"Those days were remarkable. In one day we collected enough graphite from all of the country. The regular bureaucratic system was in shock and it was possible to operate on science, on common sense. One call, a scrap of paper, and there were troops and heavy machinery on the move." Their final makeshift design was a snakelike formation of pipes cooled with water and covered on top with a thin graphite layer, all between two concrete layers—each one meter thick—to stabilize the creation. In short, Bolshov says, "it was done as a sandwich."
Bolshov's graphite-concrete "sandwich," similar in concept to "core-catchers" used in many nuclear reactor designs, paved the way for the ones Russia uses today—steel vessels filled with neutron-absorbing metallic alloys cooled by water flow and built directly under a reactor to catch the molten core material, known as "corium," in the case of meltdown. (A New York Times interview with Mr. Bolshov directly following the Fukushima disaster lays out more detail on the core-catcher's history and Russia's safety assurances in the post-Chernobyl marketplace).
Today many of Russia's potential customers for nuclear power plants are countries like Vietnam and Turkey, which are turning to nuclear for the first time and looking for cost-cutting perks the Russians can offer. In the case of Turkey, for instance, Russia is negotiating a plan called "Build–Own–Operate," in which it will finance and build four reactors in Turkey but retain ownership.
The reactor design of choice for these "nuclear newcomers," as Rosatom officials like to call them, is the VVER—Voda-Vodyanoi Energetichesky Reaktor, Russia's version of the pressurized water reactor, which has several indigenous distinctions from Western-designed reactors ranging from fuel assembly arrangements to a new passive residual heat-removal system, already being used in Russia and recently constructed in India. Russia has also built VVERs in Iran, China and across the former Eastern Bloc.
European regulators are increasingly requiring large new reactors to have some kind of core-catcher or similar device to trap melting reactor core, according to the World Nuclear Association. But other nuclear vendors have different approaches to protecting the bottom layers of nuclear plants. For example, in case of core melt, says Rosatom competitor Westinghouse's spokesman Scott Shaw, Westinghouse's AP1000 pressurized water reactors do not include core-catchers, yet compete for the same market the VVERs do. Instead, the former has a retention wall build into the reactor vessel itself, which he says would mitigate any core meltdown. In addition, an AP1000 operator "can act to flood the reactor cavity—the space immediately surrounding the reactor vessel—with water from the in-containment refueling water-storage tank, submerging the lower portion of the reactor vessel." The French company Areva also makes its EPR (for European Pressurized Reactor, or Evolutionary Power Reactor) with a core-catcher, helping it compete with the Russian VVER. Its device is focused on the idea of molten corium spreading along a sufficiently large area equipped with a special pipe system for basement cooling. But the Russians say their core-catchers are more compact and less costly than the European designs.
Russia's core-catchers have yet to be tested by a real-world China Syndrome. But there is some evidence that they might come in handy. During the Fukushima disaster one core "slumped" into the concrete beneath the reactor, which was built in the 1960s and did not have core-catcher, says Princeton physicist Frank von Hippel, a former assistant director for national security in the White House Office of Science and Technology Policy. The core leaked into the concrete below the reactor but did not breach the containment vessel.