Expert available on nuclear power, safety
Note: This advisory was updated on March 15 at 11:50 a.m. to reflect the changing situation in Japan.
Michael Corradini, University of Wisconsin–Madison professor of engineering physics, is an expert on nuclear power and nuclear safety. He can discuss aspects of nuclear power and reactor safety as they relate to the events at the Fukushima power plant in Japan.
Japanese nuclear regulations regarding radiation release dictated the plant announce a site emergency; however, says Corradini, radiation levels outside the plant are low. “The sun, radioactive elements in the ground, and our own radioactivity, make up the natural radioactivity we receive over the course of our lives,” he says. “The Japanese site emergency was announced because the amount of radiation release per hour approached 10 percent of the annual natural background radiation. That means it would take about five to 10 hours to reach an annual dose from natural background radiation. It fell below that threshold and has spiked after the hydrogen combustion in each of the plants.”
He says it’s likely that, as part of the process for cooling the nuclear reactors, some radiation was released. “Their procedure for letting out steam will release some radioactive gases, likely noble gases and iodine. The fuel probably was damaged early in the accident due to a lack of cooling for a number of hours,” he says. “The purpose of the seawater injection and steam venting is to maintain cooling.”
In the reactors, steam caused the the fuel metal cladding to oxidize, generating hydrogen. That hydrogen was vented along with the steam and combusted with air in the building above the containment vessel. That resulted in the building demolishment.
Although the events leading up to the accident at the Fukushima plant are different from those 32 years ago at Three Mile Island in Pennsylvania, Corradini says the outcome is likely similar. “No significant levels of radiation that would adversely affect human health have been released,” he says. “From a radiological consequences standpoint, it’s probably similar to—but greater than—the Three Mile Island accident, both for the workers and for the general public.”
Corradini says that, following an earthquake and tsunami virtually unprecedented in its magnitude, it’s logical and rational that regulatory bodies reassess how natural disasters and climatological events affect not only the nuclear power industry, but all industry and civil infrastructure. However, he points out, the Japanese reactor containment vessels are intact—mainly because they are designed to the highest standards and safety specifications. “Look at everything around the plant that was destroyed,” says Corradini. “The plant survived.”