for modeling kinetics and heat and mass transport in an adiabatic reactor in which the low-temperature mitigation of nitrogen oxides occurred. Taking into account the given spatial limitations inside the reactor and the allowable temperatures, the layer heights were evaluated to ensure a residual NOX and N2O content of less than 50 ppm. Catalyst loading using layers in a commercial reactor was estimated for the tail-gas flow rates of 46,040–58,670 m3/h. Simulations showed that the optimum inlet temperature was 260 °C; in this case, the NOX and N2O conversion targets were achieved in the range of 46,040–58,670 m3/h while adhering to catalyst bed height and outlet temperature limitations.

Design and Suitability Analysis of FPGA-Based TCP/IP Offload Module for Control Systems of FBRs

Transmission Control Protocol/Internet Protocol (TCP/IP) offload modules play a crucial role in India’s first commercial fast breeder reactor (PFBR) distributed digital control system architecture by providing networking capabilities to the real-time control systems used in safety-critical and safety-related applications of the PFBR. These modules enable operators to remotely control various mechanisms, facilities, and process loops via real-time control systems from the main control room display stations. The malfunctioning of these modules may hamper the overall plant’s availability; hence to improve further upon safety, security, reliability, and performance, these modules have been indigenously developed for upcoming fast breeder reactors in India. This paper proposes methods to justify the suitability of these communication modules as per the D-25 design guidelines issued by the Atomic Energy Regulatory Board of India. The design and testing aspects are covered, including an approach toward hardware descriptive language-based design and testing with respect to the IEEE standard and the TCP/IP protocol specifications. Module design validation based on ethernet frame transactions is detailed in this paper. The test platform design, which includes the diagnostics software design for CPUs designed with these TCP offload modules, and the design of a graphical user interface to detect and record TCP connection anomalies are detailed. The network interface response to postulated events of TCP packet corruption, packet drop, packet delay, out-of-order packets, duplicate packets, and heavy traffic is characterized.

Enhanced resistance to helium irradiations through unusual interaction between high-entropy-alloy and helium

Finding high performance plasma-facing materials (PFMs) is one of the most important and challenging tasks for realizing the commercial application of fusion reactors. Herein, we found the CrMoTaWV high entropy alloy (HEA) is highly resistant to low-energy and high-flux He plasma exposure. The nanochannel HEA film has 20 times higher initial fluence for the formation of fuzz and a remarkable 8.9 times slower fuzz growth rate than those of W. Combining the in-situ TEM observation and the Molecular dynamics (MD) simulation of the He bubble growth process, a new mechanism for the enhanced radiation resistance in HEA with the unusual interaction between HEA and He is found, where, differing from traditional metal, bubble growth in HEA leads to non-directional emission of interstitial atoms while HEA greatly suppress the growth of He bubbles. The special nanochannel structure further rise the radiation resistance through releasing He out of the HEA film and reducing the He concentration. This new nanochannel refractory HEA material presents a promising choice as the PFMs with excellent performance and a much longer serving lifetime for future commercial fusion reactors.

Measurements of Droplet Size and Velocity Distributions During Rod Bundle Core Reflood

As part of the Organisation for Economic Co-operation and Development/Nuclear Energy Agency Rod Bundle Heat Transfer (RBHT) project, an experimental study was performed to investigate the entrained droplet sizes and velocities in a rod bundle under reflood conditions. Experimental results were obtained from the U.S. Nuclear Regulatory Commission/The Pennsylvania State University RBHT test facility using advanced dual laser measurement systems that allow for the simultaneous measurement of droplet behaviors at two axial locations during reflood transients. The RBHT facility is highly instrumented and contains a 7×7 electrically heated bundle with dimensions matching those in commercial pressurized water reactors. The combination of the measurement capabilities of the RBHT facility and the choice of appropriate experimental conditions allows for the measurement of unique droplet size and velocity distributions under different transient reflood conditions.

A Techno-Economic Study of Catalytic Decarboxylation Process for Naphthenic Acids Utilizing Protonic Zeolite Socony Mobil Type 5 (HZSM-5) Catalyst

