Nuclear experts are increasingly nervous about the escalating crisis at the Fukushima Daiichi Nuclear Power Station, particularly its No. 3 reactor that uses mixed uranium-plutonium fuel and another reactor where, according to several reports, operator Tokyo Electric Power Co. acknowledged a nuclear reaction has begun in a spent fuel rod pond where water was boiling.
Meanwhile, U.S. officials are painting a much bleaker picture of what is happening at the six-reactor complex in northern Japan near the epicenter of the 9.0 earth quake and a 30-foot-high tsunami that struck on March 11, effectively knocking out cooling systems at the complex. Energy Secretary Steven Chu told Congress on Wednesday (March 16) that “we think there is a partial meltdown” at Fukushima.
Also on Wednesday, the U.S. Nuclear Regulatory Commission recommended that U.S. residents in Japan within 50 miles of the Fukushima reactors should evacuate. Japan is recommending a 12.4-mile evacuation zone.
“None of this has happened before," said Damon Moglen, director of the climate and energy project at Friends of the Earth. "The stricken reactor No. 3 has experienced at least a partial fuel meltdown, and it contains nearly a quarter of a metric ton of plutonium. They are venting that reactor into the air, to reduce the pressure inside, but that allows particulate matter from the melting rods--including plutonium--to be released into the environment as radioactive gas."
For now, the biggest concern at the No. 3 reactor is the uranium-plutonium fuel, called MOX (for mixed oxides of uranium and plutonium), that was loaded into the reactor last year, Moglen said. Hence, it is likely that spent fuel rods stored outside the reactor’s containment vessel are uranium-only.
"So far, the world has had no major accidents involving release of the plutonium fuel called MOX," said Ira Helfand, a member of the board of Physicians for Social Responsibility. "However, with plutonium inside reactor No. 3, if it melts down or explodes, then even microscopic quantities of particulate will cause lung cancer in anyone who inhales it. The whole area will have to be cordoned off."
Helfand noted that plutonium has a half-life of 24,000 years, warning that if it burns through a containment vessel, it could release vast amounts of radioactive steam wherever the molten material encounters ground water.
"The use of plutonium in MOX fuel generated a lot of Japanese resistance, especially locally, including the mayor, who expressed worry about safety at the reactor. But it was loaded into reactor No. 3 last year anyway," Moglen said. "Now, what the Japanese authorities need to report on [are] the constituents of the radioactive materials being released."
Plutonium is weak emitter that registers low on radiation detectors, but it is an intensely radio-toxic material. If inhaled by humans even in microscopic quantities, it would likely cause fatal lung cancer within 18 to 20 years, Moglen estimated. Authorities have confirmed that radioactive iodine, which causes thyroid cancer, and cesium, which causes leukemia, have been detected in the air around Tokyo, according to Moglen. However, if the No. 3 reactor's core melts down, plutonium will likely be one of the constituents discharged directly into the air.