Japan Earthquake: Nuclear Plants at Fukushima Daiichi

In summary: RCIC consists of a series of pumps, valves, and manifolds that allow coolant to be circulated around the reactor pressure vessel in the event of a loss of the main feedwater supply.In summary, the earthquake and tsunami may have caused a loss of coolant at the Fukushima Daiichi NPP, which could lead to a meltdown. The system for cooling the reactor core is designed to kick in in the event of a loss of feedwater, and fortunately this appears not to have happened yet.
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  • #8,682
If fuel is indeed molten, what are the chances of heavier elements collecting together?

Can the Uranium and Plutonium separate from the boron and steel?
 
  • #8,683
  • #8,684
jmelson said:
YES! This is the doomsday scenario, and it is VERY hard to tell if such a process is happening or not!
You can think everything is heading toward a stable outcome, and then suddenly, BOOM! a huge radioactive steam blast.

The scale of such a blast could be estimated. The cores are currently producing between 4-8 megawatts of thermal decay heat each. That amount of heat will generate 5-10 tons of steam per hour, roughly speaking.
TEPCO is currently cooling the reactors with about double that amount of cooling water each hour. This is not quenching all of the steam, but we do not currently have volcanic steam eruptions, but rather a steady strong boil.
So afaik the risk from a core melt into a flooded drywell is that the steam that continues to be produced cannot be released effectively and consequently ruptures the containment more seriously. Or am I missing something?
 
  • #8,685
It's a waiting game. Chernobyl timeline is another 125 years (give or take) before the remnants of the melted core (corium) can be approached for removal because to this day it is so radioactive.

Here you have 3 cores melted down awaiting enough time to elapse for cooling down just to begin containment, let alone worry about where all the contaminated cooling water ends up.

If the design works for the corium then its path is meant to flow to the bottom of the secondary containment (drywell), spread out, sit there and cool down. Bottom of the drywell is concrete with part of the steel containment shell embedded in the concrete which the corium would have to dissolve/melt through both and then encounter a mass of thick concrete below the shell before it could find natural earth. Cracks in the concrete would not have been envisioned neither would the corium traveling somewhere it's not suppose to like the torus (wetwell). Still it would have a thick concrete foundation to dissolve and melt through but should cool down before that happens.

So, you need time, cooling and keep the corium in place until it cools down. Further contamination is a given, hopefully it can be just localized.

Aside:
Concrete consists mainly of small rocks (example 3/4" or 1") and sand with cement as the binder (glue) and its major usefulness in this case is a hardened thick mass but nothing magical even with embedded steel reinforcement or maybe some type of plating. As the cement itself hardens over its approximate 116 year lifetime (before becoming inert) it takes about 45 years for it (the cement) to become as hard as the natural rock it contains (now concrete is referred to as having a half life of 50 years or so depending on the mix design).
 

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  • #8,686
I have two questions/comments:

1. All the news stories about cooling the #2 SFP say that the point of this operation is to reduce the humidity inside the #2 building. Does anything establish that the humidity actually comes from the SFP? Presumably, there are holes in the containment vessel, and probably in the RPV, and steam is escaping. The steam can be seen in photos of the blow(n)-out panel in the east wall of unit #2. Can the high humidity result from the reactor steam instead of from the SFP steam?

2. A lot of Cs and Sr isotopes have already been washed out of the cores (and, for Cs, vaporized in the first couple of days). Over time, more will be washed out. If the core is molten and covered with a solid shell that is permeable is any way, and the core is immersed in flowing hot water, then almost all the soluble radioisotopes will eventually be washed out. I am pretty sure that the chemical forms of Cs and Sr that occur in corium are readily soluble in water (generally, these are oxides, which dissolve in water to make the corresponding hydroxides). This dissolution will have a very bad effect on the water collection and purification efforts. However, the loss of these materials from the corium should greatly reduce its heat-generating ability and its radioactivity. The fissionable materials should have already decayed (or mostly decayed?), and most of the heat produced now (and in the longer term) is from radioactive decay (unless I'm missing something). It seems to me that TEPCO could end up with very hot water (that Areva thinks they can cleanse and I think will mostly end up in the ocean) and not-that-hot cores that will actually solidify and not pose the type of explosion risk that some posts suggest.
 
