Coming clean [nuclear waste]

What will it take to deal with the UK's nuclear waste? The author reports from a special meeting called to discuss the problem. Managing one of the biggest engineering projects of the coming decades in a way that satisfies everyone involved will rest with a new body the Nuclear Decommissioning Authority (NDA). A Liabilities Management Unit (LMU) at the Department of Trade and Industry is working to ensure the NDA hits the ground running. There is clear government intent to get on with decommissioning. The Unit has already completed the first national look at what needs to be done, carrying out site assessments to create a catalogue of assets and liabilities and establishing links with stakeholders like BNFL and UKAEA.     

Daintiest dynamos [nuclear microbatteries]

Research groups at Cornell University and the University of Wisconsin have been working on a way to harvest the energy released naturally by tiny bits of radioactive material, specifically, the energy that comes from high-energy particles spontaneously emitted by radioactive elements. Their research involves developing devices, called nuclear microbatteries, made from thin radioactive films that pack in energy at densities thousands of times greater than those of lithium-ion batteries. Nuclear microbatteries may ultimately change the way many electronic devices are powered. The prevalent power source paradigm is to have all components in a device's circuitry drain energy from a single battery. With nuclear microbatteries, it will be possible to provide a power source for each component. Thus, even if a main battery is still necessary for more power hungry components, it could be considerably smaller and the multiple nuclear microbatteries could run a device for months or years, rather than days or hours. The future of nuclear microbatteries depends on several factors such as safety, efficiency and cost. If the amount of radioactive material in the devices is kept small, they emit so little radiation that they can be safe with only simple packaging. It is also important to find ways to increase the amount of energy that nuclear microbatteries can produce, especially as the conversion efficiency begins approaching the targeted 20 percent.     

Mending nuclear fences [arms control]

The end of the cold war brought with it the hope, and even the expectation, that the dreaded nuclear sword of Damocles would no longer hang over the heads of Russians, Americans, and, indeed, over all the world's peoples. Yet 10 years after the Berlin Wall was torn down, that hope seems further from being realized than before. Instead of the bold visions enunciated by President Mikhail Gorbachev and President Ronald Reagan-not to speak of the citizens and scientists urging them on-the world now witnesses foot-dragging on conclusion of agreements, nitpicking and haggling over details, and a deterioration of trust and even mutual comprehension. The authors discuss the reasons for this and discuss whether the deadlock on arms control can be broken. Possible courses of action that could be taken are outlined     

Not so unthinkable [nuclear weapons]

Discusses developments which offer scenarios that, to some military strategists, would justify the use of nuclear weapons. The sorts of nuclear weapons likely to figure into war planners' recommendations are much smaller than those designed to wipe out entire cities, and they would be targeted at hardened, isolated military installations. Broadly speaking, nuclear weapons fall into two categories. Strategic weapons have explosive yields in the range of several hundred kilotons up to several megatons. Tactical weapons have much lower yields, down to a few kilotons. Strategic weapons were meant to destroy an entire city. Tactical nuclear weapons were intended for use at closer range-for example, on a battlefield, perhaps launched by a large artillery cannon.     

Canned heat [nuclear waste storage]

Fifty-nine years after the dawning of the nuclear age, not one country has managed to find anything more than a temporary resting place for its tons of nuclear detritus. Improvements in the design and operation of power reactors and scattered shortages of electricity this past summer have made the waste problem the biggest obstacle to any resurgence of nuclear power. Such a reemergence is needed, supporters say, to reduce acid rain and to keep more than a billion tons of greenhouse gases from fossil fuel plants out of the atmosphere over the next 10-20 years. It would also help reduce the dependence of the US, European, and Japanese economies on oil, thereby lessening their exposure to the seemingly endless cycles of instability, violence, and terrorism in parts of the Middle East. But there is no agreement anywhere as yet on a permanent solution for dealing with the waste, which will remain radioactive enough to harm human beings for thousands of years. Still, consensus over a temporary fix has finally emerged in the United States, Europe, and Japan. With dry-cask storage, as the technique is known, workers seal spent nuclear fuel or high-level waste in metal or metal-and-concrete containers that are guarded and monitored, typically in a fenced-in compound or warehouse near the reactor where the fuel was used. The casks are roughly 5 meters tall, 2.5 meters in diameter, and weigh more than 100 metric tons when loaded. After decades of uncertainty, utilities finally have a direction, at least, and a sorely needed one     

Six-sigma design [quality control]

The approach to customer satisfaction taken at Motorola is described. It is based on two conclusions derived from various studies: A product is built in the shortest time and at the lowest cost if no mistake is made in the process; and if no defect can be found anywhere in the process of building a product for the customer, then the customer probably will not find one either. Beginning in 1987, Motorola designers were required to adopt ±6-sigma tolerance limits, i.e., product design margins were to be twice the normal variation of the process. The way in which this was implemented in a six-step design process is described     

Grand designs [IC design]

Engineers will soon be designing ICs with hundreds of millions of transistors. Philips Semiconductors, in a $1.4 collaboration with STMicroelectronics (ST) and Motorola are staying in the advanced CMOS business with a common CMOS process at a plant in Crolles, France. Over five years, the process will take feature sizes down to an extraordinary 32 nm. Each company will develop its own variant of the process, but for Philips the emphasis will be on low cost and low power.     

