Saturday, March 12, 2011

Fukushima Nuclear Power Station information (following earthquake)

reactorIntroduction
All our wishes go out to friends and strangers alike in Japan, in light of the terrible events of the last two days. I am preparing this article to provide information on the status of the nuclear power facilities in the Sendai region. I am doing so to counter inflammatory and irresponsible misinformation I have encountered in various forums and social networks of which I am a part (e.g. statements that a "nuclear explosion" has occurred).

For the record I am resolutely anti-nuclear for three main reasons: a) it incontrovertibly leads to the proliferation of materials for nuclear weapons, b) it produces extremely hazardous waste that we will never be able to clean up, c) is not economically viable if one considers the true costs of the reactors, infrastructure, storage, clean-up and other costs. But in this article I am not here to preach but rather accumulate basic facts. I mention this only in case some more rabid elements assume I am pro-nuke.

Background
There are two power stations directly affected by this natural disaster, both located in Futaba District, Fukushima Prefecture, Japan. Fukushima Dai-ichi Nuclear Power Station (aka Fukushima I) has six reactors (784 MW except Unit 1 at 460 MW), of which units 1-4 were running on 11 March 2011. (Units 5-6 were shut down for regular maintenance.) Fukushima Daini Nuclear Power Station (aka Fukushima II) has four reactors of 1100 MW each. Each are old-style reactor systems using a simple steam conduction principle. The nuclear reaction produces intense heat with converts water liquid to vapour (steam), which then drives turbines for electricity. Fukushima I Unit 1, the oldest, had been operational since 1971.

The earthquake ID usc0001xgp, magnitude 8.9, occurred at 14:46:23 local time, on 11 March 2011 centred about 130 km east of Sendai, Honshu. Nine minutes later a tsunami warning was sent out from the Pacific Tsunami Warning Center. Since the wave front was reported (where?) as travelling at a speed of 10 km per minute or greater, this would have meant the warning would have been received onshore at most four minutes before the wave impacted.

Despite this, it now appears that those on the coast of Sendai had advance warning by way of sirens and announcements through public address speakers. The Japanese are well trained for earthquakes and knew to move to higher ground, even without such announcements. However, no-one expected a wave of up to ten metres in height and reports now indicate that many simply could not evacuate fast enough. The largely low-lying ground meant that water travelled up to 10km inland, depending on the lie of the land.

Consequences
This earthquake broke the mains electricity connection and triggered automatic shut-down procedures at Fukishima I at 14:48. This involves full insertion of control rods into the material in the core. This prevents further nuclear reactions at which time the reactor is said to be "subcritical". The main steam isolation valves are closed, so that there is no longer a direct connection from the reactor core to the outside world. (In any case, I believe there is no direct connection in this design, since there is an intermediary circuit of water.)

It then takes some time for the reactor to cool down (on the order of days) during which time cool water must be pumped into the core. Due to flooding caused by the tsunami, the generators supplying power to these pumps failed (either for a period or entirely -- information is unclear). As a third system, batteries would be brought online, but these last only for a short period. What is required in the longer term is either: a continuing supply of charged batteries, working diesel generators, or restoration of the power grid. In this regard, news reports of the US Army flying in "coolant" was misinformation, unless there was some reason for them to fly in water when there was plenty at hand. It might instead be presumed they were arriving with more fuel for the generators or more batteries.

Issues with getting enough coolant into the cores meant that temperatures in the suppression chambers exceeded 100 degrees in the various units. It was thus deemed necessary to release pressurised air, in order to cool the buildings. This air would contain radiation in terms of Nitrogen 14. Before the venting occurred, residents were evacuated from an area 3km in radius. This would be to avoid them breathing in radiation that, though low in itself, might cause long-term health issues.

Following this, on-site radiation stations (at the perimeter of each plant) read high enough to trigger the report of an "incident" under Article 15, Clause 1 of the Act on Special Measures Concerning Nuclear Emergency Preparedness.

