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.
  • #10,151
tsutsuji said:
http://www.asahi.com/national/jiji/JJT201106220097.html : The filtration efficiency of the absorption facility and the coprecipitation facility put together was found to be OK in the tests with highly contaminated water. The efficiency of the absorption facility is lower with highly contaminated water than during the tests with low contaminated water, but that is still high enough.

http://www.yomiuri.co.jp/science/news/20110622-OYT1T00967.htm provides filtration rates :

Kurion (absorption facility) : 1/50 (instead of the expected 1/1000)
Areva (coprecipitation facility) : < 1/400※ (expected 1/1000)

and a more prudent conclusion: "It is unclear whether putting both systems together can provide a stable water treatment".

※below the measurement limit.

EDIT : see also the measurement results in the following press release : http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110622_04-j.pdf : left column is before treatment, (1) is after the Kurion treatment, and (2) is after the Areva treatment.
 
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Engineering news on Phys.org
  • #10,152
Working conditions improve at Fukushima unit
22 June 2011
http://www.world-nuclear-news.org/RS-Working_conditions_improve_at_Fukushima_unit-2206114.html

Hopefully, we will learn more about the condition of the Units as TEPCO regains access.

The point of filtering the water is too clean up the radionuclides and reduce activity in the areas where workers ultimately must access. The collected radionuclides will obviously have to be consolidated and placed in a repository.

The cleaner water will provide shielding for subsequent work to remove the fuel from the SFPs and the damaged cores. However, it will take years to accomplish much of that.
 
  • #10,153
Astronuc said:
Working conditions improve at Fukushima unit
22 June 2011
http://www.world-nuclear-news.org/RS-Working_conditions_improve_at_Fukushima_unit-2206114.html

The cleaner water will provide shielding for subsequent work to remove the fuel from the SFPs and the damaged cores. However, it will take years to accomplish much of that.

Hopefully the cleaner water will improve the high levels of radiation in the basement (430mSv(/hr?) in the top left stairwell and 388 mSv(/hr?) in the bottom right stairwell reported in http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110622_02-e.pdf").

I really feel for those guys...

A technical question. If we assume that:
1. The general radiation in Unit 2 1st floor is ~30 mSv/hr.
2. The people working in there are wearing protective equipment (Tyvek coveralls etc.)

Does the dose received equal the radiation they are exposed to (e.g. if I were to walk about there for an hour, would it add 30 mSv to my dose). Or is there an attenuation due to some factor like the protective equipment I would be wearing? Or my (average) 1 m distance from the floor?

Thanks.
 
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  • #10,154
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  • #10,155
Bandit127 said:
Hopefully the cleaner water will improve the high levels of radiation in the basement (430mSv(/hr?) in the top left stairwell and 388 mSv(/hr?) in the bottom right stairwell reported in http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110622_02-e.pdf").

I really feel for those guys...

A technical question. If we assume that:
1. The general radiation in Unit 2 1st floor is ~30 mSv/hr.
2. The people working in there are wearing protective equipment (Tyvek coveralls etc.)

Does the dose received equal the radiation they are exposed to (e.g. if I were to walk about there for an hour, would it add 30 mSv to my dose). Or is there an attenuation due to some factor like the protective equipment I would be wearing? Or my (average) 1 m distance from the floor?

Thanks.
There would be attenutation with distance and shielding. The problem is mostly gamma radiation which is highly penetrating. Beta particles go a relatively short distance in air, and much less in metal.

A dosimeter measures at the location of the dosimeter.

With respect to any dose rate, I'd want to know the portion that is beta and the portion that is gamma.
 
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  • #10,156
http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html : alongside the poor decontamination factor at the Kurion facility, an unexplained phenomenon took place. Although the radioactive substances were expected to accumulate more in the first absorption tower upstream, it is in the last absorption tower downstream that a 3 mSv/h radiation was observed on June 21st or even 15 mSv/h on June 22nd.
 
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  • #10,157
Astronuc said:
There would be attenutation with distance and shielding. The problem is mostly gamma radiation which is highly penetrating. Beta particles go a relatively short distance in air, and much less in metal.

A dosimeter measures at the location of the dosimeter.

