Helium Mass Flow Rate Research Articles

Optimization of the first wall cooling circuits to achieve an efficient coolant flow distribution in the DCLL breeding blanket

In the current design proposal of the Dual Coolant Lithium Lead (DCLL) breeding blanket for the EU DEMO reactor, the first wall is cooled down by a succession of He channels arranged along the poloidal length. In this scheme, since He extracts around 30% of the blanket thermal power, a conservative oversizing of the coolant mass flow rate compelled by highly heterogeneous heat loads, can severely jeopardize the blanket thermal efficiency and the consumption of the auxiliary systems. A meticulous design of the hydraulic network can enhance the cooling system efficiency by ensuring that each channel is fed with a mass flow rate according to its specific needs.In this study, a novel approach employing genetic algorithms has been developed to optimize the geometry of the first wall, encompassing the feeding/collecting manifolds and channels. This optimization aims to replicate the mass flow rate distribution obtained from TOMFLOW (Tool for Optimization of Helium Mass Flow Rate Distribution), a code dedicated to determine the minimum mass flow rate required in each channel to maintain the EUROFER steel structure below 550 °C.

Numerical simulation of tritium extraction from liquid PbLi by gas–liquid contactor

As one key component of the fusion reactor, the blanket is in charge of breeding tritium, shielding neutrons and extracting thermal energy for electricity generation. An efficient tritium extraction unit (TEU) is a necessary guarantee for the tritium self-sufficiency in the fusion reactor. The gas–liquid contactor (GLC) is considered to be one of the most efficient devices for the liquid blanket that uses the lead–lithium (PbLi) as the functional materials. Understanding the characteristics of gas–liquid two-phase flow and mass transfer is beneficial for guiding the design and optimization of contactor. However, it is difficult to carry out the tritium experiments due to the scarcity in nature, the strong permeability, as well as the radioactivity. In this paper, the turbulent two-phase model coupled with dilute mass transfer is adopted to numerically study the process of tritium extraction from the liquid PbLi, and the numerical model is evolving step-by-step. Firstly, based on the models of single bubble and helium purge, the effects of different design parameters on the tritium extraction efficiency of the contactor are further investigated (i.e. mass flow rate of helium, initial tritium concentration and liquid PbLi filling height). The results are in good agreement with previous experimental results, and this validates the feasibility of the numerical model used in this work. Then, the entire model of GLC is numerically analyzed, which illustrates that the tritium extraction efficiency of one single unit is only 20.8%. However, the total efficiency can achieve 95% when there are 13 units working together in series. On this basis, the schematic diagram of tritium extraction system is proposed for the fusion blanket.

A simple study for an optimized operation of the ITER Cryodistribution cold rotating machines

The ITER superconducting (SC) magnet system is composed of 4 distinct units: the Central Solenoid (CS) coils, the Toroidal Field (TF) coils, the coil encasing and supporting Structures (ST), and the Poloidal Field and Correction Coils (PF&CC or simply PF). Including another cold component unit, which is the Cryopump (CP) system, each unit is assigned its own Auxiliary Cold Box (ACB) with cold rotating machines (CRMs) to ensure efficient operation from a cryogenic perspective. The CRMs, which are the cold circulator (CCr) and cold compressor (CCp), are respectively in charge of generating the high mass flow rate (2.0–2.7 kg/s) and low temperature (3.7–4.2 K) of supercritical helium (SHe) that is supplied to each magnet unit and CP system. To maintain the proper cryogenic conditions of the magnets and CPs during fusion experiments, the ITER Cryogenic System can produce an average cooling power of 75 kW at 4.5 K, including the need for the 50 K gaseous helium (GHe) cooled high-Tc SC current leads. Depending on the operation mode of the ITER Tokamak, up to 28 kW of that power can be consumed by the CRMs due to compression of helium.In this study, we will explore possibilities for optimized operation of the CRMs by adjusting the mass flow rate and temperature of the SHe to minimize the heat of compression while maintaining the thermal stability of the ITER SC magnets and CP. By doing so, the CRM-heat-of-compression at 4.5 K can be reduced by more than 3 kW, providing additional “cryogenic” margins for higher-heat-load plasma experiments.

