High Temperature Helium Loop Research Articles

Effect of geometry on the evolution of DLOFC transients in high temperature helium loop

Generation IV high-temperature gas-cooled reactors (HTGR) are designed to exhibit passive safety under all off-normal circumstances. One such scenario, known as depressurized loss of forced circulation (DLOFC), occurs after a break in the inlet/outlet header, allowing helium to leak from the reactor. Upon depressurization, the onset of natural circulation (ONC) can occur causing bulk air ingress leading to the oxidation and degradation of core components. The Transformational Challenge Reactor (TCR) has similar features to those of an HTGR, but the primary difference is the use of a more complex, additively manufactured (AM) fuel geometry. The more compact, additively manufactured, ceramic fuel elements can be conveniently produced with optimally configured channels that suppress the air ingress progress and improve thermofluidic performance. DLOFC and air ingress are experimentally studied in a scaled HTGR flow test setup. The experiments use an AM test element embedded with a distributed temperature sensor as well as a test geometry comprised of spherical pebble bed elements. With the test geometries aligned within a lowercase h-shaped tube flow setup, further data was obtained to improve the understanding of DLOFC. The thermal transient and air ingress data gathered for both test geometries are compared. The results show that the AM part delayed ONC as compared to the pebble bed test piece at higher temperatures. The distributed temperature sensor shows intra-leg circulation at higher temperature tests.

Modelling Production of Renewable Energy from Water Splitting High Thermal Electrolysis Processes

Recently, fuel gas from water has become the center of attention because it is a renewable source of energy and eco-friendly. In this study, the hydrogen gas simulated was obtained from the high-temperature water splitting electrolysis model, because it is more efficient than the low-temperature water splitting electrolysis process. It also releases oxygen as a byproduct. The high-temperature electrolysis model is made up of three loops: primary high-temperature helium loop, secondary helium loop, and high-temperature electrolysis loop. Hydrogen gave a temperature of 27.20C, a pressure of 49.5 bars, and a molar flow of 84.02MMSCFD. The hydrogen gas from a high-temperature electrolysis model is simulated with a CO2 gas stream to produce methane and water, also releasing unreacted carbon dioxide and hydrogen. Key parameters such as molar entropy, molar enthalpy, heat flow, and cost flow were evaluated by Aspen HYSYS V8.8. The simulation model used for this work is the Sabatier Process Model. In this model, Continuous stirred tank, Converter, Equilibrium, Gibbs, Plug flow reactors were used to generate methane. The Converter reactor gave the highest yield of methane gas with a mole fraction of 0.2390. Key benchmarks, including temperature, heat flow, cost flow, cost factor were varied to see how they can affect methane gas and other products.

Modelling Production of Renewable Energy from Water Splitting High Thermal Electrolysis Processes

Recently, fuel gas from water has become the center of attention because it is a renewable source of energy and eco-friendly. In this study, the hydrogen gas simulated was obtained from the high-temperature water splitting electrolysis model, because it is more efficient than the low-temperature water splitting electrolysis process. It also releases oxygen as a byproduct. The high-temperature electrolysis model is made up of three loops: primary high-temperature helium loop, secondary helium loop, and high-temperature electrolysis loop. Hydrogen gave a temperature of 27.20C, a pressure of 49.5 bars, and a molar flow of 84.02MMSCFD. The hydrogen gas from a high-temperature electrolysis model is simulated with a CO2 gas stream to produce methane and water, also releasing unreacted carbon dioxide and hydrogen. Key parameters such as molar entropy, molar enthalpy, heat flow, and cost flow were evaluated by Aspen HYSYS V8.8. The simulation model used for this work is the Sabatier Process Model. In this model, Continuous stirred tank, Converter, Equilibrium, Gibbs, Plug flow reactors were used to generate methane. The Converter reactor gave the highest yield of methane gas with a mole fraction of 0.2390. Key benchmarks, including temperature, heat flow, cost flow, cost factor were varied to see how they can affect methane gas and other products.

Licensing activity and code validation for generation IV SCW technology

Centrum Výzkumu Řež has a vast R&D program which was financed through the SUStainable Energy project. Several state-of-the-art facilities were designed in order to cover the demand of the energy community and to face new challenges for such advanced technologies. Two new experimental loops are to be inserted inside of the LVR-15 Research Reactor. Their purpose is to analyze cladding and structural material behaviour under different pressures, temperatures and coolant media conditions in comparison to the Light Water Reactors. The loops in question are the High Temperature Helium Loop and the Super Critical Water Loop. This paper focuses solely on the supercritical water loop. The first task of the Safety Research Section within the CVŘ was to select and to assess a code in order to simulate the media used in the loops. The second task was to use the selected codes to prepare the facilities models in order to simulate the possible consequences of the accident scenarios on the LVR-15 reactor. Based on the criteria set by the authors of this paper, through a comprehensive selecting procedure the ATHLET 3.1A code was chosen for the super critical water simulation. The paper is presenting the methodology followed in assessing the code’s capability for simulation of SCW.

