Japan Nuclear Coverage

[JimC]

From today's Age: http://www.theage.com.au/world/radioact ... 1bt0w.html

Radioactive releases range from benign to dangerous William Broad
March 14, 2011

THE radioactive materials reported at the nuclear accidents in Japan range from relatively safe to extremely worrisome.

The central problem in assessing the degree of danger is that the amounts of various radioactive releases into the environment are now unknown, as are the winds and other atmospheric factors that determine how radioactivity will disperse around the stricken plants.

Still, the properties of the materials and their typical interactions with the human body give some indication of the threat.

In the types of reactors involved, water is used to cool the reactor core and produce steam to turn the turbines that make electricity. The water contains two of the least dangerous radioactive materials now in the news - radioactive nitrogen and tritium. Normal plant operations produce both of them in the cooling water, and they are even released routinely in small amounts into the environment, usually through tall chimneys.

Nitrogen is the most common gas in the Earth's atmosphere, and at a nuclear plant the main radioactive form is known as nitrogen-16. It is made when speeding neutrons from the reactor's core hit oxygen in the surrounding cooling water. This radioactive form of nitrogen does not occur in nature.

The danger of nitrogen-16 is an issue only for plant workers and operators because its half-life is only seven seconds. A half-life is the time it takes half the atoms of a radioactive substance to disintegrate. The other form of radioactive material often found in the cooling water of a nuclear reactor is tritium.

It is a naturally occurring radioactive form of hydrogen, known as heavy hydrogen. It is found in trace amounts in groundwater throughout the world. Tritium emits a weak form of radiation that does not travel very far in the air and cannot penetrate the skin.

It accumulates in the cooling water of nuclear reactors and is often vented in small amounts to the environment. Its half-life is 12 years.

The big worries on the reported radiation releases in Japan centre on radioactive iodine and caesium.

The active core of a nuclear reactor splits atoms in two to produce bursts of energy and, as a byproduct, large masses of highly radioactive particles. The many safety mechanisms of a nuclear plant focus mainly on keeping these so-called fission products out of the environment. Iodine-131 has a half-life of eight days and is quite dangerous to human health.

Fortunately, an easy form of protection is potassium iodide, a simple compound typically added to table salt.

If ingested promptly after a nuclear accident, potassium iodide, in concentrated form, can help reduce the dose of radiation to the thyroid.

Over the long term, the big threat to human health is caesium-137, which has a half-life of 30 years. At that rate of disintegration, John Emsley wrote in the book Nature's Building Blocks, ''it takes over 200 years to reduce it to 1 per cent of its former level''.

Caesium-137 mixes easily with water and is chemically similar to potassium. It thus mimics how potassium gets metabolised in the body and can enter through many foods, including milk

[klr]

On a note of irony, my Year 11 Physics class have an important assessment task this Tuesday.

They are to write an essay on the advantages and disadvantages of generating power from nuclear reactors. I think there is another paragraph or two that they can add at this point...

Jim, show them this picture. Ask them what the significance of the valley to the left is.



(Clue: It's a fault line. San Onofre Nuclear Power Generating Station, just south of LA.)

The fact that it's also slap bang on the coastline might now also be giving people more food for thought. A collapsing volcanic island in (say) the Hawaiian archipelago could generate a serious Tsunami wave ...

[Feck]

http://morgsatlarge.wordpress.com/2011/ ... -reactors/

[JimC]

http://morgsatlarge.wordpress.com/2011/ ... -reactors/

Good link, Feck.

Seemed to make a fair bit of sense, although I sensed that he was leaning as far as he could to a "no problems" reassuring scenario. It is not a catastrophic release, but there are still some serious deficiencies in the emergency cooling plans; it will be difficult for the industry to convince the Japanese public, and much of the world, that it it can manage events in the future...

[Gawdzilla Sama]

[youtube]http://www.youtube.com/watch?v=95zMdTvo ... ded#at=241[/youtube]

[.Morticia.]

[youtube]http://www.youtube.com/watch?v=95zMdTvo ... ded#at=241[/youtube]

a comet, a teensy weensy comet

Is she serious?