Design and performance of a novel compact high-effectiveness transparent-wall counter-flow heat exchanger fabricated using additive manufacturing

Compact high-effectiveness counter-flow heat exchangers (CFHEX) are an essential building block of remote cooling systems and Reverse Turbo-Brayton coolers. This technology enables a wide variety of on-ground and space applications, including the cooling of infrared detectors, cryogenic chains of quantum computers and ultra-sensitive superconducting SQUID sensors. A mesh-based CFHEX design was previously proposed for such applications and demonstrated a great potential to meet the high effectiveness and compactness needs [1]. This paper presents a novel improved mesh-based CFHEX concept with a “transparent” inner wall and outlines the methods used for its manufacturing. Two of such CFHEXs are constructed and integrated in a technology demonstrator of a remote cooling system. Their performance is tested in the ▪ temperature, 1bar–5bar pressure and 50mg/s–250mg/s helium mass flow rate ranges. An effectiveness of ▪ (NTU=39–124) has been experimentally achieved with a pressure drop of less than 10mbar per stream at the nominal operating conditions of the system. The experimental effectiveness and pressure drop results are analysed and compared to numerical predictions. The implications of the achieved high effectiveness on the final performance of the designed remote cooling system are also discussed.

Preliminary Experimental Quantification of Helium Leakages from Flanged Connections at HCPB TBS Operative Conditions

The HCPB TBS (Helium-Cooled Pebble Bed Test Blanket System) is one of the two European TBSs that will be installed and tested in the ITER reactor. The use of flanged connections in the Helium Coolant System and the Tritium Extraction System of the HCPB TBS would make the remote maintenance operations easier and faster. Therefore, investigating the helium leakage from flanges becomes a fundamental step toward the control of the tritium activity in the Port Cell, as the helium flow will contain a variable but not negligible amount of tritium. The first set of experiments on helium leakages from flanged connections is described in this paper. The experiments were performed in a HeFUS3 facility, an eight-shaped helium loop designed to work at HCPB-TBS-relevant conditions. The facility can provide a helium mass flow rate in the range of 0.27–1.4 kg/s and can reach a pressure as high as 80 bar and a temperature up to 530 °C. Two types of gaskets were tested in this campaign: a spiral-wound gasket and an oval ring joint. The gasket/flange assemblies are described in detail in this paper, together with the test section that hosts them and the performed commissioning tests. The tests were carried out at 500 °C and 80 bar. In these conditions, the leak rate from the flange with the oval ring joint resulted in being, on average, 1.42·10−6 mbar∙L/s, while the leak rate from the flange with the spiral-wound gasket resulted in being, on average, 3.73·10−3 mbar∙L/s.

Numerical investigation on the thermal load heterogeneity of multi-assembly helical coil steam generator in high temperature gas-cooled reactor

The thermal load heterogeneity will lead to inhomogeneous local heat flux and thermal stress, extremely detrimental to the operational stability of heat exchangers with multi-assembly structure. In this paper, a full-scale analysis method for the helical coil steam generator in industry was developed and implemented. The validation was performed against flow boiling heat transfer experiment of helical tube. The simulation of single assembly and full-scale helical coil steam generator in high temperature gas-cooled reactor was performed, and the distributions of thermal-hydraulic parameters in heat exchange region were obtained. The results show that the nonuniform helium flow distribution with the inhomogeneous factor Dm value of 34.83% has a significant influence on the heat transfer characteristics. The peak heat transfer power of central assembly increases by 33.76% against design condition, introducing large thermal load heterogeneity with the inhomogeneous factor Dp value of 30.45%, even threating the structural integrity of helical tube in long-term operation circumstances. The structural elements design in the superior compartment should be optimized to increase the helium mass flow rate of the assemblies below the nozzle and behind the helium baffle, improving flow distribution uniformity and reducing the peak value of local heat flux and thermal stress.

