The Fukushima Daiichi nuclear power plant was turned upside down after the traumatic events last March, communication between the on-site emergency control center and each control room was limited to a single wired telephone line. The off-site nuclear emergency response headquarters had to be evacuated because it was so under-prepared. Of the 3 fire engines TEPCO staged at the Plant, one had already been used for injecting seawater and second one was unable to use because of the tsunami. The remaining one, mobilized at the Unit 5 – 6 area of the site, was unable to be moved because the earthquake damaged the road and the tsunami scattered debris over the already treacherous terrain.
With no electricity to power the cooling systems, water inside the reactors began to boil off, causing meltdowns of the uranium fuel rods inside of the nuclear reactor cores. While evacuations were being carried out, multiple explosions destroyed multiple reactor buildings, and caused a fire of the spent fuel pond of reactor 4. TEPCO believes that as a result of fuel rods being damaged, 800 kilograms of hydrogen was created at the No. 1 reactor, 400 kilograms at the No. 2 reactor and 600 kilograms at the No. 3 reactor. The gas which was escaping the Fukushima reactors into the concrete and steel containment vessel, built up while mixing with oxygen, and exploded, blowing out large portions of the walls and roof structures of the reactor buildings.
Since it became evident that a nuclear meltdown was possibly taking place in the reactor cores, a 20 km zone around the power plant (with an area of about 600 km) was declared an evacuation zone and a total of 200,000 people were forced to leave their homes.
On March 25th, people living in the 30 km radius were asked to voluntarily evacuate their homes and leave the contaminated areas. On April 12th, the Fukushima nuclear meltdowns were categorized as a level 7 nuclear accident – the highest level on the International Nuclear Event Scale (INES), which had previously only been reached by the Chernobyl disaster. TEPCO has reported that it will take decades to completely dismantle Fukushima, and will require new special equipment to be designed and built to weather the brutal environment, but there’s no estimated time frame for when the area around the crippled plant will be restored to allow for the safe return of Japan’s evacuees.
Fukushima Daiichi was trouble-prone
The Wall Street Journal reported that the Fukushima Daiichi power plant was already one of the most trouble-prone nuclear facilities in Japan before the devastating March 11th earthquake, having highest accident rate of any big Japanese nuclear plant, according to data collected by the Japan Nuclear Energy Safety Organization.
Fukushima Daiichi had documented 15 accidents since 2005, the most of any Japanese plant with more than three reactors. The Daiichi plant also exposed its workers to more radiation than other plants, prior to the Fukushima disaster, the regulatory documents showed. Daiichi employees have received the highest average radiation doses of those at any Japanese plant every year over the past decade.
Teruaki Kobayashi, head of Tepco’s nuclear-plant-management section, said that since “Fukushima Daiichi has older reactors, it requires more frequent repairs and checks than new nuclear plants.” Because the plant is of an old design, “radiation tends to be higher.”
Tepco’s Mr. Makigami said “the main reason” some numbers for the Fukushima plant look poor in the report is that “they’re old reactors.” All of Daiichi’s reactors first came online in the 1970s. Tepco does frequent repairs, and has “replaced the various individual parts with the latest equipment, and in so doing we aimed to give old plants the same functionality as new plants. However, in reality it is quite difficult.”
Work delays may have saved larger disaster
Reactor 4 is hypothesized to have been saved from a spent fuel pool meltdown by bungled work being carried out in the days leading up to March 11th. The core shroud, a large structure in the reactor core, was undergoing replacement at the No. 4 reactor at the time of the tsunami. The reactor was undergoing its most extensive upgrade since it entered commercial operation in 1978.
The Asahi Shimbun reported, when workers were about to insert a shroud-cutting tool into the reactor core, they discovered that auxiliary equipment to guide that tool into the reactor core was the wrong size. Retooling that equipment caused a delay in the process and, as a result, the reactor well was still filled with water on March 11, the day the Great East Japan Earthquake struck. The injection of outside water into the storage pool is proposed to have began around March 20. As a result, the fuel in the pool was kept at relatively safe levels during the crisis.
Science yet to explore Fukushima unknown
Water that has been continuously pumped into the pressure vessels to cool the fuel rods, becoming highly radioactive in the process, has been confirmed to have leaked out of the containment vessels and outside the buildings that house the reactors. TEPCO said it is trying to contain the contaminated water and prevent it from leaking into the sea, but elevated levels of radiation have been confirmed in the ocean off the plant.
“What I realized while watching all of this was how little we actually knew about what happens if you take hot seawater and pour it on nuclear fuel,” said Rodney Ewing in a physorg interview, a professor in the Department of Earth and Environmental Sciences, the Department of Nuclear Engineering and Radiological Sciences, and the Department of Materials Science and Engineering. Ewing is also a member of the U.S. Nuclear Waste Technical Review Board.
“No one, as far as I know, had asked the question, ‘Well, what happens when you do this? Are we doing something really good or really bad?’” Ewing said. “That kind of information really wasn’t available, and that expertise, as far as I could see, wasn’t there to be called upon.”
