Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[joewein]

Ques--maybe I am missing it, but i would assume the Pig nose to be really big, like 20 square meters or more in area...

The "pig nose" must be those short pipe stubs sticking out to the right of the http://img.ibtimes.com/www/data/images/full/2011/05/25/103517-fukushima-daiichi-unit-1.jpg , in the top centre "cloud" section of the right hand wall.

There are probably two of them because of the two IC units. It don't see why it would take much more than those pipes to release the steam from the boiling condenser water -- they look right.

 

[zapperzero]

I'd guess the blurred out 'words' are the workers names written in Sharpie. But that's just a guess.

That's a pretty long name... stretching on at least two rows, from side to side. Take a closer look.

 

[Borek]

If memory serves me well in the past blurred names were names of some agencies/organizations that wanted to stay anonymous.

For whatever reasons.

 

[clancy688]

Thanks for the translation, tsutsuji!

What's the purpose of that "fail-safe" function? Isn't closing the valves (shutting down the IC) in case of total power loss exactly the wrong thing do? This separates the reactor vessel from the only cooling function still available.

Furthermore, the shift operators on duty were even worried that if the quantity of coolant water inside the condenser tank is small, the high temperature, high pressure steam from the reactor would run in a loop through the IC pipes without cooling down, causing the damage of IC pipes, and that reactor steam polluted with radioactive substances would be directly released into the atmosphere.

That's the only probable purpose of that function I can imagine.
SBO -> reactor is doomed anyway -> so don't give it a direct path to the atmosphere

------------------

Not even one among the shift operators on duty who operated unit 1 had had a real experience of operating an IC until the March 11 tsunami occurred. Among the shift operators on duty, one of them(some of them) had heard from an older operator(s) that when the IC is working normally, the water in the condenser tank is heated and evaporated due to the heat exchange, and the steam bursts vigorously and horizontally from the two gas exhaust vents which are installed in a row on the western wall of unit 1's reactor building (the so-called "pig nose"), and that on such occasions, static electricity is generated, producing a blue light similar to a lightning, while a roaring sound resonates.

That's hilarious. The IC is their last line of defense and those guys had no idea on how to operate it. That's like sailors who don't have any idea on how to lower rescue boats to the sea.

 

[tsutsuji]

What's the purpose of that "fail-safe" function? Isn't closing the valves (shutting down the IC) in case of total power loss exactly the wrong thing do? This separates the reactor vessel from the only cooling function still available.

Tepco's internal investigation report is also questioning the suitability of the fail-safe function:

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111203/0735_reikyoku.html (3 December) Tepco's internal investigation report says that the suitability of the mechanism which makes the IC's valves automatically close when battery power is lost must be investigated. The mechanism is intended to prevent radioactive substances to be released outside of the plant in case of emergency, but in this case, it prevented the emergency cooling function from being performed.

That's hilarious. The IC is their last line of defense and those guys had no idea on how to operate it. That's like sailors who don't have any idea on how to lower rescue boats to the sea.

It seems that they had been trained (on a simulator?) to use the IC from the control panel, and that they were able to run it in accordance with the operation manual between the earthquake and the tsunami. Yet I wish the investigation committee would elaborate on what they mean with "they did not remember the open or closed status of that valve". I don't think one can so easily forget this sort of things. It would seem more natural that they had in their mind the fact that the valve had been left in a closed position when the tsunami struck, and that they would be worried that under such condition the IC is shutdown and that no cooling is being performed. And even if they were not remembering and not worrying on the IC issue, should not Tepco higher-ups or the NISA have worried and asked them to remember ?

