uring his annual State of the Laboratory address on March 9, 1994, ORNL Director Alvin Trivelpiece said that he has come to realize there is "no such thing as a normal year."
uring his annual State of the Laboratory address on March 9, 1994, ORNL Director Alvin Trivelpiece said that he has come to realize there is "no such thing as a normal year."
Trivelpiece, who is also vice president of Martin Marietta Energy Systems, Inc., told an audience of ORNL employees and guests that the inauguration of President Clinton, and his subsequent appointment of Secretary of Energy O'Leary, had greatly affected ORNL. He noted that O'Leary's strategic plan, released in 1994, is based on input from DOE staff, laboratories, and other stakeholders.
Still, Trivelpiece said, things "can't be too gloomy," because President Clinton has shown support for the Advanced Neutron Source (ANS) by including it as a line item in his proposed budget this year.
In discussing highlights for 1993, Trivelpiece mentioned the celebration of ORNL's 50th anniversary and recognized the creators of the special ORNL Review issue, saying "the publication makes one realize that ORNL has a proud history and has been involved in many matters that have shaped world affairs."
Trivelpiece recognized the ORNL winners of the three R&D 100 Awards presented by R&D magazine in 1993. This achievement brings the Laboratory's total of these awards to 72. He also commended former Metals and Ceramics Division staff member Bill Manly for receiving the National Medal of Technology and Larry Hawk of the Engineering Technology Division for receiving the Rolex Award.
Trivelpiece said he is optimistic about ORNL's future projects, explaining that some form of the Center for Biological Sciences may eventually be funded. " He also is confident that the ANS, a research facility that will accommodate up to 1000 users, will be constructed at ORNL.
Other construction projects he discussed included a new Guest and User Building at the main portal and a new Measurement and Controls Center near Building 2000. Trivelpiece commended the Engineering Organization of Energy Systems for devising a "master building plan" for ten new office buildings to be constructed at ORNL over the next few years.
Trivelpiece reminded the staff of an important DOE mission for the national laboratories: to provide science education to help inspire students to enter fields of science, technology, and mathematics. "The Laboratory has done a good job in this area," he said. "We recently welcomed our 100,000th student at the Ecological and Physical Sciences Center."
Because of the importance of educating and inspiring students as well as attracting highly qualified scientists and engineers to ORNL, Trivelpiece said the new vision statement for the Laboratory is the following: "ORNL should strive to be a place that is so well recognized for its excellence that students in certain fields of science and engineering regard working at the Laboratory as an essential element in their education."
Noting that greater than one-third of the 4400 guest scientists at ORNL are from private industry, Trivelpiece said that increased external attention has posed many questions for ORNL. "The Laboratory must show the public the value of science. We must now explain what we do and why we do it." --Sharon Boudreaux
Box, inventor of the pressure-driven PNEU-WORM robot for inspecting pipes and the 1994 Scientist of the Year for Martin Marietta Energy Systems, Inc., thought of a way to clean up the trash left by the manufacturer in a diesel fuel tank it sent to ORNL. He lowered a camera and lights into the tank through a 15- centimeter (6-inch) hole and observed slag, pellets, wire, and styrofoam. He decided he needed a vehicle to pull a vacuum hose around the bottom of the tank to suck up the trash.
So Box bought a $50 radio-controlled car and attached a camera, lights, and vacuum hose to the chassis. Then he removed the wheels so he could fit the chassis and its attachments through the hole. Finally, he lowered the wheels into the tank by hand and reattached them to the car.
Guided by the camera images, Box remotely steered the radio-controlled car around the bottom of the tank to the scattered piles of trash. All together, Box vacuumed up a half cup of trash.