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  • #8,687
The water level in the basement of the incinerator building has stopped decreasing. As the water leaked into the corridor between buildings, the measured radiation increase in nearby ground water is believed to be mainly caused by the rain : http://www3.nhk.or.jp/news/html/20110601/t10013241691000.html .

The water level decrease in the basement of unit 1 reactor building is suspected to be caused by a leak on the unit 2 side : http://mainichi.jp/select/jiken/news/20110603k0000e040073000c.html

If nothing is done, the contaminated water from unit 2 and unit 3 will start leaking into the sea on June 20th, but the water purification system is supposed to start on June 15th. However it is possible that heavy rains may cause a leak before June 15th : http://mainichi.jp/select/jiken/news/20110603k0000e040073000c.html

In mid-August, [Tepco] will also install an underground storage tank that can hold 100,000 tons of highly radioactive water.
http://www3.nhk.or.jp/daily/english/03_19.html
 
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  • #8,688
dh87 said:
I have two questions/comments:

1. All the news stories about cooling the #2 SFP say that the point of this operation is to reduce the humidity inside the #2 building. Does anything establish that the humidity actually comes from the SFP? Presumably, there are holes in the containment vessel, and probably in the RPV, and steam is escaping. The steam can be seen in photos of the blow(n)-out panel in the east wall of unit #2. Can the high humidity result from the reactor steam instead of from the SFP steam?

No, I don't think that it is from SFP, unit 2 SFP power is much smaller than in unit 4, and unit 4 wasnt generating steam always, also unit 2 SFP temperature was for example 45C but steam was still there, and unit 2 core and drywell are at atmospheric pressure, also on pne of movies when they zoom in into hole in wall we can see some debris and that steam is not only from left (sfp location) but also from center
 
  • #8,689
elektrownik said:
Maybe I am stupid but I can't understand how unit 5 have 300m3 from ground water and unit 6 13500m3 from ground water, they are so close and 45 times difference...

~kujala~ said:
That's a good question.
I guess the level of groundwater doesn't have to be the same although they are near each other.
Also the size of leak (through damaged waterproof systems or through concrete only) can differ - it can be "small", "big" or something in between.
Also the tsunami might have left more water in one place than other. Remember that two dead guys were found in the unit #4 turbine building and they were probably killed by tsunami waters. So the tsunami was probably able to hit directly at least turbine buildings.

According to the following Tokyo Shinbun article, the earthquake caused cracks in the walls of unit 5 and unit 6, through which ground water has been leaking. From April 4th, about 10000 tons of that water were released into the sea in order to prevent the diesel generator(s) and pump(s) at those units from being flooded : http://www.tokyo-np.co.jp/article/feature/nucerror/list/CK2011052002100005.html

I see one more possibiliy explaining the larger amount of water remaining now in unit 6 : the sea discharge could have been mostly from unit 5.
 
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  • #8,690
elektrownik said:
No, I don't think that it is from SFP, unit 2 SFP power is much smaller than in unit 4, and unit 4 wasnt generating steam always, also unit 2 SFP temperature was for example 45C but steam was still there, and unit 2 core and drywell are at atmospheric pressure, also on pne of movies when they zoom in into hole in wall we can see some debris and that steam is not only from left (sfp location) but also from center

As far as the documentation suggests, that temperature is for the skimmer surge tank, not the fuel pool itself. Thats why the temperature goes up when they inject water, because it causes some of the hot pool water to move into the skimmer tank.

