We are all tuned to the ongoing suffering in Japan, the result of a terrible earthquake, one of the worst in history, at 8.8 or 8.9 on the Magnitude scale.The earthquake lasted several minutes, was and is still being followed by aftershocks which by themselves would be considered devastating quakes, and to estimate the number of lives lost is seen as irresponsible. In one town alone, 15,000 homes were destroyed. Photos depict water rushing into cities, deep as buildings are tall, and moving at 300 to 500 miles per hour. Houses and cars by the thousands are swept helplessly in the terrible current. We wonder how many of those vehicles may be occupied, the occupants now likely dead, caught up even as they drove.
If destruction from the earthquake and the tsunami are a consideration, we must also consider that we are confronted with a potential nuclear accident at Japan’s nuclear power generating plants. The quake and tsunami eliminated all power to the electrical production plants, even generators and in some cases batteries were rendered useless. In nuclear reactors, cooling is fundamental. When cooling fails, explosions and melt-downs can occur. This has happened in the past, most notably in Chernobyl, Russia. Explosions letting nuclear materials escape into the atmosphere produce toxic results; cancers over time, in those exposed.
On Friday, during and following the initial earthquake, the Japanese government issued an emergency warning and ordered 2000 people evacuated from near the Nuclear Stations. Rises in pressure, chiefly caused by failure of coolants caused the problem. The outcome is uncertain; the threat to human life is inescapable. Cooling and pressure concerns continue to rise, even as the United States and others work to bring in structures and materials for cooling. The emergency measures may take several days to incorporate. There have been explosions, and radioactive material has entered the atmosphere. The area of contamination is now estimated at about 35 miles.
In attempting to shed light on the situation regarding the Japanese reactors, I reviewed some facts about the mentioned past nuclear accidents. We may benefit from a look back at those incidents at Chernobyl, in the Ukraine, and Three-mile Island, in the United States, near Harrisburg, Pennsylvania. In both of these nuclear facility breakdowns, the absence of proper cooling water played a significant role.
Chernobyl is a city on the Pripiat River and the home of the Vladimir Lenin Nuclear Power Plant. The Chernobyl catastrophe is considered among the greatest industrial accidents of all time.
The nuclear reactor at Chernobyl is a Soviet designed graphite moderated pressure tube-type reactor utilizing 2% enriched uranium dioxide fuel. Boiling water feeds steam to turbines without any heat moderation. The boiling water feeds the twin turbines and acts also as a coolant. This type of reactor is significant because it is a “refueling machine” allowing fuel bundles to be changed without shutting down the reactor. In that then-modern reactor, an increase in voids (steam bubbles) produces an increase in core reactivity. As steam production increases, new neutrons produce denser water, and increased fission. On April 25, 1986, the reactor crew was preparing a test to see what would result in the event of failure of the main electric power supply; how long turbines would continue to spin on their own volition.
The operator was slow to shut down the reactor following the malfunction of automated shutdown mechanisms. In spite of simultaneous malfunctions, nothing prevented rods from automatic insertion into the reactor, causing a power surge. Hot fuel and insufficient cooling led to rapid steam production and increased pressure. Overpressure caused a 1,000 ton cover plate to detach, rupturing fuel channels, jamming control rods, and led to the destruction of the reactor. At that point, rods were only half covered in coolant water. A steam explosion sent fission products into the atmosphere. Within a few seconds, a second explosion occurred, possibly the result of hydrogen production.
The Town of Pripyat was evacuated. Hundreds of thousands of Russians, Ukrainians, and Byelorussians had to abandon entire cities within thirty kilometers, the area of extreme contamination. By mid-May of 1986, 116,000 people were relocated. Most had received low levels of radiation exposure, although in some cases the exposure was more extreme. Radiation produces cancer in those exposed. In high-dose exposure the effect is certain to occur. The exposed will definitely suffer Acute Radiation Syndrome.
The population near the Three Mile Island power station near Harrisburg, Pennsylvania, was not so unfortunate. In 1979 a cooling malfunction caused part of a core in reactor #2 to melt. At one point, a valve failed to close properly causing the temperature of the coolant to rise. The reactor was destroyed but high-pressure injection pumps pushed replacement water into the system. There are no reported injuries or health affects reported.
BlogCritics readers may know by the time this goes to print more details of the crisis at the Japanese Nuclear Plants.Powered by Sidelines