Box says he chose the radio-controlled car over other devices for the job because of the cross braces that connect the sides of the rectangular 3.6 meter (12 foot) by 1.5 meter (5 foot) by 1.2 meter (4 foot) tank to hold its shape under pressure. The car could be more easily placed in the tank and manuevered around it. "The radio-controlled car," he notes, "was best able to do the job at hand." --Carolyn Krause
The document, published by the Department of Energy, tells flood victims how to return to their damaged homes safely, clean and dry out their homes, deal with the effects of flood water, rebuild their homes, and upgrade insulation and replace appliances for increased energy efficiency.
"We were asked to do this report because of the opportunity for improving energy efficiency in homes that needed to replace wet insulation and damaged appliances such as water heaters, air conditioners, heat pumps, and refrigerators," says George Courville, head of the Efficiency and Renewables Research Section in ORNL's Energy Division.
Here's a sample paragraph: "A considerable effort will be expended to dry, repair, and restore most electrical equipment in the home. It may be much more cost effective to replace these appliances outright. By so doing, you will (1) gain a new system with manufacturer warranty, (2) have fewer maintenance problems, (3) be more confident in the reliability of the system, and (4) lower your utility bill by replacing appliances that are inefficient."
In late August 1993, DOE asked ORNL to produce a report to guide flood victims in restoring their homes. The need for such a document was recognized at a meeting of relief agencies dealing with the Midwest flood disaster.
ORNL drafted a report in a month and sent it to DOE. The department published the report and mailed copies quickly to a long list of state and local energy offices throughout the United States.
"This document," Courville says, "had a fast turnaround, thanks to a good team effort." As a result of this work, the ORNL team was recognized for exceptional support to recent "emergency" requests by the director of the DOE's Office of Building Energy Research.
ORNL's Energy Division also provided display materials on buildings for Secretary of Energy Hazel O'Leary's kickoff of Energy Awareness Month and President Clinton's announcement of the Climate Change Action Plan.
Flood Damage: Guidelines for Restoring Your Home was researched and written by John Tomlinson, Jan Kosny, and Melissa Voss, with help from Pat Love and Jeff Christian; all are with ORNL's Energy Division. Editing and assembly of the document were done by Deborah Counce and Leroy Gilliam, both of Information Management Services of Martin Marietta Energy Systems, Inc. Information was also provided by Brookhaven National Laboratory and Joseph Lstiburek, a consultant from Building Science Corporation.
A DOE-hired support contractor has prepared a new version of the ORNL document complete with figures.
In March 1993, Russian and French researchers reported in the journal Nature that a new material composed of mercury, barium, and copper oxides becomes a superconductor at 94 K. In May 1993, researchers at ETH in Zurich reported in Nature that a mixture of mercury, barium, calcium, and copper oxides remained superconducting at 133 K.
Then Paul C. W. Chu, the University of Houston scientist who discovered in 1987 that yttrium-barium-copper oxide could be a superconductor at 91 K, published a paper on mercury compounds in Nature. He announced that these mercury compounds show a drop in electrical resistance at around 153 K under high pressures of about 150,000 atmospheres. Chu also told Time magazine in October 1993 that he had pushed the temperature for the onset of superconductivity up to 164 K (-109 degrees C) for the same compound. However, the sample resistance becomes zero only at 134 K.
At ORNL Mariappan Paranthaman and Jorulf Brynestad, both of the Chemical and Analytical Sciences Division, have made mercury, barium, and copper oxide superconductors with a Tc of 95 K. Recently, they have also reproduced the Tc of 134 K with a mercury-based material.
"The studies using high pressures can predict only the upper limits of the Tc's of these materials," Paranthaman says. "The race is still on to stabilize these materials at 164 K by suitable chemical substitutions."
Jim Thompson and Dave Christen, both of the Solid State Division, and Don Kroeger of the Metals and Ceramics Division have been characterizing the materials for their magnetic properties and their capabilities for pinning magnetic flux lines (produced when super-conductors are placed in a magnetic field) to ensure that electrical conductivity will continue without energy loss. Based on their work, several papers have been published already. Christen and Thompson have also reviewed the current problems at high Tc in the July 1993 issue of Nature.
