![]() "The release of that steam is the way they're getting rid of energy" in order to keep cooling the damaged nuclear fuel rods, he explains. "That's going to be radioactive steam."įilters should capture some of the radioactive materials, according to Richard Meserve, president of the Carnegie Institution for Science and former chairman of the U.S. "There is no way to carry the heat away to cool down the core unless the steam that is generated is vented," Makhijani notes. The TEPCO operators of the stricken nuclear power plant-a minimal staff of 50 as all non-essential personnel have been evacuated-now face a balance between venting the steam building up in the reactor (since the main danger for a widespread release of radioactive material is steam bursting the thick steel container holding the reactor) and keeping any radioactive materials inside the power plant itself. "If the temperature gets high enough then you get a self-propagating reaction and a fire that would burn like a sparkler," says physicist Arjun Makhijani, president of the Institute for Energy and Environmental Research. If the suppression pool is damaged or cracked and can no longer help cool the reactor-and 2.7 meters of the fuel rods in that reactor remain exposed, according to Tokyo Electric Power Company-radioactive material might escape.Īnd if the temperature continues to rise-and the reaction of zirconium and oxygen produces yet more heat-the cladding itself can spontaneously combust. 2 is potentially more serious as it seems to have affected pressure in the suppression pool-a massive pool of water stored in a torus-shaped chamber beneath the reactor itself that both cools and captures any escaping radioactive materials. 1 and 3 destroyed the surrounding buildings but have apparently not damaged the massive steel containment vessel-as much as 20 centimeters thick-that surrounds each reactor's nuclear core.īut the explosion at reactor No. ![]() That hydrogen can then be released from the reactor core and containment vessel and, if it accumulates in sufficient quantities-concentrations of 4 percent or more in the air-it can explode, as has apparently occurred at reactors No. Once the rods reach more than 1200 degrees Celsius, the zirconium will interact with the steam and split the hydrogen from the water. If no fresh water is introduced to cool the rods then they continue to heat up. The high temperatures that the fuel rods create boil water and continually turn it into steam. If the fuel rods are no longer being cooled-as has happened at all three reactors at the Fukushima Daiichi power plant operating at the time of the earthquake-then the zirconium cladding will swell and crack, releasing the uranium fuel pellets and fission byproducts, such as radioactive cesium and iodine, among others. Though control rods have stopped the uranium fission process that drives normal operation of a nuclear reactor, the byproducts of that continue to split and generate heat. The 3.7-meter-long nuclear fuel used at Fukushima is composed of uranium oxide pellets encased in a zirconium cladding. "The cesium and iodine showing up in releases shows the fuel has been damaged." ![]() You get enough and some spark source and you get an explosion," explains nuclear engineer Michael Golay of the Massachusetts Institute of Technology. "The hydrogen accumulates outside of containment but inside the reactor building. in 1979 as a result of the meltdown there-caused by nuclear fuel rods experiencing extremely high temperatures stripping the hydrogen out of the plant's steam. The culprit in all three cases is likely a build-up of explosive hydrogen gas-as occurred at Three Mile Island in the U.S. This followed an explosion March 11 that ripped the roof off reactor No. 2 at the stricken Fukushima Daiichi nuclear power plant. Just after 6 AM local time on Tuesday in Japan, a sound like an explosion was heard near the suppression pool of reactor No. ![]()
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