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Liquid metal flows in circular insulated ducts in nonuniform magnetic fields.

Description: Magnetohydrodynamic flows in insulated circular ducts in nonuniform magnetic fields are studied with reference to liquid metal blankets and divertors of fusion reactors. Particular emphasis is made on C-MOD. The ducts are supposed to be straight, while the gradient of the magnetic field to be inclined by an angle {alpha} to the duct axis. The results are presented for the values of the Hartmann numbers, Ha, of 1000 and 100. Three-dimensional pressure drop, development length, three-dimensional length and nonuniformities of the velocity profiles have been evaluated. It has been shown that for Ha = 1000 the three-dimensional effects are of considerable importance, while for Ha = 100 they may be neglected.
Date: March 6, 2002
Creator: Reed, C.B.
Partner: UNT Libraries Government Documents Department

Sidewall flow instabilities in liquid metal MHD flow under blanket relevant conditions

Description: A flow instability has been observed in a rectangular thin conducting wall duct in MHD experiments at ANL's ALEX facility. It developed in a side layer jet attached to a side wall parallel to the applied B-field. The nature of the instability resembles very strongly that of a classic laminar instability in ordinary fluid mechanics. The phenomenon is distinguished from ordinary turbulence by its strong periodicity and its lack of small scale structure. A preliminary identification of the factors which may influence the instability has been made. For the conditions and test section geometry reported here, the instability appears at an approximately constant critical Reynolds number 2650 < Re/sub cr/ < 5100, independent of Hartmann number in the range 2700 < M < 5400. 6 refs., 18 figs.
Date: October 7, 1988
Creator: Reed, C.B. & Picologlou, B.F.
Partner: UNT Libraries Government Documents Department

Experimental investigation of 3-D MHD flows at high Hartmann number and interaction parameters

Description: Experimental investigations of 3-D MHD flows in uniform thin conducting wall ducts of circular and square cross section, conducted at Argonne National Laboratory's ALEX facility, are reported. The three-dimensional nature of the flow arises from the spacial variation of the applied transverse magnetic field. Measurements were performed at several Hartmann numbers, M, and interaction parameters, N, with the peak value for M exceeding 6 /times/ 10/sup 3/ and the peak value for N exceeding 10/sup 5/. Typical results and their comparison to numerical analysis reported in a companion paper are given, as is a brief description of the ALEX facility and the experimental methods employed. Ongoing activities and plans for future experiments are also discussed. 6 refs., 3 figs.
Date: January 1, 1988
Creator: Picologlou, B.F. & Reed, C.B.
Partner: UNT Libraries Government Documents Department

Review of free-surface MHD experiments and modeling.

Description: This review paper was prepared to survey the present status of analytical and experimental work in the area of free surface MHD and thus provide a well informed starting point for further work by the Advanced Limiter-diverter Plasma-facing Systems (ALPS) program. ALPS were initiated to evaluate the potential for improved performance and lifetime for plasma-facing systems. The main goal of the program is to demonstrate the advantages of advanced limiter/diverter systems over conventional systems in terms of power density capability, component lifetime, and power conversion efficiency, while providing for safe operation and minimizing impurity concerns for the plasma. Most of the work to date has been applied to free surface liquids. A multi-disciplinary team from several institutions has been organized to address the key issues associated with these systems. The main performance goals for advanced limiters and diverters are a peak heat flux of &gt;50 MW/m{sup 2}, elimination of a lifetime limit for erosion, and the ability to extract useful heat at high power conversion efficiency ({approximately}40%). The evaluation of various options is being conducted through a combination of laboratory experiments, modeling of key processes, and conceptual design studies.
Date: June 2, 2000
Creator: Molokov, S. & Reed, C. B.
Partner: UNT Libraries Government Documents Department

Flow of two-dimensional liquid metal jet in a strong magnetic field.