Integrated hydrogen liquefaction process with a dual-pressure organic Rankine cycle-assisted LNG regasification system: Design, comparison, and analysis

Improving the efficiency and reducing the cost of hydrogen liquefaction systems have become a subject of importance nowadays. Through the comparison and analysis of existing processes, a hydrogen liquefaction system that can enhance the utilization efficiency of liquefied natural gas (LNG) cold energy is developed. The system includes a dual-pressure organic Rankine cycle (DORC)-assisted LNG regasification process and improved cascade Joule-Brayton refrigeration cycles. To assess the performance of the proposed process, two forms of ORC and three Brayton refrigeration cycles are compared, respectively. The genetic algorithm is applied to optimize the proposed process. The coefficient of performance, exergy efficiency, and specific energy consumption of the proposed process is 0.20, 46.9%, and 6.61 kWh/kgLH2, respectively. Owing to the efficient utilization of LNG cold energy, the power output of the DORC is 16.2% higher than that of a regular ORC. Furthermore, the improved cryo-cooling process exhibits a significant performance enhancement. Compared to two existing processes, the UA value of the heat exchangers in the proposed cryo-cooling process is reduced by 47.6% and 8.3%, respectively, and the required mass flow rate of helium is reduced by 45.3% and 8.6%, respectively. Moreover, the exergy analysis performed on the system indicates that the exergy utilization rate of the hydrogen pre-cooling process is 80.2%, while that of the cryo-cooling process is only 48.7%.

Stability Analysis of 14-T-Level High-Performance Nb3Sn Cable-in-Conduit Conductor for a Toroidal Field Coil

In view of the fact that the fusion power of fusion reactor is proportional to the fourth power of the toroidal magnetic field, the design of toroidal field (TF) magnetic system is particularly important for achieving higher operating parameters. In order to meet the confinement requirements of high plasma parameters, the high field region of the TF magnetic system can be wound by high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable-in-conduit conductor (CICC), with a maximum magnetic field reaching 14.32 T. Since the stable operation of the TF magnetic system relies heavily on the stability of the superconductor, a stability analysis of high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor has been performed. The results indicate that the current sharing temperature of the conductor is 6.9 K under extreme working conditions ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> = 14.32 T), which meets the design requirements; the minimum quench energy (MQE) is 116 mJ/cc under short perturbation, but under long perturbation it is only 20.3 mJ/cc. Therefore, several options may be available to increase the MQE of the conductor, such as reducing the strain, operating current and thermal resistance, or increasing the helium mass flow rate. In addition, the quench behavior of the CICC conductor is also evaluated. Studies have shown that increasing the area of copper and decreasing the thermal resistance and quench detection threshold voltage can lower the hot spot temperature. These analyses provide references for the design of 14-T-level high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor and its quench protection system.

Heat Transfer Measurements of a Transpiration-Cooled Stagnation Point in Transient Hypersonic Flow

This paper presents a novel experimental technique where infrared thermography is employed to directly measure the surface heat transfer of a transpiration-cooled porous material in transient hypersonic flow. Experiments were conducted in the Oxford High Density Tunnel on a flat-faced hemispherical probe at a single Mach 7 freestream condition () with nitrogen, air, argon, krypton, and helium injection gases and mass flow rates ranging from 0.01 to . Surface heat transfer measurements were extracted by imaging directly on the porous material using a FLIR A6751 high-speed long-wave infrared camera. Porous alumina was chosen due to its favorable thermal properties for infrared analysis and its very small pore sizes () enabling a uniform outflow. It was found that the surface Stanton number reduction matched to within 10% of both computational fluid dynamics results and correlations.

Design and thermal-hydraulic analysis of a printed circuit heat exchanger for ADS applications

Printed circuit heat exchanger (PCHE) is considered a promising candidate for accelerator driven systems (ADS) due to its high compactness and efficiency. The preeminent high-temperature, high-pressure and corrosion resistance enables it to withstand the severe conditions of ADS and ensure the safe and efficient operation. In this paper, a PCHE applied to the ADS is proposed, adopting helium as the cold source and lead-bismuth eutectic (LBE) as the heat source. On this basis, a three-dimensional model is established and the flow and heat transfer characteristics of the PCHE are numerically investigated. The thermal performance is further improved by optimizing structural and operating parameters. The results indicate that the high thermal conductivity and superior field synergy degree of LBE ensures a strong heat transfer performance of PCHE. The velocity disturbance and double-vortex secondary flow generated in modified channels, which intensify the fluid mixing and improve the field synergy level, help to further enhance the overall heat transfer coefficient. Structural and operating parameters of the helium side are more critical to the thermal-hydraulic performance, an increase of helium mass flow rate within allowable pressure drop is conducive to the comprehensive performance.

