TOKYO—There is no shortage of contradictory information concerning the danger of the radiation emanating from the devastated Fukushima nuclear power plant. But critics here and in the United States say the U.S. government is not helping things with evacuation recommendations that are far more stringent than those adopted by Japan.
To minimize the chance of exposure to hazardous levels of radiation from the crippled reactors, Japan has ordered everyone other than emergency workers to evacuate from the area within 20 kilometers of the plant. The government recommends that those living 20 to 30 kilometers away stay indoors.
"Japan's measures are in line with IAEA policy," Yukiya Amano, director general of the International Atomic Energy Agency, said at a press conference here on 18 March. He emphasized that IAEA's guidelines are recommendations; each country is free to set its own policy.
The United States is doing just that: Its embassy in Tokyo is urging U.S. citizens to stay at least 50 miles, or 80 kilometers, away from the plant. The U.S. government also offered "voluntary departure" to family members of diplomats and military personnel serving even in Nagoya, about 400 kilometers from the nuclear disaster zone. "We took this step out of an abundance of caution," U.S. Ambassador to Japan John Roos said in a video posted on the embassy's Web site yesterday.
The 50 mile radius evacuation was recommended by U.S. Nuclear Regulatory Commission (NRC) Chair Gregory Jaczko in Congressional testimony on 16 March. Part of the basis for that recommendation, according to Jaczko, was NRC's information at the time indicating that water keeping nuclear rods cool in a spent fuel pool at reactor 4 had boiled away and that radiation levels were "extremely high."
Jaczko's testimony gave many in Japan the impression that Japanese officials either didn't know or were not telling the whole truth and that the situation at Fukushima was much worse than they were letting on.
At a press briefing the next day, Hidehiko Nishiyama, deputy director-general of Japan's Nuclear and Industrial Safety Agency, explained that experts reviewing videos shot from a helicopter were divided over whether water could be seen in the pool. So on 18 March they got more video images and even sent a site worker to reactor 4. Both confirmed there is water in the pool.
The current status of the pool, particularly whether it is leaking, is unclear, according to the latest posting on the situation by IAEA. But at a press conference here yesterday, Shunichi Yamashita, a radiation health expert at Nagasaki University's Atomic Bomb Disease Institute, said that at the moment someone living 31 kilometers from the plant is no more at risk of harm from radiation from the Fukushima plant than someone living in London. The United States's 50 mile recommendation "risks [creating] misunderstandings among Japanese." He added that he "could not understand" how the agency reached its conclusions.
To go along with its recommendation, NRC released a document containing calculated radiation doses at various distances from the plant, based on both a four-reactor and a single-reactor model. Based on a four-reactor model, NRC projected a dose of 150 milliSieverts (mSv) about 24 kilometers out, and, at the 80.5 kilometer limit, a relatively high dose of 99 mSv. A dose of 100 mSv, although it still has no immediate effects, elevates the risk of cancer. Meanwhile, radiation readings from Fukushima Province on 23 March, collected by Japan's Ministry of Ministry of Education, Culture, Sports, Science and Technology, show hourly doses about tens of thousands of times smaller than that, with a peak reading of about 0.1 mSv per hour at a station about 30 kilometers northwest of the plant. That elevated level is equivalent to a chest x-ray.
NRC released the calculations with little indication of their provenance. NRC spokesperson Scott Burnell says the numbers are based on a model that takes into account the plant's design, the fuel composition, weather patterns, and conditions at the plant. Burnell refused to say exactly what conditions were assumed, although he said that "the understanding we have of spent fuel pool issues factors into our modeling." He added that the model was "project[ing] out in time." When asked whether that projection was based on conditions deteriorating into a worst-case scenario, Burnell said, "When people ask in the United States about worst-case scenarios, we have to do a fair amount of hypothesizing. At this point there is no need to hypothesize in Japan."
Meanwhile, other scientists are echoing Yamashita's request for NRC to shed light on its black box of a model. In a statement to ScienceInsider, Massachusetts Institute of Technology nuclear scientist Richard Lester said NRC should clarify how it reached its recommendation. U.S. officials "should be very careful to be sure of their facts before making official pronouncements, because when there are differences between what they are saying and what the Japanese government is saying there will inevitably be a negative impact on Japanese public confidence," he wrote.
The differing recommendations are "confusing to people," said Robert Gale, a radiation oncology expert at Imperial College London, at a press briefing here today. Gale, who was involved in efforts to mitigate the health effects of the Chernobyl disaster, says that during an emergency it is common for different governments and even different ministries to issue conflicting information. "But the net effect is to make people frightened and confused," he said.
With reporting by Eli Kintisch and Lauren Schenkman.