I am very interested to learn how much of the steam in unit 2 is from the pool vs the reactor. I doubt that TEPCO or the regulators are very sure either, I have heard them say that steam may be coming from both, but that they believe a lot comes from the pool and cooling it will help a lot. This may be based more on wishful thinking than evidence, but it is possible that their explorations inside unit 2 building taught them something. We will all just have to see what happens when they get the pool cooling working for long enough to make a theoretical difference. I would not be shocked if the reactor was causing a lot of the problem, and they are just dealing with the fuel pool because its much easier to solve this than the reactor problems, but you never know, a lot of the steam really might be from the pool.
 
  • #8,692
It seems the discussion here about unit 2 cooling was timely, we don't have long to wait to see if the pool cooling has helped humidity:

http://www3.nhk.or.jp/daily/english/03_03.html

TEPCO cools storage pool in No.2 reactor building
The operator of the Fukushima Daiichi nuclear power plant says it has succeeded in lowering the temperature in a storage pool for used nuclear fuel at the No.2 reactor after it started operating a cooling system there.

Tokyo Electric Power Company says the temperature in the pool dropped to 38 degrees Celsius on Thursday from about 70 degrees previously.

TEPCO had anticipated that it would take about one month to lower the temperature to about 40 degrees.

In the No. 2 reactor building, steam released by the storage pool has been pushing up the humidity level to 99.9 percent. Such excessive humidity has prevented recovery efforts so far.

The company installed a circulatory cooling system to lower the pool temperature in order to reduce humidity and began operating the system on Tuesday.

Since the temperature has sharply decreased TEPCO plans to inspect the interior of the building as it suspects humidity has also declined. If the situation has improved, it will install systems to remove radioactive substances.

The company plans to start operating similar cooling systems at the storage pools in the No.1 and 3 reactor buildings in June, and in the No.4 reactor building in July.
Friday, June 03, 2011 05:11 +0900 (JST)

I'll have to double check my time correlations but I think I was looking at TEPCOS live feed early Friday JST and the usual steam coming from reactor 2 building was apparent, so I do have my doubts as to whether TEPCO will discover a much better situation in reactor 2 when they enter, but I hope to be wrong.
 
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  • #8,693
tsutsuji said:
According to the following Tokyo Shinbun article, the earthquake caused cracks in the walls of unit 5 and unit 6, through which ground water has been leaking. From April 4th, about 10000 tons of that water were released into the sea in order to prevent the diesel generator(s) and pump(s) at those units from being flooded : http://www.tokyo-np.co.jp/article/feature/nucerror/list/CK2011052002100005.html

Thanks, I translated it using Google translate. One paragraph says:
According to the Toukyoudenryoku and Nuclear Safety Agency, METI, diesel generator No. 6 reactor building basement, five or six pumps were in the basement of the turbine building of the Unit. The earthquake cracked walls, underground water had flowed.

Original:
経済産業省原子力安全・保安院や東京電力によると、ディーゼル発電機は６号機原子炉建屋の地下、ポンプは５、６号機のタービン建屋の地下にあった。地震で壁にひびが入り、地下水が流れ込んでいた。

It's really hard to tell if they mean unit 6 turbine building walls were cracked or unit 6 reactor building walls also. The latter would be more serious.
 
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  • #8,694
~kujala~ said:
Thanks, I translated it using Google translate. One paragraph says:Original:It's really hard to tell if they mean unit 6 turbine building walls were cracked or unit 6 reactor building walls also. The latter would be more serious.

I would translate the sentence quoted from http://www.tokyo-np.co.jp/article/feature/nucerror/list/CK2011052002100005.html as follows :

According to sources such as the NISA and Tepco, the diesel generator(s) were located in the basement of unit 6 reactor building and the pumps were located in the basements of unit 5 turbine building and unit 6 turbine building. Cracks were created in walls during the earthquake and the groundwater flowed inside.

