The Ultimate in Protection
Following the Fukushima Daiichi nuclear disaster, the need for preventative changes was clear: Setting up safeguards to protect against environmental catastrophe was a must. Because adequate emergency safeguards for cooling weren’t in place, radioactive material was released outside the facility.
In the United States, the Nuclear Regulatory Commission now requires that nuclear plants have additional equipment in a protected building onsite to house pumps, hoses, and generators that can serve as backups to the regular nuclear plant should systems go down. These backups would be used to pump water from the structure and cool the reactor, minimizing the likelihood of environmental contamination like that in Fukushima. The building is designed for a “beyond-design event” in accordance with the NRC, including provisions to resist wind-driven tornado missiles.
Buildings designed to house backup systems have to be virtually disaster proof, and in recent years, Dome Technology has built 10 of them. “We were able to build the dome much more economically than any of the other solutions (companies) were looking at. The major savings really come from the shape and the ability to withstand high loads,” Dome Technology vice president of engineering Jason South said.
The dome: Nature’s strongest shape
Geometry gives a dome its strength. The dome’s monolithic construction and curvature help distribute applied forces across the entire surface of the structure.
A seamless shell makes it possible for a dome to withstand high concentrated loads and pressures. Monolithic construction means a dome is free from corners or concrete beams meeting up to create a joint, a construction interface that creates a weak point you don’t have in monolithic construction. The absence of weak points in the shell allows the structure to convert loading to an axial force going across the surface of the dome, rather than channeling the pressure to a weak spot.
The dome’s geometry is complemented by concrete and rebar for reinforcement. Each dome shell consists of polyurethane foam insulation, steel reinforcing, and concrete.
For these projects, officials at every nuclear plant determine their own disaster loading, based on the threat and likelihood of earthquake, wind, hurricane, or other natural-disaster. By identifying specific criteria for each site, the dome is tailored specific to its needs. But in general, “the dome is such a rigid structure, and it has tremendous redundancies. There are no connections that can fail—it’s continuously reinforced everywhere. It’s ideal in that sense,” South said. Couple that strength with aerodynamics, and the dome is naturally suited for nuclear sites.