 

[jim hardy]

wow. in a so stressful event i can see priorities being muddied.

there's a certain psychological makeup needed to be a good operator. that's an ability to remain detached and aware of the "big picture".

engineers tend to be capable of focusing on one detail to exclusion of all else. that's how they get through school. just opposite makeup is needed for operations.

releasing reactor contents is a big release of radioactive stuff and i can understand how that could become a focal point, for these guys' families live just downwind.

recall that 1970's Eastern Airlines plane that got flown into the ground - all 3 guys in the cockpit were focused on the nosewheel "down" light and not aware of altitude.

having too many engineers is as bad as having too few. when i got obsessive my guys used to tell me "Go away and calculate something, we'll call you when this is working.""

i wasn't there so don't know what went on. only thing I'm sure of is everybody's sadder but wiser now.

 

[clancy688]

recall that 1970's Eastern Airlines plane that got flown into the ground - all 3 guys in the cockpit were focused on the nosewheel "down" light and not aware of altitude.

Fascinating, after reading your second line, exactly that specific accident crossed my mind. If I remember correctly, it was a turning point for the whole aircraft industry regarding security issues.
There was another accident, I don't know which one, which prompted the development of efficient checklists.
If those guys in Fukushima would've been using checklists while operating the condenser, they should've noticed the actual operation and valve status (steam discharge, etc.).

Airplanes and NPPs are not so different after all. If you screw up during a status change (landing, SCRAM), it's effectively over. So there are numerous ways to prevent screw up. The most notable probably being the checklists. In airplanes, there are checklists not only for landing and starting, but for all kinds of emergencies - engine failure, whatever. So whatever happens, they have a guideline which should lead them in NOT forgetting the crucial single one button-press-operation out of several dozens they have to perform during the emergency.

Many users posting here have experience in working in NPPs. I have not. So I ask them - is there something similar to the checklists used in aircrafts?

 

[nikkkom]

That's the only probable purpose of that function I can imagine.
SBO -> reactor is doomed anyway -> so don't give it a direct path to the atmosphere

Why dry IC should be a direct path from reactor coolant to atmosphere?
To not design IC to be able to withstand boiling dry would be a serious design mistake.

 

[clancy688]

Well, of course. But apparently, the TEPCO operators didn't think that the IC (or rather the piping) could survive boiling dry.

Furthermore, the shift operators on duty were even worried that if the quantity of coolant water inside the condenser tank is small, the high temperature, high pressure steam from the reactor would run in a loop through the IC pipes without cooling down, causing the damage of IC pipes, and that reactor steam polluted with radioactive substances would be directly released into the atmosphere.

 

[tsutsuji]

Why do nuclear power plants rely so much on electric control systems? Would not pneumatic logic systems and pneumatic motors be stronger against being flooded under several meters of seawater ? For example, instead of having IC(A) and IC(B) being both electric-controlled, couldn't we have at least one air-controlled IC(B) ?

 

[jim hardy]

""Airplanes and NPPs are not so different after all. ""

NPP operators are on instruments 100% of the time. There's no sensory feedback beyond noise of steam blowing.

yes there's checklists. operation is very procedurized.

one of the changes after Three Mile Island was a change in philosophy, from problem oriented to symptom oriented procedures...

procedures were change from "If you have (this problem) do that" approach

to

"IF you SEE this, do that."

reason is operators can't see all the pipes, they only see their instruments. So they may not be able to discern what is the problem - only that temperature and pressure are changing. That's what they were confronted with at TMI.


Some very different troubles give similar symptoms.

yes there are checklists. sadly, total loss of power may not have been bounded - again i don't know.

A procedure is like a computer program , it might crash if handed an unexpected input.

in NPPs fine tuning them to handle all possible conditions is a never ending activity. you never achieve perfection , to wit the pyramid on back of US one dollar bill is missing top brick.