In the following article published on May 8th, Tepco is reported as acknowledging the presence of cracks in the underground walls of turbine buildings, but the article does not say which units are concerned. An unnamed Tepco manager is quoted as saying "Because of the earthquake, cracks have expanded and new cracks have been created, so that there is a possibility that ground water is leaking inside. The earthquake resistance of turbine buildings is not as high as that of reactor buildings" : http://www.tokyo-np.co.jp/article/national/news/CK2011050802000039.html

A Chunichi article published on May 4th quotes an unnamed Tepco employee who was working at unit 6 when the earthquake struck : "cracks were formed on a part of the inside wall of the turbine building". Plant manager Masao Yoshida is quoted as saying that originally water was seeping in large amounts at units 5 and 6 before the earthquake : http://atmc-tokyo.com/radiation/1285/

~kujala~ said:
So the tsunami was probably able to hit directly at least turbine buildings.
Tsujitsu proposed this direct hit might also have happened in the reactor buildings. About that I don't know.

1) Do you mean I (Tsutsuji, not Tsujitsu) ?

2) Could you provide a link to the post where I could have said this ? I don't remember.
 
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  • #8,695
tsutsuji said:
2) Could you provide a link to the post where I could have said this ? I don't remember.

Sorry, I guess what you meant was the unit 6 turbine building was hit by the tsunami and then from there a flow of water could reach also the unit 6 reactor building:

What about #4 : Unit 6 hit and flooded by a tsunami ?

I thought you were referring to the unit 6 reactor building here as I was also talking about the reactor building:
https://www.physicsforums.com/showpost.php?p=3310809&postcount=7821
https://www.physicsforums.com/showpost.php?p=3310818&postcount=7822
 
  • #8,696
~kujala~ said:
I thought you were referring to the unit 6 reactor building here as I was also talking about the reactor building:
https://www.physicsforums.com/showpost.php?p=3310809&postcount=7821
https://www.physicsforums.com/showpost.php?p=3310818&postcount=7822

Thanks for the links. I must have overlooked the fact that the preceding discussion dealt specifically with the reactor building. I confess that what I had in mind when I made that reply was unit 6 as a whole.

Anyway, the inundated area extends west of unit 6 reactor building, above the OP+13 m ground level as reported on http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110409e9.pdf and even west of units 5 and 6's high voltage transformer building as reported on page 29 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf
 
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  • #8,697
It is strange that tepco doesn't show us any pictures from unit 5 and 6, there is no much information about those units, they are working in control rooms there ?
 
  • #8,699
Steve Elbows wrote:
"""Re: Japan Earthquake: nuclear plants
A new pressure indicator for reactor 1 is being installed, tech details here:

http://www.tepco.co.jp/en/nu/fukushi...10602_02-e.pdf

Same planned for reactors 2 & 3 if they can ever get working conditions inside the buildings improved."""

At Last! that will put to rest wondering about the sense point locations, elevation differences and health of existing instruments. i note their elevation head equates to 0.18Mpa not quite two atmospheres.
 
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  • #8,700
The following article is reporting the detailed contamination data for the two nuclear power plant operators previously reported ( page 531 of this thread : https://www.physicsforums.com/showthread.php?p=3329327#post3329327 ) as "may exceed the 250 mSv limit" :

The 30 year old one has 210~580 mSv of internal contamination adding to the 74 mSv external contamination.

The 40 year old one has 200~570 mSv adding to 89 mSv.

http://www.yomiuri.co.jp/national/news/20110603-OYT1T00778.htm
 
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  • #8,701
One of the many things about the ongoing disasters in Japan is the almost complete lack of data about the most simple and easy to achieve measurements.

Like what is in the constant steam coming out of a reactor building. Or what's left of one. You would think there doesn't exist the technological ability to put sensors in the steam to measure the radioactivity and materials coming out a ruined reactor, or ruined fuel ponds.

That sort of information would seem important to my simple mind. Yet I have never, since day one, even heard of a discussion about it. (I may have missed it here of course).

