A Rational Look at the Japanese Nuclear Plant Leakage

Guest: Academician Wang Naiyan, Former Chairman of the Chinese Nuclear Society
Opinion:
"The explosion at the Japan s Fukushima nuclear power plant was a hydrogen-involved explosion, not a nuclear explosion, and so it is not anything like the nuclear accident at Chernobyl. Still, we can t rule out the possibility of future supercritical radiation.
"When developing a nuclear power capability and building a nuclear power plant, nuclear safety should be the first priority. We should learn a lesson from the Fukushima accident, which was caused by an earthquake. Obviously, not enough attention was paid during the planning phase to the effects of an earthquake on that plant, and so corresponding measures were not taken. The public should learn more about radiation and ways to prevent it.
Reporter: This magnitude 9 earthquake in Japan triggered the explosion of the four generating units of the Fukushima First Nuclear Power Plant, and leakage occurred. The world was shocked. People can t help but associate this with the Chernobyl nuclear accident in 1986. What s the difference between the two events?
Wang Naiyan: Four generating units at the Fukushima First Nuclear Power Plant exploded. But we have to understand that these were hydrogen explosions, not nuclear explosions. And the explosions didn t occur in the reactor but were caused by either the failure of the water cooling system of the reactor core or the spent fuel pool. The resultant high temperature created a large amount of hydrogen, which in turn led to the explosion. When there s an earthquake, especially a strong earthquake like the one Japan experienced, the security system of the plant s generating units will immediately trip a control rod, stopping the reactor.
The Chernobyl accident was also a water gas explosion and hydrogen explosion, not a nuclear explosion, but this accident happened during the reactor startup phase, so the reactor didn t stop functioning. More importantly, there was no pressure vessel and no containment at Chernobyl, which proved fatal. At that plant, graphite was used as the moderator and water as the coolant. When graphite is dipped in water, the temperature can stay at 100 , but the water will slowly boil away, and then the graphite (which is connected to the reactor core) will reach a high temperature and begin to burn, which in turn will produce a large amount of water gas and hydrogen, leading to an explosion. The purpose of the Chernobyl Nuclear Plant in the first place was to produce military-grade plutonium nuclear fuel. This plant was used to produce nuclear weapons, not to generate power. There was a similar accident at the U.S. Three-Mile Island nuclear power plant: there the reactor core melted, but because there was a pressure hull and containment, there was almost no impact on the surroundings.
Generally speaking, the Fukushima explosion happened during the reactor shut-down phase and it was a hydrogen explosion and not a nuclear explosion, so the Japanese people don t have to fear anything like the accident at Chernobyl. A core melt in a nuclear power plant can t cause a nuclear explosion because the nuclear fuel used in nuclear weapons is uranium-235 with an enrichment of more than 90%, but the nuclear fuel used in a nuclear power plant is about 3%-enriched uranium. The detonation of nuclear weapons requires a high degree of time synchronization and an implosion compression of spatial symmetry or high-speed aggregation, which doesn t occur when the core melts.
Looking at Japan s rescue work, we can see that the Japanese are trying hard to save their reactors. They are trying to save the nuclear power plant, to cool down the reactor core and the spent fuel pool to stop the deterioration of the situation. If effusion works, the whole situation will be under control. If the water cooling system starts to work again, then the plant will be safe. If effusion fails and the cooling system doesn t re-start, then Japan will have to take decisive measures. Japan has many world-class nuclear power experts and workers. They will solve these problems.
Reporter: On March 15, 2011, Naoto Kan, Japan s Prime Minister, announced that the Fukushima First Nuclear Power Plant was leaking radiation. What did he mean exactly by leaking radiation ? What is the transporting medium? What are the factors that affect the proliferation? What s the difference between nuclear plant radiation and the radiation in daily life from such things as mobile phones and computers?
Wang Naiyang: Nuclear radiation refers to the radioactive rays emitted by nuclear interaction or nuclear decay. These radioactive rays are caused by fission products, which exist in the form of particulates in the air or dissolved in water. The life span of these fission products is sometimes long, sometimes short.
Radiation is mainly spread by air and water. From the experience of the U.S. Three- Mile Island nuclear accident we know that water-spread pollution is actually small. Most pollution is spread by air.
