Large areas along the Japanese coast were devastated by an earthquake and resulting tsunami March 11. The disaster disabled the cooling systems of the Fukushima I Nuclear Power Plant in Fukushima Prefecture, Japan, which caused some degree of meltdown in three of the plant’s reactors. The explosions triggered fears of radiation-related illnesses and international concern over the safety of nuclear energy. Almost one month after the earthquake, The Chronicle’s Matt Barnett spoke with radiation safety expert Dr. Robert Reiman, general secretary of the Duke University Medical Center’s Radiation Safety Committee.
The Chronicle: Can you describe what happened to the facility and how that damaged the reactors?
Robert Reiman: Following the earthquake, the four active reactors at the plant all shut down automatically and safely as designed. Unfortunately, the tsunami caused both the primary and backup cooling water supplies to the reactor cores to fail. Even when a nuclear reactor is shut down, excess heat from the decay of radioactive byproducts must still be removed, so the cooling system pumps must still work. Without sufficient cooling water, this buildup of heat has caused the damage to the reactors.
TC: What part of the reactor is leaking radiation?
RR: Fortunately, the initial releases into the air due to hydrogen fires and explosions have stopped. Radioactivity at very high levels has been found in surface water near the plant and in seawater. It isn’t clear exactly where the water containing radioactive material is coming from. Candidates include pooling of water beneath the reactor cores, or cracks in concrete electrical conduits that filled with contaminated water during attempts to cool the reactor cores by pouring huge amounts of seawater directly on them.
TC: What kind of radiation is leaking?
RR: Radioisotopes released in this type of accident include xenon-133, iodine-131, cesium-137 and strontium-90. By far the most abundant is xenon-133, followed by iodine-131. The others are released in much smaller amounts.
TC: How does radiation travel through the environment, and how long will it persist?
RR: The good news about xenon-133 is that it isn’t soluble in water and doesn’t chemically react with anything, so it simply disperses in the atmosphere and decays away in a few days. The bad news about iodine-131, if released into the atmosphere as particulates, is that it will settle out onto farmland and dairy pasture. When eaten by cows, iodine-131 in the contaminated grass can get into milk, which may be consumed by people. Iodine-131 concentrates in the thyroid gland, and irradiation of the thyroid gland can lead to health problems later in life, especially for infants and children. Strontium-90 and cesium-137 can settle into the soil, where they may be incorporated into groundwater or certain plants such as lichens and mushrooms. They may get into people after they drink contaminated water or eat meat from large game like wild boar or elk. These radionuclides have long half-lives, and may persist in the environment for decades.
TC: What steps can be taken to remove radiation from the environment?
RR: Based upon our experience with the Chernobyl reactor meltdown in 1986, most things people can do to remove contamination from the environment aren’t very effective. However, there are ways to minimize the adverse effects. For example, natural dilution in the atmosphere and ocean by winds and water currents can reduce radioactivity levels to the point where there are no health concerns. Iodine-131 has a radioactive half-life of about eight days, so it doesn’t persist in the environment for more than a few months after the release of radioactivity stops. In the same way, non-perishable milk products like cheese and evaporated milk need not be discarded, but can be safely used after a few months of storage.
TC: How will the radiation affect people living near the damaged reactors?
RR: Unless the situation gets significantly worse, there will probably be no measurable health effects among people living near the reactors. To be conservative, the Japanese government has evacuated most residents from areas within about 20 kilometers of the plant.
TC: With respect to the radiation, what would you say is Japan’s biggest concern at this point?
RR: Unfortunately, the biggest concern is the economic impact on the Japanese seafood export, farming and dairy industries. Irrational fears about eating foods that may be contaminated at levels far too small to cause health effects will harm those industries.
TC: Is there a risk of an earthquake in North Carolina causing a similar situation?
RR: That’s hard to say. Significant earthquakes haven’t occurred in North Carolina in the past few centuries, and future earthquakes aren’t likely. But that doesn’t mean they can’t occur, so nuclear reactors are designed to survive earthquake damage. Having said that, accidents like the one in Japan that are the result of natural disasters are causing the regulatory agencies in the United States to review power reactor safety.
TC: Anything else you’d like to add?
RR: Everyone’s been pretty focused on the radiation aspects of this disaster. Let’s not lose sight of the fact that over 10,000 people have died, hundreds of thousands have suddenly been made homeless and many others whose homes survived are still without electricity or clean water. Although the minimal health risks from radiation need to be addressed, the Japanese people have a lot of other more urgent things to worry about.
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