Not all nuclear reactors are built alike. Power plant designs can vary in their fuels, coolants and configurations, a fact beautifully illustrated by a series of reactor wall charts originally published in issues of Nuclear Engineering International during the 1970s and 1980s.

Since then, the charts have been lovingly collected by Ronald Knief, a nuclear engineer at Sandia National Laboratory. Recently, he completed his collection with help from the Idaho National Laboratory library and began to digitize the drawings. The first eight out of more than 100 have now been permanently archived online by the University of New Mexico libraries.

"This is not a CAD/CAM-type thing," Knief said. "This really is art."

Like the maps that accompanied many issues of National Geographic, the charts were inserts that could be pulled out and tacked up like a poster. They also served as teaching aids for Knief during his tenure at the University of New Mexico, and served to illustrate his books.

"He saved most of them, and it turns out that hardly anyone else saved them, including the publisher," said Donna Cromer, a librarian at the University of New Mexico, who has worked with Knief on the project.

Drawn from reactors built in different nations, the cutaways direct attention to the variety that exists in reactor design. Knief chose these eight as a cross-section of the industry.

"Each of them is representative somewhat of the state-of-the-art version of a particular reactor type," Knief said.

Douglas Point, pictured above, is a boiling-water reactor. In this type of plant, the coolant water flows directly through the fuel, boils and becomes steam, which drives a turbine.

"It's a direct cycle," Knief said, "similar to a standard coal plant."

Boiling-water reactors are a common form of American reactor.

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Image: Nuclear Engineering International/University of New Mexico

The dominant nuclear power plant type in the United States is the pressurized-water reactor. SNUPPS, or Standardized Nuclear Unit Power Plant System, is one of a series of pressurized-water reactors built by Westinghouse. In this kind of system, high pressure keeps the water flowing through the core from boiling. The superheated water is then directed to a heat exchanger where it transfers its energy to a second set of lower-pressure pipes. The water in them turns into steam, which then turns a generator.

Image: Nuclear Engineering International/University of New Mexico

Grand Gulf is a boiling water reactor designed by General Electric. GE, Westinghouse and Babcock & Wilcox engineered the vast majority of American power plants.

Image: Nuclear Engineering International/University of New Mexico

The designs used by the nuclear industry aren't the same worldwide. In Canada, natural — not enriched — uranium is used to power the CANDU reactors. Natural uranium is composed of more than 99 percent uranium 238, with just a small percentage of uranium 235. Enriching uranium increases the uranium 235 concentration in the material, which increases the amount of fission that occurs in a given amount of uranium.

The moderator in the CANDU reactor is heavy water, which has extra deuterium isotopes. It's used because it's less likely to absorb neutrons than regular water, keeping the reaction from being "snuffed" out.

Image: Nuclear Engineering International/University of New Mexico

Fulton differs from the standard reactor because it uses graphite interlaced with uranium for fuel, like the very first critical nuclear "pile" built by Enrico Fermi and his colleagues under the football stadium at the University of Chicago. Its coolant is helium gas.

Image: Nuclear Engineering International/University of New Mexico

Although China's thirst for power has mostly been slaked by coal, the country has also completed some nuclear reactors like this Westinghouse-derived station built by the French company Framatome, now known as Areva.

Image: Nuclear Engineering International/University of New Mexico

The Oskarshamn nuclear power plant is one of 10 operating in Sweden. The country, which also has large amounts of hydroelectric power, gets about 45 percent of its electricity from its reactors. This plant is a boiling-water reactor.

Image: Nuclear Engineering International/University of New Mexico

The Super-Phenix was the only full-scale, liquid-metal, fast-breeder reactor. That might sound esoteric, but for many years, a big chunk of the United States' nuclear R&D program was devoted to just this kind of power plant.

Breeder reactors yield more fissile material than they use. In other words, you get more plutonium out than you put uranium and plutonium in. During an era when plutonium for weapons was considered essential and uranium supplies were thought to be scarce, breeders were a hot item.

Construction began on SFX in 1976. It was connected to the grid in 1986 and closed down in the late '90s. The reactor experienced a variety of problems throughout its lifespan and spent a lot more time switched off than running.

Image: Nuclear Engineering International/University of New Mexico