Courtesy of Derek Visser (CC-BY-SA). Damage to reactors 3 and 4 (left and right, respectively).
The portrayal of the nuclear accident at Fukushima Daiichi by the Japanese government appears to have taken a more serious tone in the past week. The severity of the accident was raised to 7, comparable to Chernobyl. Evacuations of people outside the 30 km zone were announced. More dire estimates of the amount of radiation have also been made by TEPCO, the power utility responsible for the plant. None of this is based on new information, though. It is a reflection of the Japanese government’s sluggish response to the information at hand.
Most people were somewhat surprised by the initial rating of the accident as a “Level 5,” comparable to the partial meltdown at Three Mile Island. What the Japanese authorities were doing was rating the severity level for each of the four afflicted reactors separately, rather than rating the overall accident. All that has changed this week is that reactors 1 to 3 have been lumped together, and combined they are considered a Level 7 accident.
As early as March 16, the Japanese government had simulations showing the possibility that people outside the 30 km zone could receive radiation doses of 10 rem (100 millisieverts). That is an important threshold, as at that level, it is known that cancer rates increase. The government’s response was to study it further. Now the measurements are in and, in fact, towns northwest of the reactor complex will be evacuated — after people have already received a significant amount of radiation.
Those simulations were done with a computer program called SPEEDI. The same program can be used to estimate the total amount of radiation that has been released by the accident. It was reported this week that the amount of radiation released so far at the Daiichi plant is about 20 percent of the official estimate of radiation released at Chernobyl. More astonishingly, a spokesperson for TEPCO admitted that the Daiichi plant could end up emitting more radiation than was released in the Chernobyl disaster. A significant difference is that at Chernobyl, massive amounts of radiation were thrown high into the atmosphere whereas in Japan it is more contained, although significant amounts are entering the sea.
The Japanese government has moved slowly to acknowledge the true extent of the problems it faces. While this may have been motivated by a desire to minimize panic, it is probably having an unintended consequence: People are becoming distrustful of the reassurances of the Japanese leadership. When Japanese officials say, “our products are safe,” they may indeed be correct, but they have sown the seeds of doubt by reacting slowly to reactor crisis.
Paul Padley, Ph.D., is a professor of physics and astronomy at Rice University.