 

[jim hardy]

Why do nuclear power plants rely so much on electric control systems? Would not pneumatic logic systems and pneumatic motors be stronger against being flooded under several meters of seawater ? For example, instead of having IC(A) and IC(B) being both electric-controlled, couldn't we have at least one air-controlled IC(B) ?

in 1950's pneumatic controls were the best. our plants all had them.

around 1960 solid state made electronics reliable enough to be considered for industrial controls and they got so cheap they just took over...

i too asked why do i need a box full of op-amps to replace a pressure switch.
i have long been of the opinion the best balance would be robust analog controls , perhaps pneumatic, with a fancy computer to monitor them and help you keep it in good repair.

pneumatics are absolutely impervious to lightning and walkie-talkies. power failure is gradual as the air reservoir slowly bleeds down, and you have time to start a backup compressor . when one watches them in operation, hissing and balancing, one realizes they're pretty well matched to the big clunky machines they are controlling.

but i am a luddite. computers should be allowed only to think - never trust one with anything important.
see Robert Sheckley's "Watchbirds"

old jim

 

[tsutsuji]

If a key system like the scram system is an hydraulic system, why shouldn't the IC, which is also a top level safety system, be also an hydraulic system ?

Googling a few keywords I found the following:

http://www.nrc.gov/reactors/new-reactors/design-cert/abwr/dcd/tier-2/CH_15/15_08.pdf "The ABWR, however, uses a FMCRD design with both hydraulic and electric means to achieve shutdown"

so it seems that some people have a concern for not relying on "electric only" or "hydraulic only".

 

[I_P]

Can it be definitively determined that there was no critical damage to the cooling systems from the earthquake prior to the tsunami (the workers reported broken pipes and flooding during the quake), or containment structures - based on the available sensor data? What was going on with #2 and #3? We see only the rundown on the status of #1 in this report (yes?).

Has this scenario been discussed: http://lewrockwell.com/orig4/goddard2.1.1.html ?

 

[clancy688]

Has this scenario been discussed: http://lewrockwell.com/orig4/goddard2.1.1.html ?

Yes, I think so. But it's probably in the temporarily removed "Unit 3 explosion" thread. As for containment breaches before the meltdowns:

Then, from around 17:19, the shift operators on duty, in order to check if enough water is secured in the IC condenser tank(s), decided to go to check the water level gauge(s) installed on the side of the condenser tank(s) on unit 1 reactor building's 4th floor. At that time, the shift operators on duty made preparations to check the water level gauge(s), but did not put protective masks and protective clothing on. Then, the shift operators on duty left the units 1 and 2 central control room, and as they arrived near unit 1's reactor building airlock, as the needle on their dosimeter (Geiger tube) reached the maximum value of 300 cpm (note 29) and stopped moving, they gave up their checking mission, and went back to the units 1 and 2 central control room.
note 29: The detected radiation is thought to be almost gamma rays, and assuming it is gamma rays, a 300 cpm value corresponds to about 2.5 μSv/h. However, though the probability is low, if the detected radiation is alpha, 300 cpm corresponds to about 50 μSv/h.

That's one hour before the top of the fuel even got uncovered, much less melted.

And right before the tsunami hit, a monitoring post at the vicinity border went off: http://www.bloomberg.com/news/2011-05-19/fukushima-may-have-leaked-radiation-before-quake.html

 

[tsutsuji]

Can it be definitively determined that there was no critical damage to the cooling systems from the earthquake prior to the tsunami (the workers reported broken pipes and flooding during the quake), or containment structures - based on the available sensor data?

There is a lengthy discussion in the cabinet investigation committee interim report on whether unit 1's IC was damaged by the earthquake prior the tsunami, and their conclusion is "no". I thought this is not the most interesting and I thought it would be more interesting to translate other parts of the report.

What was going on with #2 and #3? We see only the rundown on the status of #1 in this report (yes?).

The report is also talking about unit 3 (you can check by reading the "Poor handling of alternative water injection at Unit 3" section in the http://icanps.go.jp/eng/111226ExecutiveSummary.pdf ).

 

[I_P]

There is a lengthy discussion in the cabinet investigation committee interim report on whether unit 1's IC was damaged by the earthquake prior the tsunami, and their conclusion is "no". I thought this is not the most interesting and I thought it would be more interesting to translate other parts of the report.

Thanks Tsutsuji for this and all your translations/posts.

Did you find their reasoning convincing? Did they have enough evidence to support this conclusion?

