Hello James,
It is with a heavy heart that I watch the nuclear incident unfold in Japan. I am watching my nightmare come true, and I pray for the safety of the people in Japan. As you know, my article that was published in your blog last September was primarily written to alert the public about the possible EMP effects on nuclear power plants. While the initiating event may have been different, the results of the loss of all AC power at the site results in virtually identical consequences. Events are playing out very similarly to those that I had described. There are certain differences, however, since I had described the events for a pressurized water reactor (PWR). The reactors involved in the accident in Japan are boiling water reactors (BWRs).
I would like to take the opportunity to both alert your readers about the truth of what is happening and also dispel some rumors and incorrect assumptions regarding the events at the nuclear plant in Japan. I have seen many “talking heads” on the news this past week that have virtually no nuclear background and frankly are not qualified to be making assumptions or assertions.
The Fukushima Units #1 through #5 at Daiichi are older GE designed BWR-3 and BWR-4 Mk.I, boiling water reactors that were all built in the 1970’s. I used to design fuel for these types of reactors when I worked at GE some years ago. In general, I would say that BWRs are actually inherently safer than PWRs. When I was at GE they used to say that BWR stood for “BEST Water Reactor.” This older design, however, is not the best design for accident scenarios. It has a torus or “doughnut” for the suppression pool and it is limited in its capacity. Also, these containment structures are smaller than later designs, and generally considered not as robust.
I found these excellent papers on the internet about Japan’s BWR reactor designs:
http://www.ansn-jp.org/jneslibrary/npp2.pdf
http://www.ansn-jp.org/jneslibrary/BWR_Safety_Design.pdf
Also, this from Wikipedia regarding the older BWR-3, Mk.I containment:
“Though the present fleet of BWRs are less likely to suffer core damage from the 1 in 100,000 reactor-year limiting fault than the present fleet of PWRs are (due to increased ECCS robustness and redundancy) there have been concerns raised about the pressure containment ability of the as-built, unmodified Mark I containment – that such may be insufficient to contain pressures generated by a limiting fault combined with complete ECCS failure that results in extremely severe core damage. In this double worst-case, 1 in 100,000,000 reactor-year scenario, an unmodified Mark I containment is speculated to allow some degree of radioactive release to occur. However, this is mitigated by the modification of the Mark I containment; namely, the addition of an outgas stack system that, if containment pressure exceeds critical setpoints, will allow the orderly discharge of pressurizing gasses after the gasses pass through activated carbon filters designed to trap radionuclides.”
I found this document in the NRC reading room. Basically, a Station Blackout Event (loss of off-site an on-site AC power), is perhaps the worst event that these types of BWRs can face.
Here is an excerpt. I added the bold type:
“For station blackout accidents, containment systems will not be functional and the drywell floor will often be dry, leaving the plant susceptible to drywell shell melt-through. In addition, the reactor vessel will normally be at elevated pressure, which increases the containment loads at vessel breach. This means that station blackout accidents pose a severe challenge to Mark I and Mark II containments, and therefore, these accidents are often important contributors to the frequency of containment failure.”
I will say that even though the 9.0 magnitude earthquake was beyond the design basis of the Fukushima 1 nuclear plant, the plant actually weathered the earthquake itself quite well and shut down as designed. It is the tsunami that caused the bulk of the problems that the plant operators now face.
The backup emergency diesel generators actually started as designed and began to power the auxiliary pumps designed to circulate cooling water in the reactors. However, the tsunami arrived at the site and overflowed the seawall that was created to protect it from a tsunami. The height of the tsunami was also beyond the design basis of the plant. It is my understanding that the seawall was about 6.5m tall, and the height of the tsunami was above 7.0m. The tsunami destroyed the diesel fuel tanks for the emergency diesel generators and then flooded the below ground switchgear rooms that contain the diesel generators themselves. Therefore, the diesels stopped running about an hour after they started.
The loss of both AC and DC power and the flooded switchgear room also meant the loss of most of the instrumentation that tells the operators what is going on inside the reactors. (Imagine trying to drive your car blindfolded.)
To their credit, the operators at Fukushima understood their predicament. They quickly made the decision that they had an emergency on their hands. They also made the decision to pump sea water into the reactors to stem the overheating cores. This decision was a fateful one, and one I am sure was not taken lightly, since it meant that they understood that the reactors would be permanently ruined. Their once multi-billion dollar asset was turned into a multi-billion dollar liability. It is my understanding that the sea water was pumped via fire suppression system diesel pumps and fire trucks. However, these pumps cannot generate the kind of pressure that was needed to overcome the rising pressure inside the reactor.
Without the added cooling water, the reactor units experienced what is known as a Loss of Coolant Accident (LOCA). Water level fell, exposing the fuel rods. This lead to fuel damage and release of radionuclides into the containment.
Water levels continued to drop, uncovering the reactor cores by varying amounts. The exposed fuel rods caused the temperature and pressure to rise rapidly, generating steam.
Operators were forced to vent pressure from the reactors. This lead to very high pressures in the containment structures. It is my understanding that pressures inside the containment structures reached about 120 psi, about twice the design basis. This could cause the containment structures to fail.
