Hi Blog. I’m sorry to keep quoting sources who wish to remain anonymous, but this is another person I trust, who says: “Prefer to remain in the background – for now. Please rest assured, my sources are VERY HIGH up in the industry in the United States and are working 24 hours a day to follow this incident due to the dramatic potential ramifications if multiple units ‘meltdown’.” However, he wishes for this information to be known, and chose Debito.org to be his venue. Take this letter within that context. Arudou Debito
March 18, 2011
In light of the debate occurring over the scope of the nuclear catastrophe on Debito-san’s blog I would like to present some information.
I am not the individual that made the original post (which some have asked Debito to remove) and I agree with some of the arguments refuting that post. Those who have asked Debito to remove the post should also state their credentials as well and provide a more detailed rebuttal to each issue (I do agree with some of the refuting conclusion). My credentials are presented further below.
However I would like to deal with one specific issue, using seawater to cool the reactor and reactor cooling, as this is within my area of expertise. Essentially the only thing that matters now is reactor cooling.
I am glad Debito displayed the original post. It has been interesting for me to watch others debate and react to this issue. I am flabbergasted that the Japanese government and TEPCO still call this a Level 5 incident. I believe it will end up being a Level 6, or if meltdown occurs, Level 7.
Regarding credentials; I have over 25 years experience as a registered professional engineer and have worked in the nuclear power industry. I have performed SSFI inspections (Safety System Functional Inspections) on several power plants and have performed one post accident investigation. My roles in the assessments related to the power distribution system for the reactor cooling system.
I have been discussing this issue with several colleagues, some of whom are top level experts in the nuclear industry and one who is in a position to have access to whatever information the U.S. government has. Because TEPCO has not been at all transparent and has been hesitant to issue any specific technical information on this disaster it is difficult to say for sure what is happening. We also have reason to believe that TEPCO or the government has not been completely forthright (for whatever reason) regarding radiation levels near the plant (but that is outside of my area of expertise).
One of the individuals I have been in contact with has been very accurate in predicting the events as they are unfolding. He was wrong in one of his predictions, that the situation would have resolved itself by now (either meltdown/melt through of the reactor pressure vessel of one of the units or restoration of station power).
We believe radiation is being released in three forms:
1. Slightly radioactive steam from the initial explosions. The initial explosions were caused when TEPCO vented the reactor pressure vessel, hydrogen was released and exploded.
2. Higher levels of radiation being released from burning fuel rods, especially in Unit 4, which was being used for spent fuel storage.
3. Higher levels of radiation from compromised containment in Unit 2 (and possibly other units) due to cracking or some other type of compromising of the containment. This was confirmed last Tuesday when TEPCO and the government reported the pressure in the reactor pressure vessel was at 1 atmosphere (the normal atmospheric pressure outside). Normally these are operating much higher. The fact that these units lost pressure indicates a crack or some type of other event that caused pressure to remain at atmospheric.
At this point the radiation being released is very serious and will undoubtedly cause deaths (most likely in the long term in the form of cancer) in the areas near the reactors (admitted yesterday by the head of TEPCO).
However, the level of radiation released if there is a meltdown of one reactor pressure vessel will dwarf the levels of radiation being released now (up to 10 x 10 to the 5th power higher). This is why cooling is imperative.
Below is our assessment of the situation (this is speculative because TEPCO has not released further information, which may lead us to draw more severe or less severe conclusions). I hope the situation is less severe and they have been able to provide at least minimally cooling.
We believe the cooling situation has become dire. We think at this point, barring a miracle, they clearly are not going to be able to establish any reasonable means of core cooling for the affected units before suffering severe core damage, which means the potential for large fission product release. The wind direction will be up to Mother Nature. The spent fuel pool fire is interesting and very troublesome. There are no barriers against fission product release if the spent fuel rods are involved in the fire. We don’t know the cause of the spent pool fire and nobody’s talking either, which may lead one to draw much more interesting conclusions which are too highly speculative for me to mention.
Below is a technical explanation upon which we base these conclusions.
