•A methodology developed for thermal-hydraulic analysis of fluoride salt cooled reactor (AHTR)•ANSYS/Fluent used for 2D/3D thermal-hydraulic simulations of online refueling.•Online refueling causes ...asymmetric temperature and flow distribution in upper/lower plenum.•Recommendations on the assembly design are provided to reduce the lift force.•The study demonstrates the viability of online refueling for improving the economics of the AHTR.
As part of the effort to move forward the Fluoride salt-cooled High-temperature Reactor (FHR) technology, the Advanced High Temperature Reactor (AHTR) is being developed at Oak Ridge National Laboratory (ORNL) and several other institutions. Due to its plank fuel design and inherently low heavy metal loading, which challenges fuel utilization, online refueling is considered as an option for improving the economic viability of this reactor.
This work presents the thermal hydraulic modeling of the online refueling for the AHTR. Analyses at the single channel and fuel assembly level have been performed in order to develop a model of the reactor. The reactor modeling has been integrated with CFD studies for characterizing the steady state conditions and the refueling transient. The simulations of the transient have been complemented by the analysis of the stability of the refueling operation.
This work demonstrates the viability of online refueling from a thermal hydraulic standpoint and develops a modeling approach for this type of operational transient.
•High-temperature fluoride salt cooled reactor is evaluated.•A comprehensive method for the analysis of the on-line refueling has been developed.•On-line refueling eliminates cycle length issue and ...improves fuel utilization.•On-line refueling provides a reduction of the fuel cycle cost.•On-line refueling maintains adequate safety with respect to multi-batch refueling.
Several academic and commercial organizations around the world are developing the Fluoride salt-cooled High-temperature Reactor (FHR) technology, due to its safety features and potential to generate high temperature energy for electricity and process heat applications. The Advanced High Temperature Reactor (AHTR) being considered in this study is a FHR design developed at Oak Ridge National Laboratory (ORNL). It is based on the use of graphite as moderator, FLiBe as coolant, and hexagonal fuel elements with fuel plates (or “planks”) composed of TRISO particles embedded in a carbonaceous matrix.
The AHTR reference design is based on traditional batch refueling approach, which requires to shut down the reactor and replace/reshuffle a certain amount of fuel assemblies in the core at a specific frequency. Several options have been evaluated in the design process, in order to maximize the cycle length and optimize the use of fuel. However, the relatively short cycle and poor fuel utilization are intrinsic features of this family of reactors, due to the low heavy metal loading in the core and insufficient moderation, which are competing aspects in terms of core volume fraction. Since the fuel is expected to be more expensive than the fuel of light water reactors (LWR), this issue might challenge the economic viability of the AHTR.
In order to eliminate or ameliorate this issue, a novel approach to refueling has been developed and proposed, consisting of continuous on-power refueling, or on-line refueling, in which the refueling procedure is performed at full power or partially reduced power (the reactor is not shut down) and a single assembly is removed for each refueling operation. A systematic neutronic and thermal-hydraulic analysis approach has been developed and performed to assess the viability and safety of the refueling operations, followed by the evaluation of the core design requirements and a quantification of the economic advantages resulting from the implementation of this procedure.
The new generation internal beam dump of the Super Proton Synchrotron (SPS) at CERN will have to dissipate approximately 270 kW of thermal power, deposited by the primary proton beam. For this ...purpose, it is essential that the cooling system features a very efficient heat evacuation. Diffusion bonding assisted by hot isostatic pressing (HIP) was identified as a promising method of joining the cooling circuits and the materials of the dumps core in order to maximize the heat transfer efficiency. This paper presents the investigation of HIP assisted diffusion bonding between two CuCr1Zr blanks enclosing SS 316L tubes and the realization of a real size prototype of one of the dump’s cooling plates, as well as the assessments of its cooling performance under the dump’s most critical operational scenarios. Energy-dispersive x-ray spectroscopy, microstructural analyses, measurements of thermal conductivity, and mechanical strength were performed to characterize the HIP diffusion bonded interfaces (CuCr1Zr-CuCr1Zr and CuCr1Zr-SS 316L). A test bench allowed to assess the cooling performance of the real size prototype. At the bonded interface, the presence of typical diffusional phenomena was observed. Moreover, measured tensile strength and thermal conductivity were at least equivalent to the lowest ones of the materials assembled and comparable to its bulk properties, meaning that a good bonding quality was achieved. Finally, the real size prototype was successfully tested with an ad hoc thermal test bench and with the highest operational thermal power expected in the new generation SPS internal beam dump. These results demonstrated the possibility to use HIP as a manufacturing technique for the cooling plates of the new generation SPS internal beam dump, but they also open up the way for further investigations on its exploitability to improve the cooling performance of any future high intensity beam intercepting device or in general devices requiring very efficient heat evacuation systems.
