We are now over 3 months into the Fukushima accident, progress is creeping along at a steady pace. Since our last update there has been lots and lots of new and I won't try to cover it all. The biggest news I want to share now is that TEPCO has gotten some kind of recirculation cooling working, it was reported today by Will Davis at Atomic Power Review(by far the best blog to keep an eye on for Fukushima news, I highly recommend to read it).
In short water is leaking out of the containment buildings into the turbine buildings, the water is pumped from the turbine buildings into the water treatment facility, then from there its pumped back into the reactor. Its like I described in the last update on may 18th (shown on the picture below) and one of the steps in the plan TEPCO released that month.
If everything goes well now the volumes of contaminated water will start to creep down, a proper toast is in order!
Another fairly recent news is that NRC announced that the spent fuel pools in Fukushima never went dry. That really calls into question Chairman Jaszco's recommendation for a larger evacuation zone for american citizens in Japan than what the Japanese authorities had decided.
There has also been a lot of bullshit flying around about the situation in Fort Calhoun due to the river flooding around the nuclear power plant. Claims about goverment cover ups, Russian authorities warning about disaster etc. I haven't bothered to look more in detail into it yet, but so far the reactor has both working diesels and connection to the external grid and quite a bit of margin before the river even comes near to flood over the flood protections. Here is a good post by Neutron Economy about the situation.
TEPCO has released a video that shows work being done at the Fukushima plant. Very interesting to watch.
One gets a real sense for the devastation the tsunami inflicted while watching that clip.
TEPCO also recently released this PDF file that gives an overview of work being done. I will add some pictures from it:
In the above picture one can see how they plan to rig up the new heat exchangers for reactor 1. Within the reactor building, but outside the containment, they will put a water to water heat exchanger. They will pump water from within the containment through this heat exchanger, where it transfers the heat to a secondary circuit that in turn flows to a heat exchanger outside of the reactor building that dumps the heat to the air. This is the original plan TEPCO had before they realized the full extend of the damage to the number 1 core and containment, so it is not sure they will progress as described. But the secondary heat exchanger and its piping is already being built.
Tepco also shows the above picture on how they plan to reuse leaking water from the containment as cooling for the reactor. It is not clear how the two plans are connected to each other. I would assume the second plan is the one that is going to be used instead of the first plan. Instead of taking water directly out of the containment they will use the existing leakage paths, purify the water and pump it back into the reactor.
For the number 2 reactor shown above the main problem is to stop the leakage from the suppression pool. They plan to excavate the reactor building in order to access the room where the suppression pool is housed and then fill the entire volume with grout. Considering that (probably) the suppression pool is leaking at number one as well then maby this plan will be implemented there as well (just my speculation).
Both in unit 2 and 3 are they planning to reuse the leaking water in the same manner as in unit 1.
In the rest of the document they give some basic information on how they plan to clean the massive amounts of contaminated water that exists on the site, some details on the protective building they want to build around the reactors and how to prevent more contamination of soil, water etc. Well worth scrolling through, massive work is certainly ongoing at the site and it seems TEPCO has a solid plan that they are implementing. Of course more surprises will without a doubt pop up during work, but it looks promising. We are still waiting for more in depth information on the situation of the number 2 and 3 reactors.
During the last days a lot of news has been released by TEPCO. TEPCO has released this presentation that gives more details of the events that took place in the number 1 reactor from the beginning of the earthquake up until now. To summarize the content of the presentation.
The water level gauge has been giving wrong readings, the reading has been stating that the water level is about 1.7 meters below the top of the fuel assemblies. In reality the water level has been 8 meters below the top of the fuel assemblies, this means the entire length of the fuel has been uncovered completely.
16 hours after the earthquake the entire core had suffered a meltdown and all of it dropped down to the lower part of the pressure vessel.
The temperature readings on the vessel indicate that the core is still mostly within the vessel and adequately cooled.
Some parts of the core is suspected to have melted small holes in the bottom of the containment, which explains why they could not increase water level despite increasing pump rate.
They don't mention the reading of the pressure gauge that indicates the vessel pressure is about 14 atmospheres. I was personally fooled by this reading and assumed the number 1 vessel is in better shape than the number 2 and 3 reactors. The question is what readings can be trusted at all.