With respect to any dose rate, I'd want to know the portion that is beta and the portion that is gamma.

The sievert is (as far as i understand it) is a dose equivalent based on gamma. If the radiation were reported in grays, then you would indeed want to know the proportion of beta and gamma. But I am hoping we can ignore this for the sake of this question since the proportion should be accounted for.

Let us assume that the dosimeter was placed at my average height of (just under) 1m, then we can ignore height.

My question remains, if I stand in an area of ~30 mSv does this mean my dose is ~30 mSv?

I ask this beacuse 3 workers who stood in water containing 2-6 Sv were reported to have a recived a dose of http://www.cbsnews.com/stories/2011/03/24/501364/main20046609.shtml".

In fact, thinking it through as I am typing - perhaps I should ask a different question.

If I were a worker on Floor 1 of Unit 2 where the radiation appears to average ~30 mSv/hr, would I accumulate 30 mSv/hr of dose in 1 hour and therefore reach my annual limit after (250 / 30 = 8.333 hrs] 8 hours and 20 minutes?
 
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  • #10,158
Astronuc said:
A dosimeter measures at the location of the dosimeter.

Presumably workers wear their dosimeters inside their protective suits, whereas the ambient contamination measurements are taken with unshielded meters; is this correct?
 
  • #10,159
tsutsuji said:
http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html : alongside the poor decontamination factor at the Kurion facility, an unexplained phenomenon took place. Although the radioactive substances were expected to accumulate more in the first absorption tower upstream, it is in the last absorption tower downstream that a 3 mSv/h radiation was observed on June 21st or even 15 mSv/h on June 22nd.

Seems that there is considerable incremental performance potential once they get this system properly balanced.
TEPCO should be happy to have the performance starting at 99+% removal, simply to free up some space in the plant. Additional improvements will require tweaking the process.
 
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  • #10,160
tsutsuji said:
http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html : alongside the poor decontamination factor at the Kurion facility, an unexplained phenomenon took place. Although the radioactive substances were expected to accumulate more in the first absorption tower upstream, it is in the last absorption tower downstream that a 3 mSv/h radiation was observed on June 21st or even 15 mSv/h on June 22nd.

Chromatography?
 
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  • #10,161
Bandit127 said:
My question remains, if I stand in an area of ~30 mSv does this mean my dose is ~30 mSv?

I ask this beacuse 3 workers who stood in water containing 2-6 Sv were reported to have a recived a dose of http://www.cbsnews.com/stories/2011/03/24/501364/main20046609.shtml".

In fact, thinking it through as I am typing - perhaps I should ask a different question.

If I were a worker on Floor 1 of Unit 2 where the radiation appears to average ~30 mSv/hr, would I accumulate 30 mSv/hr of dose in 1 hour and therefore reach my annual limit after (250 / 30 = 8.333 hrs] 8 hours and 20 minutes?

How long did they stand in the water for? You have already acknowledged that length of exposure time is an important factor, so should not miss it out of that example as it will be a huge difference maker.

The dose a worker receives will be based on what the dosimeter records, and this will reflect the changing levels of radiation depending on exactly where they are standing in relation to radioactive hotspots, not some average figure like the one you speak of. We have seen from various surveys of different reactors that the detected radiation levels have varied considerably in different areas, and a key to minimising workers exposure is to locate these hotspots and either avoid them or find ways to shield workers from them.

I doubt that dosimeters are perfect, and it is possible to imagine scenarios where they fail to capture a decent picture of the radiation a person is actually exposed to. Especially early on TEPCO struggled badly in this regard, since they were not even able to give each individual human their own device.

Despite protective clothing & breathing apparatus designed to guard against internal exposure, to evaluate workers exposure as best as possible they also need to do forms of scanning on people, and add any results to the ones from dosimeter history to get a persons total.

Finally, if the workers are involved in some sort of incident where solid data personal to them is not available, or is suspected of being inaccurate, it may be necessary to estimate doses based on whatever incident factors that are known and measured. I am not sure entirely how the dose was calculated for the workers who got their feet wet, but I tend not to lose too much sleep over it because at the end of the day these Sievert figures are not a perfect guide to the health consequences in any given person anyway, they just give us some sense of the magnitude of risk that people are being exposed to.
 