The beam dump facility (BDF) project is a proposed general-purpose facility at CERN, dedicated to beam dump and fixed target experiments. In its initial phase, the facility is foreseen to be ...exploited by the Search for Hidden Particles Experiment. Physics requirements call for a pulsed400GeV/cproton beam as well as the highest possible number of protons on target each year of operation (4.0×1019/year), in order to search for feebly interacting particles. The target/dump assembly lies at the heart of the facility, with the aim of safely absorbing the full high intensity Super Proton Synchrotron beam, while maximizing the production of charmed and beauty mesons. High-Z materials are required for the target/dump, in order to have the shortest possible absorber and reduce muon background for the downstream experiment. The design of the production target is one of the most challenging aspects of the facility design, due to the high energy and power density deposition that are reached during operation, and the resulting thermomechanical loads. The nature of the beam pulse induces very high temperature excursions between pulses (up to100°C), leading to considerable thermally induced stresses and long-term fatigue considerations. The high average power deposited on target (305 kW) creates a challenge for heat removal. During the BDF facility comprehensive design study, launched by CERN in 2016, extensive studies have been carried out in order to define and assess the target assembly design. These studies are described in the present contribution, which details the proposed design of the BDF production target, as well as the material selection process and the optimization of the target configuration and beam dilution. One of the specific challenges and novelty of this work is the need to consider new target materials, such as a molybdenum alloy as core absorbing material and Ta2.5W as cladding. Thermostructural and fluid dynamics calculations have been performed to evaluate the reliability of the target and its cooling system under beam operation. In the framework of the target comprehensive design, a preliminary mechanical design of the full target assembly has also been carried out, assessing the feasibility of the whole target system.
As part of the effort to move forward the Fluoride salt-cooled High-temperature Reactor (FHR) technology, the Advanced High Temperature Reactor (AHTR) is being developed at Oak Ridge National ...Laboratory (ORNL) and several other institutions. Due to its plank fuel design and inherently low heavy metal loading, which challenges fuel utilization, online refueling is considered as an option for improving the economic viability of this reactor. This paper presents the thermal hydraulic modeling of the online refueling for the AHTR. Analyses at the single channel and fuel assembly level have been performed in order to develop a model of the reactor. The reactor modeling has been integrated with CFD studies for characterizing the steady state conditions and the refueling transient. The simulations of the transient have been complemented by the analysis of the stability of the refueling operation. This work demonstrates the viability of online refueling from a thermal hydraulic standpoint and develops a modeling approach for this type of operational transient.
The beam dump facility (BDF) is a project for a new facility at CERN dedicated to high intensity beam dump and fixed target experiments. Currently in its design phase, the first aim of the facility ...is to search for light dark matter and hidden sector models with the Search for Hidden Particles (SHiP) experiment. At the core of the facility sits a dense target/dump, whose function is to absorb safely the400GeV/cSuper Proton Synchrotron (SPS) beam and to maximize the production of charm and beauty mesons. An average power of 300 kW will be deposited on the target, which will be subjected to unprecedented conditions in terms of temperature, structural loads and irradiation. In order to provide a representative validation of the target design, a prototype target has been designed, manufactured, and tested under the SPS fixed-target proton beam during 2018, up to an average beam power of 50 kW, corresponding to 350 kJ per pulse. The present contribution details the target prototype design and experimental setup, as well as a first evaluation of the measurements performed during beam irradiation. The analysis of the collected data suggests that a representative reproduction of the operational conditions of the beam dump facility target was achieved during the prototype tests, which will be complemented by a postirradiation examination campaign during 2020.
