Photoman; In these breeder reactors, fission is always occurring and is controlled by the moderator rods and the operating water. The moderator rods increase the output by increasing the transmuting of U238 into plutonium which is a much higher yield fuel than U235. What the corporate quackers refer to as a full shut down is simply the withdrawal of the moderator rods from the core, which leaves the reactor at a minimal output which could be as high as 20 per cent of it's max. I have seen no reports or data which shows that there was a full shutdown prior to the tsunami. If indeed there was no full shutdown, there were moderator rods inserted in the core when the tsunami flooded the reactors and shut down all the electrical systems. Even with a full shutdown, the reactors need a large volume of cooling water to remain undamaged; with no cooling, meltdown was a certainty. From what I have seen of the design, the moderator rods are below the fuel rods. Gravity would bring any meltdown into contact with the moderators which would increase the Plutonium output.
This design is a disaster waiting to happen, but what is more disastrous is that the government quackers allowed the corporate quackers to ignore all the advice of nuclear engineers who wanted to build the reactor three hundred feet higher to avoid damage from the worst case scenario; a tsunami such as the one that occurred.The government quackers issued the permits to build this reactor complex at tidewater.
The decay heat is from all the surrounding metals and materials of the reactor that have absorbed radiation and are re-radiating it; the decay heat generally tapers off relatively quickly in a matter of hours or days. it is only a small percentage of the full output of the reactor. It is two and a half years now and the radiation and heat output have increased
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This disaster has been left in the hands of mindless corporate profit seekers and equally mindless politicians. The disaster was set up by building the reactor at virtually high tide in a known earthquake and tsunami region where evidence showed that a previous tsunami wiped out a village over 300 feet above tidewater. The puny little seawall that was built to protect the reactor from a tsunami was a ridiculous lie to the Japanese people so that the corporation could maximize profits and the politicians could laud their own good economic sense.
The corporation has allowed this disaster to escalate in order to save money while the politicians quacked mindlessly about their proper actions in this farce.
There is a simple procedure that would allow the opening and and remedial action on the meltdown reactors. It involves the use of Boron slurries pumped into the reactors to slow or halt the nuclear reactions producing the heat and radiation that is preventing the workers and robotic devices from breaking up the critical mass of the fissioning material.
The only solution for this problem, is to break up the fissioning mass and separate the pieces; once the pieces are small enough and separated past the minimal distance, the fission process will decrease or even halt, especially if contained in a boron slurry.
The cost of the boron pumping system would have been expensive to begin with but would have been far cheaper than the cost of the pretend procedure of the corporate quackers and the escalated cooling problem and eventual cleanup costs. There has been no plan or procedure to fix the primary problem which has allowed this disaster to escalate to the point where all available funds are being used for the escalating cooling procedure. These are breeder reactors which incorporate fuel rods containing U238 which is transmuted by neutron radiation into plutonium, which is a higher yield nuclear fuel.
The actual amount of fissionable fuel in these broken reactors is increasing while the control mechanisms are non functional. How long before the heat and radiation output exceeds any possible water cooling system?
Worst case scenario; The most damaged reactor increases it's plutonium to the point where it's output exceeds any water cooling effort; a further melt down occurs which melts and mixes the moderator rods with the fuel rods (moderator rods contain materials which slow down fast neutrons which can then be captured by U238 which transmutes it into Plutonium). Without the moderator material, Plutonium cannot be made; mix the two together and you have uncontrolled production of Plutonium. The heat and radiation output curve will go vertical. The resulting explosion will scatter much radioactive material including plutonium.
This is the primary problem and should have been addressed from day one.
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I have been posting in several newsgroups about solutions to these problems.
First and foremost; the cooling problem is secondary to the primary concern for the crippled reactors.
There is a procedure for reducing the cooling requirements; I will paste some of it here from a previous post xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx01/09/2013
These government quackers still haven't the vaguest clue about the real magnitude of this disaster. They allowed the corporate quackers to pretend to be fixing the melted_down reactors, while the real problem mushroomed.
These type of reactors are modeled after the fast breeder design; they incorporate fuel rods, which besides the fissionable material, contain U238 which absorbs neutron radiation and is transformed into Plutonium. This type of breeder reactor increases it's fissionable mass, which increases it's radiation and heat output, which increases it's cooling requirements. It is a losing battle for the corporate quackers and the longer that they have been allowed to pretend at fixing the reactors, the greater the problem the government quackers will inherit. It is absolutely imperative that they begin a proper program to fix the melted_down reactors.
Entombment may be another disaster in the making; these reactors are in a steady increase of radiation and heat output; entombment would be just screwing a cap on a pipe bomb and lighting the fuse. The only feasible course is to begin cycling a boron slurry through the reactors to reduce the heat and radiation output.
Boron is a non_toxic material which has little or no adverse affect on the environment and can absorb a great deal of neutron radiation without becoming appreciably radioactive itself. Boron is used in the "CONTROL RODS" of proper safe reactors. Such control rods are held suspended above their holes in the reactor core and will fall into the core and shut down the reactors when the power is cut. These breeder reactors have no control rods and no failsafe mechanisms. They are disasters waiting to happen.
If a boron pumping system had been implemented at the beginning, they would have only required a few dozen tanks and the radiation would have been reduced a thousandfold. Unfortunately, corporate quackers,are only concerned with saving money. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
There is more; I will include in my next post
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