Fail-Safer Fission Reactor

First, a bunch of background info:
A nuclear-fission reactor is a device that needs to maintain a somewhat delicate balance in order to produce power at a chosen specific rate. The key thing to control is called a "chain reaction". Each fuel-atom that fissions can potentially cause, on the average, up to two-and-a-half other fuel-atoms to fission. And in turn those fuel-atoms can cause yet more fuel-atoms to fission, and so on.

In a device designed to explode nuclearly, we want to maximize the quantity of fissions that each fissioning atom causes, and we want the rate of fissions to increase as quickly as possible. In a power reactor, however, we want to allow fissions to cause greater numbers of fissions ONLY when turning the thing on, and SLOWLY ramping up the rate energy is released from near-zero to the designed power-rating of the reactor.

At the designed power rating, the reactor needs to ensure that each fissioning atom causes, as exactly as possible, only one other fuel-atom to fission, thereby maintaining the chain reaction at a constant power-production rate.

Therefore all fission-power reactors have a group of things called "control rods", which are able to interfere with the chain reaction. The reactor core contains a regular pattern of control rods mixed with "fuel rods". The control rods are gradually pulled out from among the "fuel rods" to allow a chain reaction to begin, among the fuel rods. The control rods are often pulled out individually and by different amounts.

It is a peculiarity of just about EVERY large electric-power plant, whether of nuclear or other type, that it needs a source of external electric power in order to start working. On the rare occasions when some section of a national power grid fails, and a widespread blackout occurs, one of the reasons it can take days to restore power is that, usually, each power plant inside the affected zone needs to receive some external electric power in order to become turned on again. (And, sections of the grid need to be temporarily isolated, as explained below.)

Each type of power plant uses that external electric power in different ways. A hydroelectric facility, for example, may use external electric power to control the valves that allow water from the dam to reach the power turbines.

I don't know that the valves automatically close in the event of a power failure, so possibly hydropower is a little less susceptible to the generic problem just described. On the other hand, no single power plant can run the entire power grid by itself (its generators would overload), which means that usually each power plant in the grid MUST shut down, if only to protect itself.

Power-plant power can always be used to close the valves. But after that, then external power would be needed to open them again! After the local section of the grid is isolated, an external feed can allow the dam to once again begin to power its local section.

In a nuclear-fission plant, external power is used for such things as running the cooling pumps for the reactor core, and for moving the control rods. Once power starts being generated, of course, the external power is not needed. But if the internal power generation fails....

Recently in Japan, as most of us already know, a fission-power plant at a location named "Fukushima" lost power as a result of one of the largest earthquakes in recorded history. When such an event happens, the power-plant operators don't immediately know the extent of the damage. It is naturally DESIRABLE to restore power as quickly as possible.

"External power" does not necessarily automatically mean power from a distant source. The Fukushima facility had an auxiliary emergency power plant (fossil-fuel power), which naturally could be used for such purposes as initially getting the main fission reactors up and running --or to take over the powering of the reactor-coolant pumps. For a short time, until the fossil fuel tank was exhausted.

Well, the damage caused by the earthquake (and the tsunami that followed it) was rather more extensive than was initially understood to be the case, by the power plant operators. According to the "Pro-Nuclear" link below, all the reactors correctly shut down their chain reactions (control rods were pushed back into the reactor cores) in the aftermath of the quake. But the coolant pumps were not all working!

There exists a kind of "thermal inertia" which must be dealt with, even after a fission chain reaction stops. That's because not all of the energy of a fission reactor comes from nuclear fission; quite a lot also comes from the radioactive decay of the various atomic nuclei created by fission. So, that decay-heat still needs to be carried away from a "shut-down" reactor core. How much heat?

It happens that a "typical" large power plant these days is rated at approximately 1 Gigawatt of electricity production, 1000 Megawatts, enough energy to power 10 million old-fashioned 100-watt incandescent light bulbs. It also happens that a large modern heat-creating power plant is able to generate electricity from that heat at a rate of about 50% efficiency. This means that the amount of heat-energy being produced must actually be 2 Gigawatts, for 1 Gigawatt of electric power to be produced.

The Fukushima facility had 6 operational reactors, with 2 more planned. 3 of the operational reactors were down for maintenance at the time of the earthquake; the other 3 were running at their design capacity (see "Disaster Details" link for the individual power ratings). Even if only 1% of the total heat-production of the reactors was from radioactive-decay products, that's still roughly 1 Megawatt of heat (your oven is rated at maybe 4000 watts) that MUST be removed as fast as it is produced, lest it cause various bad things to happen....

The damaged systems were unable to cope with this heat-production, which has since increased the scope of the crisis at the Fukushima power plant (the related linked articles may need some updating, as both were written in March).

This Obviously Means More Types Of Backup Heat Removal Are Needed. Which brings us to the present Idea.

There is a "passive" type of heat-removal system known as a "heat pipe". See link. In theory, multiple large-diameter heat pipes can carry an enormous amount of heat from Point A to Point B. And heat pipes don't need external power to do their jobs!

So suppose each Point A, of several heat pipes, is a location NEAR, but not quite adjacent to, a nuclear reactor core. Each associated Point B could be at any nearby body of water (build several large artificial cooling ponds, if necessary). The reason we don't want each Point A to be right next to the reactor core is that we want this heat-conduction system to be used only in an emergency; we don't want heat escaping along that path when we are trying to produce electric power!

Note that the heat-pipes themselves should be made of a somewhat flexible material, so that they don't break (they would bend) if a large earthquake sends shock waves through the region.

If an emergency shut-down happens, now we do want each Point A to somehow become adjacent to a reactor core. I'm envisioning a kind of rotate-able "plug" of solid material located in-between the reactor core and each Point A. Each rotate-able plug would consist of two completely different materials.

At least half the plug would be an excellent heat-insulator, for when the reactor is producing power normally. When an emergency shut-down happens, and while the control rods are pushed into the reactor core, each plug is physically rotated so that instead of an excellent heat-insulator being between the reactor core and each Point A, the near end of one heat pipe, now an excellent heat-conductor is in place. The very best solid heat conductor is diamond, so that's the logical choice.

Each piece of solid diamond (it will have to be synthetic "grown" diamond, of course!) now conducts large amounts of heat from the reactor core to the Point A end of one of the heat pipes. Each heat pipe (remember, multiple heat pipes have been specified) now carries heat to Point B and the cooling water. Even if the normal cooling system fails, and the power plant goes dark, this system should prevent the sort of increasing emergency that happened at Fukushima.