Design Of Reactor System Research Articles

Massimo Salvatores’ seminal ideas and comprehensive views on nuclear fuel cycle studies

Massimo Salvatores provided fundamental innovations to the European and international Nuclear Fuel Cycle (NFC) studies, in particular on analysis of Partitioning and Transmutation (P&T) strategies, and introduced them to KIT. His visions and guidance triggered an advanced approach to such studies, with the final aim to maximize synergies of different nuclear energy policies at local and regional levels. He recognized that several different aspects have to be taken into account in the NFC activities, ranging from national polices, to the role of Pu as resource or as a waste, up to the implementation of P&T options with innovative reactor concepts. Such huge contribution inherited from Massimo is a result of the key role he played in the main projects worldwide related to both the NFC studies and the design and assessment of ADS and Low Conversion ratio fast reactor systems. In the present paper, we provide an overview of the work performed by Massimo and his colleagues at the Karlsruhe Institute of Technology, emphasising the innovative elements introduced by Massimo on the back-end of the fuel cycle with focus on P&T of the spent nuclear fuel. The key innovations achieved by Massimo and his KIT team presented hereafter are the introduction of NFC regional scenario studies, the consideration of safety and transmutation assessments of innovative burner reactor concepts, and the effect of the propagation of the existing uncertainties on fuel cycle scenarios simulation results.

Design and operation of a multi-stage reactor system for chemical looping combustion process

A chemical looping combustion (CLC) system with a multi-stage fuel reactor (FR) and a two-stage air reactor (AR), was constructed and operated in an experimental study and simulated via the computational particle fluid dynamics (CPFD) method. Hydrodynamic results with a bubble-based EMMS drag model agreed well with the experimental measurements. The wall effect in the small-scale AR led to an uneven particle distribution and irregular fluidization at a small NAR. The bubble size and velocity were limited in the FR, thereby significantly boosting the gas-solid contact. The particle residence time in the FR was prolonged, resulting in a high carbon capture rate. With the increase in fluidization number in FR and AR, the mass flux increased, but the residence time decreased. Adding a secondary gas flow in the FR has a positive impact on the solid circulation rate. The results in the thermal test indicated that a high CO2 capture rate and a low oxygen demand were achieved; thus the proposed reactor design improved the fuel conversion in the CLC process.

Plantwide optimization coupled with column sequencing and stacking using a process simulator automation server

A method is proposed for plantwide process design and optimization that solves the column sequencing and stacking problems while also accounting for the tradeoff between reactor system design and separation system design. The plantwide process is represented by two flowsheets in a process simulator. One flowsheet represents the reactor network and the other flowsheet contains a single distillation column which is used to optimize each column in every sequence. When reactor design variables are specified, the reactor effluent flowrate and composition can be determined by simulating the reactor network flowsheet. Since the outlet from the reactor network is the feed to the separation system, the optimal separation system for this feed can then be designed. Finally, by looping over reactor design variables, a nearly-optimal plantwide process design can be determined. This permits plantwide optimization accounting for tradeoffs between the reactor section and separation section of a process while using rigorous modeling of both parts of the flowsheet. The rigorous models can still be constructed rapidly using commercial process simulation software. The method is illustrated with two case studies: the butane alkylation process and the cumene process.

Conceptual design of reactor system for hybrid micro modular reactor (H-MMR) using potassium heat pipe

Hybrid micro modular reactor (H-MMR) combining MMR with renewable energy and energy storage systems (ESS) is designed using heat pipe. H-MMR could produce 10 MW of electric power more flexibly and efficiently through load following. LOCA accident is precluded in advance as there is no primary coolant due to the use of potassium heat pipe. Reactor solid core consist of hexa-annulus UN fuel with a heat pipe inserted, which connects a sodium pool of intermediate heat exchanger (IHX). The annular gap wick heat pipe (ACHP) using potassium is optimized to maximize the heat transport performance. Reactor core configuration is designed through core analysis and thermal analysis using 1D lumped finite differential method. Reactor core of H-MMR make 18 MW of thermal power for 56 years without refueling when diameter of heat pipe is 22 mm. The feasibility of heat pipe safety system and sodium pool is evaluated in normal operation. Reactor vessel auxiliary cooling system (RVACS) is designed to cool down decay heat within safety margin using implicit transient analysis.