Assessment of the TRACE Code for the He-Cooled Systems Simulation Capability Against Some He-FUS3 Experimental Measurements

This paper focuses on the TRACE code assessment for helium-cooled systems thermal-hydraulic analysis. In the frame of the GoFastR (gas cooled fast reactor) European Collaborative Project, ENEA has offered some selected experimental data for the organization of a benchmark exercise aimed at the validation of the system and CFD codes for the gas reactor transient analyses. One of the Research Center Řež teams participated in it with a CFD code application. Now, the experimental data are used in order to assess the TRACE code for the ongoing high-temperature helium loop (HTHL-2) licensing process. The results of the TRACE calculations agreed very well with the experimental measurements (often within the experimental uncertainties) data provided by the He-FUS3 facility, indicating that the code, despite developed for water coolant applications, if an appropriately tuned input is adopted, it can also be suitable for reasonably accurate gas technology thermo-hydraulic simulations.

Numerical study of air ingress transition to natural circulation in a high temperature helium loop

The generation-IV high temperature gas cooled reactors (HTGRs) are designed with many passive safety features, one of which is the ability to passively remove heat under a loss of coolant accident (LOCA). However, several common reactor designs do not prevent against a large break in the coolant system and may therefore experience a depressurized LOCA. This would lead to air entering into the reactor system via several potential modes of ingress: diffusion, gravity currents, and natural circulation. At the onset of a LOCA, the initial rate of air ingress is expected to be very slow because it is governed by molecular diffusion. However, after several hours, natural circulation would commence, thus, bringing the air into the reactor system at a much higher rate. As a consequence, air ingress would cause the high temperature graphite matrix to oxidize, leading to its thermal degradation and decreased passive heat (decay) removal capability. Therefore, it is essential to understand the transition of air ingress from molecular diffusion to natural circulation in an HTGR system. This paper presents results from a computational fluid dynamics (CFD) model to study the air ingress transition behavior. These results are validated against an h-shaped high temperature helium loop experiment (McIlroy et al., 2010). Details are provided to quantitatively predict the transition time from molecular diffusion to natural circulation.

Transition from molecular diffusion to natural circulation mode air-ingress in high temperature helium loop

High Temperature Gas-cooled Reactors (HTGRs) have significantly robust passive heat removal capabilities owing largely to conduction and radiation heat transfer through graphite-fuel matrix and reactor vessel wall respectively. However, these capabilities may be significantly impacted if air was to replace Helium in the high temperature graphite under accident scenarios. In case of break in the coolant system high pressure Helium will escape into the reactor cavity leading to depressurization of the reactor. This will allow air from reactor cavity to enter the plenum or core of HTGRs via different mechanisms – diffusion, gravity currents, or natural circulation. Experimental studies were conducted in a geometrically scaled set-up with a shape of small English letter ‘h’, to depict the role of upper plenum in this process. Main focus of these studies was to understand and observe the transition time from diffusion to natural circulation. Thermal camera is used to identify this transition and flow transducer is used to measure the flow rates. The experimental results on incipience time of natural convection after a chamber pre-filled with Helium is opened to atmosphere are qualitatively similar to observations reported in literature using ‘inverse U’ shaped experimental setup, but also show distinct quantitative effect of extended leg on the transition times. Prior to onset of natural circulation (ONC), molecular diffusion plays the significant role in air-ingress. However, at higher temperatures convection currents may be influencing air ingress and in-turn ONC times.

Microstructural analysis of 800H steel exposed at test operation in HTHL by using FIB-SEM and HRTEM techniques

To understand the degradation process of metal materials which are used in power engineering, appropriate evaluation procedure is necessary to ensure. In that order, the degradation of alloy 800H during the first period of test operation in High Temperature Helium Loop (HTHL) was tested. Experiment was carried out in atmosphere of pure technical helium with purity 4.6 containing only residual concentration of moisture up to 300vppm. Parameters during the operation test were not constant, process was interrupted several times. The maximum temperature on specimens during this period was 750°C, average temperature was 460°C, gas pressure ranged from 3 to 6MPa and gas flow from 3 to 9gs−1. Total duration of the test was 264h. After the exposure the degradation of specimens was investigated by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Using the technique of Focused Ion Beam (FIB) integrated within SEM the transparent samples with quality surface parameters were obtained for TEM analysis. FIB technique in combination with High Resolution TEM ensured the guaranteed methodology of exposed sample preparation and precise description of changes in this kind of material.