Parametric study and optimization of the cryo-magnetic system for EU DEMO at the pre-conceptual design phase

The pre-conceptual design phase of the EU DEMO magnet system relies on mechanical, electromagnetic and thermal-hydraulic analyses of different conductor designs for the Toroidal Field (TF) coils, the Poloidal Field (PF) coils and the Central Solenoid (CS) magnet. The cryo-magnetic system includes the superconducting magnets cooled by forced flow of supercritical helium at about 4.5 K, the cryo-distribution lines and valve boxes, and the cryogenic system with several cold boxes. The present analysis focuses on the cooling requirement of the TF coils with three winding pack options for the cable in conduit conductors based on 2015 DEMO baseline, featuring pancake or layer winding approaches. This analysis methodology would be further developed with the latest conductor designs and more complete heat load assumptions for the future conductor design studies and the specification of the cooling requirements. Parametric studies on the cold source temperature and on the supercritical helium mass flow rate have been performed on the three conductor designs in order to identify for each one the impact of the cooling conditions onto the temperature margin with respect to the current sharing temperature. In this study, the heat load contribution have been limited to the estimation of the neutron heating and some joint resistance heat loads when available. In addition, Simcryogenics, a dynamic modelling tool developed by CEA, is used to model supercritical helium loops for cooling different conductor designs. An algorithm has been developed to optimize both the cold source temperature and the supercritical helium mass flow, in order to minimize refrigeration power for each conductor design. Optimization studies are analyzed and compared in order to estimate for each TF winding pack design, the impact on refrigeration power. The interest of such quick cross-check analyses is to identify design improvements for the conductors and the cryo-distribution, keeping acceptable temperature margins and minimizing the refrigeration power.

Comprehensive Numerical Analysis on Flow and Heat Transfer Characteristics of Printed Circuit Heat Exchanger With Fins

Abstract Printed circuit heat exchanger (PCHE), as a high-efficiency and compact heat exchanger, shows a high potential in high temperature, high pressure, and some extreme environments, thus, it is widely used in nuclear power generation, refrigeration, aerospace, etc. In this paper, the flow and heat transfer characteristics of heat transfer channels with different fins were numerically analyzed, by changing helium inlet temperature and mass flowrate. The results indicate that, with the increase of helium mass flowrate, Nusselt number and pressure loss grow, while Colburn factor and Fanning friction factor drop. As helium inlet temperature rises, Nusselt number, Colburn factor, and pressure loss grow, whereas Fanning friction factor decreases. In addition, the heat transfer characteristics of the channels with different fins are higher than that of the finless channel, among which the circular finned channel has the best heat transfer performance. In spite of a slightly degraded flow performance, the comprehensive performance of the finned channels is superior to that of the finless channel, and the elliptical finned channel has the best performance, followed by airfoil finned channel and circular finned channel.

Preliminary design and analysis of 20 K helium cooled MgB2 based superconducting current feeder system for Tokamak application

Current feeders system (CFS) is one of the most critical part of a large-scale superconducting (SC) magnets based machines like a tokamak or accelerator. One end of the SC feeder is connected to magnets and another end is connected to the power supply via optimised current leads (CL) for energizing the magnets. So far, low temperature superconductor (LTS) is the popular choice for such applications. For high temperature superconductor (HTS) applications, cuprate oxide based coated conductors or magnesium diboride (MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) wires are the options. MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> despite of its superconducting transition temperature of 39 K,is now gaining wide attention for SC feeders system due to its lower raw material cost and ease of availability than 2G HTS tapes. To assess its suitability, we report 1-D thermo-hydraulic study of 10 kA rated MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> current feeders system cooled with 20 K helium for SST-1 tokamak as a case study. For varying mass flow rate, temperature margin along the feeder are calculated considering helium at 20 K, 4 bar (a) with cooling inlet from magnet side. Such a feeder yields a temperature margin of 6 K–16 K across its entire length depending up on mass flow rate of helium. There is also a possibility of cooling the binary current lead (HTS + MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) from cold helium coming out from the feeder. From our study, MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> current feeder system provides benefits of higher temperature margin, lower mass flow requirement and cryogenic savings by use of 20 K helium as coolant compared to LTS based feeders. In future, it could provide a safe, reliable and cryogenic operational cost saving solution for SC current feeders for Tokamak applications.