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  • #10,162
Jorge Stolfi said:
Presumably workers wear their dosimeters inside their protective suits, whereas the ambient contamination measurements are taken with unshielded meters; is this correct?

I am not sure about that. I've seen them using meters packed in all kind of plastic and stuff, that ought to be protective against radiation in a fashion quite similar to the personal Tyvek suits.
 
  • #10,164
Bandit127 said:
If I were a worker on Floor 1 of Unit 2 where the radiation appears to average ~30 mSv/hr, would I accumulate 30 mSv/hr of dose in 1 hour and therefore reach my annual limit after (250 / 30 = 8.333 hrs] 8 hours and 20 minutes?

Yes, that would seem to be the case, as a first approximation of the potential exposure it ought to do.
 
  • #10,165
Also depends on the part of the body exposed. Say the feet vs whole body.
 
  • #10,166
tsutsuji said:
http://www.yomiuri.co.jp/science/news/20110622-OYT1T00967.htm provides filtration rates :

Kurion (absorption facility) : 1/50 (instead of the expected 1/1000)
Areva (coprecipitation facility) : < 1/400※ (expected 1/1000)

and a more prudent conclusion: "It is unclear whether putting both systems together can provide a stable water treatment".

※below the measurement limit.

I can see that the Kurion filtration rates are lower than expected, but the final outcome is "ND" (below detection level), which is presumably what you would want.

Lest anybody misread the above, the result for the Areva stage did not achieve a 1:400 instead of a 1:1000 reduction, it's input was 400 times as radioactive as the detection limit for the output (which came out ND), so it must have achieved at least a 1:400 reduction.

tsutsuji said:
EDIT : see also the measurement results in the following press release : http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110622_04-j.pdf : left column is before treatment, (1) is after the Kurion treatment, and (2) is after the Areva treatment.

The overall cesium decontamination factor came out as at least 1:20,000 on Cs-134 and 1:22,000 on Cs-137.

If they were expecting a higher decontamination factor, presumably they would have used a more sensitive test on the final output? Their cutoff was at 100 Bq/cm3, which still is 500 times the limit for drinking water, but then they're not hoping to be able to drink this, only use it for reactor cooling or perhaps send it by boat to a nuclear reprocessing plant.
 
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  • #10,167
WhoWee said:
Another quake with tsunami warnings
http://www.usatoday.com/news/world/2011-06-22-Japan-earthquake-tsunami_n.htm
They shouldn't get much of a tsunami from that.

http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0004e5w.php

A mag 6.7, close to the coast, 39.980°N, 142.247°E at a depth of 32 km (19.9 miles).

Edit: I looked up the location of Fukushima Daiichi:
Code: 
Fukushima 37° 25' 17'' N, 141° 1' 57'' E
          37.421389, 141.0325

Then applied: Distance = sqrt(x2 + y2)

where x = 69.1 * (lat2 - lat1)
and y = 69.1 * (lon2 - lon1) * cos(lat1/57.3)

x = 176.8, y = 66.65
distance (earthquake to Fukushima Daiichi) ~ 189 mi, 304 km.

The quake is a challenge to nearby structures, but not a tsunami threat.

http://ptwc.weather.gov/ptwc/text.php?id=pacific.2011.06.22.215933

EVALUATION

NO DESTRUCTIVE WIDESPREAD TSUNAMI THREAT EXISTS BASED ON
HISTORICAL EARTHQUAKE AND TSUNAMI DATA.

HOWEVER - EARTHQUAKES OF THIS SIZE SOMETIMES GENERATE LOCAL
TSUNAMIS THAT CAN BE DESTRUCTIVE ALONG COASTS LOCATED WITHIN
A HUNDRED KILOMETERS OF THE EARTHQUAKE EPICENTER. AUTHORITIES
IN THE REGION OF THE EPICENTER SHOULD BE AWARE OF THIS
POSSIBILITY AND TAKE APPROPRIATE ACTION.

THIS WILL BE THE ONLY BULLETIN ISSUED FOR THIS EVENT UNLESS
ADDITIONAL INFORMATION BECOMES AVAILABLE.

It's the vertical displacement of the sea floor or solid/liquid (crust/ocean) interface, particularly abrupt vertical displacement, that matters.