Effect of thermal exposure in helium on mechanical properties and microstructure of 316L and P91

In this paper, the effects of high temperature exposure in air as well as in impure He on mechanical properties of 316L and P91 steels were investigated. The experimental programme was part of material design of new experimental facility – high temperature helium loop. Some of the specimens were exposed in air at 750 °C for up to 1000 h. Another set of specimens were exposed in impure helium containing 1 ppmv CO2, 2 ppmv O2, 35 ppmv CH4, 250 ppmv CO and 400 ppmv H2 at 750 °C for up to 1000 h. Metalographical analysis, tensile tests, fracture toughness and hardness tests of exposed and non-exposed specimens were carried out. After the exposure both in air and He, the ultimate tensile strength of P91 decreased significantly more than that of 316L. After the exposure in He, the fracture toughness of 316L was reduced to 60% while fracture toughness of P91 showed no significant changes. The hardness of P91 decreased with exposure time in air. The measurement of the hardness of 316L was very scattered the most probably due to the heterogeneities in microstructure, the trend was not possible to evaluate.

The design and utilization of a high-temperature helium loop and other facilities for the study of advanced gas-cooled reactors in the Czech Republic

This paper focuses on the research infrastructure of advanced gas cooled reactors in the Czech Republic, particularly on the high-temperature helium loop HTHL, which is a unique facility of its kind. HTHL is intended mainly for testing structural materials. It also can be used to research technologies relating to helium coolant. The maximum temperature and pressure that can be used within the specimen testing space are 900 °C and 7 MPa, respectively, and the maximum gas flow rate in the main loop is 38 kg/hr. Originally, the equipment was envisaged as a device for corrosion tests of materials in the reactor LVR-15 but, according to current plans, a different equipment will be built for this purpose within the frame of the SUSEN project. At the same time, an additional helium loop (S-Allegro) will be built to test selected components of advanced gas-cooled reactors.

Experimental facility for development of high-temperature reactor technology: instrumentation needs and challenges

A high-temperature, multi-fluid, multi-loop test facility is under development at the Idaho National Laboratory for support of thermal hydraulic materials, and system integration research for high-temperature reactors. The experimental facility includes a high-temperature helium loop, a liquid salt loop, and a hot water/steam loop. The three loops will be thermally coupled through an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX). Research topics to be addressed include the characterization and performance evaluation of candidate compact heat exchangers such as printed circuit heat exchangers (PCHEs) at prototypical operating conditions. Each loop will also include an interchangeable high-temperature test section that can be customized to address specific research issues associated with each working fluid. This paper also discusses needs and challenges associated with advanced instrumentation for the multi-loop facility, which could be further applied to advanced high-temperature reactors. Based on its relevance to advanced reactor systems, the new facility has been named the Advanced Reactor Technology Integral System Test (ARTIST) facility. A preliminary design configuration of the ARTIST facility will be presented with the required design and operating characteristics of the various components. The initial configuration will include a high-temperature (750 °C), high-pressure (7 MPa) helium loop thermally integrated with a molten fluoride salt (KF-ZrF4 ) flow loop operating at low pressure (0.2 MPa), at a temperature of ∼450 °C. The salt loop will be thermally integrated with the steam/water loop operating at PWR conditions. Experiment design challenges include identifying suitable materials and components that will withstand the required loop operating conditions. The instrumentation needs to be highly accurate (negligible drift) in measuring operational data for extended periods of times, as data collected will be used for code and model verification and validation, one of the key purposes for the loop. The experimental facility will provide a much-needed database for successful development of advanced reactors and provide insight into the needs and challenges in instrumentation for advanced high-temperature reactors.

Development of gas cooled reactors and experimental setup of high temperature helium loop for in-pile operation