It just seems (again, to my simple mind) that knowing what is coming out of steaming nuclear pile of rubble would be important. Especially to the people working nearby. But I imagine anyone downwind would also want to know.

Sometimes (usually at night) I see these huge steam clouds escaping into the air. We know it's from melted fuel rods, we know melted nuclear fuel rods are dangerous, so why no data on what is simply going into the air, 24/7?

Is that too much to ask?
 
  • #8,702
tsutsuji said:
The following article is reporting the detailed contamination data...

http://www.yomiuri.co.jp/national/news/20110603-OYT1T00778.htm

NHK article: http://www3.nhk.or.jp/daily/english/03_32.html
 
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  • #8,703
swl said:
No, yes, no yes, Maybe?

http://nuclearstreet.com/nuclear_power_industry_news/b/nuclear_power_news/archive/2011/06/01/tepco-starts-spent_2d00_fuel-cooling-system-at-fukushima-unit_2c00_-reports-oil-leak-060102.aspx"

Congratulations to the people at the sharp end of this situation.

It may only be a small solution in a mass of big problems, but the establishment of closed loop cooling for the SFP in Unit 2 is a turning point I think and it gives me a sense of optimisim that we will have improved success in working our way through this.

No more radiation washed out or steamed off of at least part of the site.

Good news.
 
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  • #8,704
tsutsuji said:
The following article is reporting the detailed contamination data for the two nuclear power plant operators previously reported ( page 531 of this thread : https://www.physicsforums.com/showthread.php?p=3329327#post3329327 ) as "may exceed the 250 mSv limit" :

The 30 year old one has 210~580 mSv of internal contamination adding to the 74 mSv external contamination.

The 40 year old one has 200~570 mSv adding to 89 mSv.

http://www.yomiuri.co.jp/national/news/20110603-OYT1T00778.htm

Is this total dose so far? Expected total lifetime dose? Or what?
 
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  • #8,705
The NHK writeup here http://www3.nhk.or.jp/daily/english/03_32.html indicates that most of the internal dose was concentrated in the thyroid gland.
That suggests iodine contamination. Hopefully, that means the incremental dose beyond this point will be small, given the short half life of the iodine 131.
Against that, it also probably means most of the early responders are in the same boat, with 250+ mSv thyroid doses. TEPCO did not hand out potassium iodide pills to the first responders afaik.
 
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  • #8,706
razzz said:
It's a waiting game. Chernobyl timeline is another 125 years (give or take) before the remnants of the melted core (corium) can be approached for removal because to this day it is so radioactive.

Here you have 3 cores melted down awaiting enough time to elapse for cooling down just to begin containment, let alone worry about where all the contaminated cooling water ends up.

If the design works for the corium then its path is meant to flow to the bottom of the secondary containment (drywell), spread out, sit there and cool down. Bottom of the drywell is concrete with part of the steel containment shell embedded in the concrete which the corium would have to dissolve/melt through both and then encounter a mass of thick concrete below the shell before it could find natural earth. Cracks in the concrete would not have been envisioned neither would the corium traveling somewhere it's not suppose to like the torus (wetwell). Still it would have a thick concrete foundation to dissolve and melt through but should cool down before that happens.

So, you need time, cooling and keep the corium in place until it cools down. Further contamination is a given, hopefully it can be just localized.

Aside:
Concrete consists mainly of small rocks (example 3/4" or 1") and sand with cement as the binder (glue) and its major usefulness in this case is a hardened thick mass but nothing magical even with embedded steel reinforcement or maybe some type of plating. As the cement itself hardens over its approximate 116 year lifetime (before becoming inert) it takes about 45 years for it (the cement) to become as hard as the natural rock it contains (now concrete is referred to as having a half life of 50 years or so depending on the mix design).

Isn't this true ONLY if fission doesn't restart? The high levels of Iodine-131 reported recently makes be strongly doubt that fission has not been ongoing, at least in Unit 2.
 