ORNL researchers Masanori Murakami and Charles Bush were present at the Tokamak Fusion Test Reactor (TFTR) as scientists beat by 4 times the previous record of 1.7 million watts, set in 1991 by a European reactor. This record-setting experiment used a fuel mixture composed of equal amounts of deuterium and tritium, the mixture required for practical amounts of fusion power.
ORNL researchers began participating in the TFTR experiments more than 10 years ago. Murakami, who served as group leader of the 15-member ORNL team, returned to the Princeton Plasma Physics Laboratory 2 years ago and was present at the record-setting event. "We have been dreaming about producing fusion power for a long time," Murakami says. "It was a real honor that we could participate in the actual experiment."
Experiments at the TFTR, which will continue through most of 1994, will yield data important to the design of future reactors. For the first time, these experiments will enable researchers to confirm that the particles produced will help sustain the temperature of the fusion reaction.
Fusion, the process that powers the sun, is a reaction in which lightweight atoms, such as hydrogen, are squeezed together at high temperatures until they fuse, releasing energy in the process. The researchers' goal is to harness more energy from the reaction than is needed to run a fusion reactor.
"We felt really honored to be part of this event, as well as participants in the development of a process that eventually should benefit mankind," says Bush, who has participated in the fusion work at Princeton University for nearly 10 years. "Our next goal will be to increase the output to 10 million watts."
As part of the effort leading to the historic accomplishment in December 1993--which scientists compared to the Wright brothers' initial flight or the first time humans rubbed sticks together to make fire--ORNL researchers helped monitor the temperature (up to 400 million degrees Celsius, or 720 million degrees Fahrenheit) of the reacting materials, which included mixtures of special forms of hydrogen. They also helped to determine how efficiently reactions occurred, how well the materials burned, and how effective the reactor was in containing the energy.
In citing key benefits of fusion, Bush says, "It would replace fossil-fuel burning plants that put a lot of pollutants into the air. It would create less waste than that produced from the current fission method. Fusion is a clean energy source, and the radioactivity produced is much less than that from a fission reaction."
Murakami says that achievement of the goal of using fusion to generate electric power is probably still billions of dollars and three or four decades away. A near-term goal is to sustain a fusion reaction that requires no input of energy after the reactor starts.
Other scientists from ORNL's Fusion Energy Division most recently involved in experiments leading up to and including the historic experiment include Larry R. Baylor, Timothy S. Bigelow, Stephen K. Combs, George R. Dyer, Charles R. Foust, Michael J. Gouge, Gregory R. Hanson, Stanley L. Milora, A.L. (Lou) Qualls, David A. Rasmussen, and John B. Wilgen.--Brian Daly
A major problem facing researchers in their effort to achieve fusion energy--the release of considerable energy from the joining of light nuclei to form heavier nuclei--is containing the plasma. To achieve fusion, matter must be heated to hundreds of millions of degrees. At such temperatures, matter exists only in the form of plasma, so solid surfaces cannot be used to contain the plasma. Thus, magnetic fields are used to confine plasmas.
"It is critical that plasmas stay confined long enough for the necessary fusion reactions to take place," says Benjamin Carreras, a researcher in ORNL's Fusion Energy Division and one of the leading theoreticians in the international fusion program. "However, the time they remain confined is limited by turbulence. Plasma turbulence is the major cause for energy losses from the plasma. The understanding of plasma turbulence is the outstanding physics problem for magnetically confined plasmas."
Carreras, a corporate fellow of Martin Marietta Energy Systems, Inc., says that turbulence creates disorder and increases energy losses within the fusion device, causing the "magnetic bottles" to be less effective in holding a plasma in place. However, under certain conditions, turbulence can heal itself and confinement of the plasma improves. The normal mode of operation is called the low-confinement mode, or L mode, and the improved mode is called the high-confinement mode, or H mode. "The L mode is disordered," Carreras says, "and the H mode is ordered."