Bubble size fractal dimension, gas holdup, and mass transfer in a bubble column with dual internals

As the scale of residual oil treatment increases and cleaner production improves in China, slurry bubble column reactors face many challenges and opportunities for residual oil hydrogenation technology. The internals development is critical to adapt the long-term stable operation. In this paper, the volumetric mass transfer coefficient, gas holdup and bubble size in a gas–liquid up-flow column are studied with two kinds of internals. The gas holdup and volumetric mass transfer coefficient increase by 120% and 42% when the fractal dimension of bubbles increases from 0.56 to 2.56, respectively. The enhanced mass transfer processing may improve the coke suppression ability in the slurry reactor for residual oil treatment. The results can be useful for the exploration of reacting conditions, scale-up strategies, and oil adaptability. This work is valuable for the design of reactor systems and technological processes.

Advance Electrochemical CO2 Utilization Towards Higher Industrial Readiness: Across Multiple Scales from Catalyst Design, Electrode Decoration, to Reactor Engineering

The challenges in electro-catalytic mitigation of CO2 press innovations across multiple scales going from catalyst structure at microscale to the complex multiphase thermofluids network at system scale. In this presentation, I will demonstrate a molecular electrocatalyst active for CO2 to methanol conversion, a pioneering catalyst restructuring technique to realize 12-day CO2-formate inter-conversion, a polymer-molecular catalyst hybrid gas diffusion electrode to reduce CO2 in presence of O2 just like the industrial flue gases, an alkaline based micro-flow reactor to boost the CO2 electro-reduction performance, and an unprecedented in-situ platform to reveal the near-electrode local environment in a flow reactor. At microscale: catalyst design. An integration combining the functions of a CO2 electrolyzer and a formate fuel cell is a new option for carbon‐neutral energy storage but entails rapid, reversible and stable interconversion between CO2 and formate over a single catalyst. We develop a new catalyst with such functionalities based on a Pb–Pd alloy system that reversibly restructures its phase, composition, and morphology and thus alters its catalytic properties under controlled electrochemical conditions. Under cathodic conditions, the catalyst is relatively Pb‐rich and is active for CO2‐to‐formate conversion over a wide potential range; under anodic conditions, it becomes relatively Pd‐rich and gains stable catalytic activity for formate‐to‐CO2 conversion. The bifunctional activity and superior durability of our Pb–Pd catalyst leads to the first proof‐of‐concept demonstration of an electrochemical cell that can switch between the CO2 electrolyzer/formate fuel cell modes and can stably operate for 12 days. At mesoscale: electrode design. The electrochemical reduction of CO2 in the presence of O2 would allow the direct valorization of flue gases from fossil fuel combustion and of CO2 captured from air. However, it is a challenging task because O2 reduction is thermodynamically favored over that of CO2. Typically, 5% O2 in the CO2 feed gas is sufficient to completely inhibit the CO2 reduction reaction. We developed an O2-tolerant catalytic CO2 reduction electrode inspired by part of the natural photosynthesis unit. The electrode comprises of heterogenized cobalt phthalocyanine molecules serving as the cathode catalyst with > 95% Faradaic efficiency (FE) for CO2 reduction to CO coated with a polymer of intrinsic microporosity that works as a CO2-selective layer with a CO2/O2 selectivity of ~ 20. Integrated into a flow electrolytic cell, the hybrid electrode operating with a CO2 feed gas containing 5% O2 exhibits a FECO of 75.9% with a total current density of 27.3 mA/cm2 at a cell voltage of 3.1 V. A FECO of 49.7% can be retained when the O2 fraction increases to 20%. Stable operation for 18 h is achieved. The electrochemical performance and O2 tolerance can be further enhanced by introducing cyano and nitro substituents to the phthalocyanine ligand. At macro scale: reactor system design and probing the cathode surface environment. The promise and challenge of electrochemical mitigation of CO2 calls for innovations on both catalyst and reactor levels. Enabled by high-performance and earth abundant CO2 electroreduction catalyst materials, we developed alkaline microflow electrolytic cells for energy-efficient, selective, fast, and durable CO2 conversion to CO and formate. With the above-mentioned cobalt phthalocyanine-based cathode catalyst, the CO-selective cell starts to operate at a 0.26 V overpotential and reaches a Faradaic efficiency of 94% and a partial current density of 31 mA/cm2 at a 0.56 V overpotential. With a SnO2-based cathode catalyst, the formate-selective cell starts to operate at a 0.76 V overpotential and reaches a Faradaic efficiency of 82% and a partial current density of 113 mA/cm2 at a 1.36 V overpotential. In contrast to previous studies, it was found that the overpotential reduction from using the alkaline electrolyte is mostly contributed by a pH gradient near the cathode surface, which was validated by direct observations in a Raman-enhanced novel in-situ platform.