I find myself wondering now how many years it will be before a definitive post-mortem can be worked up and a bit surprised at how many basic questions remain at this point.

Clancy, is that thread (about unit 3 explosion) accessible?

 

[clancy688]

Nope.

But I'm sure it'll come back soon enough. Isn't the first time it got sacked because of unnecessary speculation. Some folks sadly just can't hold their conspiracy theories back. So it's probably somewhere only moderators and administrators have access to and will come back once it's been cleaned of unnecessary speculation and related offtopic posts.

http://webcache.googleusercontent.com/search?q=cache:szk1ehUU7UQJ:www.physicsforums.com/showthread.php%3Ft%3D505630the first page in google cache.

Use this link to access the other pages. Just change the page number at the end of the URL pasted in the search window (from 1 to 47) and then access the cached version of the first search result.
That's annoying as hell, but not as annoying as not being able to read the thread. ;)


Edit:
http://webcache.googleusercontent.com/search?q=cache:tyJNyw1Flm8J:www.physicsforums.com/showthread.php%3Ft%3D505630%26page%3D39+http://lewrockwell.com/orig4/goddard2.1.1.html+physicsforums&cd=1&hl=de&ct=clnk&gl=de

 

[jim hardy]

here was another forum with a pretty decent level of discourse.

like PF, the moderator chased off the tinfoil hat types.

http://tickerforum.org/akcs-www?post=182121

but it's three hundred something pages.
around 314 was another hypothesis, about steam explosion but in-vessel.
Since you can set browser for so many posts per page, page number is unreliable.
so around may 7th is date.

 

[tsutsuji]

Follow-up of the translation started on https://www.physicsforums.com/showpost.php?p=3687263&postcount=11983

We had left on page 107 (31/170) when the operators close the MO-3A valve at around 18:25.

http://icanps.go.jp/111226Honbun4Shou.pdf translation of pages 107 (31/170) - 110 (37/170) :

At that time, the shift operators on duty thought that as the IC was not functioning normally, it was necessary to build alternative water injection means, and as a means the shift operators in duty can use in a situation of total loss of electric power, they came up with no other idea than the method of injecting water into the reactor through the FP line using the D/DFP. Then the shift operators in duty started the D/DFP at around 17:30 on the same day, and put it in standby mode, and at around 18:30 on the same day, in such places as the reactor building and the turbine building, they manually performed the valve switching operations that are necessary to enable water injection into the reactor through the FP line and the condensate feed line (MUWC line).

4) At around 21:30 on March 11, the shift operators on duty noticed that the green indicator lamp on units 1 and 2 central control room's control panel, that indicates the status of the IC's return line isolation valve (MO-3A) was beginning to fade out, and they feared that if the electric power is lost, it will be impossible to open that valve. By that time, as a result of checking the operation manual, etc. the shift operators on duty had understood that the IC can be run for several hours without needing to refill the condenser tank with cooling water.

Hence, the shift operators on duty thought that it is highly probable that the reason why from around 18:18 the quantity of steam generated by the condenser tank became small was not that the condenser tank was running out of coolant water, but that the two isolation valves on the inner side of the primary containment vessel (MO-1A, 4A) were not open due to the fail-safe function.

The shift operators on duty thought that even in that case, as long as the return line isolation valve (MO-3A) is left closed, under the hypothesis that the isolation valves on the inner side of the primary containment vessel (MO-1A, 4A) would be found slightly open, if the driving electric poser is lost, it will become definitely impossible to open the return line isolation valve (MO-3A). Furthermore, the shift operators on duty thought that notwithstanding the fact that there is no need to refill the condenser tank with coolant water even if the IC is continuously used for several hours, under the hypothesis that refilling the condenser tank with coolant water would become necessary, it is admissible to refill by operating the D/DFP and performing the valve operations that are needed to refill the condenser tank through the FP line.