This steam reacted with the zirconium fuel cladding to form hydrogen. It is this hydrogen that is believed to have caused the explosions seen in reactor #1 and reactor #3 buildings. It may also be responsible for what may be an explosion that potentially has caused a crack or leak in the containment vessel in Unit #2, perhaps in the region of the suppression pool.
In Unit #4, there were no assemblies currently in the reactor vessel. All assemblies had been off-loaded into the spent fuel pool. It should be noted that all spent fuel pools at the Fukushima Daiichi plant have not been properly cooled since all power was lost. Just like fuel in the reactors, spent fuel also retains heat for a long period of time and must be cooled. There was also an explosion in reactor building #4, and a fire was seen. It is not yet clear what the cause of the fire was or if the fire has actually been put out. There have been conflicting reports on this issue. However, it is my opinion that the fire may have been caused by the interaction of the zirconium fuel rods with the steam in the then boiling spent fuel pool.
Measurable amounts of Iodine and Cesium have been detected even more than 30km from the plant, which indicates that fission products have been released and that fuel cladding has been compromised for at least some of the fuel rods. Radiation levels inside the control room reached over 1000 times normal.
Radiation levels around the reactor buildings are currently too high for personnel to respond properly to ongoing issues such as possible spent fuel pool fires. On Tuesday, radiation levels just outside of the reactor buildings had reached a high of 400 milliseverts (equal to 40 REM). Twelve to fifteen hours at this level is a fatal dose of radiation. All but essential operations personnel were evacuated from the plant site as result of this level of radiation.
Currently, the concerns revolve around two issues, 1) the status and integrity of the containment vessels surrounding the three reactors that were operating, and 2) the status of the spent fuel pools. In fact, since the reactor buildings are no longer intact, and there is no containment structure surrounding the spent fuel pools, it is actually the spent fuel pools that are the greater danger.
It is clear that there has likely been fuel damage in all of the operating reactors and possibly also in the spent fuel pool in reactor building #4. Spent fuel pools in reactor buildings #5 and #6 are also still heating up.
We have seen continuing variation in measured radiation levels at the plant. This may be because of fluctuating winds blowing the airborne particles around to various directions, sometimes toward detectors and sometimes away from them.
It should be noted that this event is far from over. As of Wednesday morning, Japan time, white smoke or steam was coming out of the #3 reactor building, and higher levels of radiation were being observed. It is unclear if the increased levels of radiation are coming from reactor #2, where the containment vessel may be compromised, reactor #3, from which steam or smoke is being observed or reactor #4, where fire was observed yesterday. There are large holes in the side of the #4 reactor building which may have been caused by the fire or from the explosion of hydrogen. The spent fuel pool in reactor #4 may also be boiling or may be on fire. This fuel in the spent fuel pool will melt if the water boils away and it may even catch fire. Preparations are being made to inject water into this spent fuel pool as soon as possible. Helicopters from the Japanese Self-Defense Forces (SDF) have already attempted to drop water from the air into the spent fuel pool in the Unit #3 reactor building. Attempts to use water cannon from police riot trucks apparently failed due to the inability of the personnel to get close enough to accurately place enough water into the desired location. However, special fire trucks used to put out hazardous aviation fires were successful in getting at least some water into the Unit #3 reactor building. How much of this water actually made it into the spent fuel pool is not clear. Certain Japanese experts have declared this as “somewhat effective,” since steam was seen rising from the building and the levels of radiation around the unit supposedly dropped very slightly, but the volume of water required to completely re-cover the fuel rods is higher than what has so far been sprayed or dropped onto the site.
It should be noted that this is an unprecedented situation. Japanese officials are struggling to contain and resolve this situation. Lack of functioning instrumentation is hampering both interpretation and mitigation of this event. This is event will go on for many weeks, if not months.
TEPCO has now started efforts to restore high voltage power lines to the stricken plant. This would be the best chance to regain control over the situation, by restoring AC power to the cooling systems.
What everyone wants to know is, what are the best case and worst case scenarios and other possible outcomes?
The best case is that TEPCO operators regain control of the plants by adding adequate cooling water to the reactors and the spent fuel pools and the containment vessels remain intact. There will still be a huge cleanup effort required, and the plant will never operate again. This event will still last for many months as removal of the fuel at least from the spent fuel pools must occur (since the spent fuel pools are now exposed to the environment) and most operations will initially need to be done remotely due to the radiation levels. The cost of even this best case will be in at least the tens of billions of dollars, and may be in the hundreds of billions.
The worst case is what everyone fears, but those in the know don’t want to talk about. Officials are all trying to put on a good face and spin things in a positive way. However, the worst cases are these:
1. One or more of the operating cores meltdown, the containment vessels fail, and at least part of the contents of the contained fuel is released into the environment. This would be a disaster exceeded only by Chernobyl. Chernobyl is still a worse disaster than this, since that reactor had no containment at all. I believe that it is still likely that the containment vessels will contain most of the radioactive fission products.