Design-oriented tool for Unprotected Loss Of Flow simulations in a Sodium Fast Reactor: Validation and application to stability analyses

Within the framework of the Generation IV Sodium-cooled Fast Reactor (SFR) R&D program of CEA (French Commissariat à l’Energie Atomique et aux Energies Alternatives), the reactor behavior in case of severe accidents is assessed through experiments and simulations. Such accidents are usually simulated with mechanistic calculation tools (such as SAS-SFR and SIMMER-III). As a complement to these codes, which give reference accidental transient results, a new Best Estimated Plus Uncertainty approach has been developed by CEA; its final objective being to derive the variability of the main outputs of interest for the safety. This approach involves a fast-running description of extended accident sequences coupling physical models for the main phenomena with advanced statistical analysis techniques. It enables to perform a large number of simulations in a reasonable computational time and to describe all the possible bifurcations of the accident transient. In this context, this paper presents a physical tool (models and results assessment) dedicated to the primary phase of an Unprotected Loss Of Flow accident (ULOF) in a SFR, i.e. before the first hexagonal can failure. This paper focuses on the modeling of neutronic phenomena and of the pin degradation and on their validations, the two-phase sodium thermal–hydraulic behavior having largely been assessed in a previous paper. The physical tool called MACARENa is described before presenting the comparison of its results with experimental tests results for the pin degradation behavior modelling and with mechanistic SIMMER-III code results for the global core behavior evolution during an ULOF transient. This tool is demonstrated to be capable of reproducing the mass-flow rate, reactivity, power evolution, and global pin degradation behaviour during an ULOF with a low discrepancy regarding the same transient simulated with SIMMER-III. In particular, observed discrepancies concerning mass flow rates and power evolutions are under 3% before boiling occurs and, later during the transient, the power excursion starts only 2s earlier in the MACARENa simulation than in the SIMMER-III one. The fast-running tool has then been used for safety-informed design and flow stability analyses of fast reactor systems, more specifically dealing with the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) core concept. It allowed to emphasize the main dominant phenomena and the significant trends for safety assessment. This work has pointed out the strong impact of the modelling of reactivity feedback due to thermal expansion on the resulting core degradation during an ULOF. It has also highlighted the main scenario parameters and models influencing this transient evolution.

Comparison of Isobutane/n-Butenes Alkylation over Y-Zeolite Catalyst in CSTR, Fixed Bed and Circulating Flow Reactors

Isobutane/olefin alkylation is an important route to obtain high-quality gasoline. There is an apparent interest to apply zeolite based catalysts for this process to eliminate large scale usage of liquid catalysts such as H2SO4 and HF. Solid catalysts require a specific reactor system design involving frequent catalyst regeneration and operation at low concentration of the olefin. The aim of this work was to compare different reactor types: CSTR, “once-through” fixed bed type and circulating flow reactors (CFR), which are typically considered as suitable options for industrial implementation. The experiments were done on decationated Y-zeolite catalyst. Different paraffin/olefin ratios, temperature and circulation rates were studied. Catalysts and process performance are discussed based on the catalyst lifetime and the alkylate octane number. Analysis of diffusion limitations in different reactor types and optimization of the circulation rate in CFR were done. It was found that isobutane alkylation in a circulating flow reactor shows approximately the same catalyst lifetime even at a high circulation rate not exhibiting any positive impact of back-mixing on this process. However, a circulating flow reactor has demonstrated a much better quality of alkylate with the research octane number higher by 4.9 points. Additional operational costs related to the reactor effluent recycle are fully covered by the alkylate quality improvement even at a high circulation ratio.