It's all about the physics (and the math)!
 
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  • #10,168
MadderDoc said:
Yes, that would seem to be the case, as a first approximation of the potential exposure it ought to do.
But the individual is also picking up exposure to ionizing radiation while on the Grounds of the plant and on the way to the plant.
 
  • #10,169
""Presumably workers wear their dosimeters inside their protective suits, whereas the ambient contamination measurements are taken with unshielded meters; is this correct?""

common sense applies it's just a little hard when you are unfamiliar to know what makes sense.

where i worked we wore dosimetry outside protective clothing. Not for shielding value of the clothing ( basically zero) but so it'll be obvious if you lose it and your buddies will holler at you.. It goes at chest level so as to be not far from most of your organs.
If you're going someplace that's contaminated you put it in a teeny ziplock bag and affix that with masking tape and a twistie-tie, still on outside of clothes. The ziploc bag keeps the dosimeter from picking up radioactive dirt. It needs to be kept clean so you can take it to the clean area of plant at shift's end.


and to bandit's question regarding dose vs rate...

yes, in a 30 mr(or mSv) per hour field you will accrue that amount every hour and reach your limit in the time you proposed.

Standing water in a radiation area is a red flag - stay away because it may be chock full of Beta contamination.
Beta rays go only inches in air so at chest level your dosimiter may read safe while your feet are getting a pretty good dose. Survey meter won't see it either unless you put it right down at surface.
That's what happened to those poor guys laying cables - they just didnt know to stay away from water. Their feet took a big dose but fortunately Betas mostly go only skin deep. And there's not many important organs in our extremities, maybe a little bone marrow.

if i can help others with practical basics that's my contribution here.

old jim
 
  • #10,170
tsutsuji said:
http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html : alongside the poor decontamination factor at the Kurion facility, an unexplained phenomenon took place. Although the radioactive substances were expected to accumulate more in the first absorption tower upstream, it is in the last absorption tower downstream that a 3 mSv/h radiation was observed on June 21st or even 15 mSv/h on June 22nd.

http://www.tokyo-np.co.jp/article/national/news/CK2011062302000200.html : There was a mistake on a command panel. One or more bypass valves marked "closed" on the command panel were actually open, so one or more absorption towers were being bypassed.

http://www.asahi.com/national/jiji/JJT201106230039.html : As a result of the mistake, only 1 out of 4 cesium absorption towers was actually being used. After checking the valves and correcting the mistake, the test has been started again with a 50 ton/hour flow.

If my understanding is correct, what this Asahi/Jiji article is saying is that in a normal operation, one cesium tower is bypassed for maintenance, while the other 3 are active. As a result of the mistake, they were doing just the opposite. Yet only one valve was wrong.

Tepco provides a diagram explaining the mistake : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_01-e.pdf
 
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  • #10,171
  • #10,172
tsutsuji said:
<..>Yet only one valve was wrong.

Tepco provides a diagram explaining the mistake : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_01-e.pdf

Good old Murphy. Does the 3 mSv/h radiation observed on June 21st and 15 mSv/h on June 22nd represent the radioactive contamination density of the water leaving the tower, or the amount absorbed in it?
 
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  • #10,173
MadderDoc said:
Good old Murphy. Does the 3 mSv/h radiation observed on June 21st and 15 mSv/h on June 22nd represent the radioactive contamination density of the water leaving the tower, or the amount absorbed in it?

From http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html , it is impossible to say if this is a measurement made before or after flushing, and at which absorption tower these radiations were observed. My best guess is that it was at one of the iodine removal towers because they say "the most downstream tower", but it could be the most downstream of the 4 cesium removal towers.

I am still trying to figure out where these sensors are located. Are they on the inner side or on the outer side of the concrete shield ? If the purpose is to figure out how much radiations the workers are facing when working nearby, I would tend to think that they must be located outside the shield.

There is a section view of the towers here : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110619_04-e.pdf but I am looking forward for a drawing with the location of the radiation sensor.
 
