I watched Nuclear Aftershock on PBS Frontline a few weeks ago. I think everyone should watch this, because nuclear power affects almost everyone of us.
I went on a group tour of SONGS (San Onofre Nuclear Generating Station). The rep gave his spiel and when finished he asked “are there any questions?” I raised my hand and asked “Where does the nuclear fuel come from and how much does it cost?”. He quickly dodged my question by giving information unrelated to the question. I got the feeling that I had asked him to give away some sort of secret.
I´m telling a brief, simplified version of what I have learned, in the hope that the casual reader will learn enough to pursue further information on their own. A good source on this subject is NHK World nhk.co.jp. UPDATE: watch “Inside Japan’s Nuclear Meltdown” online at www.pbs.org/frontline
The way it works When the fuel rods are put into a nuclear reactor core, they are enriched uranium. The control rods are partially pulled out and the core reaches critical, and begins to produce enormous amounts of heat, which is what is used to make steam to generate the electricity. The amount of heat is enormous, billions of watts in the space of a house. The coolant must be kept circulating to prevent the heat from melting the core.
After it has been in operation awhile, the byproducts of fission have accumulated and the fuel rods are no longer just enriched uranium. These byproducts of fission are unstable and will keep on breaking down, producing more heat.
When a nuclear reactor is shut down, the control rods are inserted into the core and stop the uranium from fissioning. But even so, the byproducts of fission are still there, breaking down and making decay heat. The heat is nowhere as much as it was while the reaction was going on, but it is still a huge amount of heat, and can melt the core. Therefore the reactor must be fed coolant for weeks until the byproducts slow down their breakdown and the core reaches cold shutdown. If
In order to keep the coolant circulating, the reactor has pumps and power, and backup power and backup generators, and backups to the backups, just to prevent the core from melting after it has been shut down. These must keep the coolant circulating for weeks until the core has cooled down. If this cooling system fails, it is the beginning of a major catastrophe.
What happened Fukushima Daiichi was built in a location that had been hit by huge tsunamis in the past, one of which was the massive tsunami of 869, a part of Japanese historical records. Even though it was known that that tsunami had done severe damage, the builders of the plant chose not to build the sea wall around the plant high enough to prevent damage from another tsunami like those of the past.
As a result, when the earthquake came on March 11, 2011, the nuclear reactor plants in Japan, including Fukushima, shut down as they were supposed to. The following tsunami was so huge that it breached the sea walls of Fukushima Daiichi, flooded the plants and damaged the plants and backup generators, and the coolant could not be kept circulating in the core. The temperature of the cores rose, finally causing meltdown and explosions that spread radioactive material over an area tens of kilometers downwind. These areas had to be evacuated and people have not been allowed to go back because of the radiation. It has been nearly a year since the accident happened. The evacuated people cannot go back to the contaminated areas, possibly for decades.
The plant had 6 reactors, and some were not running at the time of the disaster. The plant was damaged beyond repair and may take many years to demolish or encapsulate. It was eventually brought under control, but the cleanup of radioactive material spread over so much area will take massive amounts of money and manpower. The accident and coverage by newsmedia has given the nuclear power industry a black eye and the public has the perception that nuclear power is unsafe. This is especially true in Japan, where the atomic bombs were dropped at the end of World War 2.
Update Apr 10 – I ordered Nuclear Aftershocks on DVD, and watched it again. More tidbits from the program.
“We have not found a pollution free(?) baseload electric power .. other than nuclear power.”
I don’t think this statement is valid. Geothermal and hydroelectric power are pollution free and can deliver power 24 hours, 7 days a week. There has also been discussion about storing solar thermal energy in molten salts so that the solar thermal plant can still produce power after sunset and during cloudy days. I’m not sure if there are any installation utilizing this, though.
He said, “Nuclear power has a great future. But I’m biased – I’m an engineer.”
The NRC required Ft. Calhoun Nuclear Reactor in Nebraska to install watertight doors.
The North Anna Nuclear Power plant was just 11 miles from the 5.8 earthquake last year.
“I think we still have some lingering issues that we want to get resolved.” Jaczo, of NRC on fire hazard issues.
Indian Point NPP is very near the Ramapo fault.
“The U.S.has 104 nuclear reactors, the largest number in the world, but they are all old plants.”
The Fukushima nuclear accident released one tenth of the radioactive materials that were released at Chernobyl.
“It will probably take 25 years to cleanup Fukushima.”
It took (from March) until December to achieve cold shutdown.
My thoughts. After the Fukushima meltdown, the Japanese and German people say they do not trust nuclear power. But the nuclear power is not the problem, it is the failure of the people who designed the plants with two problrms. The first failure was to design a system that has a critical vulnerability. This is the vulnerability that caused the Fukushima nuclear accident.
The second problem was they understood that the vulnerability had to have safety systems to prevent it from occurring, but they failed to anticipate every possible adverse situation (such as a strong earthquake) that might initiate a series of events that could cause a catastrophic meltdown, as in the case of Fukushima. And failure of the system to upgrade the deficiencies in a timely manner when they are later discovered, as in Fukushima.
Perhaps this deserves further explanation. “For want of a nail, the kingdom was lost.“ Or in other words, the smallest details can make or break a system. In the program, they discussed how the above nuclear power plants installed, among other things, water tight doors to prevent flooding of the emergency backup power system. One could also argue that it is not possible to anticipate every adverse situation and therefore nuclear power cannot be inherently safe.