Twisted Musings

This was provided by Sad Sam’s cousin and is informative but disconcerting. I am taking him at his word as I know nothing about nuclear reactors.

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My family knows, but some of you may not. I spent 6 years in the Naval Nuclear Power Program. I was a certified reactor operator and reactor technician and served 4 years on the U.S.S Enterprise in that capacity. Unfortunately, I seem to know way more about reactor technology and reactor protection analysis than most of the “experts” you have read in the paper or seen on TV.

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Update:  I started writing this 18 hours ago before the latest news. Now it’s much worse.  Read below to get context and then at the end I’ll update with what is happening now.

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The situation at the Fukushima reactor complex in Japan is very bad! Much worse than we are being told. The economic loss is $billions. The environmental and human health costs are yet to be determined but could be incalculable.

The basic problem is heat. Most commercial reactors are rated to produce between approximately 1.2-2.5 BILLION thermal watts of heat. The heat is used to boil prodigious amounts of water, to make steam which then runs a turbine-generator to produce 500-1000 Megawatts (1 megawatt = 1 million watts) of electricity. You can shutdown a reactor (stop the fission chain reaction, which successfully happened at Fukushima). But even after shutdown the reactor still produces about 6% of total reactor power in what is known as “decay heat”. This is heat caused by the intense radioactivity of the “fission fragments” (what’s left after you split a uranium atom) the most common being Iodine-131, Cesium-137 and Strontium-90. That is the crux of the problem. Even after shutdown those fission fragments from a 1.2 Billion (a relatively small commercial reactor) thermal watt reactor are still producing 72 MILLION watts of heat! The core has to be constantly cooled to remove that heat. Take away the cooling and the core will heat up incredibly fast to very high temperatures.

If those fission fragments get into the environment they are extremely dangerous because of their intense radioactivity. Your body and Mother Nature can’t tell the difference between a naturally occurring non-radioactive element and one that is highly radioactive. Your body absorbs them all the same. Iodine-131 get’s absorbed in the thyroid. Cesium- 137 mimics potassium and gets absorbed in muscle tissue and strontium-90 mimics calcium and gets absorbed in the bones.

Getting back to the situation at Fukushima, putting seawater into an operating reactor complex is an act of total desperation. It means that all the normal, backup and emergency cooling systems have failed. It means they have given up hope of ever being able to operate the plant again. This has NEVER, EVER happened before in any light water reactor, military or otherwise.  (The one possible exception is a Russian submarine that suffered a serious reactor malfunction that released enough radiation to cause casualties in the crew and force them to abandon ship. The submarine sank. It’s classified how much radiation was released, but in any case a submarine reactor is 1/10^th the size of a commercial power plant reactor)

It’s clear there has already been some core damage at 3 of the 4 reactors at Fukushima. The fact that they resorted to seawater cooling is proof positive because once they did that, they essentially destroyed them. There is no going back from that choice. There is only one course of action for these plants now… decontamination and decommissioning… in the best case scenario.

Here is an example to illustrate what is happening. Take a large rectangular piece of aluminum foil and fold it like an accordion. Imagine it’s the core. Imagine that it’s 5000 degrees F. If you put the aluminum foil under a rapidly running faucet so that water can course down the folds, it cools rapidly. But suppose the water is cut off. And remember this aluminum foil is constantly generating heat. With no cooling, it’s going to keep getting hotter and hotter until it starts melting. As it starts to melt it warps and clogs up the water channels. So, even if cooling is restored there will be channels that get no water and can’t be cooled.   Eventually, what you end up with looks like a superheated crushed ball of aluminum foil.  At that point, the best you can do is tantamount to putting the ball (which is constantly producing more heat) in a teacup and fill the cup with water. That’s the situation in Fukushima. Except the teacup is closed. It’s actually a pressure cooker. And the only thing they can do is to (metaphorically) loosen the lid and let pressure (and radioactivity) out until the pressure is low enough that you can fill up the cup again. Then the water boils again, the pressure builds up and you repeat. It’s called a “bleed and feed”. It’s never been tried before. No one knows if it will work.

And with the instrumentation not working, they don’t know whether they are successfully keeping the core covered or whether the water is instantly flashing to steam. And every time any section of the core is out of contact with cool water and instead is surrounded by steam or air, it will start heating up again. It means that a  total core meltdown is not only possible but probable. I would say it’s probably 50-50 at this point.

In the best case scenario, which is that the bleed and feel process is preventing a total core meltdown, you are looking at months, maybe years of controlled releases of radioactive steam that will contain highly radioactive Cesium 137, Iodine 131, and Strontium 90 (because they are no longer contained in the fuel assemblies but are coming directly into contact with the seawater which is then being vented to the air).  If there has only been slight core damage then the releases will probably not be huge immediate danger. If the core damage is significant, then the releases may pose an immediate short term public safety threat and will  certainly pose a long term threat to the environment and public health.

