Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Edano]

hi there, i just signed in here to point to some interesting links:

reactor plots with all the data from tepco's csv files: http://www.houseoffoust.com/reactors/graphs.html they update automatically twice a day, with added notes by tepco and a timeline of events.

http://www.houseoffoust.com/edano/2rad.bmp

there is a very active community behind it, the discussion is here http://www.scribblelive.com/Event/Japan_Earthquake5 . no registration needed. emphasis is on news and techi stuff.

thank you for your valuable work, we are also following this board here. :)

 

[Edano]

http://www.houseoffoust.com/edano/2tem.bmp

 

[Edano]

http://www.houseoffoust.com/edano/3wat.bmp

 

[etudiant]

It seems that some of those problems were addressed in Tepco's report to the NISA in June:



According to the same document, the cover fabric can withstand a pressure of 30 cm of snow. My understanding is that the air blowers must be powerful enough to compensate the loss of pressure caused by the filters, but that does not mean that the vacuum inside the structure must be intense (significantly intense compared to a 30 cm snow pressure). As the report to NISA does not even mention the pressure caused by the vacuum, it is probably because it is negligible compared to snow and wind.

30 cm of snow has about the same weight as 3 cm of water, so the fabric is good for about 3 gm/cm**2. Atmospheric pressure is about equal to 1000 cm of water/ cm**2, so clearly the covering will allow only very modest pressure differentials. Yet pressure differentials are essential to sweep out the ongoing emissions.
My concern is that the volume of air getting processed looks to be so limited by the nature of the covers that what may feel like a hurricane at the filter unit will be a very modest slow drift from intake to the filter within the reactor buildings, resulting in condensation and contamination throughout the structure.

 

[tsutsuji]

Yet pressure differentials are essential to sweep out the ongoing emissions.

What is essential is to ensure a given flow rate. According to Tepco, 40,000m³/h would be enough. In my opinion, there is no need for a big pressure differential. If you remove fumes in a kitchen using a hood, you may open the window, which means that there is nearly no pressure differential between inside and outside the room. The key point is that the blower is powerful enough to overcome the pressure loss caused by the filter.

 

[etudiant]

What is essential is to ensure a given flow rate. According to Tepco, 40,000m³/h would be enough. In my opinion, there is no need for a big pressure differential. If you remove fumes in a kitchen using a hood, you may open the window, which means that there is nearly no pressure differential between inside and outside the room. The key point is that the blower is powerful enough to overcome the pressure loss caused by the filter.

Thank you very much, Tsutsuji-san, for your patience and helpful follow through.

Allow me to expand a bit more on my concern that this covering has not been fully thought through, especially given that the reactors residual decay heat is evidently so poorly dissipated that some areas within the confinements are boiling.
Say the new containment is 50x50x50 meters, about 125,000 cubic meters, so at 40,000 cubic meters/hr the air is exchanged every three hours.
That means the radioactive steam emissions may only reach a filter several hours after leaking out of the containment. Unless TEPCO dries and/or preheats the incoming air to improve its moisture capacity, condensation inside the tent seems very likely, at least imho.
Building standards generally require much higher rates of air exchange. Specifically, the standard for electric substations and turbine rooms is 5-10 changes/hr, or 15-30 times as much, according to this site:
http://www.engineeringtoolbox.com/air-change-rate-room-d_867.html

 

[Caniche]

Thank you very much, Tsutsuji-san, for your patience and helpful follow through.

Allow me to expand a bit more on my concern that this covering has not been fully thought through, especially given that the reactors residual decay heat is evidently so poorly dissipated that some areas within the confinements are boiling.
Say the new containment is 50x50x50 meters, about 125,000 cubic meters, so at 40,000 cubic meters/hr the air is exchanged every three hours.
That means the radioactive steam emissions may only reach a filter several hours after leaking out of the containment. Unless TEPCO dries and/orpreheats the incoming air to improve its moisture capacity, condensation inside the tent seems very likely, at least imho.
Building standards generally require much higher rates of air exchange. Specifically, the standard for electric substations and turbine rooms is 5-10 changes/hr, or 15-30 times as much, according to this site:
http://www.engineeringtoolbox.com/air-change-rate-room-d_867.html

So with a seasonal drop in ambient temperatures it might not be wise to stand too close to the tent wall??