Due to this new information on the status of the reactor TEPCO has decided to scrap the original plan to flood the containment up to the level of the fuel assemblies. Since all the fuel is now located at the bottom of the vessel there is no need to flood the containment that high. The containment is also confirmed to be breached and water leaking out of the it like in the case with reactor number 2.
Another theory for the explosion in the number 4 reactor building has appeared. The videos from the pool show that it is largely intact and no major fuel damage can be seen. That means it seems unlikely hydrogen from a zircalloy+water reaction in the spent fuel pool can be the cause of the explosion. Instead TEPCO now believes hydrogen leaked into the number 4 building from a shared ventilation system with the number 3 reactor.
TEPCO is going to do more complete analysis of the status of reactor 2 and 3 and the information will be released within days. It will be interesting to see if the RCIC system (see this blog post for a description of the system) worked in the other 2 reactors and, if it did, to what extent it mitigated the consequences of the station blackout.
Work is progressing on all fronts to build a enclosure around the number 1 reactor, to build a water processing plant, create more redundancy in the electricity supply, clear the area of debris and to pump away the junk water from the turbine halls and trenches. IAEA as usual reports the release of radioactive material and dose rates.
The Fukushima accident has unfortunately seen its first death with a 60 year old worker that lost consciousness while working on a drainage system to the radioactive waste storage. He was brought to a hospital but could not be revived. So far there is no report that the death was related to radiation.
Another week has passed and more steps have been taken to get the situation under control. Lets start with the usual reactor status table made out of NISA data:
Water level (meter)*
Core pressure (kPa)
Containment pressure (kPa)
Wetwell pressure (kPa)
Feedwater nozzle temp (Celsius)
Bottom head temp (Celsius)
Wetwell temperature (Celsius)
Containment dose rate (Sv/hour)
Wetwell dose rate (Sv/hour)
*Distance from top of assembly
- broken gauges or missing data
Everything looks pretty stable except the wetwell dose rater in the number 2 reactor. It has increased to well over 100 Sv/hour from 37.1 in the last update I made (i wrongly wrote 0.371). I haven't been able to follow the news so closely the last week so I have not seen if this has been mentioned in any TEPCO press release. Below is a graph of the increase. If anyone know of any action done on the number 2 reactor, starting the 3 or 4th of may please write a comment to this blog post.
A air filtration system has been connected to the reactor building of reactor number 1. The purpose of it is to get airflow through the building and clean out the air activity by filtrating the air. It is hoped that it will be enough to allow workers to enter the building and work safely without getting to much dose.
Kyodo reports that TEPCO plans to send in workers on monday in order to measure dose rates within the building. Seems strange that they would send in people when they have already used robots once for that purpose.
A longer video clip of the number 4 spent fuel pool can be seen over at Atomic Power Review. It doesn't appear to be very damaged.
The big news of the week is that the prime minister of Japan has asked Chubu electric to shut down its Hamaoka nuclear power plant. Hamaoka has 3 operational nuclear power plants, all of them quite new. Started at 1987, 1993 and 2004. The newest one is a ABWR and would presumably have state of the art eartquake protection. The reason for the prime ministers request is a estimate that the site has a high probability to be hit by a 8.0 earthquake within 30 years. If the reactors indeed can not handle such a quake then the closure request is rational. But it does smell a bit like political posturing at this point. There is no legal precedence for such a situation and it is not clear if Chubu electric has to obey the request.
Just a short update for today. The number 2 turbine building basement is filling up with water as quickly as TEPCO is pumping it out. No word is said about how the similar work in number 1 and 3 is proceeding. Temperatures are on a downwards trend in all reactors. Pressure in the number 1 pressure vessel continues to climb slowly, containment pressures are stable. Not much new happening on that front.
The Japanese Nuclear Society has reported that their analysis shows that parts of the fuel of all 3 reactors has melted and dropped down to the bottom of the vessels. Small parts of molten fuel has according to their analysis dropped from the rods, solidified when hitting the water and then sunk to the bottom forming small grains. The grains are easily cooled since they have large surface area to volume ratio and they don't form a geometry that is prone to re-criticality.