Description: Steady, two-dimensional flow of a liquid metal jet pouring vertically down from a nozzle in the presence of crossed magnetic and electric fields has been investigated. The magnetic field is supposed to have a single component transverse to the flow. An asymptotic, high Hartmann number model has been used to study a combined effect of surface tension, nonuniform magnetic field, gravity and inertia. Relations have been obtained for a jet issuing from a duct, pouring into a draining duct, pouring from one duct into another, and that in a liquid bridge. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases. It has also been shown that for gradually varying fields characteristic for the divertor region of both C-MOD and NSTX tokamaks, inertial effects are negligible for N &gt; 10, where N is the interaction parameter. Thus, provided the jet remains stable, the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Surface tension plays a crucial role in shaping the jet profile at the nozzle. Partial flooding of the nozzle walls is predicted. Finally, proposals have been made to investigate a possibility of using an axisymmetric curtain along the perimeter of the bottom of a tokamak as an alternative to the film- or jet-divertors, or to use a system of plane liquid metal sheets.
Date: November 4, 2002
Creator: Reed, C. B. & Molokov, S.
Partner: UNT Libraries Government Documents Department

Flow of a two-dimensional liquid metal jet in a strong magnetic field.

Description: Two-dimensional, steady flow of a liquid metal slender jet pouring from a nozzle in the presence of a transverse, nonuniform magnetic field is studied. The surface tension has been neglected, while gravity is shown to be not important. The main aim of the study is to evaluate the importance of the inertial effects. It has been shown that for gradually varying fields characteristic for the divertor region of a tokamak, inertial effects are negligible for N &gt; 10, where N is the interaction parameter. Thus the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Simple relations for the jet thickness and velocity have been derived. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases.
Date: February 22, 2002
Creator: Reed, C.B. & Molokov, S.
Partner: UNT Libraries Government Documents Department

Liquid metal MHD flows in circular ducts at intermediate hartmann numbers and interaction parameters.

Description: Magnetohydrodynamic (MHD) flows in circular ducts in nonuniform magnetic fields are studied with reference to liquid metal blankets and divertors of fusion reactors. Flows in small and medium size reactors are characterized by moderate and low values of the Hartmann number ({approx}50-2000) and the interaction parameter ({approx}0.1-1000). The validity of the high-Hartmann number flow model for the intermediate range is discussed and the results of theoretical and experimental investigations are presented.
Date: September 16, 2002
Creator: Reed, C. B. & Molokov, S.
Partner: UNT Libraries Government Documents Department

Flow of a two-dimensional liquid metal jet in a strong magnetic field.

Description: A combined effect of surface tension, gravity, inertia and a transverse nonuniform magnetic field on the steady, two-dimensional jet (or curtain) flow is studied with reference to liquid metal divertors of tokamaks [1] and coating flows [2]. Here main fundamental aspects of the flow are presented. More details on the assumptions, analysis and results are given in [3].
Date: August 1, 2002
Creator: Reed, C. B. & Molokov, S.
Partner: UNT Libraries Government Documents Department

Magneto-fluid-dynamic issues for fusion first wall and blanket systems

Description: Magnetohydrodynamic considerations are shown to be of paramount importance in self-cooled liquid-metal blankets for fusion reactors. Coupling of the stress and MHD pressure drop through the conduit wall thickness is such that, self-cooled liquid-metal blankets without electrical insulators may not be feasible, unless acceptable designs that address satisfactorily MHD-related constraints can be developed. Such an acceptable design, based on current understanding and available analyses and/or experimental data on high Hartmann number, high interaction parameter MHD, is presented. The confidence in the success of the design is directly related to uncertainties on the validity of assumptions necessary to carry out the MHD calculations. Thus, the need for developing analytical tools, supported by experiment is identified and a program for addressing this need is formulated. The experimental facility and the first tests are outlined and the broad goals of companion analytical work are discussed.
Date: January 1, 1984
Creator: Picologlou, B.; Reed, C.B.; Nygren, R. & Roberts, J.
Partner: UNT Libraries Government Documents Department