 

[tsutsuji]

SARRY started again:

After that, we identified that the cause of the shutdown was closure of a valve in the system due to malfunction of an air compressor for valve actuators. After replacing the compressor, at 5:02 pm on September 25, we restarted the 2nd Cesium absorption apparatus and at 5:05 pm, reached the rated flow.
http://www.tepco.co.jp/en/press/corp-com/release/11092602-e.html

 

[rmattila]

Attached is a simple Excel timeline I sketched in order to get a better idea of the early events at the different units. Nothing new in it, but I guess someone might still find it useful.

 

[cockpitvisit]

Just another layman question, as I keep reading about the radioactive steam.

Why is the steam radioactive at all? Since the original water from the reactor has evaporated or leaked long ago, the steam should not contain any tritium.

Are there any other radiactive elements or compounds with a boiling point similar to that of water? Otherwise, I just don't understand why steam releases should have any significant influence on the release of radioactivity. If something radioactive still evaporates, it will likely continue to evaporate when the temperature drops a few degrees below the boiling point.

 

[Edano]

@cockpitvisit: the water is in direct contact with hot fuel. it washes away all kinds of decay products. these products, mainly cesium-137, are carried with the "dirty" water steam outside. it is not tritium that makes problems. it is everything from iodine over xenon to plutonium, as long as there is criticality. but the steam is not tritium steam.
furthermore, nobody knows where the fuel is located now. the thermometers are mainly located around the rpv, they do not show the fuel temperature. when they spray the vessel, the temperatures may decline, but this does not mean much towards the corium state.

 

[Rive]

Where is the 'hot stuff' going from U3?

In U2 after the CSS started the S/C CAMS data also started rising. But in U3, I could not find anything similar.
Where is the water going?

Ps.: the problem is the same for temperatures. In U2 the S/C related temperatures are rising now: in U3 there is no change.

 

[zapperzero]

@cockpitvisit: the water is in direct contact with hot fuel.

the water is in direct contact with hot corium.
FTFY

 

[cockpitvisit]

@cockpitvisit: the water is in direct contact with hot fuel. it washes away all kinds of decay products.

I understand that the water is highly contaminated. What is unclear, is how these products make it from the liquid water into the steam. Isn't the water being distilled during the evaporation? Can chemicals be dissolved in steam at all?

When I boil water containing NaCl at home, the water remains "contaminated" with the salt, but the vapor isn't - it is clean. Why is it different in Fukushima?

 

[Edano]

indeed, that's a valid question. "highly volative particles" are entrained in the steam.

from wikipedia: http://de.wikipedia.org/wiki/Destilliertes_Wasser#Herstellung

"distillied water is produced by distillation (evaporation and recondensation) of normal water. it is free of salts, organic material and microorganisms. it can still contain small amounts of highly volative particles and compounds."

 

[etudiant]

In the earlier phase of the accident, the emissions were mostly volatile fission products, noble gases plus cesium and iodine.
I do not know if the cesium compounds are still the largest contributor to the ongoing emissions.
TEPCO may have provided a comprehensive analysis at some stage, but if so, I've missed it.

 

[LabratSR]

Plan to cover SFP of Unit 4

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110927_01-e.pdf



Rad survey of Units 2 and 3 first floor

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110927_02-e.pdf

 

[etudiant]

Plan to cover SFP of Unit 4

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110927_01-e.pdf
Rad survey of Units 2 and 3 first floor

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110927_02-e.pdf

Pretty serious readings.
An hour's work to max out in some places, at best a shift in others.
This cleanup is going to be like WW 1, trench warfare for a very long time, with brutal human costs.
No quick fixes, no expedient solutions.

The cover of the SPF is presumably to keep out debris as the wreckage around the pool gets cleaned up.
As long as the pool is kept cool and full, that cover should be the nearest thing to a low radiation zone on that floor.

 

[Rive]

As long as the pool is kept cool and full, that cover should be the nearest thing to a low radiation zone on that floor.