Carreras compares the laboratory plasmas to the sun. He says that the sun's intense heat causes turbulent motions and loss of its internal heat. However, part of the turbulent energy goes into the rotation of the solar atmosphere, which is an organized process. This process is similar to the H mode of fusion device operation.
Carreras, Ker Chung Shaing, Donald Spong, and others in the Fusion Energy Division in collaboration with researchers at the University of California at San Diego have provided theoretical understanding of the transition of plasma from the L mode to the H mode in the DIII-D Tokamak operated by General Atomic in San Diego, California. They have modeled the plasmas on supercomputers using the equivalent of a million coupled nonlinear differential equations.
"Because plasmas have charged particles that spiral around magnetic field lines, they can induce their own currents in the confining magnetic fields," Carreras says. "These induced currents modify the magnetic field and can break confinement, leading to plasma instabilities, turbulence, and energy loss."
In the normal low-confinement mode, the time of plasma confinement (energy confinement time) decreases as heating power increases. However, as the injected power increases further, a sudden transition occurs from the L mode to the H mode. At this transition, there is a sharp increase in the plasma rotation, and as a consequence, a radial electric field is generated. The generation of this electric field, which leads to "shear flow," creates a transport barrier at the plasma edge and the plasma confinement goes from L mode to H mode.
Through plasma modeling, Carreras says, ORNL researchers have linked shear flow to turbulence. "When shear flow is up," he says, "the turbulence fluctuation level is low."
The ORNL researchers use the same mathematics as population biologists, Carreras explains, noting that shear flow may be compared to cats and turbulence fluctuations to mice. "When the cat population is up," he says, "the mouse population is down, and vice versa."
The high plasma confinement in the H mode has a potential negative effect: It can retain the helium ash produced by the deuterium-tritium fusion reactions. Because helium particles can radiate away the energy of fusion, the plasma could cool down, degrading tokamak performance. Don Hillis of the Fusion Energy Division and his collaborators have experimentally investigated this effect in the DIII-D Tokamak. They have shown that edge-localized modes (ELMs), naturally occurring periodic losses of helium particles near the plasma edge, provide a mechanism for removing the helium ash (which can be exhausted from the tokamak vessel by a vacuum system). These results show the importance of the H mode operation for fusion reactors. They also point out the need to develop control systems--ways to change heating power and magnetic field configurations to regulate ELM behavior--to ensure effective operation of fusion devices.
Another important effect of the helium, or alpha, particles produced by deuterium-tritium fusion is a new form of turbulence recently observed in experiments. This turbulence is driven by the alpha particles' initial velocity, which exceeds the rate at which magnetic oscillations can propagate in the plasma, roughly analogous to the atmospheric disturbances produced as an accelerating airplane exceeds the velocity of sound. A new theoretical approach to understanding this phenomenon was presented in a recent paper by Spong, Carreras, and Lew Hedrick. For this paper Spong received the 1994 Author of the Year award from Martin Marietta Energy Systems, Inc. The fluid model they developed also indicates the linkage between shear flow generation and plasma stabilization. Products of the model include scientific visualizations available to computer network users through the Fusion Energy Division home page of ORNL's World Wide Web server (an example is shown below). The ORNL model is being used to predict plasma stability limits for the TFTR device and is expected to be relevant to the design and operation of the proposed International Thermonuclear Experimental Reactor (ITER).
Carreras' leadership has led to the development of new improved magnetic configurations for two experimental devices--ORNL's Advanced Toroidal Facility stellarator and a related Spanish experiment under construction known as the TJ-II flexible heliac. The theoretical understanding provided by Carreras and his group should continue to guide improvements in plasma confinement.--Carolyn Krause
[ Next to article | Search | Mail | Contents |
Review Home Page | ORNL Home Page ]