scholarly journals ASSESSMENT OF OXYHYDROGEN GENERATION POSSIBILITY AND ITS EXPLOSION AFTER ACCIDENT WITH WATER EFFLUENCE AND THE AIR INGRESS INTO DEMO-FNS VACUUM VESSEL

2017 ◽  
Vol 40 (2) ◽  
pp. 78-91
Author(s):  
A.Yu. Pashkov ◽  
Keyword(s):  
Vacuum Vessel ◽  
Air Ingress

Investigation of Air Ingress Into a Vacuum Vessel Related to Particle Re-Suspension and Distribution for Dust Issues in ITER

2017 ◽  
Author(s):  
Emmanuel Porcheron ◽  
Pascal Lemaitre
Keyword(s):  
Large Scale ◽  
Low Pressure ◽  
Normal Operation ◽  
Vacuum Vessel ◽  
Physical Processes ◽  
Time Resolved ◽  
Loss Of Coolant Accident ◽  
Image Velocimetry ◽  
Loss Of Coolant ◽  
Air Ingress

During normal operation of the ITER tokamak, few hundred kilograms of dust containing beryllium (Be) and tungsten (W) will be produced due to the erosion of the walls of the vacuum chamber by the plasma. During a loss of coolant accident (LOCA) or a loss of vacuum accident by air ingress (LOVA), hydrogen could be produced by dust oxidation with steam. Evaluation of the risk of dust and hydrogen explosion, that may lead to a loss of containment, requires studying the physical processes involved in the dust re-suspension and its distribution in the tokamak chamber. This experimental study is conducted by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) to simulate dust re-suspension phenomena induced by high velocity jet under low pressure conditions. Tests are conducted in a large scale facility (TOSQAN, 7 m3) able to reproduce primary vacuum conditions (1 mbar). Optical diagnostics such as PIV technique (Particles Image Velocimetry) are implemented on the facility to provide time resolved measurements of the dust re-suspension in terms of phenomenology and velocity. We present in this paper the TOSQAN facility with its configuration for studying dust re-suspension under low pressure conditions and underway experiments showing the mechanism of dust re-suspension by sonic and supersonic flows.

Implementation of a Particle Resuspension Model in a CFD Code: Application to an Air Ingress Scenario in a Vacuum Toroidal Vessel

2020 ◽  
Author(s):  
Thomas Gelain ◽  
Laurent Ricciardi ◽  
François Gensdarmes
Keyword(s):  
Initial Pressure ◽  
Dust Particles ◽  
Vacuum Vessel ◽  
Particle Resuspension ◽  
Ansys Cfx ◽  
Constant Friction ◽  
Airborne Concentration ◽  
Airborne Contamination ◽  
Dust Resuspension ◽  
Air Ingress

Abstract During a loss of vacuum accident (LOVA), dust particles that will be present in the future tokamak ITER are likely to be resuspended, inducing a risk for explosion and airborne contamination. Evaluating the particle resuspension/deposition and resulting airborne concentration in case of a LOVA is therefore a major issue and it can be investigated by using a CFD code. To this end, this article presents the implementation of a resuspension model in a CFD code (ANSYS CFX) and its application to an air ingress in a vacuum toroidal vessel with a volume comparable to ITER one. In the first part of the article, the Rock’n Roll model and its operational version with the Biasi’s correlation is presented. The second part of the article will be devoted to the implementation of the Rock’n’Roll model in ANSYS CFX for constant friction velocities and its adaptation to non-constant friction velocities. Finally, the paper presents the simulations obtained on the particle resuspension for an air ingress scenario in a large vacuum vessel. This case is particularly interesting and non-intuitive because as the initial pressure is reduced, the particle behavior is different from that at atmospheric pressure. Further, a competition between airflow forces and gravitational force occurs, due to the low pressure environment, potentially restricting the resuspension, and the pressure influence also has to be taken into account in the particle transport and deposition (Nerisson, 2011). Three particle diameters were studied allowing to show the evolution of the resuspension with this parameter and to calculate dust resuspension rates and airborne fractions during the air ingress.

Managing total reduced sulfur emissions at a Canadian kraft pulp mill

TAPPI Journal ◽  
2016 ◽  
Vol 15 (4) ◽  
pp. 265-272 ◽  
Author(s):  
ROHAN BANDEKAR ◽  
JIM FREDERICK ◽  
JAROSLAV STAVIK
Keyword(s):  
Direct Contact ◽  
Black Liquor ◽  
Pulp Mill ◽  
Packed Bed ◽  
Average Value ◽  
Emission Limit ◽  
Total Reduced Sulfur ◽  
Reduced Sulfur ◽  
Air Ingress ◽  
Solids Content

