The drawings of the plants in question, called Mark I Reactors, provide no way for venting hydrogen gas from the containment buildings, despite the fact that one of the first things that happens in the event of a cooling failure is the massive production of hydrogen gas by the exposed fuel rods in the core. This is why three of the nuclear generator buildings at Fukushima Dai-ichi have exploded with tremendous force blasting off the roof and walls of the structures, and damaging control equipment needed to control the reactors.Today The Guardian reported that the U.S.-based Atomic Energy Commission (AEC) began issuing warnings in 1972 about the hydrogen explosion risks of the GE Mark 1 reactors.
Another GE Mark 1 design issue involves the storage of spent nuclear fuel (nuclear waste). These plants store waste in pools of water on the upper level of the containment building, above the reactors. This waste contains the highly radioactive decay products of the fission process: Cesium 137, Iodine 131 and Strontium 90. To prevent evaporation, the pool water must circulate. If the containment around the spent fuel is compromised, then radiation will be released. Photos from the Fukushima facility show the roofs of two containment buildings have been blown off, calling the integrity of the spent nuclear fuel pools into question.
Two days ago, Green Mountain Daily published Maggie Gundersen's analysis of the first explosion by nuclear plant engineers familiar with the plants' design. (This must-read article contains a video and important background links). Their evaluation in short: the blast opened the fuel pool on the top floor to the environment, so years of spent fuel is not being cooled and is in direct contact with the air.
Thus, the plant is releasing significant amounts of radiation that appears to be moving towards the Pacific Ocean. Like Three Mile Island (TMI), significant amounts of radiation has been detected around the plants: radioactive Cesium (lasts in the environment for 300 years and is absorbed by muscles in the human body, especially infant hearts). People near the plants are receiving as much radiation in an hour as they would normally receive in one year.
The Guardian also reported that Robert Alvarez, a senior policy analyst at the Institute of Policy Studies, has echoed the PACE assessment, saying: "...satellite pictures of the Fukushima plant showed evidence of damage to the spent fuel pool:
"There is clear evidence that the fuel cask cranes that haul spent fuels to and from the reactor to the pool both fell. They are gone," he said. "There appears to be copious amounts of steam pouring of the area where the pools is located."The Institute for Energy and Environmental Research (IEER), also based in the U.S., has addressed the same issue. John McGlynn, editor at The Asia-Pacific Journal, posted a summary and excerpt of their report:
"A special feature of the Mark 1 design is that the used fuel, also called spent fuel, is stored within the reactor building in a swimming pool like concrete structure near the top of the reactor vessel. When the reactor is refueled, the spent fuel is taken from the reactor by a large crane, transferred to the pool, and kept underwater for a few years. This spent fuel must be kept underwater to prevent severe releases of radioactivity, among other reasons. A meltdown or even a fire could occur if there is a loss of coolant from the spent fuel pool. The water in the spent fuel pool and the roof of the reactor building are the main barriers to release of radioactivity from the spent fuel pool."Aileen Mioko Smith of Green Action just posted (via NHK) this today, as well:
NHK has now reported that the spent fuel pool at Fukushima Daiichi (Unit 3) does not have a roof over it since yesterday’s explosion.Joseph Calamia at IEEE Spectrum, a website that reports on tech issues, reports on expert discussion about the risks from radioactive nuclear waste emissions at the Fukushima facility:
There is no electric source, and there is a possibility that it has lost cooling ability. There is steam around the roof top.
In a larger discussion regarding the disaster among representatives from the watchdog group, the Union of Concerned Scientists, experts questioned whether spent fuel, stored on-site in the Japanese plants, might also pose a threat...
In Mark-I reactor designs, such as the Fukushima Daiichi plant, spent fuel is located in cooling pools in the reactor's "attic," explains David Lochbaum, director of the Union of Concerned Scientists' nuclear safety program. For exploding units, which have blown off their roofs and walls, the problem is clear: "If there's any radiation released, it's got to get to the environment." He compares that scenario with radiation released from fuel in the core, protected by the containment building which "would reduce the amount of radioactivity that reaches the public..."
Describing hypotheticals, Lochbaum explains that if there was widespread release of spent fuel, the casualties for a worst case scenario might be similar to the worst case scenario for leakage from the core.
The difference, he explains, is that the core would release a lot of short-lived radioisotopes, causing more fatalities in the first year, while a spent fuel accident might mean that primary casualties would come from cancer "down the road."