They also state it is unlikely that there is a large amount of molten fuel at the bottom due to the low temperature readings in the bottom head. Nothing really surprising there either and I pointed it out some time ago. None of this is really surprising.
Zeolite containing sandbags have been put outside the water intake for the number 2 reactors. Zeolite is a porous material that readily adsorbs different molecules (adsorbption is the process of molecules sticking to the surface layers of a material, as opposed to absorption that means its sucked into the material itself). It was used to clean contaminated water within the TMI power planet after the meltdown there.
TEPCO has ordered storage tanks from the US to use to store radioactive water in. IMO I think TEPCO is trying to do perfect when perhaps they should think about doing things adequate. It seems like the volume of water is so large that temporary solutions, like erecting temporary pools, should be considered. But then again it is always easy to be an armchair quarterback on opposite side of the Eurasian continent (other seems to share my general idea though). I haven't seen any new published analysis of the radionuclide content of the water in the number 2 basement, it would be interesting to see what it contains. The dose rates from the water should be going down due to the I-131 decay. Over 95% of the I-131 has decayed now.
Nitrogen injection into the number 1 containment continues, but pressure in the containment has stabilized. Meaning there must be a leakage somewhere. The leakage can't be very large however.
Gamma dose rates are measured daily in all 47 prefectures. The values tend to decrease over time. For Fukushima, on 13 April a dose rate of 2.0 µSv/h was reported. In the Ibaraki prefecture, a gamma dose rate of 0.14 µSv/h was reported. The gamma dose rates in all other prefectures were below 0.1 µSv/h.
Dose rates are also reported specifically for the Eastern part of the Fukushima prefecture, for distances beyond 30 km from Fukushima-Daiichi. On 13 April, the values in this area ranged from 0.2 to 26 µSv/h.
In addition to the 7 measurements referred to in yesterday's brief, (note- these measurements were made at distances of 25 km and 33 km not 32 km and 62 km as reported), 13 more measurements were made on 12 April at distances of 25 to 33 km, West and Northwest from the Fukushima Nuclear Power Plant by the IAEA team. At these locations, the dose rates ranged from 0.5 to 16.5 µSv/h. At the same locations, results of beta-gamma contamination measurements ranged from 0.05 to 2.1 Megabecquerel/m2.
Analytical results related to food contamination were reported by the Japanese Ministry of Health, Labour and Welfare on 13 April that covered a total of 98 samples taken on 4 and 11 to 13 April. Analytical results for 76 of the samples of various vegetables, pork, seafood and unprocessed raw milk in nine prefectures (Chiba, Fukushima, Gunma, Ibaraki, Kanagawa, Miyagi, Niigata, Saitama and Yamagata) indicated that I-131, Cs-134 and/or Cs-137 were either not detected or were below the regulation values set by the Japanese authorities. In Fukushima prefecture on 11 April, twenty samples of various vegetables were above the regulation values set by the Japanese authorities for Cs-134/Cs-137, and one sample of seafood (sand lance) and one sample of spinach were above the regulation values set by the Japanese authorities for both I-131 and Cs-134/Cs-137.
New JAIF update for today, I will compare it with the NISA update from yesterday.
Water level in the core: 1.65 (1.60) meters below the top of fuel assemblies
Flow rate of injected water: 133 liter/minute
Core pressure: 612(592) kPa
Containment pressure: 210(230) kPa
Core temperature(feedwater nozzle): 251.2 (270.1) Celsius
Core temperature(bottom head): 130.2 Celsius
Dose rate within containment: 37.7 Sv/hour
Water level in the core: 1.5 (1.5) meters below the top of fuel assemblies
Flow rate of injected water: 133 liter/minute
Core pressure: unknown
Containment pressure: 110 (100) kPa
Core temperature(feedwater nozzle): 174.3 Celsius
Core temperature(bottom head): Unknown
Dose rate within containment: 39.6 Sv/hour
Spent fuel pool temperature: 48 Celsius
Water level in the core: 2.3 (2.25) meters below the top of fuel assemblies
Flow rate of injected water: 116 liters/minute
Core pressure: 121 (119) kPa
Containment pressure: 173 (164) kPa
Core temperature(feedwater nozzle): 75.3 Celsius (under review)
Core temperature(bottom head): 116.0 Celsius
Dose rate within containment: 26.8 Sv/hour
Status with the reactors are pretty much unchanged. Work is proceeding with pumping away junk water from turbine halls so one can repair the coolant pumps. Work is slow however due to lack of any place to put the radioactive water.