This paper represents a detailed techno-economic analysis of a typical commercial-scale catalytic decarboxylation process of naphthenic acids over HZSM-5 zeolite. Simulation of the process has been performed in ASPEN Plus®. The performance of the modeled unit was compared to experimental results data from a similar plant. Two models were developed for the proposed industrial plant based on continuous flow reactors; the first is based on a fluidized bed reactor, and it was modeled as a continuous stirred tank reactor (CSTR) unit, and the second is a semi-regenerative process that consists of three fixed-bed reactors with intermediate preheaters and are modeled as three plug flow reactors (PFR). The outcome of the economic analysis of the two proposed commercial scale reactors of a decarboxylation process of a capacity of 11,000 bbl/day showed that the CAPEX, including the total equipment cost for the fluidized bed reactor plant and semi-regenerative process plant, was $44,319,362 and $4,447,919, respectively. The annual operating cost for the fluidized bed plant and semi-regenerative process plant is 45,269,180 $/year and 1,771,839 $/year, respectively. Our results demonstrated that catalytic decarboxylation over HZSM-5 zeolite is economically feasible using a semi-regenerative process, and is a promising method for removing naphthenic acid. The insight obtained from this work can be used as a basis for more comprehensive future financial and risk modeling of the process. The cost estimated in this work was compared to the Khartoum refinery cost for the naphthenic acid corrosion mitigation system, with a saving of $29,459,528.

In vacuo cluster tool for studying reaction mechanisms in atomic layer deposition and atomic layer etching processes

In this paper, we introduce a vacuum cluster tool designed specifically for studying reaction mechanisms in atomic layer deposition (ALD) and atomic layer etching (ALE) processes. In the tool, a commercial flow-type ALD reactor is in vacuo connected to a set of UHV chambers so that versatile surface characterization is possible without breaking the vacuum environment. This way the surface composition and reaction intermediates formed during the precursor or etchant pulses can be studied in very close to true ALD and ALE processing conditions. Measurements done at each step of the deposition or etching cycle add important insights about the overall reaction mechanisms. Herein, we describe the tool and its working principles in detail and verify the equipment by presenting results on the well-known trimethyl aluminum–water process for depositing Al2O3.

Overview of recent ITER TBM Port Plug R&D activities

The objective of ITER project is the demonstration of the scientific and technological feasibility of fusion energy. Tritium fuel is required for the fusion reaction in DEMOnstration reactors and future commercial reactors but it is not available in nature because of its instability. To investigate tritium breeding self-sufficiency, two equatorial ports in ITER are dedicated to operating test blanket modules (TBMs) using the TBM Port Plug (TBM-PP). The TBM-PP design should be investigated with the physical mock-ups to validate the leak tightness in the primary vacuum boundary and to ensure TBM replacement and refurbishment compatible with Remote Handling (RH) operations in the ITER Hot Cell Facility during the ITER lifetime. This paper summarizes the achievements on the two most relevant R&D topics as described herewith. Several TBM-PP components (i.e., back parts of the TBM-Frame, the Dummy-TBMs, the TBM-Shields, and the TBM feeding pipes) are part of the vacuum boundary implying that these components are Vacuum Quality Classification (VQC) 1A. To test and develop high vacuum sealing for the TBM-Frame flange and the TBM-Set or Dummy-TBM flange, the ITER Large Seal Test Rig (LSTR), and metallic gasket seals for the TBM application have been manufactured and installed in the ITER site. The helium leak tests were performed at different operating temperatures to investigate the vacuum performance of metallic gasket seals with VQC 1A. The TBM-PP design shall guarantee the feasibility of a rapid replacement and refurbishment compatible with ITER Remote Handling (RH) operations by using RH tools in the Hot Cell Facility during the ITER's lifetime. Therefore, an experimental program has been performed to demonstrate the feasibility of the critical RH refurbishment tasks including the insertion and removal of TBM-Set/Dummy-TBM and the RH bolting.

Future for inertial-fusion energy in Europe: a roadmap

Abstract The recent achievement of fusion ignition with laser-driven technologies at the National Ignition Facility sets a historic accomplishment in fusion energy research. This accomplishment paves the way for using laser inertial fusion as a viable approach for future energy production. Europe has a unique opportunity to empower research in this field internationally, and the scientific community is eager to engage in this journey. We propose establishing a European programme on inertial-fusion energy with the mission to demonstrate laser-driven ignition in the direct-drive scheme and to develop pathway technologies for the commercial fusion reactor. The proposed roadmap is based on four complementary axes: (i) the physics of laser–plasma interaction and burning plasmas; (ii) high-energy high repetition rate laser technology; (iii) fusion reactor technology and materials; and (iv) reinforcement of the laser fusion community by international education and training programmes. We foresee collaboration with universities, research centres and industry and establishing joint activities with the private sector involved in laser fusion. This project aims to stimulate a broad range of high-profile industrial developments in laser, plasma and radiation technologies along with the expected high-level socio-economic impact.

Toward the realization of a commercial Helical Small-Scale Steady-State Fusion Reactor

Toward the realization of a commercial Helical Small-Scale Steady-State Fusion Reactor

Mechanistic model for quantifying the effect of impact force on mechanochemical reactivity.