The thermophysical and transport properties of eutectic NaK near room temperature

Description: The purpose of this report is to compile recommended room temperature thermophysical properties of NaK/sub 78/. The report was prepared to provide a single unified collection of property values for the eutectic sodium-potassium alloy. These properties include density, kinematic and absolute viscosities, thermal conductivity, specific heat, electrical resistivity, electrical conductivity, Prandtl number, and thermal diffusivity. Each section of the report contains a completely referenced property that focuses in the 0--80/degree/C temperature range. All available data for each property have been taken from original publications. The individual sections are organized following a specific outline, considering: discussion of experimental methods, discussion of sources and error, discussion of each reference, tabular presentation of all available data, graphical presentation of the data, recommendations, tabular presentation of recommended values, an equation to calculate recommended values, and a graphical presentation of the recommended curve (0--80/degree/C) generated from the above equation. Also included are experimental methods, whether the references included equations to fit the data, and whether or not these references were primary sources. 26 refs., 12 figs., 14 tabs.
Date: February 1, 1989
Creator: O'Donnell, W.J.; Papanikolaou, P.G. & Reed, C.B.
Partner: UNT Libraries Government Documents Department

Experimental and analytical investigations of magnetohydrodynamic flows near the entrance to a strong magnetic field

Description: An experimental program on liquid metal MHD phenomena relevant to blanket engineering is being carried out at ANL's ALEX facility. The experiments carried out at the facility are aimed towards detailed measurements of 3-D MHD flow characteristics to enlarge the existing data base and to provide validation of existing analytical approaches. Results of the first series of experiments, dealing with three dimensional MHD effects in a circular thin conducting wall duct in the fringing field of a strong transverse magnetic field, are reported. Comparison of the experimental data with the predictions of pretest analysis both supports the basic premises on which the analysis is based and suggests possible improvements.
Date: January 1, 1986
Creator: Picologlou, B. F.; Reed, C. B. & Dauzvardis, P. V.
Partner: UNT Libraries Government Documents Department

The effect of laser welding process parameters on the mechanical and microstructural properties of V-4CR-4TI structural materials.

Description: V-Cr-Ti alloys are among the leading candidate materials for the frost wall and other structural materials applications in fusion power reactors because of several important advantages including inherently low irradiation-induced activity, good mechanical properties, good compatibility with lithium, high thermal conductivity and good resistance to irradiation-induced swelling and damage [1]. However, weldability of these alloys in general must be demonstrated, and laser welding, specifically, must be developed. Laser welding is considered to be an attractive process for construction of a reactor due to its high penetrating power and potential flexibility. This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. The effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld.
Date: November 12, 1999
Creator: Reed, C. B.; Natesan, K.; Xu, Z. & Smith, D. L.
Partner: UNT Libraries Government Documents Department

Theoretical investigation of liquid metal MHD free surface flows for ALPS.

Description: Free surface plasma facing components (PFCs) offer the potential to solve the lifetime issues limiting current solid surface designs for tokamak fusion reactors by eliminating the problems of erosion and thermal stresses accompanying solid surface designs. The moving PFC free surfaces provide the possibility of absorbing impurities and possibly helium for removal outside of the plasma chamber. Free surface PFCs may also offer more creative possibilities for heat removal and higher thermal conversion efficiencies for the entire system. Design requirements for PFCS include handling {approximately}50% of the plasma heat flux and 90% of the ion flux. Magnetohydrodynamic (MHD) liquid metal flows with free surfaces are discussed with reference to Advanced Limiter-divertor Plasma-facing Systems (ALPS) program. Specific MHD issues for the jet divertor are outlined. Results for the rivulet flow and for the thermocapillary flow in a jet are presented.
Date: November 8, 2000
Creator: Molokov, S.; Cox, I. & Reed, C. B.
Partner: UNT Libraries Government Documents Department

Liquid-lithium cooling for 100-kW ISOL and fragmentation targets.

