ORNL developments and ideas in the nuclear field have won a prestigious award, media attention, and new funding.

Nuclear Winners

Wigner Award Winner

In 1999 Rafael Perez of the Advanced Nuclear Measurements Group in ORNL's Instrumentation and Controls Division received the American Nuclear Society's Eugene P. Wigner Reactor Physicist Award. He was cited for his outstanding contributions to the advancement of the field of reactor physics. Interestingly, the first two Wigner award winners (1990 and 1991 respectively) were Eugene Wigner and Alvin Weinberg, both of whom had previously served as ORNL directors. Wigner and Weinberg were pioneers in many fields of reactor physics, as well as in the design of nuclear reactors. They also co-authored the classic book The Physical Theory of Nuclear Chain Reactors.

Rafael Perez, shown in his office, received the American Nuclear Society's Eugene P. Wigner Reactor Physicist Award.

Perez, a native of Spain, contributed in several ways to reactor physics. From 1967 through the early 1990s, he worked with the late Gerard de Saussure on the theoretical interpretation and evaluation of neutron cross-section data resulting from measurements at the Oak Ridge Electron Linear Accelerator (ORELA). To determine the probabilities that various atomic nuclei will release neutrons by fission or capture neutrons of different energies, Perez applied a theory partly formulated by Wigner. In experimental research Perez, in collaboration with co-workers from the ORELA facility and physicists from abroad, measured the cross sections of thorium-232, uranium-235, uranium-238, protactinium-231, and protactinium-232. ORELA became a major source of "evaluated nuclear data files" for an international database that resides at DOE's Brookhaven National Laboratory. "These data," Perez says, "have been widely used by designers of nuclear reactors."

Working with ORNL's Felix Difilippo, and using neutron pulse and wave propagation, Perez also pioneered a way to measure reactor physics parameters. Since the early 1980s, he has taken an active part in the development and application of stochastic methods for the surveillance and diagnostics of commercial nuclear power plants. These methods, sometimes known as "neutron noise analysis," relate fluctuations of the neutron population in nuclear assemblies to their dynamics and operation, allowing the detection of abnormal occurrences and worn-out parts that should be replaced. In collaboration with members of the Advanced Nuclear Measurements Group, Perez has also applied stochastic methods to nuclear safeguards. More recently, he has focused on the nonlinear analysis of dynamical systems with applications to nuclear reactors.

Perez received his bachelor's degree from the University of Valencia in Spain, his master's degree from the Massachusetts Institute of Technology, and his doctoral degree from the University of Madrid. He has conducted research at ORNL for 14 years and has held faculty positions at the University of Florida and the University of Tennessee, where he is currently professor of nuclear engineering. He is a fellow of the American Nuclear Society.

Reactor Research Leads to Variable-Velocity Bullet

For years, ORNL's Rusi Taleyarkhan studied the potential problem of steam explosions in water-cooled research reactors in which fuel elements are made of uranium-aluminum alloys sandwiched between aluminum plates. The concern was that an explosion might result from the interaction between heated molten aluminum and water in a research reactor, such as ORNL's High Flux Isotope Reactor, during severe accident conditions (an unlikely event that, nevertheless, has occurred in similar reactors elsewhere). Taleyarkhan led an investigation of the forces that could initiate, or trigger, an explosion and the nature of its propagation.

Further ORNL research demonstrated that introducing noncondensable gases into the protective steam film formed by aluminum-water contact would cushion external triggers, virtually eliminating the conditions that initiate melt-water explosions. This key finding is being confirmed by field tests of methods for preventing explosions in the aluminum industry.

Using such information, Taleyarkhan, Marshall McFee, and Joe Cunningham, all of the Engineering Technology Division, recently developed a variable-velocity bullet propelled by aluminum-water vapor explosions. Police officers using a gun based on this concept could dial up the velocity of the bullet to meet the needs of the situation. The bullet could be used to stun, disable, or kill. The weapon system currently has a cartridge based on a standard shotgun shell, and the variable-velocity projectiles can be steel, lead, or even fluid slugs.

Rusi Taleyarkhan (right) holds a variable-velocity bullet that has been shot at a target in tests at ORNL's melt-water-explosion-triggering analyzer. Seokho Kim adjusts the controls.

The development won considerable attention in the media in the summer of 1999. It was mentioned in an Associated Press story and in articles in USA Today, The London Times, Defense News, New Technology Week, Aviation Week and Space Technology, New Scientist, and two local newspapers (The Oak Ridger and the Knoxville News-Sentinel). Radio listeners heard about it on National Public Radio, national radio shows starring Paul Harvey and Rush Limbaugh, the WIMZ radio station in Knoxville, Tennessee, and a New Zealand radio show. The technology was featured by ABC News on television and on the Internet (abcnews.com).

Nuclear Energy Research Initiative Projects at ORNL
Win DOE Funding

DOE has started a new initiative that reflects increasing support for nuclear power development because of concerns about greenhouse gas emissions from fossil fuel power plants. Of the $19 million being provided by DOE to universities, private companies, and national laboratories for 45 nuclear reactor technology projects, $1.5 million came to ORNL in 1999 for 4 projects, as part of the new Nuclear Energy Research Initiative. More than 300 proposals were submitted to DOE. ORNL is expected to receive more than $5 million over three years for this work. The projects and ORNL participants are

• Demand-driven nuclear energizer module (D. G. O'Connor, P. J. Otaduy, F. C. Difilippo, T. D. Burchell, J. W. Klett). This advanced reactor concept will use a newly developed graphite with superb heat transfer properties and high-temperature mechanical properties to carry heat away from the fuel, avoiding the use of working fluids to cool the reactor core. The transferred heat could be used to generate hydrogen and increase the efficiency of electricity production. In addition, the reactor concept will use neutrons and gamma rays to produce certain radioisotopes and destroy others.
• A new paradigm for automatic development of highly reliable control architectures for future nuclear plants (T. L. Wilson and R. T. Wood). The goal for this research is to advance reactor control system design, diagnostic techniques, and information system design to provide a path leading to fully automated operation of reactors. For example, buttons, meters, and toggle switches of the 1970s will be replaced by the computer keyboards, joysticks, and touch screens of the 1990s.
• Development of improved burnable poisons for commercial nuclear power reactors (M. L. Grossbeck and J. P. Renier). The researchers will investigate the use of separated isotopes of rare-earth elements as substitutes for conventional burnable poisons, such as boron and gadolinium. Burnable poisons are neutron absorbers that are intentionally added to the reactor because they burn up at about the same rate as the fuel, permitting the use of a much smaller control system. The problem is that, because the conventional poisons don't completely burn up, they leave a residual negative reactivity that prevents some fuel from being used to produce additional energy. Use of a substitute material that would be totally consumed would cause the reactor to consume less fuel, reducing both waste generation and operating costs.
• Mapping flow localization processes in the deformation of irradiated reactor structural alloys (K. Farrell). Through study of plastic strains in irradiated reactor alloys, particularly dislocation channel deformation, deformation maps will be developed to help designers of new reactors select suitable materials, predict their performance, and avoid materials problems experienced in older reactors.