  • #8,707
dh87 said:
I have two questions/comments:

1. All the news stories about cooling the #2 SFP say that the point of this operation is to reduce the humidity inside the #2 building. Does anything establish that the humidity actually comes from the SFP? Presumably, there are holes in the containment vessel, and probably in the RPV, and steam is escaping. The steam can be seen in photos of the blow(n)-out panel in the east wall of unit #2. Can the high humidity result from the reactor steam instead of from the SFP steam?

2. A lot of Cs and Sr isotopes have already been washed out of the cores (and, for Cs, vaporized in the first couple of days). Over time, more will be washed out. If the core is molten and covered with a solid shell that is permeable is any way, and the core is immersed in flowing hot water, then almost all the soluble radioisotopes will eventually be washed out. I am pretty sure that the chemical forms of Cs and Sr that occur in corium are readily soluble in water (generally, these are oxides, which dissolve in water to make the corresponding hydroxides). This dissolution will have a very bad effect on the water collection and purification efforts. However, the loss of these materials from the corium should greatly reduce its heat-generating ability and its radioactivity. The fissionable materials should have already decayed (or mostly decayed?), and most of the heat produced now (and in the longer term) is from radioactive decay (unless I'm missing something). It seems to me that TEPCO could end up with very hot water (that Areva thinks they can cleanse and I think will mostly end up in the ocean) and not-that-hot cores that will actually solidify and not pose the type of explosion risk that some posts suggest.
Sounds correct to me, except that it is only true if critical level fission doesn't restart which is not supported by the little data we have from TEPCO about the Iodine-131/Cesium-137 ratio in the sea water inlet from the 27 or 28th of May reported the next day...
 
  • #8,708
elektrownik said:
No, I don't think that it is from SFP, unit 2 SFP power is much smaller than in unit 4, and unit 4 wasnt generating steam always, also unit 2 SFP temperature was for example 45C but steam was still there, and unit 2 core and drywell are at atmospheric pressure, also on pne of movies when they zoom in into hole in wall we can see some debris and that steam is not only from left (sfp location) but also from center

For whatever is worth, I agree. Also close to Unit 2 sea water inlet is that TEPCO reported huge increases of the ratio of Iodine-131 to Cesium-137, suggesting re-criticality
 
  • #8,710
robinson said:
One of the many things about the ongoing disasters in Japan is the almost complete lack of data about the most simple and easy to achieve measurements.

Like what is in the constant steam coming out of a reactor building. Or what's left of one. You would think there doesn't exist the technological ability to put sensors in the steam to measure the radioactivity and materials coming out a ruined reactor, or ruined fuel ponds.

That sort of information would seem important to my simple mind. Yet I have never, since day one, even heard of a discussion about it. (I may have missed it here of course).

It just seems (again, to my simple mind) that knowing what is coming out of steaming nuclear pile of rubble would be important. Especially to the people working nearby. But I imagine anyone downwind would also want to know.

Sometimes (usually at night) I see these huge steam clouds escaping into the air. We know it's from melted fuel rods, we know melted nuclear fuel rods are dangerous, so why no data on what is simply going into the air, 24/7?

Is that too much to ask?

No, it is a basic source of data that should be reported, same on the radioisotipic monitoring of the water in the basements of all the buildings with spectrums available for people to check and double check their measurements. Everytime they don't report something it has been because it is bad. You can verify this by just checking what happened with the variables that they stop reporting on when they are able to improve them and they start reporting on them again. One of those instances that I followed in detail was the temperature in RPV of Unit 3
 
  • #8,711
I can get more info (or I could in March) about the various isotopes being released from the reactors from monitoring stations in California than ever came out of Japan.
 
  • #8,713
zapperzero said:
Is this total dose so far? Expected total lifetime dose? Or what?

They are talking about internal contamination, so this will accumulate for their lifetimes if they can't remove the contaminants... It is not clear in the English article what type of dose they are talking about, I can't translate Japanes accurately enough to infer from the other article
 
  • #8,714
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