That floor has no known 'high radiation zone'. The most recent survey map I could found: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110630_03-e.pdf

 

[etudiant]

That floor has no known 'high radiation zone'. The most recent survey map I could found: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110630_03-e.pdf

Thank you for that helpful link.
I had assumed the floor was dangerous to work on based on TEPCOs decision to jury rig a remote cooling system for the SFP after discovering piping damage.

 

[Rive]

It's dangerous, but not on radiation basis. IMHO, it's more dangerous than the 5th floor of U2 which is expected to be seriously contaminated...

 

[Booomboxxxx]

http://www.youtube.com/watch?v=4Mcn6MFut9U&feature=channel_video_title

recent measurement in no 3 reactor building

 

[curious11]

amusing that they have a hole in the "floats" to observe water level... surely if they are using floats, they would notice the floats dissapearing down a hole if the water lever were to fall?

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110929/index.html The hydrogen concentration in unit 1 PCV spray line was found to be 61~63%. The remaining more than 30% is thought to be nitrogen added after the accident.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110928_02-e.pdf "Unit 1 Re-measurement of hydrogen density in plumbing for spray of primary containment vessel"

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110928_03-e.pdf "Unit 1 Replacement of nitrogen at connector of gas monitoring system of containment vessel"

http://www.tepco.co.jp/cc/press/betu11_j/images/110812d.pdf Report in Japanese about worker exposure at Fukushima Daiichi. The positions (green, orange, pink circles) and movements (red and black arrows) of the workers inside control rooms and the direction of the wind (blue arrows) are shown on the maps on page 53 (units 1&2 control room) and 54 (units 3&4 control room) (pdf page numbers). Pages 35, 36, 52, 53 provide detailed timelines of the tasks performed by four workers named "C", "D", "E", and "F". The table on page 40 describes the exposure circumstances for twenty workers (A ~ F, ア ~　セ). The column 1 on the left is their internal contamination in mSv, column 2 says if they wore a mask, column 3 if they ate or drank(有=yes, 無=no), column 4 if they wore glasses (temples may create an interstice through which contaminated air can leak), column 5 if they worked near the door. The table page 42 provides the radiations in cpm measured at units 3&4 control room on 13 March from 10:00 AM to 01:30 PM. Column 1 (on the left) at the front door, column 2 at the emergency door, column 3 at the desk unit 3 side, column 4 at the desk unit 4 side.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110812e14.pdf Full English translation of the above mentioned report

 

[Astronuc]

Cold shutdown - http://www.nrc.gov/reading-rm/basic-ref/glossary/cold-shutdown.html
The term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200 degrees Fahrenheit [100 degrees Centigrade] following a reactor cooldown.

Don't read more into it than the temperature.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ2011092111472

Sep 21 - Under the government's conditions for cold shutdown, the Fukushima reactors' temperatures must remain under 100 degrees and authorities must confirm that new radioactive materials are not being released.

The temperature at the No. 1 reactor was about 82 degrees on Sept. 20, while the No. 3 reactor had a temperature of about 88 degrees. The temperature at the No. 2 reactor was about 112 degrees, but officials plan to increase the volume of cooling water pumped into that reactor.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ2011092912644
Sep 28 - Water at 3 Fukushima reactors under 100 degrees for first time

 

[etudiant]

Asahi :

Sep 21 - Under the government's conditions for cold shutdown, the Fukushima reactors' temperatures must remain under 100 degrees and authorities must confirm that new radioactive materials are not being released.

It would seem we are still far from reaching 'cold shutdown' by this definition, as the current emissions of radioactive material were stated to be around 200,000,000 bequerels.
Are these emissions likely to be concentrated in the steam plumes shown earlier in the videos of reactors 2 and 3 or is it just remobilization of pollutants spewed out earlier?

 

[Astronuc]

Asahi :

Sep 21 - Under the government's conditions for cold shutdown, the Fukushima reactors' temperatures must remain under 100 degrees and authorities must confirm that new radioactive materials are not being released.

It would seem we are still far from reaching 'cold shutdown' by this definition, as the current emissions of radioactive material were stated to be around 200,000,000 bequerels.
Are these emissions likely to be concentrated in the steam plumes shown earlier in the videos of reactors 2 and 3 or is it just remobilization of pollutants spewed out earlier?