Now, people are worrying that the Japanese nuclear pollution will spread to China. Actually, though, there are many factors that can affect the proliferation of nuclear materials. Take air, for example. If the air flow is stable and wind speed is low, the spread of nuclear materials will be low and will be limited to a certain area. On the other hand, if the wind speed is high, pollutants will spread in the downstream direction. Currently, the wind is blowing mainly westward, and once the pollutants get into the atmosphere, they will be gradually diluted and the concentration greatly reduced. That s why we don t need to worry about it.
Mobile phones work by electromagnetic waves, which are very different from nuclear radiation and do little harm to human health.

Reporter: Now in many places in China there is panic buying of iodized salt and iodine tablets. Does eating iodine really prevent the bodily harm that can be caused by nuclear radiation?
Wang Naiyan: One cannot take iodine arbitrarily. For hypertension patients, for example, it can be fatal. And if a pregnant woman takes iodine arbitrarily, there can be problems for the baby's thyroid gland.
The leaked radiation materials include iodine -131, cesium -137, and other fission products. Iodine has an affinity for the human thyroid. The thyroid will absorb iodine to the point of saturation. Thus, when iodine -131 can t be absorbed anymore, it can reduce or prevent the absorption of iodine -131 that is breathed in. One kilogram of salt contains about 30 milligrams of iodine. One iodine tablet contains 100 milligrams of iodine. So the iodine content of 3.3 kilograms of salt equals that of one iodine tablet. It is only in the case of extreme pollution that workers need to take iodine tablets. However, the current amount of radiation in Tokyo is only over 20 times the norm, which still doesn t harm human health. Therefore, people in Tokyo are being encouraged only to wear breathing masks. It is not recommended that they take iodine tablets, because that will do more harm than good. Radiation also includes external irradiation. The particles involved here don t enter the body but rather attach to skin. Usually, putting on a mask, changing clothes, and standing under an umbrella should be enough protection here. Generally speaking, then, the situation isn t that bad now. Beijing is more than 1,000 meters from Fukushima, and so there has so far been no negative impact. The Chernobyl accident, on the other hand, was a serious accident that had a very bad impact on the world. But there was also false propaganda that exaggerated the situation.
Reporter: Are there some laboratories in or around BNU that conduct nuclear or other radioactive experiments? Will that influence our daily life?
Wang Naiyang: We have a small accelerator, but it s a totally different thing from a reactor. And when an accelerator stops, there s no radiation.
The nearest nuclear plant is in Fangshan, where the Institute of Atomic Energy of China built a nuclear reactor; but it s safe.
In fact, the public doesn t have a good understanding of how to prevent radiation in daily life. For example, there s radiation from X-ray fluoroscopy in hospitals; radiation from marble materials in households; there is cosmic radiation when we fly, and so on. People should be aware of this to better protect themselves.
At the same time, we should have confidence in the development of nuclear power. After all, nuclear power is rather environmentally friendly and low carbon power. And Japan s current efforts can lead to a revelation: even if a big earthquake occurs, and a reactor is damaged, and there is a bad result, still the situation can be brought under control. The Fukushima nuclear accident isn t another Chernobyl.
Reporter: It s pointed out in this year s Twelfth Five-Year Plan passed by the National People's Congress, that nuclear power will be one of the major power sources in the future. It s estimated that in 2015 China s nuclear power installed capacity will be 40 million kilowatts. What kind of effect will Japan s nuclear leakage have on China s nuclear power development?
Wang Naiyan: This nuclear accident in Japan will directly influence China s nuclear power development. The health of many will be affected by this accident. It can t be allowed that there be large-scale nuclear leakage. I believe the Japanese people can overcome the difficulty. Right now, we all believe that the Fukushima accident isn t so bad it can t be brought control. If the effusion succeeds and the reactor cools down, Japan will become a model for the whole world. So we re looking forward to Japan s action. We should have confidence.
Currently, there are 11 nuclear power generation units in China, safely generating 700 billion kilowatts of electricity each year. In fact, our country s economic development is dependent on nuclear power development. But there is one rule: the public must accept it. This is very important. We must develop nuclear power, but we must pay attention to safety. So keep in mind that safety is the first priority and strictly execute President Hu s instruction: build our nuclear power plants well, fast, and safely.