At that point, the shift operators on duty thought that the probability that the IC would work is not zero, and they performed the valve opening operation of the IC's return line isolation valve (MO-3A). At that time, the shift operators on duty heard a sound sounding like a steam release, but shortly after that, they could not hear the sound any longer, and, of course, they did not think that the IC was functioning normally (note 33).

Then the shift operators on duty reported to the power plant response headquarters that the return line isolation valve (MO-3A) had been opened.

Note 33: At that time too, the shift operators on duty were not directly observing the gas exhaust vent through which the steam is discharged, but their testimony that the steam generation sound did not continue is corroborated by informations such as the about 65% water level value indicated by the IC condenser tank water level gauge more than 200 days after the accident, and it is thought that if the IC had been operating normally, this kind of steam generation situation would not have occurred.

c Judgement of IC operation status by the power plant response headquarters and by the main office response headquarters

1) After around 15:37 on March 11, total loss of AC power and DC power occurred for unit 1, and the power plant response headquarters received a report from the shift operators on duty on this situation. However, at that point of time, nobody had pointed out the possibility that the IC's four isolation valves could have been brought to a fully or nearly fully closed status by the fail-safe function.

Furthermore, at around 16:45 on the same day, the power plant response headquarters received a report from the shift operators on duty saying that unit 1's reactor level gauge became available. However, the power plant response headquarters received reports about this reactor water level gauge until around 17:07 on the same day, saying that at around 16:42 on the same day the indication was wide band -90 cm, that the later trend was a decline, that at around 16;56 on the same day the indication was -150 cm, and that finally the gauge went down scale and became unavailable again. The same information was shared with the main office response headquarters via the teleconferencing system. Then, at around 17:15 on the same day, the power plant response headquarters' technical team calculated a prediction of the time it takes until TAF is reached, and concluded that TAF would be reached in one hour's time. However, even at that point of time, nobody among the power plant response headquarters or the main office response headquarters, by linking together the observed phenomenons and estimates with the IC function, pointed out that the IC might not be operating normally.

Furthermore, at around 17:50 on the same day, the power plant response headquarters received from the shift operators on duty a report saying that a high radiation had been found when approaching unit 1's reactor building in order to check the IC's condenser tank water level, and this information was shared with the main office response headquarters via the teleconferencing system. At that point of time, nobody among the power plant response headquarters and the main office response headquarters pointed out the possibility that large quantities of radioactive substances were generated inside the reactor pressure vessel as a result of the decline of the reactor water level, because the IC was not functioning.

2) At around 18:18 on March 11, the power plant response headquarters received a report from the shift operators on duty saying that they had opened the feed line isolation valve (MO-2A) and the return line isolation valve (MO-3A) of IC (system A), and believed that the IC was working. The main office response headquarters, receiving the same information as the power plant response headquarters via the teleconferencing system, also believed that the IC was working.

No evidence can be found that at that time, the power plant response headquarters and the main office response headquarters were conscious of the problem arising from the fact that both isolation valves had been opened, meaning that until then they had been closed and that the IC had not been operating for 3 hours after the total loss of electric power, and that no water had been injected into the reactor either.

3) No sufficient mutual understanding was attempted at Fukushima Daiichi nuclear power plant between the units 1 and 2 central control room and the power plant response headquarters in the seismic-isolated building concerning the fact that the closure operation of return line isolation valve (MO-3A) had been performed at around 18:25 on March 11, and later the power plant response headquarters believed that the IC was still running.

For that reason, for example, because unit 2's RCIC's operation status could not be checked and because unit 2's reactor water level could not be measured, fearing that the water level would decline and that fuel exposure would lead to meltdown, until between 21:00 and 22:00 the power plant response headquarters had a stronger feeling of danger regarding unit 2 than regarding unit 1, and later the measures that are necessary to control each plant unit were studied, based on the prejudice that unit 1's IC was working normally and that the cooling function was obtained.