Increasing Revenue of Nuclear Power Plants With Thermal Storage

AbstractIntroducing large amounts of electricity produced from variable renewable energy sources such as wind and solar decreases wholesale electricity price while increasing the volatility of the market. These conditions drive the need for peak-load power generation, while regulation requirements fuel the push for flexible power generation. The increase of variable renewable energy in the market share, along with falling natural gas prices, makes nuclear power plants less competitive. Thermal storage is being considered to increase the nuclear power plant revenue. Thermal storage increases the flexibility of the nuclear plant system without sacrificing its efficiency. There are multiple opportunities to increase the nuclear power plant revenue, including increased capacity payments, arbitrage, and ancillary services. An economic analysis was performed to investigate the revenue increase of the system with thermal storage. The investment cost was assessed, and net present value was evaluated for the considered scenarios. Two system designs were considered in the analysis: a thermal storage system using the existing power conversion infrastructure and an integrated design with thermal storage fully incorporated into the reactor system design. The preliminary analysis showed that introducing a thermal storage system is profitable for some scenarios considered. Profitability depends significantly on the storage size, output flexibility, share of variable renewable energy, and market characteristics.

Design of a Flow Reactor System for Safe Handling of Phosgenation Reactions: Scale-Up Study of T-Shaped Mixers for Industrial Chemical Production

Design of a Flow Reactor System for Safe Handling of Phosgenation Reactions: Scale-Up Study of T-Shaped Mixers for Industrial Chemical Production

Influence of reactor and condensation system design on tyre pyrolysis products yields

This study investigates the effect the pyrolysis reactor and the condensing system type have on the tyre derived oil (TDO) and dl-limonene yield, as well as benzothiazole concentration in the TDO. All the experiments were performed at 475 °C and three technologies were investigated, fixed bed reactor (FBR), bubbling fluidised bed reactor (BFBR) and conical spouted bed reactor (CSBR), with the latter being the reactor that provided the highest TDO yield (58.2 wt.%). Furthermore, the CSBR enhances dl-limonene production due to its excellent features (low residence time of volatiles and high heat and mass transfer rates), which minimize secondary cracking reactions. Moreover, in order to maximize the TDO retention efficiency and selectively reduce the concentration of certain heteroaromatic species, two types of condensation systems were evaluated: tube-and-shell condenser (indirect contact) and quenching condenser (direct contact). The quenching condenser not only promoted the condensation efficiency for dl-limonene, but also reduced the concentration of benzothiazole in the collected TDO. Indeed, the direct contact between water (fed into the quencher) and the hot volatile stream favours the dissolution of some polar heteroaromatic species, thus reducing the nitrogen and sulphur content in the TDO and increasing the applicability of TDO as fuel.

Thermal hydraulic considerations of nuclear reactor systems: Past, present and future challenges

Thermal hydraulic analysis of nuclear reactor core and its associated systems can be performed using analysis system, subchannel or computational fluid dynamics (CFD) codes to estimate the different thermal hydraulic safety margins. The safety margins and operating power limits under different conditions of the primary as well as secondary cooling system such as the system pressure, coolant inlet temperature, coolant flow rate, and thermal power and its distributions are considered as key parameters for thermal hydraulic analysis. Considering the complexity of rod bundle geometry, boiling heat transfer and different turbulent scales bring about the many challenges in performing the thermal hydraulic analysis to ensure the safe design and operation of nuclear reactor systems under normal and abnormal conditions. A comprehensive review is presented of past, present and future challenges in state-of-the-art thermal hydraulic analysis c overing various aspects of experimental, analytical and computational approaches.

Perspectives of Microwaves-Enhanced Heterogeneous Catalytic Gas-Phase Processes in Flow Systems.

The paper discusses the currents status and future perspectives of the utilization of microwaves, as a selective and locally controlled heating method, in heterogeneous catalytic flow reactors. Various factors related to the microwave-catalyst interaction and the design of microwave-assisted catalytic reactor systems are analyzed. The analysis clearly shows the superiority of the traveling-wave systems over the mono-mode and multi-mode cavity-based systems when it comes to the design and application of microwave flow reactors at relevant production scales.