2. All of the fuel assemblies in the spent fuel pools, which have no containment structure, either melt or catch fire, and release much of their contained fission products into the environment. This is an absolute worse case scenario, and locally could even be worse than Chernobyl, since the volume of fuel contained in the spent fuel pools exceeds the volume contained in any one reactor core. However, since there has not been a large explosion at the site that has lofted large amounts of radionuclides into the air, the area which will be affected is likely to be much smaller than the area affected by Chernobyl.
People are asking if a similar accident could happen in the USA. The honest answer is yes, but it is not nearly as likely. Many lessons were learned as a result of the accident at Three Mile Island in Pennsylvania, and modifications were made to all US reactors as a result of these lessons learned. The east coast of the USA is not generally prone to tsunami. There are only two reactor sites on the west coast of the USA, the plant at San Onofre in southern California and the Diablo Canyon plant, located near San Luis Obispo. Of these two, the San Onofre site is perhaps the more at risk. The Diablo Canyon plant has its critical systems far above the level of the ocean. Per haps the most vulnerable sites in the USA are the St. Lucie plant on the east coast of central Florida, the Turkey Point plant, south of Miami, and the Crystal River plant, on Florida’s west coast. The most likely risk to these sites is hurricane storm surge. Hurricane Andrew in 1992 greatly affected the Turkey Point power plant and that event became the NRC standard for hurricane storm events and Station Blackout events.
There has been a run on potassium iodide and potassium iodate pills in the USA as a result of the event in Japan. Let me dispel some misconceptions and alleviate some of the fears of your readers. How radiation (or rather, radioactive particles that give off radiation) travels is highly dependent upon the direction, speed and altitude of the prevailing winds, and the weight and size of the particles. The closer to the area of the incident that you are, the more likely that there will be particles which fall to the ground in that area.
Californians have nothing to worry about from this incident in Japan, and anyone there who purchases KI tablets for this event is wasting their money. Any possible radiation that might reach there would be so diluted and dispersed by the time that it arrived that while it may be measurable, it will have virtually no health effects.
Also, the event at Chernobyl involved an explosion that lofted particles much higher into the atmosphere than anything that has so far happened in Japan. While there were apparently several hydrogen explosions in Japan, these apparently did not contain significant radionuclides, as the reactor containment structures were at that time still intact.
Even the fire in reactor building #4, which had assemblies only in the spent fuel pool, did not have a large explosion. Therefore any radioactive particles that were released from this fire will likely be deposited much closer to the site itself and are not likely to travel very far before falling to the ground. The latest radiation readings at the site boundary are currently only between 2 to 3 millirem per hour. This is not a significant dose rate, and workers could work in this environment for many days or even weeks without experiencing any radiation symptoms. (See the NEI web site for the latest updates.)
At this time, prevailing winds seem to be taking any particles directly out to the open ocean due east of Japan. I see no cause for alarm for any US mainland state (or even Hawaii).
Calculations have been performed which show that the area of maximum danger area is 50 miles or less, and safer areas would be in the 100 to 200 mile range. Beyond 300 miles from the site, I wouldn’t be concerned. If I were the Japanese officials, however, I would recommend extending the evacuation zone to at least 50 miles.
We have seen how significantly that not just Japan but the world has been affected by these events. While panic has generally been averted in Japan, and people there are behaving in an orderly manner, there have still been shortages of food, water, fuel and other commodities. Many people have been displaced from their homes. Financial markets have been roiled. There is even a shortage of salt now in stores in China, as people there are [mistakenly] afraid that the sea will be affected and the sea salt which they obtain from the sea will be contaminated!
All of this from an incident at just one nuclear power plant. What would happen if this incident happened in the USA? What if it happened at dozens of nuclear plants at the same time? What if communications, banking, power, water distribution, sewage treatment, internet access and transportation were all crippled at the same time?
I would like to again emphasize the point that an EMP event resulting in an extended grid down situation could cause a very similar event. There is only adequate diesel fuel on site to power emergency diesels for 7 days for most commercial nuclear plants in the USA. After that, you are in essentially the same situation as the Japanese find themselves – lack of power to provide any cooling to either the reactors or the spent fuel pools. Imagine if this event were to happen at multiple sites in the USA simultaneously! How to mitigate this? One way is to ensure that additional diesel fuel and spare parts are available at all commercial reactors. Diesel generators and their fuel tanks should be shielded and protected (many reactors in the USA have already done this). Another is to pre-stage diesel electric locomotives and a train load of diesel tank cars that could be brought to each reactor site in time of emergency (most reactors sites in the USA have a railroad spur). Diesel locomotives are very robust against EMP, and could act as an emergency generator. There is also a petition that is now before the Nuclear Regulatory Commission (NRC) which recommends certain modifications to nuclear power plants to ensure their continued safety in the event of an EMP event. Write to them and urge them to take this petition seriously!
What is the best way to protect against EMP or a catastrophic infrastructure collapse? Write your Congressman and urge them to join in the passage of the SHIELD Act! The EMP Commission has already outlined what can and must be done to protect our national infrastructure from catastrophic collapse. I urge that these recommendations be carried out with all of the swiftness that the nation can muster. Protection of the grid is the best defense. Sincerely, – B.Z.