Description: Advanced exotic beam facilities that are currently being developed will use powerful driver accelerator for the production of short-lived rare isotopes. Multi-beam-drivers capable of producing high power beams from very light to very heavy ions are now technically feasible. A challenge for such facilities is the development of production targets to be used for a variety of reaction mechanisms with beam powers of about 100 kilowatts. This paper presents engineering concepts that have been developed recently for using liquid lithium coolant for two types of targets, one for use with light-ion beams on high atomic number (Z) targets and the other for heavy-ion beams on low-Z targets.
Date: November 10, 2000
Creator: Nolen, J. A. & Reed, C. B.,Hassanein, A.,Gomes, I. C.
Partner: UNT Libraries Government Documents Department

Pulsed laser surface hardening of ferrous alloys.

Description: A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.
Date: September 30, 1999
Creator: Xu, Z.; Reed, C. B.; Leong, K. H. & Hunter, B. V.
Partner: UNT Libraries Government Documents Department

Real-time monitoring of laser surface hardening of ferrous alloys.

Description: An infrared process monitor was used to monitor in real-time the infrared emissions during laser surface hardening of gray cast iron and 1045 steel. The signal from the monitor was correlated with the hardness and case depth of the laser-treated tracks. Test data show that a linear relationship exists between the monitor output DC level voltage and hardness up to the maximum hardness possible and also between the monitor output DC level voltage and case depth. This simple relationship of the monitor voltage signal with hardness and case depth makes it easy to monitor process hardness, case depth and quality. A calibration test on prototypic material can be used to determine at what voltage level melting occurs and the heat treating process hardness and case depth can be monitored easily by setting an upper and lower bound for the voltage signal. The monitor is also capable of tracking changes in surface quality or flatness of the part that is being treated.
Date: September 30, 1999
Creator: Xu, Z.; Leong, K. H. & Reed, C. B.
Partner: UNT Libraries Government Documents Department

Summary report for ITER task - T68: MHD facility preparation for Li/V blanket option

Description: A key feasibility issue for the ITER Vanadium/Lithium breeding blanket is the question of insulator coatings. Design calculations show that an electrically insulating layer is necessary to maintain an acceptably low MHD pressure drop. To enable experimental investigations of the MHD performance of candidate insulator materials and the technology for putting them in place, the room-temperature ALEX (Argonne`s Liquid Metal EXperiment) NaK facility was upgraded to a 300{degrees}C lithium system. The objective of this upgrade was to modify the existing facility to the minimum extent necessary, consistent with providing a safe, flexible, and easy to operate MHD test facility which uses lithium at ITER-relevant temperatures, Hartmann numbers, and interaction parameters. The facility was designed to produce MHD pressure drop data, test section voltage distributions, and heat transfer data for mid-scale test sections and blanket mockups. The system design description for this lithium upgrade of the ALEX facility is given in this document.
Date: August 1, 1995
Creator: Reed, C.B.; Haglund, R.C. & Miller, M.E.
Partner: UNT Libraries Government Documents Department

Modeling of liquid metal duct and free-surface flows using CFX.

Description: Liquid metal free-surface flows provide an option of a renewable surface for heat absorption, removal of impurities, and eliminating the problems of erosion and thermal stresses [1], [2]. In a tokamak liquid metal flows through a strong magnetic field, which results in a magnetohydrodynamic (MHD) interaction. For a free-surface flow the MHD interaction may be even more important than for the duct flows in blankets, because the electromagnetic forces may significantly deform the free-surface and thus make it unfavorable for heat extraction. The MHD-related problems for the free-surface flows have been reviewed in [3]. Among the most important ones are the effects of nonuniform magnetic fields, inertia, surface tension, wettability and roughness of walls on both the jet/drop shape and trajectory. The main problems for the jet divertor are shown in Figure 1 and Figure 2 [4]. Particular issues related to some of the problems listed in these figures have already been tackled (Problem 1 in [5]-[7], 4 in [8], [9], 5 in [9], 6 in [4], 7 and 10 in [9], 9 in [10]). Once main fundamental aspects for each of these sub-problems are understood, the analysis will have been performed for a particular divertor design.
Date: July 23, 2002
Creator: Aleksandrova, S.; Molokov, S. & Reed, C. B.
Partner: UNT Libraries Government Documents Department