Inverse uncertainty quantification using the modular Bayesian approach based on Gaussian process, Part 1: Theory

In nuclear reactor system design and safety analysis, the Best Estimate plus Uncertainty (BEPU) methodology requires that computer model output uncertainties must be quantified in order to prove that the investigated design stays within acceptance criteria. "Expert opinion" and "user self-evaluation" have been widely used to specify computer model input uncertainties in previous uncertainty, sensitivity and validation studies. Inverse Uncertainty Quantification (UQ) is the process to inversely quantify input uncertainties based on experimental data in order to more precisely quantify such ad-hoc specifications of the input uncertainty information. In this paper, we used Bayesian analysis to establish the inverse UQ formulation, with systematic and rigorously derived metamodels constructed by Gaussian Process (GP). Due to incomplete or inaccurate underlying physics, as well as numerical approximation errors, computer models always have discrepancy/bias in representing the realities, which can cause over-fitting if neglected in the inverse UQ process. The model discrepancy term is accounted for in our formulation through the "model updating equation". We provided a detailed introduction and comparison of the full and modular Bayesian approaches for inverse UQ, as well as pointed out their limitations when extrapolated to the validation/prediction domain. Finally, we proposed an improved modular Bayesian approach that can avoid extrapolating the model discrepancy that is learnt from the inverse UQ domain to the validation/prediction domain.

Inverse uncertainty quantification using the modular Bayesian approach based on Gaussian Process, Part 2: Application to TRACE

Inverse Uncertainty Quantification (UQ) is a process to quantify the uncertainties in random input parameters while achieving consistency between code simulations and physical observations. In this paper, we performed inverse UQ using an improved modular Bayesian approach based on Gaussian Process (GP) for TRACE physical model parameters using the BWR Full-size Fine-Mesh Bundle Tests (BFBT) benchmark steady-state void fraction data. The model discrepancy is described with a GP emulator. Numerical tests have demonstrated that such treatment of model discrepancy can avoid over-fitting. Furthermore, we constructed a fast-running and accurate GP emulator to replace TRACE full model during Markov Chain Monte Carlo (MCMC) sampling. The computational cost was demonstrated to be reduced by several orders of magnitude. A sequential approach was also developed for efficient test source allocation (TSA) for inverse UQ and validation. This sequential TSA methodology first selects experimental tests for validation that has a full coverage of the test domain to avoid extrapolation of model discrepancy term when evaluated at input setting of tests for inverse UQ. Then it selects tests that tend to reside in the unfilled zones of the test domain for inverse UQ, so that one can extract the most information for posterior probability distributions of calibration parameters using only a relatively small number of tests. This research addresses the "lack of input uncertainty information" issue for TRACE physical input parameters, which was usually ignored or described using expert opinion or user self-assessment in previous work. The resulting posterior probability distributions of TRACE parameters can be used in future uncertainty, sensitivity and validation studies of TRACE code for nuclear reactor system design and safety analysis.

Numerical investigation on the effects of steam and water parameters on steam jet condensation through a double-hole nozzle

Steam jet condensation through multi-hole nozzles in a pressure relief pool is important for the design and safe operation of a nuclear reactor system. In this study, stable steam jet condensation through a double-hole nozzle was investigated at different water temperatures and steam pressures by CFD method. Simulation results indicated that the shape of steam cavity changed from conical to ellipsoidal with an increase in water temperature and steam pressure, and steam jet length gradually increased. Meanwhile, the interaction between two steam cavities was enhanced and they even merged under certain conditions. Expansion and compression waves were found by analyzing the thermal hydraulic parameters along the hole centerline. Water temperature and steam pressure exerted different effects on the intensity of expansion/compression waves and the positions of maximum expansion/compression. Finally, thermal hydraulic parameters along the nozzle centerline were analyzed. Steam volume fraction, temperature, and velocity initially increased and then decreased as axial distance increased, which appeared as evident peaks under the present conditions. When water temperature and steam pressure increased, the peak values of steam volume fraction, temperature, and velocity gradually increased and their positions moved downstream.