Rapidly increasing energy and electricity demands, global concerns over the climate changes and strong dependence on foreign fossil fuel supplies are powerfully influencing greater use of nuclear power. In order to establish the viability of next-generation reactor concepts to meet tomorrow's needs for clean and reliable energy production the fundamental research and development issues need to be addressed for the Generation-IV nuclear-energy systems. Generation-IV reactor concepts are being developed to use more advanced materials, coolants and higher burn-ups fuels, while keeping a nuclear reactor safe and reliable. One of the six Generation-IV concepts is a very high temperature reactor (VHTR).The VHTR concept uses a graphite-moderated core with a once-through uranium fuel cycle, using high temperature helium as the coolant. Because helium is naturally inert and single-phase, the helium-cooled reactor can operate at much higher temperatures, leading to higher efficiency. Current VHTR concepts will use fuels such as uranium dioxide, uranium carbide, or uranium oxycarbide. Since some of these fuels are new in nuclear industry and due to their unknown properties and behavior within VHTR conditions it is very important to address these issues by investigate their characteristics within conditions close to those in VHTRs. This research can be performed in a research reactor with in-pile helium loop designed and constructed in Research Center Rez Ltd. One of the topics analyzed in this article are also physical characteristic and benefits of gas coolants.The purpose of the high temperature helium loop (HTHL) is to simulate technical and chemical conditions of VHTR's coolant. The loop is intended to serve an as experimental device for fatigue and creep tests of construction metallic materials for gas-cooled reactors and it should be also employed for research in field of gaseous coolant chemistry. The loop will serve also for tests of nuclear graphite, dosing and helium purification systems. Because the VHTR is a new reactor concept, major technical uncertainties remain relative to helium-cooled advanced reactor systems. This paper summarizes also the concept of the HTHL in the Research Centre Rez Ltd., its design, utilization and future plans for experimental setup.

New experimental device for VHTR structural material testing and helium coolant chemistry investigation – High Temperature Helium Loop in NRI Řež

The High Temperature Helium Loop (HTHL) is an experimental device for simulation of VHTR helium coolant conditions. The purpose of the HTHL is structural materials testing and helium coolant chemistry investigation. In the HTHL pure helium will be used as working medium and its main physical parameters are 7MPa, max. temperature in the test section 900°C and flow rate 37.8kg/h. The HTHL consists of an active channel, the helium purification system, the system of impurities dosage (e.g. CO, CO2, H2, H2O, O2, N2, and CH4) and the helium chemistry monitoring system (sampling and on-line analysis and determination of impurities in the helium flow). The active channel is planned to be placed into the core of the experimental reactor LVR-15 which will serve as a neutron flux source (max. 2.5×1018n/m2s for fast neutrons).The HTHL is now under construction. Some of its main parts are finished, some are still being produced (active channel internals, etc.), some should be improved to work correctly (the helium circulatory compressor); certain sub-systems are planned to be integrated to the loop (systems for the determination of moisture and other impurities in helium, etc.). The start of the HTHL operation is expected during 2011 and the integration of the active channel into the LVR-15 core during 2012.

Conceptual and preliminary engineering design of experimental helium loop for China HCCB TBM components test

Chinese Helium Cooled Ceramic Breeder Test Blanket Module (CN HCCB TBM) had been confirmed to be one of the leader concepts, which will be tested in half of ITER equatorial port. It is responsible for each TBM does not jeopardize ITER operation. In order to ensure the future CN HCCB TBM safely and effectively operating in ITER, components and even full scale of TBM should be tested before delivery to ITER site. Therefore, a new high temperature and high pressure experimental helium loop will be constructed to validate the thermal-hydraulic and thermal-mechanical capability of those components. In this article, a rational conceptual design of the experimental helium loop was presented. At the same time, preliminary engineering design includes thermal-hydraulics assessment of equipments, thermal stress of pipes in the loop were performed. The assessment results show that technical issues of helium loop construction are expected to be solved successfully. Finally, possible test strategies have been presented to fulfill the TBM thermo-hydraulics campaigns.

New Experimental Loops for Research Reactor LVR-15

Two experimental loops for operation in research reactor LVR-15 in ÚJV Řež are recently under preparation: High Temperature Helium Loop (HTHL) and SuperCritical Water Loop (SCWL). Pure helium will be used as working medium in HTHL and its main physical parameters are: operating pressure 7MPa, max. temperature in the test section 900°C and flow rate 36kg/h. HTHL will include helium purification system, system for dosage of impurities (e.g. CO2, H2, H2O, O2, N2 etc.) and helium sampling. Helium purification experiments and testing of materials in simulated HTR conditions will take place in HTHL in the future. Main parameters of the SCWL are 25MPa, max. temperature in the test section 600°C, flow rate max. 200kg/h. SCWL will be used for corrosion tests of candidate materials, studies of water radiolysis at supercritical conditions and for testing of water chemistry suitable for operation. Both loops possess an irradiation channel with quite complicated internals design, whose complexity is imposed by current constraints on constructional materials of nuclear experimental devices, which limit the choice and maximum surface temperature of material of construction to 500°C for austenitic stainless steel. The working temperature will thus be attained only in a restricted volume of the test section. The channel internals will be briefly described. The mentioned loops will represent novel experimental devices, whose objective is to gain and extend knowledge on materials and environment performance under the influence of radiation.