Two-dimensional retiming [VLSI design]

This paper considers two-dimensional (2-D) retiming, which is the problem of retiming circuits that operate on 2-D signals. We begin by discussing two types of parallelism available in 2-D data processing, which we call inter-iteration parallelism and inter-operation parallelism. We then present two novel techniques for 2-D retiming that can be used to extract inter-operation parallelism. These two techniques are designed to minimize the amount of memory required to implement a 2-D data-flow graph while maintaining a desired clock rate for the circuit. The first technique is based on an integer linear programming (ILP) formulation of the problem, and is called ILP 2-D retiming. This technique considers the entire 2-D retiming problem as a whole, but long central processing unit times are required if the circuit is large. The second technique, called orthogonal 2-D retiming, is a linear programming formulation which is derived by partitioning ILP 2-D retiming into two parts called s- and a-retiming. This technique finds a solution in polynomial time and is much faster than the ILP 2-D retiming technique, but the two sub problems (s- and a-retiming) can give results which are not compatible with one another. To solve this incompatibility problem, a variation of orthogonal 2-D retiming called integer orthogonal 2-D retiming is developed. This technique runs in polynomial time and the s-retiming and a-retiming steps are guaranteed to give compatible results. We show that the techniques presented in this paper can result in memory hardware savings of 50% compared to previously published 2-D retiming techniques     

Relative timing [asynchronous design]

Relative timing (RT) is introduced as a method for asynchronous design. Timing requirements of a circuit are made explicit using relative timing. Timing can be directly added, removed, and optimized using this style. RT synthesis and verification are demonstrated on three example circuits, facilitating transformations from speed-independent circuits to burst-mode and pulse-mode circuits. Relative timing enables improved performance, area, power, and functional testability of up to a factor of 3/spl times/ in all three cases. This method is the foundation of optimized timed circuit designs used in an industrial test chip, and may be formalized and automated.     

Managing signal integrity [PCB design]

As system clock rates race to 100 MHz and beyond, designers of printed-circuit boards and multichip modules must watch out for such high-speed effects as ground bounce, ringing, reflections, and crosstalk. The author describes how today's high-speed printed-circuit boards and multichip modules require integrated design systems that include signal integrity analysis tools     

Bubble power [other sources of nuclear energy]

Research teams from various organizations have joined forces to create the Acoustic Fusion Technology Energy Consortium (AFTEC) to promote the development of sonofusion and its related science and technology. Technically known as acoustic inertial confinement fusion, sonofusion was derived from a related phenomenon, sonoluminescence. Sonofusion involves the application of sound waves to a deuterium-rich liquid to create pressure oscillations that implode tiny bubbles filled with deuterium vapor. The bubbles' violent collapse can cause some of the deuterium nuclei to undergo fusion. Fusion produced no greenhouse gases and, unlike conventional nuclear fission reactors, it produces no noxious radioactive wastes that last for thousands of years. Much more extensive research, however, is required before it is clear whether sonofusion can become a new energy source.     

Money for nothing [Hanford nuclear waste reservation]

In the desert of eastern Washington State, about 350 km from Seattle, rests more than 200000 m³ Of radioactive and chemically hazardous waste. A legacy of over 50 years of nuclear weapons production, the waste is a mix of liquids, solids, sludges, and gases that sits in 177 aging steel tanks. So far more than a third of these tanks, which are buried underground, have leaked or are suspected to have done so, releasing an estimated 3800 m³ of hazardous radioactive materials into the soil. Some of this leakage has seeped more than 60 meters down into groundwater about 10 km from the Columbia River, the most important waterway in the northwestern United States. For more than 10 years, the US Department of Energy (DOE) has tried to devise a plan to treat this waste, first to stabilize it and then to dispose of it. To date, more than U S $5 billion has been spent on this challenge, with little to show for it. Construction of facilities to treat the waste has not yet begun, and the history of this radioactive cleanup has been punctuated by failed designs, false starts, a variety of technical and financial problems, and changing policies. By DOE's own calculations, to complete this project, it will have to spend roughly $1 billion a year at Hanford for the next 40 years. The reasons for this state of affairs are complex. They involve technical and managerial shortcomings in the face of unique challenges that are unlike anything else the world has ever seen. The tank waste itself is extremely difficult to retrieve, and can be safely manipulated or sampled only by workers who are shielded and trained     

Core studies make comeback [nuclear engineering education]

A number of surprised nuclear engineering department heads are reporting their enrollments are up, in some cases for the first time in almost a decade, and are cautiously optimistic that this heralds a turnaround. Several explanations are possible. There's the Bush administration's pro-nuclear energy plan and the concern about the effects of burning fossil fuels on global warming. Also, some 40-year nuclear plant licenses nearing their end are being extended for 20 years, and new reactor designs are on the drawing boards. So a nuclear career looks less of a dead end than it did only a few years ago; there may be a new positive attitude toward the field as universities, industry, and the US federal government have stepped up efforts to recruit students in the past few years with an infusion of scholarship money