Safety Features of Advanced and Economic Simplified Boiling Water Reactors

The Advanced Boiling Water Reactor (ABWR) and the Economic Simplified Boiling Water Reactor (ESBWR) are two kinds of contemporary, advanced, commercially available nuclear power reactors. Reactor internal pumps in an ABWR improve performance while eliminating the large recirculation pumps in earlier BWRs. The utilization of natural circulation and passive safety systems in the ESBWR design simplifies nuclear reactor system designs, reduces cost, and provides a reliable stability solution for inherently safe operation. The conceptually reliable stability solution for inherently safe ESBWR operation is developed by establishing a sufficiently high natural circulation flow line, which has a core flow margin at least 5% higher than the stability boundary flow at 100% rated power of a conventional BWR, and then by designing a high flow natural circulation system to achieve this high natural circulation flow line. The performance analyses for the ESBWR Emergency Core Cooling System (ECCS) show that: (1) the core remains covered with a large margin and there is no core heat up in the ESBWR for any break size, (2) the long-term containment pressure increases gradually with time, in the order of hours, and the peak pressure is below the design value with a large margin, and (3) the margins depend on the containment volumes and water inventories. These safety design features ensure inherently safe ESBWR operation. Enhanced safety features based on lessons learned from the Fukushima nuclear accident are added in ABWR’s and ESBWR’s safety designs. The major enhancements are the further prevention of station blackout and loss of ultimate heat sink.

A novel experimental system for the exploration of CO2-water-rock interactions under conditions relevant to CO2 geological storage

This paper describes the design and experimental validation of a novel flow-through reactor system conceived for experimental studies to determine the kinetics and thermodynamics of mineral precipitation and dissolution in environmental conditions relevant to CO2 geological storage. The experimental system was designed to work under a confining pressure of up to 150 bar, temperature up to 150 °C and corrosive conditions. The unique design allows the injection of precise amounts of liquid CO2 into the reactor while avoiding the formation of multiple CO2 phases. The modular design enables the in-situ measurement of pH using a pressure resistant in-line probe and electronic gauges which record pressure and temperature at multiple points. The system enables the user to withdraw liquid samples without disturbing the experimental conditions in the reactor. Customized computer software was developed and connected to the system to provide automatic data-logging capabilities, remote process control and the ability to partially shut-down the system in case of safety issues.

The Energy Multiplier Module (EM2): Status of Conceptual Design

The Energy Multiplier Module (EM2) is a helium-cooled fast reactor with a core outlet temperature of 850°C. It is designed as a modular, grid-capable power source with a net unit output of 265 MWe. The reactor employs a convert-and-burn core design that converts fertile isotopes to fissile and burns them in situ over a 30-year core life. The reactor is sited in a below-grade sealed containment. It uses passive safety methods for heat removal and reactivity control to protect the integrity of the fuel, reactor vessel, and containment. The plant also incorporates a below-grade, passively cooled spent fuel storage facility with capacity for 60 years of full-power operation. EM2 employs a direct closed-cycle gas turbine power conversion unit (PCU) with an organic Rankine bottoming cycle for 53% net power conversion efficiency assuming evaporative cooling. The high-power conversion efficiency and long-burn fuel cycle reduce the electricity cost by 35% when compared with the conventional light water reactor.The conceptual design has been conducted for the EM2 plant with focus on the reactor, fuel, and safety system designs. A detailed model of the passive direct reactor auxiliary cooling system was created to demonstrate functionality for selected design-basis accidents. The bench-scale fuel development campaign demonstrated high-quality uranium carbide pellet fabrication as well as β-SiC composite cladding and SiC-joining technologies. Irradiation tests of reactor materials are also being conducted. The PCU variable-speed generator mechanical design was validated with operational testing of its novel rotor at speeds >13 000 rpm. The design of the turbo-compressor with active magnetic bearings continues. A large cost database and financial model have been constructed for use as a key driver for the design to be economically competitive with competing generating technologies after 2030.

Continuous Flow Processes As an Advanced Manufacturing Platform for Electrolyte Materials

New electrolyte materials (solvent, salt, additives) are required to enable HE/HV cells and to improve battery performance and safety. An advanced electrolyte solvents that allow for a wide electrochemical window and have low flammability (higher flash point) are the key components of a superior electrolyte. Continuous flow processes, an emerging technology in chemical industry offer an advanced manufacturing platform for electrolyte materials The flexible modular design of the flow reactor system allows for various chemistries and conditions not feasible in a batch process. The processes are cost and energy efficient and adhere to other principles of green chemistry including improved safety. The presentation will discuss continuous processes for manufacturing advanced electrolyte solvents via catalytic transesterification and catalytic hydrosylilation.