Based on measurements of I-131 and Cs-137 in soil, sampled from 18 to 26 March in 9 municipalities at distances of 25 to 58 km from the Fukushima Nuclear Power Plant, the total deposition of iodine-131 and cesium-137 has been calculated. The results indicate a pronounced spatial variability of the total deposition of iodine-131 and cesium-137. The average total deposition determined at these locations for iodine-131 range from 0.2 to 25 Megabecquerel per square metre and for cesium-137 from 0.02-3.7 Megabecquerel per square metre.
NISA has not released any new update today, JAIF has released one more update since this morning. I won't paste updated tables this time, but they can be seen in the link provided. There is no major changes to any reactor. Both number 2 and number 3 reactors are now getting their freshwater pumped with temporary electric pumps that have replaced the fire pumps used up untill now. In their latest written report they say that they have found highly contaminated water in a tunnel with pipes and cables connected to the turbine hall, the activity level is similar to the water found in the turbine hall basement and they are investigating the source of the water. They continue to se high levels of, among other things, I-131 in the seawater and suspect it is due to the contamination in the tunnel.
Kyodo reports that plutonium has been found in the soil outside the reactors. The source of the plutonium is unknown and the level is comparable to what was found in japan after the nuclear tests done by Russia and the US during the cold war. TEPCO has provided a report that gives the concentration as about 1 Bq/kg of soil of Pu-239 and less than 0.5 Bq/kg of soil of Pu-238. The levels are very low and one could practically eat tons of soil before ingesting getting a dangerous amount. There is 0.44 billionths of a gram of Pu-239 per kg of soil*, a lethal dose of plutonium-239 is half a gram. So one would have to eat more than one million metric tons of soil to get a lethal dose of the plutonium contained within the soil. That is how low the amount is (that also gives a good example how exceptionally low concentrations of radioactive materials can be detected).
NHK reports that the 3 exposed workers have been sent home and that they don't show any symptoms of radiation sickness.
It seems like the number 2 reactor is leaking quite significant amounts of radioactive water. It's not clear if it is coming through a breach in the containment or if it is through some of the pipes. If for instance the valves, closing the reactor from the pipes that are coming in through the containment, is leaking. The highly radioactive water is a big problem since it prevents access to the turbine halls and delays work to restore the reactors internal coolant pumps. They have found similar build ups of radioactive water in the number 1 and 3 reactors turbine halls, but not as strongly radioactive. Since it is a problem in all three reactors to some extent my bet would be that it is the valves that are leaking.
JAIF has released their update but not NISA. I will wait to write down the status of the reactors until the NISA update arrives and for now I just paste JAIF's tabels.
Kyodo reports that TEPCO measured the radionuclide content of the water in the turbine halls wrongly, they overestimated it by a factor of a hundred. Confirming our suspicion that they are measuring wrong. Kyodo also reports that the Nuclear Safety Comission states that there has been a partial meltdown in the number 2 reactor. I am a bit surprised by this statement because it has been quite clear since the first few days that there has been a partial meltdown.
The workers that where exposed to radiation while working in the turbine hall basement have left the hospital and are reportedly in perfect health.
According to TEPCO's latest update they have switched the cooling of the number 2 reactor from the fire pumps to temporary electric pumps.
Reuters report that the levels of radioactive material in the sea outside the plant is dropping.
The King of Lagom claims that an incident that took place in 2006 at the Forsmark nuclear power plant could have escalated into a Chernobyl-type accident. Well... first he says that, and then he says it could have become something entirely different. If this sounds confusing it is because the King of Lagom probably doesn't quite know what he's talking about but rather builds this statement on misconceptions about what actually happened at Chernobyl and Forsmark respectively. So let's examine the incidents and compare.