Nevertheless, according to the power plant response headquarters' members' notebooks and other records, there is evidence that the power plant response headquarters grasped the information that the shift operators on duty were fearing that the IC's condenser tank was running out of water. However, the condenser tank water replenishment was eventually not performed, and also, no evidence whatsoever was found that any preparation for an alternative water injection task using fire trucks or for reactor depressurization had been started on the same day concerning unit 1.

Also, via the teleconferencing system, the main office response headquarters thought the same as the nuclear plant response headquarters, which is that unit 1's IC was under operation, and that for the time being, the cooling function could be maintained for several hours. The ministry of economy and industry's emergency response center (ERC) was also reporting that unit 1's IC was under operation.

4) At around 21:30 on March 11, the power plant response headquarters received a report from the shift operators on duty saying that they had opened the IC's return line isolation valve (MO-3A). However, at that time, nobody among the power plant response headquarters and the main office response headquarters, including plant manager Yoshida was conscious of the problem arising from the fact that this report implied that the IC's return line isolation valve (MO-3A) had been in a closed status until then, and nobody asked the shift operators on duty whether they had previously closed that valve.

At that time, the main office response headquarters and the power plant response headquarters were not grasping that at around 18:25 on the same day the shift operators on duty had closed the IC's return line isolation valve (MO-3A) and they were both believing that the IC was operating normally.

d Response of the safety inspectors

According to the Nuclear Industry Safety Agency (NISA), from the off-the-Tohoku-Pacific-coast-earthquake occurrence at around 14:46 on March 11 until the early morning of March 12, the safety inspectors were present on the second floor of the seismic-isolated building, and staying in the conference room on the side of the emergency response room, they received the plant parameters made available by the power plant response headquarters, and using mobile telephones or satellite telephones, they only reported these contents to the offsite center or to the ERC.

However, the safety inspectors being in a position where informations similar as those of the power plant response headquarters and the main office response headquarters can be easily obtained, instead of simply and entirely focusing on the retrieval of information provided by the power plant response headquarters, they should have asked questions to the power plant response headquarters concerning the IC operation status, they should have strived to grasp a more accurate account of the situation, and when necessary, they should have given instructions or provided advice.

In fact, no evidence could be found that the safety inspectors provided necessary instructions or advice to the power plant response headquarters. There is no apparent sign of a situation where the safety inspectors in the seismic-isolated building contributed in some way to the response to the accident.

 

[tsutsuji]

Did you find their reasoning convincing? Did they have enough evidence to support this conclusion?

Basically, the IC worked quite well between the earthquake and the tsunami, and if any major damage had been caused by the earthquake alone, it would have been obvious during that early phase.

 

[Joffan]

Thanks once again tsutsuji for another superb translation job.

My earlier thought that the explosion of R/B#1 could have been averted through earlier venting and injection, although still possible, has faded into the background with these revelations about the failure to use the IC properly. The operators appear less heroic when the tools were almost certainly at hand to control the plant.

The other point I've taken notice of is that the workers going to investigate valves retreated at doses that, in the emergency circumstances, should not have stopped them.

 

[clancy688]

The other point I've taken notice of is that the workers going to investigate valves retreated at doses that, in the emergency circumstances, should not have stopped them.

Well, it was "over the scale". Since the scale was 300 cpm / 2.5 uSv/h Gamma, you can't hardly blame them. That can be everything from "temporary nuisance" to "lifethreatening double digit Sv values".
I remember a (BBC - Surviving Disaster - Chernobyl) docu drama about Chernobyl. The workers reported that they measured 3.6 R/h - but with 3.6 being the top of the scale, and the readings being off the scale. The plant director didn't believe in a big emergency and reported that value to Moscow. Turned out the real readings were 15'000 R/h.

