A recommendation for all U.S. citizens living within 50 miles of the crippled Japan nuclear power plant to leave was based on incomplete information and assumptions about the reactors' condition, U.S. nuclear officials told an independent advisory panel Thursday.
Members of the Nuclear Regulatory Commission's Advisory Committee on Reactor Safeguards pressed officials Thursday to explain how they concluded that 50 miles was a safe distance from the crippled reactors. The Japanese government had set a 12-mile evacuation zone.
On March 16, the Obama administration recommended that Americans evacuate from a 50-mile radius of the stricken nuclear plant, raising questions about U.S. officials' confidence in Tokyo's risk assessments. Japan's government established a 12-mile evacuation zone after the March 11 earthquake and tsunami and has said that people living 12 to 20 miles from the plant should stay inside.
Randy Sullivan, who leads a protective measures team, said that no data from the site was used to determine the distance. Instead, he said, it was based on the potential conditions of the reactors.
Sullivan told the committee that the calculation was based on "a big release," which U.S. officials could not confirm was happening. The scenario model assumed 100 percent fuel damage at Unit 2, leading to a radioactive release lasting 16 hours, Sullivan said.
Michael Corradini, chairman of the nuclear engineering program at the University of Wisconsin, said, "You were doing a what-if calculation."
Corradini continued: "Thirty-two years ago if Japan had done a what-if calculation about Three Mile Island and said all the Japanese living within 50 miles of Harrisburg should get out, what would our response be to that?" He referred to the partial meltdown of a nuclear reactor in Pennsylvania in 1979.
William Ruland, director of the Division of Safety Systems within the NRC's Nuclear Reactor Regulation Office said the 50-mile evacuation recommendation would be evaluated. Actual measurements taken since the March 17 decision have confirmed, according to NRC, that the decision was prudent.
"We were trying to ... protect our citizens or to make recommendations as appropriate based on the limited information we had," Ruland said. "Sometimes, during emergencies, you basically have to make a decision on the spot based on limited data. And sometimes you have to make a decision, and sometimes that is better than no decision."