At Dai-ichi a further earthquake (140 such with magnitudes up to 6.2 occurred in the period after the main quake according to the U.S. Geological Survey) caused an explosion at Unit 1 at 15:36, as widely reported in the media. Four workers were injured. Furthermore, following an earlier accident (likely the initial earthquake) a tower crane operator working in the exhaust stack was confirmed dead at 17:17. The radiation "incident" was reported at 16:17. The evacuation zone was increased from 10km to 20km at 19:11.

At Daini the radiation "incident" was reported at 15:29. The government set the evacuation zone at 3km by 17:00 and 10km at 19:00. Unit 1 was first cooled by isolation condenser, followed by sea water at 20:20pm, and then boric acid subsequently. Units 2 and 3 are being cooled by water. This indicates a more serious problem with cooling in Unit 1. Three workers were injured on-site. An employee working in Unit 1 was irradiated at 106.3mSv, enough to require decontamination procedures.

Severity
What concerns everyone is how much radiation has been let loose into the general environment as a result of the drastic measures taken to cool the multiple reactors. The Kyodo news service reports that radiation is 8x normal outside the plant, 100x normal in the control room and 1000x normal in the containment area. Evacuees are now being scanned for radiation.

The System for Prediction of Environment Emergency Dose Information (SPEEDI) is not showing figures for those power plants nor two others in the north of Japan. Rather than read any conspiracy theory into this, I suggest it is simply due to lines being down.

The International Atomic Energy Agency has established the International Nuclear and Radiological Event Scale (INES) in order to rate the severity of any nuclear mishap. Reuters has reported the current accident is rated a 4, Accident With Local Consequences. For reference, Three Mile Island was a 5, and Chernobyl was a 7. But these are only general categories and do not tell us much.

Sources
Besides those sources already linked, I have used the Tokyo Electric Power Company (TEPCO) bulletins, which seem to me remarkably frank and timely. My general information comes from the BBC, Reuters, Sky News, etc. though I remain entirely sceptical of mainstream media.

I will update this article with missing information and developments only for a short while.

Update: The TEPCO site is off-line, likely swamped with requests.

Update: Nitrogen 14 is indeed a component of the vented steam, but as this is not radioactive I am not sure why the steam has been labelled as such.

Update: Coastal areas had some (not much) time to evacuate so I have added further info to my description.

Update: As of 13 March the automated cooling system at Dai-ichi Reactor 3 has failed. Pressure has been reduced by manually opening the safety valve, injecting sea water and boric acid as in Reactor 1 previously. It can be assumed that there is now a risk of the building exploding as did Reactor 1, due to accumulated Hydrogen.

Update: I mention in the body of the article that an earthquake caused the explosion of the Reactor 1 building shell, since this is what TEPCO reported. I wish to clarify this matter. What exploded was Hydrogen gas, created when the shells of the cooling rods melt. The presence of such is indicative of a serious problem with cooling. It could well be that an earthquake triggered the explosion, since the Hydrogen has to mix with something (Oxygen, say) to become flammable.

Update: The use of sea water indicates a serious problem since the corrosive effects of this liquid means the reactor can never be used again. TEPCO is writing off these expensive installations in an attempt to forestall further problems.

Update: According to the Nuclear Information and Resource Service website, TEPCO has reported that six to ten feet of the core of Reactor 3 has been exposed for some time. The bulletin was dated 18:30 13 March but the time of the announcement is not stated.

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15 comments:

robin said...

Every technology creates also the corresponding accident scenario. In the case of nuclear power these are horrible indeed. Hype does not help further understanding, but instead only polarises opinion further. Rational analysis should convince anyone of the need for safer energy alternatives.

robin said...
This comment has been removed by the author.
robin said...

The whole purpose of a nuclear reactor is to sustain nuclear fission in a controlled reaction. A large enough density of radioactive material needs to be brought together to commence fission but not so much that an uncontrolled chain reaction occurs. The core of the reactor is composed of rods of enriched uranium in a grid, with control rods available in another grid that offsets this. All around is water, which heats very quickly due to the radiation. In normal operation this water is pumped through rapidly and the resulting steam is used to generate power.

To shut down the reactor, the control rods are fully inserted to dampen the nuclear reaction. The fissionable material then needs time to cool off, and this is aided by continuing the flows of cool water. In the case of Fukushima the first process went without hitch but the second process has been threatened by power loss and possible structural damage.