Conventional mechanochemical synthetic tools, such as ball mills, offer no methodology to quantitatively link macroscale reaction parameters, such as shaking frequency or milling ball radius, to fundamental drivers of reactivity, namely the force vectors applied to the reactive molecules. As a result, although mechanochemistry has proven to be a valuable method to make a wide variety of products, the results are seldom reproduceable between reactors, difficult to rationally optimize, and hard to ascribe to a specific reaction pathway. Here we have developed a controlled force reactor, which is a mechanochemical ball mill reactor with integrated force measurement and control during each impact. We relate two macroscale reactor parameters-impact force and impact time-to thermodynamic and kinetic transition state theories of mechanochemistry utilizing continuum contact mechanics principles. We demonstrate force controlled particle fracture of NaCl to characterize particle size evolution during reactions, and force controlled reaction between anhydrous copper(II) chloride and (1, 10) phenanthroline. During the fracture of NaCl, we monitor the evolution of particle size as a function of impact force and find that particles quickly reach a particle size of ∼100 μm largely independent of impact force, and reach steady state 10-100× faster than reaction kinetics of typical mechanochemical reactions. We monitor the copper(II) chloride reactivity by measuring color change during reaction. Applying our transition state theory developed here to the reaction curves of copper(II) chloride and (1, 10) phenanthroline at multiple impact forces results in an activation energy barrier of 0.61 ± 0.07 eV, distinctly higher than barriers for hydrated metal salts and organic ligands and distinctly lower than the direct cleavage of the CuCl bond, indicating that the reaction may be mediated by the higher affinity of Fe in the stainless steel vessel to Cl. We further show that the results in the controlled force reactor match rudimentary estimations of impact force within a commercial ball mill reactor Retsch MM400. These results demonstrate the ability to quantitatively link macroscale reactor parameters to reaction properties, motivating further work to make mechanochemical synthesis quantitative, predictable, and fundamentally insightful.

CFD modeling of the ethylene–vinyl acetate copolymerization autoclave reactor: Effects of comonomer ratio on reactor dynamics and copolymer properties

Computational fluid dynamics (CFD) modeling of an industrial ethylene–vinyl acetate autoclave copolymerization reactor was conducted to evaluate the effects of comonomer ratios on reactor dynamics and product properties, including the molecular weight distribution (MWD), and copolymer composition. To accurately predict the MWD of copolymer chains under highly nonideal mixing conditions at a reduced computational cost, the CFD-multicompartment model and probability generating function (PGF) transform were applied. The effectiveness of the developed model was validated by the satisfactorily consistent plant data and simulated results. The model revealed that an increase in the vinyl acetate (VA) content significantly decreased the temperature, promoting combinational termination and chain transfer to polymer reaction for a broad copolymer MWD. The pseudo-kinetic-based analysis showed that VA was consumed more slowly than ethylene, resulting in its lower value in the copolymer composition than that of the comonomer ratios. However, despite nonideal mixing, the copolymer composition was maintained to be uniform for the copolymers produced over the entire reactor volume. In conclusion, the proposed model can be used to understand the governing behaviors of copolymerization under nonideal mixing conditions, design commercial copolymerization reactors, and predict copolymer product qualities.

Preliminary Neutronics Study of an Accelerator-Driven Molten Spallation Target–Molten Lithium Source of Tritium

Current tritium production might not be enough for all future fusion research reactors. Different approaches for tritium production have been studied in the past, one of which was tritium production using the accelerator-driven subcritical systems. This idea was dismissed in the 1990s as uneconomical when compared to using existing commercial light water reactors. This paper presents changes to the basic idea, mainly the use of a molten spallation target and molten lithium breeding volume. This advanced design is described, optimized for tritium yield using the MCNP 6.2.0 code, and compared between different accelerators. The optimized configuration consists of a 1-GeV, 200-mA proton accelerator, a molten Pb-Bi eutectic spallation target with a length of 60 cm and a diameter of 75 cm, and molten lithium breeding volume with dimensions of 500 cm in length and 900 cm in diameter. As calculated, the annual production of the proposed accelerator-driven tritium production system could be as high as 350 g of tritium with the optimized configuration.