 

[jim hardy]

yes that's a fundamental rule

never go anyplace in a rad area where you don't know what's the radiation field
if your meter tops out you don't know how much over the top it is
so you go back and get a bigger one

clancy's example shows that.
it's part of good design - a good meter should tell you it's topped out.

russian electronics of the 80's that i encountered was regarded, well, primitive.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111229/0545_3goki.html Did unit 3's explosion result from a backward flow of hydrogen ? Checking one pipe that forks from the venting pipe and connects to the reactor building, Tepco recently found traces of the vented gas that contained hydrogen. This pipe is equipped with a valve and a device that prevents backflow, but the valve is designed to automatically open if electric power is lost, and the backflow preventing device has a low airtightness, so that it is possible that hydrogen flowed backwards into the reactor building and caused an hydrogen explosion. So far it was thought that the hydrogen would have leaked through interstices such as those of the containment vessel cover. The NISA is studying the reinforcement of backflow preventing devices in other nuclear plants.

http://www.asahi.com/national/update/1226/TKY201112260188.html [with http://www.asahi.com/national/update/1226/images/TKY201112260191.jpg] finding that the radiation decreases from the outer site to the inner side, Tepco concluded that radioactive substances had flowed backwards in the pipe. This was found at unit 3, but the same kind of backflow might have happened at unit 1 too.

http://www.nikkei.com/news/category...39180EAE2E2E2;at=DGXZZO0195583008122009000000 During a hearing of specialists organised on 27 December, the NISA publicly released the results of an analysis saying that there is a possibility that hydrogen backflow is one of the causes of the hydrogen explosions in unit 1 and unit 3.

http://www.news24.jp/articles/2011/12/27/07197167.html At the 27 December meeting, the NISA said that one of the causes of hydrogen explosions could be the degradation of the silicone gum in the joining parts of the primary containment vessel. Concerning the backflow from unit 3 into unit 4, there was no backflow preventing device, and there was no instruction to close [unit 4's] valves in the operation manual.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111226_01-e.pdf "Fukushima Daiichi Nuclear Power Station: Unit 3 Measurement of Radiation Dose of Emergency Gas Treatment System and the Result of the Status of Valves"

 

[Most Curious]

I would think getting a large butterfly valve to be "hydrogen tight" would be a big challenge! The stuff is "slippery" due to small molecule and is hard to contain.

IOW, I would expect LOTS of hydrogen leaks in that plant!

 

[Joffan]

Fair enough if their meters were maxed out. I didn't read it that way, but that would be a good reason for stopping for sure.

 

[NUCENG]

Thanks Tsutsuji for this and all your translations/posts.

Did you find their reasoning convincing? Did they have enough evidence to support this conclusion?

I find myself wondering now how many years it will be before a definitive post-mortem can be worked up and a bit surprised at how many basic questions remain at this point.

Clancy, is that thread (about unit 3 explosion) accessible?

Thinking about a Definitive Post-Mortem, what do you expect it to answer?

I will be years before health actual impacts can be determined.

It may be several years befor vessel disassembly and determination of in-vessel damage.

It will probably be a year before initial investigations can be completed. (We are starting to see preliminary information and interim reports, but a lot of it is based on best guess and analysis, not physical evidence.

Right now there are some important preliminries that are priorities including:

• Stabilizing and cooling the fuel debris and corium.
• Clearing debris and controlling radiation on site.
• Eliminating off-site releases.
• Cleaning up water and reducing inventory in buildings.
• Dealing with radiation sources in populated areas.
• Clearing debris and stabilizing buildings to provide safe work area for disassembly.

It took years to complete the "final" story on TMI2 - a single reactor with an intact contailmentm and all fuel remaining in the RPV.

 

[Pakman]

Thank you,Tsutsuji for great job!

I have a quastion. In your translation there is no even a word about IC B as if there was no such an equipment at unit 1. Is there any explanation in the report on why IC B had been never used since the time of shutting it down at 15:03 by operator? Once operators tried to restore cooling of the reactor and failed with IC A, why they did not resort to [STRIKE]plan[/STRIKE] IC B?

 

[jim hardy]

please pardon me if this report has already been linked...

http://www.power-eng.com/content/dam/pe/online-articles/documents/2011/november/fukushima report.pdf

 

[Cire]

I would think getting a large butterfly valve to be "hydrogen tight" would be a big challenge! The stuff is "slippery" due to small molecule and is hard to contain.