Performance analysis of stirling engine double-effect absorption chiller hybrid system for waste heat utilization from gas turbine modular helium reactor

In this study, a cogeneration system that consists of a Stirling engine, Double Effect H2O/LiBr Absorption Chiller, and Gas Turbine Modular Helium Reactor cycle was examined. The rejected heat from the Gas Turbine Modular Helium Reactor cycle was used as input energy for both, the Stirling engine and the Double Effect Absorption Chiller to produce additional power and chilled water, respectively. A thermodynamic analysis was performed and optimized for the proposed cycle based on the first law of thermodynamics/energy utilization efficiency. The effects of some parameters were studied, including compressor pressure ratio, turbine inlet temperature, the low-pressure compressor inlet temperature, in addition to the operating temperatures of the Stirling engine and the Double Effect Absorption Chiller. Our results indicate that integrating the two systems into the GT-MHR cycle will increase the energy utilization efficiency by 4.73%−5.46%-points at a turbine inlet temperature range of 700–900 °C. Moreover, the results show that the helium mass flow rate of the combined cycle at the same turbine inlet temperature range is lower than that of the standalone Gas Turbine Modular Helium Reactor cycle by 16.1%−17.78%.

A Study on Cooling System of HTS Quadrupole Magnets for Heavy Ion Accelerator

Quadrupole magnets located at the front end of an in-flight fragment (IF) separator in a heavy ion accelerator have large heat loads due to neutron radiation. Thus, high-temperature superconducting (HTS) magnets are used instead of low-temperature superconducting (LTS) magnets because of their high cooling efficiency and thermal stability. The cooling system of the HTS magnet uses circulation of cold helium gas. The circulating helium gas is provided from the distribution box, where helium gas lines are divided into 7 pairs of small helium lines corresponding to 7 HTS magnets. To cool down the 7 HTS magnets with different heat loads, the mass flow rate of each magnet should be individually controlled by monitoring the temperature of the magnets. This paper describes the cooling system for the 7 HTS magnets considering the heat load of each magnet and the thermohydraulic characteristics of the cooling system, including a heat exchanger, a cryogenic blower, control valves, etc. The helium mass flow rates for each magnet and the temperature at the outlet of the magnet are determined so that the magnets operate below 45 K. The optimal helium mass flow rates for each magnet were determined by analyzing the correlation between the magnet outlet temperature and flow rate.

Dynamic simulations of medium-sized hydrogen liquefiers based on EcosimPro simulation software

Dynamic simulations of medium-sized hydrogen liquefiers have been performed using process simulation software EcosimPro. Two hydrogen liquefier process flows have been simulated. One process flow is a helium refrigerator with one helium turbine providing cooling power for hydrogen liquefier, the other one is a helium refrigerator with two helium turbines providing cooling power for hydrogen liquefier. Control logics and control strategies for these two hydrogen liquefiers have been proposed. The cooling down simulations have been performed separately. One turbine hydrogen liquefier, pressure ratio is 2/16 bara, helium mass flow rate is 111 g/s, hydrogen mass flow rate is 4.3 g/s, the liquefaction rate of hydrogen is about 191 L/h. Two turbines hydrogen liquefier, pressure ratio is 1/14 bara, helium mass flow rate is 110 g/s, hydrogen mass flow rate is 5.2 g/s, the liquefaction rate of hydrogen is about 184 L/h. Comparison and discussion have been proposed.