Radiation is always a product of a nuclear reaction, but that term covers a wide range of products created by the nuclei. This is why it is meaningless to talk of "radiation leaks" without pinpointing what product one is talking about. There are two main categories: electromagnetic and particulate. Electromagnetic radiation (gamma ray, X-ray) is the same form as a radio wave, only with much higher energy. Particle radiation (alpha particles, beta particles, neutrons) are called ionising radiation since they are capable of producing ions when they pass through other matter.

"Nuclear meltdown" is a term that produces a lot of emotional reactions. But scientists use this to describe any occasion when the reactor core overheats to the point of damaging the reactor apparatus itself. Of course this is highly undesirable, but does not necessarily mean a "disaster" in the China Syndrome sense. (Except to the owner of the power plant, since the reactor would likely be a write-off.)

So the key questions become:
1. How much and of which type is the radiation that has escaped from the reactors?
2. What is the possibility of a meltdown (if one has not occurred) and what is the severity of the meltdown (once it has)?

And furthermore:
3. Are the correct steps being taken to ensure public safety in light of 1. and 2.?

robin said...

Note that I am making certain simplifications. For one, the water around the core does not, in normal operation, convert to steam. It is kept under pressure and so stays liquid, but gets very hot. This super-hot water then heats a second circuit of water that is allowed to vaporise. If the water around the core vaporises it can no longer act as a medium to inhibit neutron flow. This is a potentially disastrous eventuality which may have happened at Reactor 1, though not before the control rods were in place.

robin said...

Uranium 235 is the fissile material in nuclear reactors. When bombarded with a neutron, each nucleus creates two more neutrons (thus leading to a chain reaction if some are not otherwise captured) and four possible radioactive by-products. These will decay in turn, either into stable atoms or further radioactive atoms. The half-life is the amount of time that must pass for half the amount of the original material to decay. After ten half-lives the substance is generally considered "safe". Half-lives vary from fractions of seconds to hundreds of thousands of years; nuclear "waste" is a long-term, some would say insoluble, problem.

Normally the heavy waste material is contained in the fuel rods.But in the event of a reactor core breach, various elements can be let loose into the general environment, with various ill effects. These occur for several reasons. First, high-energy waves can instantly destroy cells they come into contact with. With lymphocytes reduced, one is vulnerable to normal infections. Nerve cells do not regenerate and their loss can be significant. And so on. Even in smaller doses, cancers and other long-term problems are increased significantly.

The most dangerous isotopes are those which appear to our body like a benign substance that we need. The isotope binds to receptors in place of that useful substance. When the unstable isotope decays, it does so in close proximity to healthy cells and so causes the most damage. We are relatively protected from decays in the environment around us, but entirely vulnerable when these happen within our body.

robin said...

So what are these dangerous by-products? Three are most important.

Iodine-131 is quickly concentrated in the thyroid, where it causes cancers or functional problems (depending on dose -- higher does can strangely be less dangerous than low doses). A common preventative measure is to take potassium iodide in an attempt to fill all the possible receptors with "good iodine" before the radioactive variation can infiltrate. This explains the Iodine pills being distributed in Japan. With a half-life of 8 days the threat from I-131 is short-term but very real.

Cesium-137 is absorbed by plants and then moves through the food-chain (when cattle eat grass, for example) to humans. With a half-life of 29 years this is a long-term problem that can be alleviated by removing contaminated soil and other methods. We are particularly vulnerable since 100% of C-137 is absorbed through our gastro-intestinal tract (whereas other isotopes are generally not absorbed or might be only minimally). C-137 is the primary long-term contaminant from the Chernobyl disaster.

Strontium-90, with a half-life of 28.8 years, binds in our bodies in place of Calcium. One famous study found that babies born after 1963, when large-scale atomic testing became the norm, had 50 times the level of S-90 in their teeth. Even twice the amount has been shown to greatly increase early death by cancer.

robin said...

*higher doses

robin said...