IOW, I would expect LOTS of hydrogen leaks in that plant!

Exactly. Hydrogen is almost impossible to stop at pressure from going anywhere it wants to.

 

[tsutsuji]

Exactly. Hydrogen is almost impossible to stop at pressure from going anywhere it wants to.

http://www.nikkei.com/news/category...39180EAE2E2E2;at=DGXZZO0195583008122009000000 says that the NISA is proposing the following countermeasure(s) : "having both pipes become independent [from each other] and installing backflow preventing valves".

[Wouldn't the best way to have pipes be really independent be the construction of a different exhaust stack for each pipe ?]

[with http://www.asahi.com/national/update/1226/images/TKY201112260191.jpg]

Translation of the diagram:

1) Hydrogen leaks from the primary containment vessel cover, from penetrations, etc.
2) Did hydrogen flow backwards during venting?

非常用ガス処理系配管
Emergency Gas Treatment System pipe

弁は開いていた
the valve was open

空気作動式ダンパ(逆流防止措置)機密性は高くない
air operated damper (backflow preventing device) air tightness is not high

Is there any explanation in the report on why IC B had been never used since the time of shutting it down at 15:03 by operator?

I have not finished reading the contents of the report concerning the IC.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111229/0715_dengen.html The Nuclear Safety Commission Of Japan has prepared a revision of its guideline concerning long time losses of electric power. Whereas the present guideline says "As the recovery of power transmission lines and the repair of emergency power generators can be expected, it is not necessary to think about it", the revised version requires to prepare alternative power generation means such as power trucks and gas turbines. The concrete measures are left to each power company to decide. The power companies have already started to implement alternative power generation means, but as a consequence of the revised guideline they will have to study again whether it is enough.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111229/0445_suibotsu.html According to a former Tepco employee, a flooding incident occurred 20 years ago, which could have been a missed opportunity to reinforce measures against tsunamis. In October 1991, water leaked from a pipe in Fukushima Daiichi unit 1 turbine building, flowed into the basement first floor, and emergency generator(s) became unusable. "Thinking that if a tsunami comes, the generators will be inundated just the same, and will be unusable, I talked to my superior", he recalls. Tepco took countermeasures such as installing watertight doors, but anti-tsunami measures such as moving the generators to higher floors were not taken. According to Tepco, the superior "is not aware" that any such talk took place with the former employee concerning the risk of tsunami.

 

[nikkkom]

Well, it was "over the scale". Since the scale was 300 cpm / 2.5 uSv/h Gamma, you can't hardly blame them.

However, I can (and will) blame TEPCO for not equipping them with radiation monitors with sufficiently wide scale.

This is, BTW, should have been one of "lessons learned" from Chernobyl.

Did nuclear power industry actully learn from it?! Doesn't look like that!

 

[clancy688]

I don't know about that. I'd figure that any device which could measure massive radiation (mSv/h to Sv/h) would be very, very unsusceptible to radiation in the uSv/h range.
Since most radiation leaks in NPPs probably only result in very small radiation doses, it's probably better to equip the workers with sensible devices. Which can't distingiush between little and much radiation, but at least indicate that there's something wrong.
And we already know that the tsunami wrecked a big part of the dosimeters stored at the plant site. So one could assume that the same happened to other devices as well. For example portable devices to correctly measure massive radiation.

 

[jim hardy]

to be accurate one needs fairly sensitive instruments .

but we have high range meters.

they could have got more stout meters,
or maybe they had one and it just didnt get mentioned,

why they didn't go back i can't say, wasn't there.

but we're trained to not go where it's unknown
and we're trained that to go into a very high area one takes special equipment and precautions and plans the entry carefully...

perhaps the reasons are simply strict adherence to procedure.

lots of tough calls to make that day... those poor guys are heroes in my book...

old jim