The Beam Dump Facility (BDF) is a proposed general-purpose facility at CERN, dedicated to fixed target and beam dump experiments, currently being developed in the context of the Physics Beyond ...Colliders program. The design of the facility will allow to host different types of experiments, of which SHiP is planned to be the initial one. The core of the facility is a high-density target/dump absorbing the full intensity of the SPS beam and generating a cascade of particles that are detected downstream the target complex. The target and its shielding blocks are positioned inside a vessel, which is planned to be passivized with helium, in order to reduce the activation of the gas surrounding the target and to extend the operational life of materials and equipment. The passivation system that will be in charge of purifying and circulating the helium is a critical component for the operation of the facility. Fluid dynamics simulations have been performed to study the circulation of the helium through the vessel. A detailed design of the helium passivation system and its main components has been developed.
•We developed MATLAB and RELAP5models of the single channel of the AHTR.•Single channel analysis indicates design envelope for effective heat removal.•The reactivity feedback evaluated by SCALE ...supports safe operation of the reactor.•We developed RELAP5 models of the fuel assembly and full core.•The fully passive DRACS protects the reactor during a LOFC accident.
The Advanced High Temperature Reactor (AHTR) is a fluoride-cooled and graphite-moderated reactor concept designed by Oak Ridge National Laboratory (Holcomb et al., 2011). The modeling and optimization of the heat removal system and the core structure is required, in order to obtain an adequate heavy metal loading and to provide effective cooling capability. The single channel MATLAB model provides a simple tool to evaluate the steady state conditions for the coolant and the fuel plate and the effects of the power distribution; sensitivity studies on the main design parameters of the fuel element are performed. A RELAP5-3D single channel model is developed for the validation and comparison with the MATLAB model; this model is the starting point for the development of a full core model, enabling the study of transients. A one-third fuel assembly model is then analyzed, consisting of six fuel plates and modeling the heat conduction of graphite through RELAP5-3D conduction enclosures. Since the assembly model is not suitable for the implementation in a full core model with the same level of detail, several simplifications have been evaluated, involving the modeling of the plate through a single heat structure and the modeling of different plates through a single plate. A SCALE model of the fuel assembly was developed for the evaluation of the reactivity feedback and the power distribution in the core. The results from the neutronic evaluations and the assembly model were implemented in a full core model, involving the core, the main reactor structures, the cooling system and the safety system (DRACS). The RELAP5-3D core model was used for the evaluation of the steady state conditions and the effects of a loss of forced cooling accident (LOFC).
For the ITER TBM Program, two equatorial ports (#16, #18) of the machine are dedicated to the operations of four independent Test Blanket Systems (TBSs). Each TBS is composed of a Test Blanket Module ...(TBM) and several ancillary systems, among them the Tritium Extraction System (TES), the Neutron Activation System (NAS), the Tritium Accountancy System (TAS). The main equipment of TES, NAS and TAS are located in different rooms of the tokamak complex. The pipes connecting such equipment from one room to another room are called Connection Pipes (CPs) and they carry tritiated fluids. A second barrier of confinement is necessary in order to fulfill some key project requirements.
The paper addresses the rational and benefits of implementing guard-pipes around the process pipes. It describes also the outcomes of the design development phase carried out over the last few years to reach the stage of detailed design, to proceed with the fabrication of some components, and also to complete the construction design ready for works execution. The design accounts for the specific sequence of assembly and welding operations. It will focus on some technical complexities which were tackled. They were triggered in particular by the required compliance with French regulations for nuclear pressure equipment.
•The Liquid Salt Test Loop (LSTL) has been modeled using the TRACE code.•Flow correlations through a pebble bed have been identified and implemented in TRACE.•LSTL operational and transient ...conditions have been simulated.•The model helped to characterize the loop shakedown testing results.
The objective of this work is to simulate the Liquid Salt Test Loop (LSTL) using the TRACE system code. The LSTL is an experimental facility built at Oak Ridge National Laboratory to test the thermal-hydraulic behavior of a circulating FLiNaK liquid salt. A literature review of the experimental work and the heat transfer and friction correlations for pebble beds was performed to identify the correlations that can be used to simulate the flow of FLiNaK through a pebble bed. The selected correlations were implemented in the TRACE source code and tested using 1-D pipe components. The modified version of TRACE was then used to develop models for each component in the loop. Each component was tested separately to assess its correct physical behavior. The components were integrated into a comprehensive loop model, including the main loop and the air cooling system. The model was used to compute the steady state conditions of the loop, in particular calculation of the pressure distribution and other global operational parameters. The loop-filling transient was analyzed, along with other specific transient conditions such as the pump trip and the loop behavior under natural circulation conditions. The TRACE model was used to help characterize loop thermal hydraulic behavior and to help interpret results from loop shakedown testing.
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