How do we measure radiation amounts? The sievert (Sv) measures the actual biological toxicity of radiation, which varies depending on the organ affected and the type of radiation. Because it attempts to take these into account, it is said to measure "dose equivalent". Practical amounts are measured in millisievert (mSv), of which there are a thousand in an Sv, and microsievert (µSv), of which there are a million in an Sv. As a baseline reference, the natural background radiation varies at different places on the Earth, but averages about 2.4 mSv per year, or .27 µSv per hour.

How much radiation is safe? According to the US Nuclear Regulatory Commission, the Annual Limit on Intake (ALI) is set at 50 mSv per year, roughly 20 times the background radiation. Canada follows the International Commission on Radiological Protection (ICRP) and limits Nuclear Energy Workers to 100 mSv over 5 years. General members of the public are limited to 1 mSv per year, which is actually below the background radiation level!

Routine or special procedure medical X-rays add significantly to your radiation intake. These vary widely from 5 µSV for a dental X-ray to 7 mSv for a chest CT and 15 mSV for a CT of the abdomen and pelvis. Thus you can get several times your usual annual radiation intake in one visit to the doctor. However, these amounts are still considered insignificant in relationship to the 1 in 5 chance we have of dying from cancer. (Reference: Radiology Info.)

How does this compare to the radiation emitted from Fukushima following the earthquake? Kyodo reported that Fukushima Dai-ichi peaked at 1,557 µSv per hour at 13:52 13 March, but this rate went down to 184 µSv/h about 50 minutes later. If one took in the maximum rate for one hour this would be equivalent to a spinal X-ray, said to increase your risk of a fatal cancer by a chance of 1 in 100,000 to 1 in 10,000.

From this we can say with some certainty that acceptable radiation limits are placed very conservatively by the regulatory bodies. The fact that these might be exceeded in this accident even by large factors should not necessarily be a cause for concern, so long as the time-frames of exposure are short.

robin said...

Corrections:
Strontium-90 is abbreviated Sr-90
Cesium-137 is of course Cs-137

robin said...

Here is a detailed document on the Boiling Water type reactors. Fukushima Dai-ichi Reactor 1 is the oldest and crudest type. In fact it was scheduled to be de-activated permanently later this very month!

robin said...

Cs-137 and I-131 have been released from the plant. This is a sure sign that a nuclear meltdown has in fact occurred to some degree... though please read above to realise that is not the end of the world.

It is however a great deal more than many websites will tell you. In my research I am discovering that the pro-nuke lobby controls large amounts of the internet reporting that takes place on blogs and supposedly independent websites. that is not surprising since many owe their jobs to the nuclear industry, which has a very deep purse indeed.

The following sites are definitely propaganda machines. Read their info with care:
http://www.world-nuclear-news.org
http://bravenewclimate.com
http://ansnuclearcafe.org
http://morgsatlarge.wordpress.com

robin said...

Source for above from Nikkei.

robin said...

This story is not going to let me sleep!

A new explosion, this time at Reactor 3, has taken place, at 02:21 14 March local time. Some reports say two explosions. Initial word is that these are hydrogen blasts as before at Reactor 1. TEPCO states the core is not damaged by these. How they would know is beyond me.

robin said...

I believe this will be the last update I will write on events as they unfold. Instead I will concentrate on explanatory articles if the need continues.

BBC and other media report mediating water in Reactor 2 is now low, indicating it may be next in line for serious cooling problems. Airborne radiation has been detected 60 miles away from the plants. The US Navy offshore have also detected unusual radiation amounts. And the seawater flushed through the reactors will also inevitably carry radiation into the ocean.

Though not catastrophic in themselves, this series of accidents has and will continue to increase the local, regional and global radiation levels. In this way it is just like all other activities (bomb tests, waste disposal, etc.) related to the nuclear industry. The Fukushima incidents should be seen as indicative of the true damage we do to the environment every single day through nuclear power. The vast amounts of money invested in such technologies and installations should be diverted to less poisonous energy sources.

robin said...

Yet another explosion (the third) and radiation levels up dramatically, peaking at 8217 µSv per hour and steadily putting out a third of that. This is many times higher than the previous amount.

It is obvious now that there is a partial meltdown at Fukushima Dai-ichi and that containment has also, at least in part, failed. I am very sad for the people evacuated from the region, who might now never return home.

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