And the experts are misleading the public on what happens if there is a core meltdown. It is well known in the nuclear industry that the early GE Mark I boiling water reactors have a deficient containment system. They don’t have the familiar very large and robust reinforced concrete dome containments that are common at most reactors in the U.S. In fact the Mark I primary containment is basically a heavy steel tank with a water filled donut (suppression pool) at the bottom. The secondary containment is the cube you see in the Japanese plants that have already been destroyed by hydrogen explosions on 2 of the 4 reactors. As early as 1971, the NRC was aware of this. There own scientists estimated that in the event of a total core meltdown the Mark I containment was likely to fail.

There is approximately 100-200 tons of enriched uranium fuel (depending on the power rating) in these reactors. If there is a complete core meltdown, the molten core will pool at the bottom of the reactor vessel. If bleed and feed of the containment vessel is the only cooling being done, that will likely not be able to prevent the core  from breaching the reactor vessel. And it is unlikely to prevent it from breaching the containment vessel. If it breaches containment it will continue melting into the earth. This is the so-called China Syndrome. It won’t reach China, it will melt downwards until it reaches the water table… at which point a steam explosion (probably a series of them) will occur that will blow apart the core and disperse huge amounts of radioactivity into the environment.  Then you are talking a Chernobyl like scenario.

Update: Apparently, in at least one of the reactors it looks like there has been at least some kind of breach of the reactor pressure vessel because high pressure, steam and radioactivity have been detected in the suppression pool that is part of the primary containment.

Further Update: One thing I omitted in the previous discussion. What is causing the explosions? Uranium fuel assemblies are coated (clad) with a coating of zirconium (it’s rare-earth metal). It’s this metal zirconium skin that under normal operating conditions keeps the fission products contained within the fuel assemblies and prevents them from entering the cooling water surrounding the core. Under conditions of high heat zirconium reacts with water to become zirconium oxide. Essentially it’s accelerated rusting. The hot zirconium steals oxygen from water and releases the hydrogen. When that hydrogen is vented out of the reactor pressure vessel and comes into contact with oxygen it forms a highly unstable and explosive mixture. This is what is causing the hydrogen explosions. Up till now the explosions have occurred outside of the reactor pressure vessels and primary containment because there is no free oxygen inside of them. However, if they are unable to reduce the pressure and temperature inside the cores, it is only a matter of time until a breach occurs, oxygen enters and a hydrogen explosion occurs inside the core/primary containment.  Then all hell breaks loose. This is what happened at Chernobyl. The reactor got out of control, went to extremely high temperatures, hydrogen formed, came into contact with oxygen, exploded, literally blew the top off of the reactor and immediately expelled about ¼ of core.  The difference between Chernobyl and Fukushima is that Chernobyl was a very old style of reactor called a graphite pile. Essentially it was huge block of graphite with a uranium core at the center. When the core exploded the graphite caught fire as well and the smoke and heat from the graphite fire spread the radiation much more rapidly and completely than it might have spread otherwise. The radiation levels in the vicinity of Chernobyl were so high that the site had to be abandoned (it is still a wasteland) and even air force helicopter pilots that lingered over the site only long enough to dump loads of boron-laced concrete on the damaged reactor suffered severe radiation sickness.

Now an additional complication and one far more immediately dangerous has occurred with Reactor 4 which wasn’t even operating at the time of earthquake. Because there is no long term repository for nuclear waste, all Japanese and American reactor plants store their spent fuel assemblies onsite in what are basically swimming pools. Even though the fuel is spent, it is still highly radioactive. (In fact, it is millions of times more radioactive than new fuel because of the build-up of fission fragments in the fuel assemblies.)  The spent fuel still generates enormous amounts of heat for years after being removed from the reactor.  Apparently, the spent fuel storage facility for Reactor 4 in the Fukushima facility, lost its cooling. The water evaporated, the fuel assemblies became partially uncovered, hydrogen formed, another explosion and fire occurred.  This situation is far more dangerous  because these fuel assemblies are NOT inside the reactor pressure vessel or inside the primary containment vessel.  They were in a secondary containment building that exploded and is now apparently on fire. That spent fuel is now exposed to the environment and releasing intense amounts of radiation inside and outside the plant.

On reactors 1,2, and 3 they were  using jury rigged fired hoses manned by humans to try and keep the cores covered via the aforementioned “bleed and feed” method. But, I believe the high radiation levels will force them to abandon that effort. I’d expect that to happen soon because working there is now essentially a self-sacrifice. Abandoning the plant will essentially be the end. The automation is down. The cooling systems were likely damaged beyond repair in the explosions. Even, if power were restored now, it’s probably too late. The radiation is too high to re-man the plant. If they did, the cores are probably so damaged now, they no longer capable of being cooled by conventional means in any case.

So, anything you hear now, about it being unlikely that there will be a major radiation release from this plant is pure bullshit. It’s over. The battle has been lost. This is a major, major disaster. Will it be as bad as Chernobyl? I don’t know. Nobody does. Anybody that says otherwise is a liar, a fool or a charlatan. I hope I’m wrong. I would love to be wrong… but I don’t think so.