The Temperature Dependence Analysis of Carbon Monoxide Conversion on CuO Bed of RDE Helium Purification System

RDE is an experimental power reactor that designed base on HTGR technology. This reactor has an indirect cycle power conversion system with primary coolant is helium and it secondary is water. RDE uses pebble fuel and multi-pass refuelling scheme. Helium coolant was predicted to be contaminated with various of gas impurities such as CO2, H2O, O2, CH4, N2, and H2 and CO. Those impurities must be maintained at certain limits by using Helium Purification System (HPS). Carbon monoxide (CO) is difficult to separate from the helium due to its small molecular size. Firstly, in HPS CO must be converted to CO2 by using cupric oxide (CuO) in the CuO Column bed and then CO2 will be adsorbed by molecular sieve. The CuO column bed operation temperature has a significant contribution to CO oxidation results. The purpose of this research was to determine the influence of temperature to oxidation process on CuO bed. The ChemCAD computer code modelling and simulation was used as a method. CuO bed is simulated by kinetic reactor and activation energy of each reaction is set up. The inlet mass flow rate of helium to CuO bed is 10.5 kg/h, 30 bar of pressure and the temperature has been varied to get the optimum result of CO2. The simulation has shown that CuO bed optimum temperature for producing CO2 is 250°C. In the HPS, this temperature can be maintained by using heater that has been installed before CuO bed.

Thermohydraulic analysis of Tore Supra/WEST TF coil quench: Associated smooth quench occurrence in tokamak

The Toroidal Field (TF) system of the Tore Supra/WEST tokamak comprises 18 NbTi superconducting coils, cooled by a static superfluid helium bath at 1.8 K and carrying a nominal current of 1255 A. The 19th December 2017, at the end of plasma run #52205, a quench of TFC-09 was detected first on a secondary thermohydraulical signal (helium liquid level) and triggered the current Fast Safety Discharge (FSD). A numerical model of this quench has been developed with SuperMagnet (CryoSoft). The whole TFC-09 circular coil is modelled by THEA as a single large Cable-In-Conduit Conductor (CICC) with 2028 large rectangular strands (monolithic conductors of length equal to coil average perimeter). The external quench helium relief circuit (cold and warm safety valves, rupture disk and magnetic valve with corresponding pressure set) is modelled by FLOWER.The helium pressure in the coil, upstream of the cold safety valve (maximum value of 9 bar), and the expulsed helium temperature have been used as comparison between measurements and calculations which depend on the Minimum Quench Energy (MQE) used in THEA with small initial heat deposition length (few tens of centimeters) at low field region (external leg). This energy, in the order of few kJ, is compared to the real shape and energy of neutron and gamma flux caused by highly energetic runaway electrons colliding the outboard plasma facing components and which induced the quench. The expulsed helium mass flow rate of nearly 6 kg/s during 5 s has also been calculated. This event confirms on one hand the criticality and the possible occurrence of a so called “smooth quench” caused by small initial heat deposition length and at low field region and on the other hand the important interest of secondary quench detection which can be useful for other tokamak magnets safe operation and protection.

Cryogenic safety considerations for Vertical Test Facility for qualifying high-β SRF cavities for the European Spallation Source

A dedicated cryogenic infrastructure has been installed at STFC Daresbury Laboratory to qualify and deliver 84 high-,0 SRF cavities for the ESS (European Spallation Source) under construction in Lund, Sweden. In order to meet the delivery schedule and optimise the test process efficiently, a large 1.6 m diameter, 3.5 m tall liquid helium cryostat has been developed. RF tests are conducted on 3 cavities at 2 K in one cool-down. There are 3 cryogenic circuits operating at 50 K, 4.2 K and 2 K designed to handle a maximum helium mass flow rates of 4 g/s. Considering the large internal beam pipe and external surface areas of the cavities under test, the pressure relief system has been designed very carefully. Various limiting scenarios and associated safety schemes are presented in detail in this paper.

Dynamic thermal-hydraulic simulations of the JT-60SA cryogenic system for preparing plasma operation

Recent measurements on the JT-60SA toroidal field coils showed a slightly higher pressure drop than expected, resulting in a lower supercritical helium mass flow rate during normal plasma operation. This paper presents some simulations of the cooling loop considering these updated thermal-hydraulic parameters and the expected pulsed heat loads. The model includes a cold circulator, heat exchangers, helium thermal buffer, the distribution system and the superconducting coils. The article presents the differences between the initial scenario which was validated during commissioning of the cryogenic system and the updated scenario to prepare plasma operation with the cryo-magnetic system. The simulation also provides the transient heat load profiles of the cooling loop, highlighting a first smoothing of the thermal loads at the interface with the cryogenic system. The Simcryogenics code, developed at CEA Grenoble, is used to simulate the dynamic loads.