The 1986 Chernobyl accident
April 26, 1986. The night shift at reactor 4 at the V.I Lenin Nuclear power plant, 20 km north west of the town of Chernobyl, Ukraine, has been ordered to do a test. Due to operator error, they accidentally poison the RBMK-type reactor which makes it almost grind to a halt. They don't know why the reactor is giving so little power though because they were mostly coal plant workers, inexperienced with nuclear power, and oblivious to things such as nuclear poisoning. The shift boss, determined to finish the test, gives orders to proceed, telling the operators to perform actions that go against several operating rules of the reactor. This puts the reactor in an unstable state.
When the test is finished and they shut down the reactor, a fatal flaw in the reactor's control system causes the reactivity to spiral out of control, making it output between ten to onehundred times normal thermal effect. The water in the reactor flash boils and the enormous steam pressure blows the building apart. A few seconds later a chemical explosion, when water that has been split into hydrogen and oxygen burns, rocks the complex again. The reactor is on fire for ten days, resulting in a large plume of radioactive fallout.
There are several factors that allowed this accident to happen.
First it was operated by poorly educated personnel, in a political system where safety came second. In the Soviet Union, you did not rise to attractive jobs like this one by being good at your craft but by kissing up to the communist party. Also you did not stay at jobs like this by speaking up against safety issues, because such things made the party look bad. For instance this particular test was supposed to have been run years ago when the plant was commissioned. But since it failed back then, it had to be done again, this time in secret from the Soviet nuclear regulatory authorities.
This shouldn't have been a problem. But the second reason the accident could take place was the deliberate violations of the operating rules of the reactor. The test was to have taken place when the reactor was outputting at least 700 MW; they started when it was at 200 MW. They were not allowed to withdraw more than a certain number of control rods; they withdrew almost all of them. They were not allowed to increase water flow in the reactor past a certain amount when operating at low power; they did. They were not allowed to disengage the safety systems that would have shut down the reactor when they did any of the aforementioned; but they did indeed disable them.
All of this made reactor come into an unstable state that let its most critical design flaw come into play: the positive void coefficient. The void coefficient is a quality in a nuclear reactor that tells us what happens when it gets too hot. When coolant boils in a reactor that has a positive void coefficient, the nuclear reaction increases. This makes the reactor hotter, which makes more water boil. This speeds up the reaction more, making it even hotter... and so forth. And not only was the void coefficient in the RBMK-reactors of the Chernobyl plant positive, it was also dangerously high.
Finally, because the reactor had no real core vessel, nor any concrete containment, the force of the explosion wrecked the building completely. A fire started in the hundreds of tons of graphite that was in the reactor. Also the building itself that was supposed to have been made from fireproof material, was not, and the debris caught fire as well.
This is what is known as a criticality accident, when the nuclear reaction goes out of control. In this case it produced so much heat that the entire reactor blew up from all the thermal energy. This accident was not a nuclear meltdown.
The 2006 Forsmark incident
July 27, 2006. At the switch-yard for Forsmark-1, an electrical arc causes a short circuit which leads to the unit being disconnected from the power grid. This is serious as the plant relies on power to keep all pumps going.
If a nuclear reactor does not have working pumps, eventually the cooling water in the reactor will boil away. If that starts to happen you must engage the emergency core cooling, reserves of water kept for this very purpose. If this too fails and the reactor boils dry, the heat can be such that the reactor core becomes damaged, popularly called a meltdown. This can happen even when the nuclear reaction has been stopped because decay heat continues to be produced a few hours after a reactor is shut down as very short-lived nuclear waste falls apart. This is what happened at Three Mile Island in 1979.
So when a nuclear plant becomes disconnected from the power grid, the reactor is shut down and on-site diesel generators start to provide power for the pumps to deal with the decay heat, and this was what happened at Forsmark 1. However in this case, two out of the four diesel generators did not start, disabling two safety trains out off four. But the two remaining diesel generators were more than enough to drive the pumps. Hence the reactor was cooled and emergency core cooling was not necessary. The reactor shutdown proceded normally.
