As the Crisis Continues- Simplifying Fukushima Daiichi
By: Patricia Morris, Scoville Fellow, Center for Arms Control and Non Proliferation
Japan is facing a nuclear crisis that seems difficult to fully grasp. On March 11, an earthquake off the Japanese coast caused a tsunami, which hit and crippled the Fukushima Daiichi nuclear power plant. Initial reports from the media and even Japanese officials’ were confusing and alarming, but as more facts emerge, so does a clearer picture of the causes and consequences of the nuclear crisis at Fukushima Daiichi.
What happened?
When the earthquake occurred, Fukushima Daiichi shut down automatically, but since nuclear reactions cannot be turned off like a light switch, the process of shut down is slower than it sounds. To stop the nuclear reactions, a chemical that inhibits nuclear fission is inserted into the core of the reactor. Nuclear fission is the process of splitting uranium and sometimes plutonium atoms in order to create energy for nuclear power. Since the inserted chemical can only slow fission and not instantly stop it, the rest of the plant must continue working to stabilize the fission reaction in the core. At Fukushima Daiichi, the emergency mechanisms in place to stabilize the core failed
Specifically, fission creates a tremendous amount energy and heat, which must be controlled to protect the reactor and the core, which holds nuclear materials. Units 1-3 of Fukushima Daiichi’s six reactor units lost the ability to cool the nuclear materials held in fuel rods, which led to an extreme build up of heat and pressure in the core. Fukushima Daiichi had back up water-pumping generators in case of an emergency to pump water to keep the fuel rods from melting, but they only worked without power for 24 hours. To release pressure and heat in Units 1-3 plant, operators vented the reactor, but hydrogen had built up outside of the core and exploded upon contact with oxygen from outside. The explosions set fire to Unit 4 as well and released radioactive particles into the air.
Inside the core, the rising heat levels caused the fuel rods to begin to melt, which is the first step towards a nuclear meltdown. There are degrees of meltdown from partial to full. A full meltdown occurs when the nuclear material that is fissionable in a reactor melts and coagulates at the bottom of the reactor melting through the containment levels into the environment. At Fukushima Daiichi, the fuel rods have not fully melted and operators have injected outside cooling water into the reactors to prevent further meltdown.
The cooling water will also pose a new challenge, because once it goes through the reactors it becomes contaminated and has to be safely stored or discarded. The plant has already released 10,000 tons of “diluted” radioactive water into the ocean to make room to store new water with even higher contamination levels. Despite precautions and the brave work of plant operators, radioactive particles are still making their way into the environment.
Richard Meserve, former chairman of the U.S. Nuclear Regulatory Commission and current President of the Carnegie Institute, described the challenge of stabilizing the plant now: "[o]n the one hand, … [containment] is getting easier over time because the rate of heat generation by the fuel is steadily declining. On the other hand, there is growing contamination in the buildings and grounds which makes the conduct of work more difficult."
What are the risks?
The government evacuated a 12-mile (20km) area directly around the plant and those in towns directly upwind of the plant, where radiation levels are thought to be the highest, so those with the greatest risk of exposure now are plant workers. Over the past month, the radiation dose inside of the plant peaked at eight-times the allowable per year exposure for U.S. radiation workers. Japan’s Health Ministry has also raised the legal amount of radiation exposure for workers, perhaps further endangering their health and safety. Chernobyl workers suffered radiation burns, radiation sickness, dozens of fatal radiation poisoning cases and thousands of cases of thyroid cancer. The Japanese workers have better protective gear and are more aware of the risks than Chernobyl workers were, however, on Monday Japan raised its assessment of the accident at the plant to Chernobyl levels. The government has changed the rating from a level 5 on the international scale of nuclear disasters, which is an accident with wider consequences beyond the local community, to the highest rating level 7, described as “a major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures."
The risk of exposure should diminish at greater distances from the plant due to normal decay and dilution of radioactive isotopes, but the new 7 rating might mean a greater population could face radiation exposure than originally predicted. Fortunately, the radiation exposure of the civilian population has been light so far, just a fraction of U.S. residents’ normal daily exposure. However, exposure to a by-product of fission – cesium- 137 – is worrying because it does not decay for decades and can cause cell mutations, increasing the risk of cancer. While there is constant exposure to natural and man-made radiation, the scientific community does not fully understand the effect of low-dose radiation on long-term health. A much higher dose of radiation could come from Unit 3, because the reactor used MOX fuel, a mixture of uranium and plutonium not used in the other units. The plutonium in MOX is thousands of times more radioactive than uranium, and when inhaled even in small amounts plutonium can cause lung cancer. The risk of Unit 3’s release of large amounts of radiation is still unknown as the struggle to stabilize the plant continues.
Other radioactive isotopes can enter the soil, water and food chain, corrupting Japan’s water and food supplies. The Japanese government has detected radioactivity that they had not anticipated in milk, meat, vegetables and tap water in parts of Japan away from the plant. This food will not immediately harm people, but the government must inform the public because radioactive milk and food can make babies and the elderly sick over time. India, South Korea, Taiwan, Singapore, Australia, the United States and Hong Kong have restricted food and milk imports from within the Japanese evacuated zone. Whether the food is dangerous or the restrictions are necessary for political reasons, the prohibitions have taken an emotional toll on an already traumatized Japanese public.
The aftermath
Beyond stabilizing Fukushima Daiichi and protecting the public from radiation, Japan must overcome the trauma of having two natural disasters with a high death toll, a nuclear emergency and a large displaced population. Fifteen years after Chernobyl, a UN report described mental health as the largest public-health problem there to date. Expert on Chernobyl, Jim Smith, wrote that locals expressed “widespread fatalism and feelings of victimization” and adds, “Resulting rises in alcohol consumption and smoking may well have done more damage than radiation exposure.” In Japan, tens of thousands of people from the evacuation zone live in temporary shelters because of the threat of radiation, with no idea when or if they will be allowed to go home. The Japanese government also caved and announced that further evacuations outside of the original radius are necessary and that more towns might be called on to evacuate if the conditions of the plant grow worse. The future promises more upheaval and disruption. Such an experience of loss, homelessness, desperation and fear is likely to plague Japan’s population for a long time to come.