Wednesday, March 16, 2011

Japan: All Nuclear Disasters Are Not Created Equal

Sadly, the headlines are once again swamped with stories of the latest natural disaster to wreak havoc on the Pacific Rim. On March 11, 2011 an earthquake (8.9 on the richter scale) and subsequent tsunami (a wave created by the shifting bedrock in the ocean following an earthquake) shocked Japan leaving thousands dead, and many more missing.

Nuclear energy is a widely used source of power in Japan. As a result of the earthquake and tsunami, damage to the nuclear power plants has resulted in several explosions and the release of radioactive material. While the media is fixated on the threat posed by the imperiled nuclear power plants, there is a significant amount of misinformation, information without context, information in the wrong context, and complex information that is just not explained adequately in the media's coverage.

The following list will hopefully clear up some of the confusing information I've seen in the popular coverage of Japan's nuclear situation.
***
Diagram of the type of reactor at Fukushima
Source: Nuclear Energy Institute
1. The design of nuclear reactors vary: The nuclear reactors in trouble in Japan are the Mark 1 design by General Electric. This design has been controversial since the 1970's when it was discovered that the cooling, ventilation, and containment systems (the areas causing trouble in the Japanese plants) could be problematic in the event of a meltdown, explosion, or other event. The New York Times' article Reactor Design in Japan Has Long Been Questioned states that the most common type of nuclear reactor is a pressurized water reactor where the system is encased in steel and cement and that, "the type of containment vessel and pressure suppression system used in the failing reactors at Japan's Fukushima Daiichi plant - and in 23 American reactors at 16 plants - is physically less robust, and it has long been thought to be more susceptible to failure in an emergency than competing designs." The New York Times' article goes on to explain that many American plants manufactured in General Electric's Mark 1 design have been modified to fix the problems in the original plans. Americans should not be panicking that the nuclear reactors in the United States have the same problems as the ones in Japan. Each nuclear power plant needs to be evaluated in its own right for safety.

2. Comparisons to Chernobyl or Three Mile Island are difficult to make: Chernobyl, located in the Ukraine, was a nuclear disaster that occurred on April 25, 1986 due to a flawed reactor design and human error. The Chernobyl reactor was of a soviet design, and according to the World Nuclear Association, "the design of the reactor is unique and the accident is thus of little relevance to the rest of the nuclear industry outside of the Eastern bloc." Chernobyl was the only nuclear accident to cause human deaths due to direct exposure to radioactive material. Comparisons can be made to the situation in Japan about the extent of damage, but only once the situation is under control has been thoroughly assessed. Three Mile Island was an American accident in 1979 that occurred when a cooling malfunction caused part of the nuclear reactor's core to melt. There were no adverse health effects associated with any radiation released from the plant after the accident. The build up of hydrogen gas following the meltdown was a factor in the Three Mile Island accident, and is causing problems in Japan but again differences in exact reactor design and protocol make it difficult to compare the situations.

3. The International Nuclear and Radiological Event Scale is not definite: Even though the INES scale is intended to help publicly convey the threat created by a nuclear event, designation of a certain level on the scale is not a reason to panic. The INES scale runs from 1 (very little danger to the general public) to 7 (widespread health and environmental impacts). Right now everyone is rushing to label the situation in Japan, but so far it is classified as somewhere between level 4 and level 6. The numbers (or levels) are not hard and fast, but it is a clear indication that this is a major event and should be treated with all necessary precautions to ensure the safety of the Japanese people.

4. Radiation is not distributed evenly: When a nuclear power plant experiences an explosion or a meltdown that causes the release of radioactive particles or debris into the environment it can be very complicated to track what areas are going to be effected by radiation. According to members of the Union of Concerned Scientists precipitation like wind or rain can cause the radioactive material to be distributed sporadically. The areas closest to the effected plant will be the first concern for scientists and policy makers assessing the radioactive fallout, but other areas (even far from the immediate vicinity of the plant) need to be assessed for radioactivity.

Map of Japanese Nuclear Sites
Source: International Nuclear Safety Center
5. Not all Japanese nuclear plants are in danger: There are 54 nuclear reactors in Japan located at 18 different sites throughout the country. The reactors in the north of the country experienced the most damage, particularly the Fukushima Daiichi plant which is located closest to the area hit by the earthquake. There are six nuclear reactors at Fukushima Daiichi. Reactors 5 and 6 have had water pumped into them and are currently at a low risk of an incident. Reactor 1 experienced an explosion on Saturday March 12th that damaged 70% of the fuel rods in the reactor, but so far it is reported that the containment vessels are intact. Reactor 2 experienced an explosion on Tuesday March 15th that damaged the suppression pool - a part of the cooling system leaving the fuel rods exposed. This reactor is leaking radiation. Reactor 4 experienced an explosion on Wednesday March 16th that caused a fire in a pool of spent fuel that is exposed to the air. The spent fuel contains more radiation than the fuel rods inside the reactor, so leaving them exposed (as they are now) means that radiation is leaking out into the environment. Reactor 3 is currently the center of an intense effort to cool the fuel rods by pumping in sea water. This reactor is the only one at the Fukushima Daiichi plant that uses plutonium, and thus contains the most radiation. The Kyodo News has a breakdown of the damage to the plant by reactor that contains more information.
***
Reuters has a great info graphic, that breaks down the earthquake, tsunami and the nuclear disaster. The BBC also has an interesting article about the way that nuclear situation in Japan will impact further nuclear development around the world. As more information comes out I'll try to update this post, but I hope that I've been able to provide some background on elements that I've seen in multiple articles about Japan's nuclear situation.

5 comments: