IN theory, fusion power is an irresistible prospect: a cheap, renewable energy source that creates a modicum of hazardous waste. Proponents call it ``nature's way of producing energy.''
But after 40 years and $10 billion of taxpayers' money, some lawmakers are calling for an end to government participation in a program that even optimistic researchers say is still 20 to 30 years shy of commercial viability.
This month, as Congress considers appropriations for the next phase of fusion research - the Tokamak Physics Experiment (TPX) - the international scientific community will be paying close attention. Few can forget Congress's 1993 decision to scrap the Superconducting Supercollider (SSC), a high-energy atomic particle laboratory that was under construction in Texas.
If fusion joins the SSC on the scrap heap, analysts say, the ability of the United States to make credible, long-term scientific commitments will be essentially destroyed.
``The budget that's been submitted for the project this year contemplates the next stage, which is to get on with the [TPX],'' says US Secretary of Energy Hazel O'Leary. ``I would like to be sitting here telling you that, in the Congress of the United States, there was a clear agreement that this will occur, but I don't have any pieces of my budget on which there is clear agreement. The tokamak is one that I believe should have clear and vigorous support, and I support it.''
Last week, the government-funded Tokamak Fusion Test Reactor (TFTR) housed at the Princeton University Plasma Physics Laboratory in Princeton, N.J., produced a world-record 9 million watts of electrical power. This record beat TFTR's December mark of 6.2 million watts.
Although most critics acknowledge fusion's potential, they express reservations about the costliness of the tokamak concept.
``I believe that fusion energy can become an important producer of economical and environmentally attractive electric power in the next century,'' US Rep. Dick Swett (D) of New Hampshire said at an April House energy subcommittee hearing. ``I am very concerned, however, about the direction of our current program.''
Congressmen Swett, who has been circulating a draft of an amendment to kill the tokamak, contends that the funds should be spread more evenly between different approaches to achieving fusion. Tokamaks, he says, will be far more costly to build and maintain than conventional nuclear reactors.
``Our current focus on only one concept is tantamount to betting billions of dollars on only one number on the roulette wheel,'' Swett says.
Fusion technology using magnetic forces was pioneered in the former Soviet Union in the 1950s. Soviet scientists Andrei Sakharov and Igor Tamm built the first tokamak (a Russian acronym for ``toroidal magnetic chamber''), a doughnut-shaped device that provides an electrically charged environment for reactions involving deuterium and tritium, two isotopes of hydrogen atoms.
Heated to a temperature of 100 million degrees Celsius (six times hotter than the interior of the sun), these isotopes - confined in a ``bottle'' of magnetic fields - begin to move rapidly. When they collide, they fuse together to produce a common isotope of helium and vast amounts of energy in the form of neutrons. Naturally occurring fusion powers the sun and stars.
According to the Princeton program's director, Dr. Ronald Davidson, the advantages of magnetic fusion are manyfold:
* Deuterium can be extracted from water and tritium from lithium.
* The amount of active materials in a tokamak reactor would be so small that a large, uncontrolled release of energy - such as the Chernobyl accident in 1986 - would be impossible. Fusion would produce only a tiny amount of radioactive waste.
* No environmentally damaging greenhouse gases would be emitted.
But the TFTR is not yet efficient enough to maintain the temperatures necessary for a continuous fusion reaction: In other words, despite improvement, it still uses more energy than it gives off.
``It's important to recognize how far fusion has come since TFTR was authorized in 1976,'' Dr. Davidson says. ``In 1976, the tokamak produced one-tenth of a watt of power. Last week, it produced 9 million watts. This is a factor of 90 million in a relatively short amount of time. During this period, understanding has improved.''
Construction of the project's third and final phase, the International Thermonuclear Experimental Reactor (ITER), is set to begin in 1998 and be operational by 2005 at a yet-to-be-determined site. The project, backed by the US, Russia, Japan, and the European Community, is expected to produce a billion watts of continuous fusion power at a projected cost of about $11 billion.
``Design authority for ITER has evolved from the outset as an international project,'' Davidson says. ``All the parties involved believe that fusion is a valued undertaking.... How far it comes, however, depends very much on how much it is funded.''
``Interestingly enough,'' Secretary O'Leary says, ``we are the most suspect partners in this deal because of our history of starting and stopping large technical science projects.''
The impetus for alternative energy sources is compelling. According to experts, US energy consumption per person is about 10,000 watts per day, five times the world's average. Even with conservation, experts project that world energy consumption will triple by 2050.
According to Princeton estimates, the deuterium contained in the top two inches of Lake Erie could produce as much fusion power as the world's entire current oil supply. ``As you look to the long term,'' Davidson says, ``you have to have fusion.''
O'Leary contends that the battle for fusion will largely be won or lost in the public arena. ``We've proved out the concept,'' she says. ``What we need to be doing now is educating the American public so that they will continue to have an appetite for such a project...,'' she adds.