The earthquake and tsunami caused a “perfect storm” event. That is total loss of onsite power, backup generation, utility station service power, and eventually a loss of DC power due to the fact that the AC power system was not available to charge the station batteries. This is an event that has not occurred before.
We believe that initially the plant did have some limited AC and DC power available, and thus could run pumps and operate valves. However, it appears that they were still unable to keep adequate water on the core. We believe that because of this the reactor pressure vessel (RPV) pressure was allowed to increase to a point that no available pumps had adequate discharge head to overcome the high static pressure in the PRV. In this case the pumps that were pumping try to pump but no water is going into the vessel. We believe with certainty that the most important pump, the High Pressure Coolant Injection (HPCI) pump was not and still is not available. This is a very big pump, 400 horsepower or bigger and is probably too big for the current power available. This pump is capable of dumping 6,000 gallons per minute of cooling water into the RPV.
When they were venting to atmosphere it was clear they were having problems reducing pressure by venting to the torus (which serves as a quench tank during an accident). This led us to believe that the torus was operating at saturated conditions, which means it is not possible to reduce pressure unless the steam bubble in the torus can be collapsed. Obviously they could not do this so they vented to atmosphere and the subsequent explosions occurred. The fact that these initial explosions occurred was due to the fact that hydrogen was vented from the RPV. The presence of hydrogen during the vent was almost certainly due to the fact that the fuel cladding was damaged and the process of a meltdown was in the early stages (likely started very late Friday night or early Saturday morning).
When the fuel cladding material (Zirconium) gets very hot in the presence of moisture it begins to breakdown and hydrogen is formed. The explosions at U1 and U3 were clearly very large, and thus indicative that the operators were venting large volumes of hydrogen gas (along with steam). Because of the magnitude of the explosions (especially Unit 3) this is unmistakably indication of partial melting and deformation of the fuel rod assemblies. This represents the first stage of “melt down.” The fact that the Unit 3 explosion was much, much stronger than Unit 1 indicates the melt down was continuing to get progressively worse. As this melting and deformation progress, the fuel material will eventually drop to the bottom of the RPV. This represents the next stage of meltdown in which the fuel then begins to corrode and melt through the RPV. When this phase of the accident is reached it’s time to clear out (which TEPCO has done, leaving only 50 people on site) since there remains only one of the three fission product barriers intact, the drywell containment structure. At this point we believe that fuel assembly damage has occurred for sure, the core has likely deformed and started to melt, and the process of melting through the RPV has started.
Once you melt down the RPV, you have a “meltdown”. This has not occurred yet, but is still a possible scenario. The only way to avert this is to cool the reactor.
Using seawater to cool the reactor as well as dumping water with helicopters and using water cannons are acts of desperation. Specifically the use of seawater contaminates the reactor cooling system and essentially makes all units scrap and virtually incapable of being reused (good these cannot be reused in my opinion). This is a decision not taken lightly by a utility such as TEPCO.
For your information the United States Nuclear Regulatory Commission (NRC) issued what they call a “generic letter” in 1988. In this generic letter, which I have sent to Debito-san, the NRC basically addressed this identical event (not tsunami, but total loss of grid power, station service, onsite generation, backup generation, and batteries) and recommended plants using GE Mark 1 reactors address this issue. This was 23 years ago and most or all plants in the U.S. have addressed this issue. It is obvious TEPCO did not with these units. The conclusions in the NRC letter are based on severe accident PRA analyses, which identified two critical areas for the older GE Mark 1 containments that should be improved.
• Alternate water supply to drywell spray & injection
• Better PRV depressurization capability
It is ironic that these were the 2 technical problems that were preventing the plants from reestablishing control in the initial stages of this incident. Had they been able to spray down the torus and drywell, thereby rapidly decreasing RPV and torus pressure, the low head pumps would likely have been available to cover the core. If this would have occurred, they probably would not have needed to resort to seawater injection.
Regarding the management of the situation I have my opinions but will withhold them until the final resolution is reached.
I read the article in the Daily Mail, showing Akio Komiri breaking down and finally admitting that the radiation levels are potentially lethal.
Source letter from United States Nuclear Regulatory Commission (NRC) issued what they call a “generic letter” in 1988 (PDF, download, click below:)