This study addresses the challenges a dissolving-grade pulp mill in Canada faced in 2014 in meeting its total reduced sulfur (TRS) gas emission limit. These emissions from the recovery boiler exit are controlled by passing the boiler exit gas through a TRS scrubber system. The mill employs a cyclonic direct contact evaporator to concentrate black liquor to firing solids content. The off-gases from the direct contact evaporator flow to the effluent gas control system that consists of a venturi scrubber, a packed bed scrubber, and a heat recovery unit. Emissions of TRS greater than the regulated limit of 15 ppm were observed for a 4-month period in 2014. The level of emissions measured during this period was significantly higher than about 12 ppm, the expected average value based on historic experience. The problem persisted from mid-June 2014 until the annual mill shutdown in October 2014. The main TRS components detected and the performance of the Teller scrubber in capturing them are examined. Other potential causes for these emissions are identified, including mechanical problems such as broken packing in the TRS packed bed scrubber, broken baffle plates in the scrubber, and cyclone evaporator leaks causing air ingress. Repairs were carried out during the mill shutdown, which eliminated the TRS emissions problem.

scholarly journals Physics basis for the ICRF system of the SPARC tokamak

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Y. Lin ◽  
J. C. Wright ◽  
S. J. Wukitch
Keyword(s):  
Alpha Particles ◽  
Fast Wave ◽  
Vacuum Vessel ◽  
Auxiliary Heating ◽  
Heating Method ◽  
Full Field ◽  
Single Pass ◽  
Wave Absorption ◽  
Port Design ◽  
Icrf Heating

Ion cyclotron range of frequencies (ICRF) heating will be the sole auxiliary heating method on SPARC for both full-field (Bt0 ~ 12 T) D–T operation and reduced field (Bt0 ~ 8 T) D–D operation. Using the fast wave at ~120 MHz, good wave penetration and strong single-pass absorption is expected for D–T(3He), D(3He), D(H) and 4He(H) heating scenarios. The dependences of wave absorption on ${k_\parallel }$ , 3He concentration, resonance location, antenna poloidal location and losses on alpha particles and ash have been studied. The antenna loading has been assessed by comparison with the Alcator C-Mod antennae. An antenna spectrum of ${k_\parallel }\sim 15\text{--}18\,{\textrm{m}^{ - 1}}$ is shown to be good for both core absorption and edge coupling. For the control of impurity sources, the antenna straps are rotated ~10° to be perpendicular to the B field and the straps can run with different power levels in order to optimize the antenna spectrum and to minimize the image current on the antenna frame. Combining the physics constraints with the SPARC port design, maintenance requirement and contingency against antenna failure during D–T operation, we plan to mount on the inner wall of the vacuum vessel a total of 12 4-strap antennae in 6 ports while keeping 3-strap antennae that are insertable and removable on port plugs as the backup option.

Design and verification status of COMPASS-U vacuum vessel and stabilization loop

2021 ◽  
Vol 171 ◽  
pp. 112568
Author(s):  
Nisarg Patel ◽  
Jakub Hromadka ◽  
Josef Havlicek ◽  
Vojtech Balner ◽  
David Sestak ◽  
...  
Keyword(s):  
Vacuum Vessel

Numerical analysis of supersonic jet flow and dust transport induced by air ingress in a fusion reactor

2021 ◽  
Vol 32 (7) ◽  
Author(s):  
Bu-Er Wang ◽  
Shi-Chao Zhang ◽  
Zhen Wang ◽  
Jiang-Tao Jia ◽  
Zhi-Bin Chen
Keyword(s):  
Numerical Analysis ◽  
Fusion Reactor ◽  
Supersonic Jet ◽  
Jet Flow ◽  
Dust Transport ◽  
Air Ingress

Investigation of Quench-16 Experiment With MELCOR Computer Code

2014 ◽  
Author(s):  
Petya Vryashkova ◽  
Pavlin Groudev ◽  
Antoaneta Stefanova
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Initial Temperature ◽  
Computer Code ◽  
Air Flow Rate ◽  
Fuel Rod ◽  
Fuel Bundle ◽  
Oxygen Starvation ◽  
Air Ingress ◽  
Good Agreement

This paper presents a comparison of MELCOR calculated results with experimental data for the QUENCH-16 experiment. The analysis for the air ingress experiment QUENCH-16 has been performed by INRNE. The calculations have been performed with MELCOR code. The QUENCH-16 experiment has been performed on 27-th of July 2011 in the frame of the EC-supported LACOMECO program. The experiments have focused on air ingress investigation into an overheated core following earlier partial oxidation in steam. QUENCH-16 has been performed with limited pre-oxidation and low air flow rate. One of the main objectives of QUENCH-16 was to examine the interaction between nitrogen and oxidized cladding during a prolonged period of oxygen starvation. The bundle is made from 20 heated fuel rod simulators arranged in two concentric rings and one unheated central fuel rod simulator, each about 2.5 m long. The tungsten heaters were surrounded by annular ZrO2 pellets to simulate the UO2 fuel. The geometry and most other bundle components are prototypical for Western-type PWRs. To improve the obtained results it has been made a series of calculations to select an appropriate initial temperature of the oxidation of the fuel bundle and modified correlation oxidation of Zircaloy with MELCOR computer code. The compared results have shown good agreement of calculated hydrogen and oxygen starvation in comparison with test data.

Multi-scenario evaluation and specification of electromagnetic loads on ITER vacuum vessel

2014 ◽  
Vol 89 (7-8) ◽  
pp. 1826-1831 ◽  
Author(s):  
Vladimir Rozov ◽  
J.-M. Martinez ◽  
C. Portafaix ◽  
G. Sannazzaro
Keyword(s):  
Vacuum Vessel ◽  
Scenario Evaluation
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