Investigations to date have failed to take a comprehensive approach to assessing this nuclear accident. Although some findings have emerged and the nuclear industry is working to create mitigation strategies to be recommended and adopted. In Japan, the Fukushima disaster prompted the government to ask utilities nationwide to draw up mid- and long-term countermeasures against future earthquakes and tsunami.
Peter Burns served on Nuclear Regulatory Commission discussion panels, a National Academy of Sciences panel on nuclear waste and created a research center for the study of actinide materials. Now his review in Science suggests the need for a national research program to develop comprehensive predictive models of nuclear accidents—a direct response to the accident at Fukushima.
“Early in a reactor accident, the priority is to minimize [radioactive] release, but as time progresses, the public needs to know information about how much radioactivity has been released,” says Burns. “What we saw coming out of Fukushima was problematic—we saw quite a few errors in radiation doses that were reported, we saw readings on some of the radiation detection systems that were unreliable. It took a little while for that to get sorted out.”
Burns and his colleagues want to understand the chemical breakdown of fuel materials, including how fuel dissolves in water, and what factors increase the movement of radioactive materials away from a reactor accident and subsequently into the paths of those living nearby.
“When isotopes from a damaged radioactive fuel are dissolved in water, these isotopes can be transported and end up somewhere else,” says Burns. “The radioactivity is now coming from those [transported isotopes] and may wind up in your pumpkin, squash or blueberry muffin. That’s a very different scenario than having them in a power plant.”
The challenges lay in the endless number of variables when nuclear fuel is introduced to different elements, the interaction of nuclear fuel with groundwater versus seawater can be remarkably different since groundwater would be very dilute compared to the seawater used and released at Fukushima.
There’s even a difference in behavior between fresh fuel, irradiated fuel and fuel following a meltdown. “Studies of the release of radionuclides from undamaged fuel generally cannot be extrapolated to the extreme conditions of temperature and radiation field that occur during and subsequent to a core-melt event,” says Burns in the review.
Scientists admit it’s possible the force of the hydrogen explosions blew out a little plutonium in the form of particulate matter. Robert Alvarez, who has served as a senior policy advisor in the U.S. Energy Department, said he would have been surprised if researchers had not found evidence of plutonium contamination near the plant. “They were irradiating plutonium in Unit 3, which experienced the biggest explosion.”
Alvarez said that much remains unknown one year after the disaster. Authorities can’t say exactly where breaches occurred in the reactor vessels and spent fuel pools that caused contaminated water to flood the plant’s lower levels, he said. In fact, the explosion was so massive that investigators found fuel rod fragments a mile away, leading to speculation that a supercritical fission event may have also occurred, Alvarez said. It is possible, and even likely, that radioactive cooling water is still leaking into the Pacific Ocean, Alvarez added, Cleanup of the immediate site could take four or five decades.
The nuclear disaster affected other power generating stations in Japan, and this unforeseen loss of power has not even been acknowledged as being a direct result of the disaster. In addition to the Fukushima Daiichi plant, and the Fukushima Daini plant, TEPCO’s Hirono thermal power station (which is inside the 20-30km evacuation zone) among other thermal power stations are still shut down due to the impact of the disaster.
Fukushima will be a real-world test that the world will scrutinize for symptoms stemming from long-term exposure to low-dose radiation. It hasn’t helped that the government has given only the most optimistic scenarios of the risks to avoid mass panic. Public confidence in Japan’s nuclear industry was shattered by the disaster at Fukushima, and until TEPCO and NISA among other entities, are thoroughly investigated, it is unlikely that the full impact of this disaster will be appreciated. “This is a major accident,” one expert said. “The huge work is to read this data and interpret it.”
TEPCO’s deficiencies were exposed by the quake and tsunami with the results of previous tsunami simulations having gone unheeded and all back-up power generators knocked offline by the wave. The government and TEPCO’s frequent upgrading in recent months of the original severity of the crisis has many people convinced that vital information was withheld in the early stages to prevent panic.
After the Chernobyl disaster, the IAEA lowered the standard for taking iodine tablets from 100 millisieverts to 50 millisieverts after a report on the accident showed cancer risks increased when thyroid radiation levels were 50 millisieverts or higher. The Japanese government, which uses the 100-millisievert standard, is expected to soon lower it to 50 millisieverts.
Many people still live in areas with high contamination, where food, milk and drinking water have been found contaminated as well, leading to internal radiation exposure. Scientists warn that children are the most severely affected, as their bodies are more susceptible to radiation damage.
Preliminary tests have shown internal radioactive contamination of children with iodine-131 and caesium-137, however it is far too early to estimate the extent of health effects caused by the nuclear disaster. Claims by scientists affiliated with the nuclear industry that no health effects are to be expected should be considered unscientific and immoral.
- Naoto Kan Writes for Foreign Affairs on March 11 Anniversary (ex-skf.blogspot.com)
- Japan Nuke Agency: 14 reactors at 4 sites were affected on 3/11 – Fukushima Daiichi had most serious damage – Daini, Onagawa, and Tokai also (enenews.com)