Many questions remained about Saturday’s explosion at the Fukushima Daiichi nuclear power plant in northeastern Japan. In general, these kinds of facilities are among the most carefully designed and heavily scrutinized structures in the world, said a top civil engineer.
Ron Hamburger, who travels the world studying earthquake-damaged buildings and other structures, says a typical nuclear power plant is designed to withstand earthquakes of the magnitude that only occurs once every 10,000 years.
Friday’s quake was the most powerful to hit the island nation in recorded history, and the tsunami it unleashed traveled across the Pacific Ocean. Reports from the National Institute of Geophysics and Volcanology in Italy estimated the 8.9-magnitude quake shifted the entire planet on its axis by nearly 4 inches (10 centimeters).
Engineers typically design nuclear facilities with very thick walls. “It’s not unusual for the reinforced concrete walls of these structures to be between 3 and 6 feet thick,” Hamburger said Friday before reports surfaced about the Japanese blast. “The reason the walls are that thick is not so much for structural strength, but rather because they use the concrete in part to shield any possible radiation.”
Typically, equipment that’s most critical to safety at these plants has been rigorously tested for earthquake resiliency on so-called “shaking tables.” The equipment being tested – pumps, control valves and electric motors - is attached to the shaking tables - which measure as large as 20 feet by 20 feet. Computers use data from past earthquakes to move the table and the equipment up and down and side-to-side to closely simulate movement from actual quakes.
“The entire design and testing process of these nuclear facilities is designed to withstand the earthquake, shut down safely and contain any radiation hazards,” Hamburger said.