No, there are no similarities between these two incidents. The Chernobyl disaster was the case of a criticality accident that caused an extremely violent explosion that completely wrecked the reactor core; the building it operated in; burned for days. The Forsmark incident was the case of slight degradation of safety features while the reactor and its cooling operated normally. The cooling system was operational the whole time; the emergency cooling did not need to be engaged; the reactor core was not damaged; the reactor tank was in no way threatened; the over one meter thick reactor contaiment remained perfectly safe. And fire? Naw... there is no graphite in Forsmark-1. Water handles that job instead.
So when the King of Lagom says that the Forsmark incident could have become another Chernobyl, he is wrong. There is no way that Forsmark-1 or any of the other Swedish nuclear reactor could undergo the process that led to the explosion in Ukraine in 1986. And this is not just because we employ people that know what they are doing; care about safety first; follow procedure; don't do things behind the back of the nuclear regulatory authorities. No, the most important reason why a Chernobyl-type criticality accident cannot happen in Sweden is the reactors themselves. Because unlike the RBMK-reactors of the Soviet Union, our boiler- and pressurized water reactors do not have a positive void coefficient. We did it the opposite way, so that when water starts boiling in the reactor, the nuclear reaction slows down because of inescapable laws of physics. It's nature's own choke collar on nuclear reactions.
The RBMK-type of reactor was employed only in the Soviet Union. The international community is working hard to get the twelve RBMK's that are still in operation closed. Even though I'm a nuclear friend I'm not an idiot, and as such I am very glad that one of the remaining RBMK's. Ignalina-2, will be shut down in 2009, meaning that Lithuania no longer operates them. Now we just need to get Russia to shut down theirs and we'll finally be rid of this blight.
When discussing nuclear safety, anyone that uses Chernobyl as an example of what could go wrong in nuclear reactors is ignoring reality. The BWR/PWR reactors of the world hold about as much in common with the RBMK-design of the Soviet Union as does slavery to common work; as does forced child soldiers to commissioned adults. There just is no comparing them as they operate differently down to subatomic level.
The Forsmark incident was not, and could not have become, another Chernobyl. This is not an opinion, it is physical reality.
ADDENDUM: As I posted a link to this entry in his blog, and called him on his Ad hominem attacks, he first approved the entry, then he cencored it and claimed that I was violating his right to have "free opinions", i.e. he doesn't want anyone telling him he's wrong.
On November 4, 2006, Europe suffered one of the largest disturbances in its electrical power grid of the past half century. 15 million households were disconnected from the grid for 20-40 minutes. A trivial error that should not have meant any significant disturbances cascaded and spanned much of continental Europe. This nearly threw the continent into a blackout that would have dwarfed the North American power-out in 2003. While the direct cause of the 2006 disturbance was operator error, a root cause of the problem and a significant factor in delaying getting the grids back online, was wind power and combined heat and power (CHP) plants.
The European power grid has been constructed, basically from scratch, since the end of World War II. The grid in itself is divided between a number of different Transmission System Operators (TSOs), like for instance E.ON (Germany), RTE (France) and TenneT (The Netherlands). Each country's domestic power grid is serviced by one or more TSOs. In order to provide stability and safety of the power supply TSOs are connected to each other. The basic idea was that if an area suffers a major disruption, neighbouring TSOs can help by pushing power from their grids into the affected area.
However over time things have changed. With the increased use of supposedly more environment friendly power plants, such as wind turbines and CHP plants, coupled with requirements to cut down on emissions, TSOs today are required to accept power from neighbours if the latter has a surplus of low-emission power. While this sounds good in theory as it forces TSOs to use "greener" power, instead of for instance coal power, this means that the power grid is used in a way which it was not designed for. Shunting power from one area to another puts high loads on the power transmission lines. In effect the European power grid is often operated close to maximum of what it can handle. To rectify this problem, more power lines should be built, but this is becoming increasingly more difficult and thus we are stuck with the problem.
Due to environmental reasons, the development of the transmission system is more and more affected by stricter constraints and limitations in terms of licensing procedures and construction times. The reality today is that many UCTE TSOs face significant difficulties to build new overhead lines due to long authorization procedures and regulatory regimes.
System Disturbance on 4 November 2006
union for the co-ordination of transmission of electricity
The windy weekend
November 4, 2006, was a Saturday. The event took place in the evening, starting at 22:10 CET. While power consumption is low in evenings and even more so during weekends, the load on the grid was still high. The reason for this was that TSOs use these low-periods to disconnect some power lines to perform maintenance on them. This means that remaining lines still operate at near full capacity even if demand is low.
