THE LIBERTARIAN ENTERPRISE
Number 610, March 13, 2011
"Much food for thought"
Attribute to The Libertarian Enterprise
Watching the almost continuous news of the magnitude 8.9 earthquake and the resulting tsunami that first shook to pieces then inundated thoroughly with seawater the northern Japan city of Sendai I was struck with the absurdity of the failure of the backup systems at the nearby Fukushima Nuclear generating site.
A typical nuclear reactor is a huge assembly of enriched uranium oxide pellets in hollow fuel rods which are placed in bundles. The entire assembly is suspended in a reactor vessel that has water continuously circulating in it in order to transfer the heat of the reaction to a heat exchanger which heats a secondary water supply to steam which runs a turbine.
The water which circulates also usually serves as a moderator which slows neutrons from the reaction which is necessary to maintain the reaction. A set of neutron absorbing rods are used to regulate the reaction to allow the facility to match the power output to the demands of the grid.
When the reactor is started up the control rods are slowly withdrawn from the fuel rod assembly which makes up the core of the reactor. Some of the neutrons which are always being generated are no longer absorbed by the control rods and instead find their way to the nucleus of uranium U-235 which if they are of the proper energy will split the nucleus into smaller atoms. This produces heat and many more neutrons which also heats the water which surrounds the core. As I said before the water also helps maintain the reaction by slowing the higher energy neutrons by trading kinetic energy for heat. Without this water moderation most of the neutrons would simply escape the system since the neutrons of a split nucleus have to great a velocity to be absorbed by a U-235 nucleus and bounce off instead. Without the water there can be no reaction.
Once the reactor has reached operating temperature the water must be pumped around a closed circuit with a heat exchanger that heats another supply of water into steam. The pressure inside the reactor is maintained very high in order to prevent the water from flashing into steam. The heat exchanger is used to separate the slightly radioactive water from the rest of the system and prevent the escape of this radioactivity into the environment. When everything is maintained in balance then the nuclear power plant will produce electrical power for many years. After the U-235 in the fuel rods is used up to the point that insufficient heat can be generated the fuel rods must be removed and reprocessed into more fuel by separating the remaining U-235 and the other by products for use in other nuclear fields or imprisoned for storage.
THIS IS NOT THE BEST OF SCENARIOS for the use of Nuclear fuel but so-called Breeder Reactors are frowned upon by the US government because they produce Plutonium in greater quantities which could be diverted into illicit nuclear bomb making. The politics assumes that enough fuel rods could be diverted to make bombs but I doubt there are any terrorist groups with the wherewithal to build facilities capable of processing spent fuel rods into enough plutonium to make a bomb. But the nuclear power industry is so persecuted by the politics of fear has prevented the widespread use of nuclear power in the U.S.
But this isn't my reason for writing this article.
As I understand it, when the earthquake struck in Japan the protocol is to shut down everything which could conceivably be damaged to prevent catastrophe. Power grids are shutdown, trains are stopped, cars and trucks are diverted from the elevated expressways onto city streets in case the road should break down. I can see the reason for diverting the traffic and even the stopping of all the trains to enable inspection of the rails and the roads. The interruption of the power grids is much more problematic however.
Even in fossil fueled power plants it is inadvisable to simply disconnect the load from the generator. Because the turbine has a big head of steam pushing it by disconnecting the load the turbine and generator could overspeed before the flame is extinguished under the boiler. The water in the boiler is already very hot to produce the superheated steam. Suddenly dumping the load is dangerous to say the least.
Now substitute the fire under the boiler with the high pressure circulating water from the reactor core and let's see what happens. The load (grid) is suddenly disconnected this will result in an overspeed of the turbine/generator. To prevent this the superheated steam in the boiler must be vented. Without water circulating into the heat exchanger the reactor high pressure loop will overheat even though the control rods have been shoved in to the core to dampen the reaction. So to prevent further problems cool water must continue to be injected into the heat exchanger to keep pulling heat out of the reactor loop to cool the reactor down.
Remember this is NOT the proper way to shut down a reactor. The proper way would be to insert the control rods into the core to quench the reaction. Then the residual heat must be allowed to continue producing power until the temperatures are bled off to the point that the turbine can no longer maintain positive power into the grid. Then the generator can be safely disconnected from the load. All that is necessary now is to allow the remaining heat to dissipate naturally or cool water can be forced fed through the heat exchanger to cool it faster.
THIS IS NOT WHAT HAPPENED!
Instead the protocol was to disconnect the generator from the grid. This led to overspeed in the turbine which is a big enough problem by itself but add in the fact that since all of the grid was without power now the pumps which normally circulated water through the systems to cool things down had to be run on backup power. OK so far so good BUT, the subsequent tsunami knocked out the diesel generators which kept the pumps running. Now the pumps must be switched over to run on battery backups. But the batteries could only supply power to run the pumps for 8 hours.
After the 8 hours elapsed and without the diesel generators the pumps could no longer run. The water in the heat exchanger all boils away to steam. There is still residual heat in the reactor core but since the water in the primary circuit can no longer circulate and isn't being cooled by the heat exchanger anyway it begins to create greater pressures which threaten to rupture the plumbing or the reactor vessel itself. Therefore the excess pressure must be vented. This of course allows radioactive steam out into the environment. But worse as the water boils to steam the level of water in the reactor vessel begins to drop. Once the level drops below the tops of the reactor core the fuel rods become exposed and since they are still too hot they begin to melt. Drop the water low enough and the reactor could experience a total meltdown.
To me the stupidity of this scenario is glaringly evident.
Had the grid not been disconnected the pumps would continue to run. The reactor could be shut down in an orderly fashion. In the event that the grid load could not be maintained the backup diesel generators should have been better protected in order to supply the required pump power to cool down the reactor. Clearly the scenario was not well thought out. If a lay person such as myself can figure it out why can't the highly educated bureaucrats?
Oh! That's why! There is nothing dumber than a bureaucrat who knows nothing of nuclear power systems but feels qualified nonetheless to set disaster policy of the entire nation. Because nobody wants to go up against a powerful and politically appointed bureaucrat is why these disaster scenarios come to pass. We saw it when Hurricane Katrina struck New Orleans. When truckloads of water donated by Walmart were prevented from being distributed. When loads of other badly needed supplies were continuously put on a circular route because the bureaucratic mind knows nothing of proper logistics. When entrepreneurs are arrested because they attempt to make a few extra bucks by hauling in supplies to sell for prices greater than retail and are charged with price gouging.
This is how the bureaucratic mind deals with disasters. It fails to plan for the very disasters it is charged to relieve. When it fails to provide the needed relief it arrests the entrepreneurs who would provide relief at a price that makes it profitable. It prevents self-help and good Samaritans because they lack the proper training? Would somebody please explain to me why FEMA would prevent one neighbor from helping another after it fails to provide the needed help?
There is nothing stupider than a bureaucrat. When you see a bureaucrat coming who says, "I'm from the government and I'm here to help you.", run for your life!