I'd like to know the radionuclides being monitored. The article contains insufficient details, and I haven't confirmed if they got it right. It's possible that some of that is Kr-85 (noble gas), Cs-134, Cs-137 (in form of hydrated hydroxide), which could be in steam. Cerainly the water being flushed through the units will be contaminated with solubles and particulates.

From the Asahi article of Sept 21

Officials have estimated that the amount of new radioactive materials released into the atmosphere from the reactors is now about 200 million becquerels per hour, about one-four-millionths the level immediately after the accident started on March 11.

The annual level of radiation at the entrance to the Fukushima plant was detected at 0.4 millisieverts, which is lower than the 1 millisievert objective for cold shutdown, according to officials.

In order to convert Bq/hr into mSv/time, one would need to know the isotopes.

"3 mSv/yr (approx) is the typical background radiation from natural sources in North America, including an average of almost 2 mSv/yr from radon in air." - from http://www.world-nuclear.org/education/ral.htm

In certain areas, e.g., along the Appalacian mountain in E. US, radon is at a higher level than most of the country, so I think the typical exposure to natural sources is more like 1-2 mSv/yr for most people.

 

[etudiant]

The report on the 'Status of countermeasures' from the JAIF ( http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1317292903P.pdf ) which is now updated every Thursday,
has this comment qualifying the 'cold shutdown' :
"...public radiation exposure by additional release is being significantly held down".
The plan appears to be for some ongoing releases to be considered acceptable, provided they are relatively small.

 

[SteveElbows]

As I had previously gone on about suppression chamber water temperature increases at reactor 2, I think I should mention that the temperatures stopped increasing and started to go back down, with the peak on September 25th. The only exception is the suppression chamber gas temperature, which continues to rise at a rate of approx 1 degree C per day.

 

[Edano]

http://www.tepco.co.jp/nu/fukushima-np/f1/images/csv_level_pr_data_1u-j.csv

#1 drywell B radiation now 512 Sv/hr, after 405.

http://www.houseoffoust.com/edano/1rad.bmp

http://www.houseoffoust.com/reactors/graphs.html

 

[Edano]

As I had previously gone on about suppression chamber water temperature increases at reactor 2, I think I should mention that the temperatures stopped increasing and started to go back down, with the peak on September 25th. The only exception is the suppression chamber gas temperature, which continues to rise at a rate of approx 1 degree C per day.

... and #2 torus B radiation still slightly rising, with increased, but very slightly falling torus B radiation.

 

[zapperzero]

http://www.meti.go.jp/english/earthquake/nuclear/iaea/pdf/20110911/chapter2.pdf

pp 203

Samples taken on June 20 in multiple locations, all approximately 500 meters away from reactor site, show Uranium, Plutonium, Americium and Curium.

EDIT: I don't remember seeing this in the first report to IAEA

 

[SteveElbows]

http://www.meti.go.jp/english/earthquake/nuclear/iaea/pdf/20110911/chapter2.pdf

pp 203

Samples taken on June 20 in multiple locations, all approximately 500 meters away from reactor site, show Uranium, Plutonium, Americium and Curium.

EDIT: I don't remember seeing this in the first report to IAEA

Wasn't the first report done before June?

Anyway here is the press release & documents that were released at the time the soil analysis was first published:

http://www.tepco.co.jp/en/press/corp-com/release/11061105-e.html

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111002/index.html Tepco's internal investigation committee is preparing an interim report into the accident. According to the draft report, the explosion at unit 2 was not a hydrogen explosion. Whereas the damage at unit 4 and unit 2 occurred almost at the same time, the seismometer readings show only one hydrogen explosion which is thought to be the one which occurred at unit 4. The pressure in unit 2's suppression chamber dropped suddenly and it is thought that, for some reason, the suppression chamber was damaged.

 

[zapperzero]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111002/index.html Tepco's internal investigation committee is preparing an interim report into the accident. According to the draft report, the explosion at unit 2 was not a hydrogen explosion. Whereas the damage at unit 4 and unit 2 occurred almost at the same time, the seismometer readings show only one hydrogen explosion which is thought to be the one which occurred at unit 4. The pressure in unit 2's suppression chamber dropped suddenly and it is thought that, for some reason, the suppression chamber was damaged.

What else could sound like an explosion, manage to break containment but not be an explosion? Any word on that?