[Gawdzilla Sama]

No. She's bat-shit crazy.

[klr]

No. She's bat-shit crazy.

Certifiably so, it would seem.

[egbert]

Why the fuck were the emergency generators not placed ON TOP of the containment building, or high enough so they could not be inundated by a tsunami?

Because - the containment building is secondary containment - if the primary containment, the reactor vessel, is breached, then radioactivity will be released into the containment building, and it will likely not be approachable because of high radiation fields (gamma) emanating from it. Thus, an emergency generator on its roof would also be unapproachable, and maintenance or repairs would be impossible, unless you could find martyrs.

[FBM]

Another nuke plant go boom.

[Feck]

Why the fuck were the emergency generators not placed ON TOP of the containment building, or high enough so they could not be inundated by a tsunami?

Because - the containment building is secondary containment - if the primary containment, the reactor vessel, is breached, then radioactivity will be released into the containment building, and it will likely not be approachable because of high radiation fields (gamma) emanating from it. Thus, an emergency generator on its roof would also be unapproachable, and maintenance or repairs would be impossible, unless you could find martyrs.

or in the case of Japan Koreans

[Seth]

Why the fuck were the emergency generators not placed ON TOP of the containment building, or high enough so they could not be inundated by a tsunami?

Because - the containment building is secondary containment - if the primary containment, the reactor vessel, is breached, then radioactivity will be released into the containment building, and it will likely not be approachable because of high radiation fields (gamma) emanating from it. Thus, an emergency generator on its roof would also be unapproachable, and maintenance or repairs would be impossible, unless you could find martyrs.

or in the case of Japan Koreans

Well, having a backup generator that can be remotely controlled that has a short-term fuel supply that can keep the system running for, say, a week that's actually INSIDE the containment structure, where it can be wired directly to the control systems and pumps and operates automatically any time the external power fails would prevent the "facility blackout" situation mentioned in the SA article. The idea is to prevent a meltdown. But if a meltdown happens, who gives a fuck what happens to the equipment inside the containment, it's all going to be radioactive forever anyway.

Each reactor should have it's own triply-redundant electric backup system for the pumps and controls consisting of a UPS system capable of running the entire reactor system for, say 48 hours, and a backup diesel generator that can run it for a week after that, that backs up the utility mains and the EXTERNAL backup generators located above the potential tsunami surge level.

There is simply no excuse whatsoever for creating a nuclear reactor that will melt down as the result of a power failure, ever. This should not be a "maximum credible event" analysis, it should be a "300 percent zero-defect, zero-fail redundancy fail-safe system" analysis, and it should cost whatever it costs to make it possible to scram the reactor and cool it down properly if aliens used an anti-gravity beam to rip the containment building from the ground and set it down in the middle of Tokyo. There should simply be no chance whatsoever that the cooling system can be shut down by an electrical failure. Period.

[FBM]

Why the fuck were the emergency generators not placed ON TOP of the containment building, or high enough so they could not be inundated by a tsunami?

Because - the containment building is secondary containment - if the primary containment, the reactor vessel, is breached, then radioactivity will be released into the containment building, and it will likely not be approachable because of high radiation fields (gamma) emanating from it. Thus, an emergency generator on its roof would also be unapproachable, and maintenance or repairs would be impossible, unless you could find martyrs.

or in the case of Japan Koreans

I see somebody here knows his history...

[JimC]

Another nuke plant go boom.

Looked just like the last, and they're saying on TV it was another hydrogen explosion in the outer space of the building after a build up of hydrogen via thermal decomposition. More release of tritium and a radioisotope of nitrogen, but they are very short-lived...

By now, the rate of heat production should have gone down a fair bit as the shorter-lived fission products decay. Should be easier to keep the cores from overheating from now on...

Stocks in Uranium mining companies in Oz went down a bit today...

[FBM]

This morning, they reported a state of emergency at a plant further north along the coast. Sounded like the same problems that led up to the first two.

By the way, Japan is calling it a 9.0.