Analysis of the tritium-water (T-H sub 2 O) system for a fusion material test facility

Description: The need for a high flux, high energy neutron test facility to evaluate performance of fusion reactor materials is urgent. An accelerator based D-Li source is generally accepted as the most reasonable approach to a high flux neutron source in the near future. The idea is to bombard a high energy (35 MeV) deuteron beam into a lithium target to produce high energy neutrons to simulate the fusion environment. More recently it was proposed to use a 21 MeV triton beam incident on a water jet target to produce the required neutron source for testing and simulating fusion material environments. The advantages of such a system are discussed. Major concerns regarding the feasibility of this system are also highlighted.
Date: April 1, 1992
Creator: Hassanein, A.; Smith, D.L.; Sze, D.K. & Reed, C.B.
Partner: UNT Libraries Government Documents Department

MHD (magnetohydrodynamic) thermal hydraulic analysis of three-dimensional liquid metal flows in fusion blanket ducts

Description: Magnetohydrodynamic flows of liquid metals in thin conducting ducts of various geometries in the presence of strong nonuniform transverse magnetic fields are examined. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, viscous and inertial effects are confined in very thin boundary layers adjacent to the walls. At walls parallel to the magnetic field lines, as at the side walls of a rectangular duct, the boundary layers (side layers) carry a significant fraction of the volumetric flow rate in the form of high velocity jets. The presence of these jets strongly enhances heat transfer performance. In addition, heat transfer can be further improved by guiding the flow toward a heated wall by proper variation of wall thicknesses, duct cross sectional dimensions and/or shape. Flows in nonconducting circular ducts are also examined. Experimental results obtained from the ALEX experiments at the Argonne National Laboratory are used to validate the numerical predictions. 6 refs., 7 figs.
Date: February 1, 1988
Creator: Hua, T.A.; Picologlou, B.F.; Reed, C.B. & Walker, J.S.
Partner: UNT Libraries Government Documents Department

Evaluation of a steady state MPD thruster test facility

Description: The successful development of multimegawatt MPD thrusters depends, to a great extent, on testing them under steady state high altitude space conditions. Steady state testing is required to provide thermal characteristics, life cycle, erosion, and other essential data. the major technical obstacle for ground testing of MPD thrusters in a space simulation facility is the inability of state-of-the-art vacuum systems to handle the tremendous pumping speeds required for multimegawatt MPD thrusters. This is true for other types of electric propulsion devices as well. This paper discusses the results of the first phase of an evaluation of steady state MPD thruster test facilities. The first phase addresses the conceptual design of vacuum systems required to support multimegawatt MPD thruster testing. Three advanced pumping system concepts were evaluated and are presented here.
Date: January 1, 1985
Creator: Reed, C.B.; Carlson, L.W.; Herman, H.; Doss, E.D. & Kilgore, O.
Partner: UNT Libraries Government Documents Department

ALEX results: A comparison of measurements from a round and a rectangular duct with 3-D code predictions

Description: Recent results of liquid-metal magnetohydrodynamic (MHD) measurements from a rectangular duct and earlier measurements from a round duct are reported. A fully three-dimensional numerical analysis of each test section in the fringing region of an applied magnetic field is briefly described. The results of the experiments and the 3-D code predictions are compared and discussed. Excellent agreement is obtained in both test section geometries for interaction parameters ranging from 500 less than or equal to N less than or equal to 1.25 x 10/sup 5/. 9 refs., 7 figs., 1 tab.
Date: January 1, 1987
Creator: Reed, C.B.; Picologlou, B.F.; Hua, T.Q. & Walker, J.S.
Partner: UNT Libraries Government Documents Department