- Category: Global Sustainability and Climate Change
- Published: Monday, 30 March 2015 22:00
- Written by MATTHEW L. WALD - NYT
IDAHO FALLS, Idaho — Filled with pits, seams and fissures, the images that Darin J. Tallman examined in a secure laboratory here looked like the surface of Mars. But they were extreme magnifications of slivers of an odd new material — half metal, half ceramic — that tolerates high heat with ease, and that several companies hope might form the basis of a new reactor technology.
Mr. Tallman’s experiments are among many being conducted here outside Idaho Falls, in the high desert, far from population centers, in search of something that will drive the nuclear industry into its next incarnation.
The industry has been in a slump. Old plants are unprofitable in the United States. In Germany, they are seen as an unacceptable safety hazard; their future in Japan is uncertain. Research has been in a slump, too.
But many experts, as well as investors, say that for the world to meet rising demand for electricity and simultaneously reduce carbon emissions, nuclear power will have to be part of the mix.
Now, 60 years after the United States adapted Navy submarine-propulsion technology to build the first civilian nuclear plants, hundreds of scientists and engineers are looking at new kinds of reactors, intended to be safer, cheaper and deployable worldwide.
From reactor designs that use sodium instead of water, to those that substantially reduce the waste that lasts thousands of years, the new reactors would represent a significant break from the past.
“There’s a whole class of reactors that are not evolutionary concepts relative to what you have out there now — they’re really different,” saidMark T. Peters, associate laboratory director at Argonne National Laboratory, another Energy Department site, this one a few miles southwest of Chicago, that is also deeply involved in new designs. Current reactors use uranium and water under high pressure; new ones could run on thorium, plutonium or more exotic materials, and in place of water might have molten metal.
There is no market for these reactors now, he and others say; in fact, at the moment most nuclear utilities are focused on trying to nurse old reactors through lean times in the electricity market, created by cheap natural gas.
But if the world decides in the 2030s and 2040s that it is time to deploy a new fleet of reactors, those will be based on work done in the few labs like this over the next decade, experts predict.
“In a carbon-constrained world, with that time frame, you better have some advanced reactors ready to go,” Dr. Peters said.
Across the Energy Department complex, researchers are using data from laboratory experiments to plug back into computer modeling, a tool of modern high-technology engineering that has been relatively little used in the nuclear design field.
One focus of the research is to use sodium, not water, to carry away the heat of the reactor so it can be converted into electricity. If reactors switched to sodium, the nuclear reaction itself would change, and they would burn up some of the material that now becomes the most troublesome parts of waste, materials that endure for eons.
In current reactors, water is held under pressure of thousands of pounds per square inch, to keep it from boiling. But sodium, a metal with a low melting temperature, does not have to be kept under pressure, vastly simplifying construction.
At Argonne, and closely paired with the Idaho lab, researchers are using a supercomputer to calculate the flow of sodium coolant through the fuel assembly of a reactor that would consume the nuclear waste accumulated from existing water-based designs.
In a 60-second simulation, with colors indicating relative temperatures and flows, colors dance over the image, making it look a little like a lava lamp. The computation is complex, with over one billion grid points.
The computer has a more detailed view than an operator ever could.
“You can predict behavior you can’t observe,” said Aleksander Obabko, a computational engineer at Argonne. The goal is to work like aerospace and other industries, and build prototypes that are so thoroughly analyzed that they approximate final production versions.
But switching to sodium from water introduces a host of complications. Technicians can see through water, but if you drop a bolt into a vessel filled with molten sodium, how do you find it? Researchers are working on ultrasonic detectors, which could also inspect parts for cracks.
General Electric has been pursuing a version of the sodium reactor.TerraPower, a company funded partly by Bill Gates, is also working on a design, as is Toshiba.
In a secure lab outside Idaho Falls, Mr. Tallman, a doctoral candidate at Drexel University, was also using a tool that is mostly new to the nuclear industry, an electron microscope. Usually, those instruments can’t study radioactive materials because that would require putting the microscope in a glove box, where it would be impossible to service. The lab solved the problem by using radioactive samples a quarter of the thickness of a human hair, and one-thousandth the thickness of a sheet of paper, too small to give off much radiation.
But unlike other energy technologies, in nuclear, venture capital cannot build a prototype without exceptionally strong government support. And today, private companies, no longer the Navy, are driving the research.
Work has also focused on the high temperature gas-graphite reactor, which would run far hotter than existing models. Today, commercial reactors in the United States all use fuel wrapped in metal, so they cannot run hotter than the metal’s melting point. But a high-temperature reactor would use fuel embedded in graphite, which does not melt.
The reactor would produce heat intense enough to split water into hydrogen and oxygen, opening up possibilities beyond electricity; the hydrogen could be combined with carbon pulled from power plant exhausts, to make liquid fuel for cars.
This has attracted the interest of Areva, a European nuclear company, which for now is struggling to market a new design based on water and uranium.
“One-third of our greenhouse gases comes from electricity generation,” said Finis Southworth, the chief technology officer at Areva. A reactor that made only electricity would solve only a third of the carbon problem, he said.
“About another third is transportation and another third is industrial heat,” he said. “We can make good high-temperature process-heat and electricity, and do both at the same time.”