Controversy and consensus in the design of a consent-based siting process for radioactive waste

Crafting a successful plan to store nuclear waste in the United States from commercial nuclear reactors and defense-related activities has been stymied by multiple technical, social, and political challenges. Recent focus has returned to the role of consent to site a deep geologic repository and interim storage facilities. However, what “consent” means has been left quite vague. We report on an empirical investigation using Q method to identify perspectives about how a consent-based siting process should be designed for one or more deep geologic repositories. We recruited twelve individuals deeply engaged with policy and regulatory questions associated with managing nuclear waste in the United States. Results reveal four perspectives: get to yes expediently, seek acceptance by gaining trust, promote inclusion and transparency for informed community choice, and develop legitimacy for the process and outcomes. Each perspective includes features meant to ensure that core concepts of consent are addressed in a process to site one or more deep geologic repositories: self-determination, understanding, and voluntariness. We discuss how perspectives emphasize them in different ways. We also highlight how perspectives reveal preferences for responding to three challenges raised by the socio-political context: what is the scope of the problem to be addressed, how the process can be protected from external pressure, and how to proceed in a context of social distrust. The perspectives suggest many areas of agreement about how a consent-based process should be designed. However, key differences are also revealed which pose a significant challenge for those that will be responsible for designing a process that achieves the promise of consent.

Reactor criticals and spent fuel systems similarities

Many conservative assumptions for subcriticality assessment calculations have to be made in current calculations of spent fuel storage systems. This is due to a fact that there is no available database of benchmarks containing spent fuel or materials with isotopic composition like spent fuel. However one potential source of spent fuel system experiments is being omitted – there are hundreds of commercial reactors around the world containing spent fuel on some level of burnup. These reactors have to be tested for safety reasons in the beginning of each cycle and parameters of these test states are well known.In this paper a possibility of using commercial reactor critical states for code validations and for subcriticality assessments of storage systems is discussed and potential approach for criticality safety analysis is given.

Recent Developments in Hydrodynamic Cavitation Reactors: Cavitation Mechanism, Reactor Design, and Applications

Hydrodynamic cavitation is considered to be a promising technology for process intensification, due to its high energy efficiency, cost-effective operation, ability to induce chemical reactions, and scale-up possibilities. In the past decade, advancements have been made in the fundamental understanding of hydrodynamic cavitation and its main variables, which provide a basis for applications of hydrodynamic cavitation in radical-induced chemical reaction processes. Here, we provide an extensive review of these research efforts, including the fundamentals of hydrodynamic cavitation, the design of cavitation reactors, cavitation-induced reaction enhancement, and relevant industrial applications. Two types of hydrodynamic cavitation reactors—namely, stationary and rotational—are compared. The design parameters of a hydrodynamic cavitation reactor and reactor performance at the laboratory and pilot scales are discussed, and recommendations are made regarding optimal operation and geometric conditions. The commercial cavitation reactors that are currently on the market are reviewed here for the first time. The unique features of hydrodynamic cavitation have been widely applied to various chemical reactions, such as oxidization reactions and wastewater treatment, and to physical processes, such as emulsion generation and component extraction. The roles of radicals and gas bubble implosion are also thoroughly discussed.

Neutronics analysis of UN-PuN fuel for 300MW pressurized water reactor using SRAC-COREBN code

Nuclear Power Plants (NPP) is one of alternative energy that can be used to replace fossil energy. NPP is a clean energy that doesn't emit CO2 as a residue from the power plant. Pressurized Water Reactor (PWR) is the most widely used commercial reactor to date. This reactor usually uses UO2 as fuel with enrich U-235 and produce plutonium as a waste nuclear. In this study, the fuel uses natural uranium and the addition of plutonium from the spent fuel of PWR, calling it Uranium-Plutonium Nitride (UN-PuN) fuel. Plutonium from spent fuel PWR (U-fueled) consists of Pu-238, Pu-239, Pu-240, Pu-241 and Pu-242, which Pu-239 and Pu-241 are fissile material. The aim of using plutonium is to reduce the amount of nuclear waste and prevent the use of plutonium as a nuclear weapon. The addition of neptunium and protactinium is also carried out in the fuel. Neptunium is one of the minor actinide materials which have high toxicity, so add Np-237 it is very useful to reduce the amount of neptunium in the world. And also, the addition of Np-237 and Pa-231 aims to decrease the keff value both in the Beginning of Life (BOL) and End of Life (EOL) in the reactor. This research calculates the neutronic calculations for PWR use SRAC2006 with COREBN Code and Japanese Evaluated Nuclear Data Library 4.0 (JENDL-4.0) for the nuclear data library. The COREBN code is a calculation method based on interpolation of macroscopic cross-section and finite-difference diffusion theory. The optimum design reached the maximum k-eff value 1.017077 and the maximum power density was 58.47 W/cc. The results obtained are the excess reactivity value of 1.68 % smaller than previous study which produces an excess reactivity value of 11.94 %. So this design has the potential to be applied in the PWR design