Such conditions also meant that the fraction of intermittent and distributed power production such as wind and CHPs was higher than normal, something that was further compounded by the fact that Germany was experiencing windy conditions that evening. Large amounts of power was therefore being routed into The Netherlands and Poland, straining the power lines.
E.ON Netz was to disconnect a power line. Calculations had predicted that this should have been alright without compromising the safety of the power grid. However due to changes in the conditions - Germany's unforeseen windy weather, and a rescheduling that was communicated late to the other TSOs - the disconnect and rerouting of power overloaded the remaining lines. These power lines tripped (automatically disconnected) in order to protect them from becoming damaged. This caused more overloads in other power lines, causing further trips. This is what is know as a cascade. The cascade had within seconds divided the European power grid into three isolated "islands": west, north east and south east.
The west area, having lost the connection to eastern Germany where much power was coming from, suffered a large deficit in power production. In order to protect the power grid and equipment connected to it, TSOs started load shedding, that is to say they started disconnecting customers from the grid in order to lighten their load. For each TSO 3-20% of all customers were disconnected and suffered power outs. In total approximately 15 million European households were affected by this.
In the north east area, the problem was the opposite. With the consumers in the west disconnected, the power generators surged as there was no-one that could accept the power they produced. Windmills are particularly sensitive to this and automatically disconnected from the power grid. Within a minute the north east area stabilized.
The south east area suffered a rather small power deficit in comparison and the impact was therefore smaller.
Trying to get back online
The west area started up power generation reserves to counter the production deficit. Within fifteen minutes the west area had stabilized to nominal production, although they were still disconnected from the north east.
In the north east however the different TSO operators had big problems. This was because the windmills and CHP plants that had tripped, automatically reconnected themselves, again causing a production surplus. There was no way to keep the windmills from doing this. To counter it the TSO operators had to manually prevent overloading the grid by instructing other power plants to cut down on production or shut down completely, and engaging power buffers such as pump storage units. This was while they at the same time tried to diagnose what had happened and why they had a disturbance in the first place. There was much confusion and which meant that the north east area was delayed in getting things back to normal.
In order to help counter the production surplus from the uncontrollable windmills, the control block leader for CENTREL (TSOs in Poland, the Czeck Republic, Hungary and Slovakia) somewhat unconventionally agreed to accept much of the surplus. However this meant that huge amounts of power was suddenly being routed eastwards, overloading some power lines up to as much as 140% of normal capacity, severely risking splitting the power grid again. Luckily this did not happen.
As the power levels were restored they tried to get the different areas connected again. Starting at about 25 minutes after the problems began, they tried to resynchronize the different networks. However for another quarter hour, the networks would not connect to each-other because they were fluctuating too much or not lining up to each-other. Either they wouldn't even attempt a connection or they would trip out again after a few seconds. At 22:47 did the networks begin to connect properly, and not until over an hour later, at 23:57, were things back to normal.
Opponents of nuclear power and proponents of "green" power such as wind and CHPs often argue that nuclear power leads to poor safety and reliability of the power production. The argument is that "putting all eggs in one basket" puts us at a risk of a serious power shortage. They argue that distributed power such as wind is better because it spreads the risk.
However the events of November 4, 2006, point to the exact opposite. While the grid was always made to handle large single-point outages, such as a nuclear power plant going offline, with fairly local load balancing, it was not made to being operated the way we are forced to do with intermittent power. With wind power being essentially uncontrollable and fluctuating there is a need to shunt power long distances through power grids that were never built to handle it. This in turn puts strain on the grids, lessening the margins and risking cascading chaotic failure of an entire continent.
With increased use of wind and other intermittent power sources, this risk can only be increased unless we basically tear out our entire transmission grid and build a new one. This is an investment that will not come cheap. Those arguing for large scale power production using intermittent sources, such as wind, must seek an answer to the following question:
Is it prudent, economical, or even feasible to replace the entire power grid of a continent, just to accommodate a notoriously troublesome source of power?