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  • #10,174
Interesting: reactor 2 water level sensor is "under inspection" and there is no data, so maybe they are recalibrating it ? If yes we should know soon what is real water level
 
  • #10,175
tsutsuji said:
From http://www3.nhk.or.jp/news/html/20110623/t10013703941000.html , it is impossible to say if this is a measurement made before or after flushing, and at which absorption tower these radiations were observed. My best guess is that it was at one of the iodine removal towers because they say "the most downstream tower", but it could be the most downstream of the 4 cesium removal towers.

Yes. In the immediate context I took it to express the puzzlement by observing high radiation in the most downstream of the cesium removal towers in operation (which they then thought had all been connected in series.) But then they found out that what was thought to be the most downstream tower, was actually not. Due to wrong valve settings it had been shunted across the other towers in operation, and hence it carried most of the flow. That's why I was interested in knowing if the figures meant it had absorbed most of the load of contaminant having most of the load injected to it -- or alternatively that it had been overloaded by this heavier load and therefore no longer retained the contaminant as efficiently.

I am still trying to figure out where these sensors are located. Are they on the inner side or on the outer side of the concrete shield ? If the purpose is to figure out how much radiations the workers are facing when working nearby, I would tend to think that they must be located outside the shield.

There is a section view of the towers here : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110619_04-e.pdf but I am looking forward for a drawing with the location of the radiation sensor.

Again from the context it would seem to me implied that the higher than expected radiation at least inconvenienced the work, and could be taken as a proxy for potential exposure. I suppose sensors outside the shield at the outlet from towers could be used for assessing the decontamination factor too, in which case sensors could serve both purposes.
 
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  • #10,176
jim hardy said:
(snip)
That's what happened to those poor guys laying cables - they just didnt know to stay away from water. Their feet took a big dose but fortunately Betas mostly go only skin deep.

(snip)

old jim


Has there ever been an update published on the progress and current condition of those guys?


As well as not knowing to stay away from water (I think they had to paddle in it anyway to do their work - plus they had not been supplied with suitable boots).

My dad had a skin cancer zapped with beta rays (he'd fooled around too much with UV lamps in the 1930's). The treatment was effective - but you really would not want a burn like his over anything other than a very small area.
 
  • #10,177
There are no updates on any of the workers killed or injured since 311
 
  • #10,179
elektrownik said:
Interesting: reactor 2 water level sensor is "under inspection" and there is no data, so maybe they are recalibrating it ? If yes we should know soon what is real water level

They are doing pretty much the same at 2 as they did previously at 1.

As far as the water level goes, this is likely to result in confirmation that water level lower than previously reported, but as they've already done an analysis based on this possibility, this probably won't generate the sort of interest that it did when it happened with reactor 1.

As for pressure, again it is likely to be less interesting than reactor 1 because the pressure has been showing as negligible for a long time anyways.

But yeah, they are doing the work, because the other day they posted a diagram of the new pressure indicator setup, as they did with reactor 1:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110622_01-e.pdf

And a photo of them working on this:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_04-e.pdf

And a photo of some shielding they have installed to protect workers in this area (an issue I touched on recently here in the discussion about what dose workers would actually receive)

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_03-e.pdf
 
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  • #10,180
Well it looks like they are really pushing the plan to reduce water injection rate to the reactors as far as they can.

According to latest status update, as of 11am on June 23rd, rates are:

Reactor 1 3.5m3/h
Reactor 2 3.5m3/h
Reactor 3 9.4-9.5m3/h

Taken from http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_06-e.pdf which also has reference to some other stuff mentioned on this thread very recently:

On June 22, we installed Reactor Temporary Pressure Meter of Unit 2.

On June 23, we injected water into instrumentation piping arrangement of Reactor Temporary Pressure Meter of Unit 2. We also installed hoses in the nitrogen injection line of Reactor Containment Vessel of Unit 2.
 
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  • #10,181
Calvadosser said:

Has there ever been an update published on the progress and current condition of those guys?

I can't find a decent link for it, but I do remember reading that they received a whole body dose of around 180 mSv and were released from hospital a few days later.
 
  • #10,182
Thank you for all your informative replies to my questions about the exposure of workers (https://www.physicsforums.com/showpost.php?p=3370408&postcount=10172").

It is good to see that they are putting measures in place to reduce exposure too.
SteveElbows said:
And a photo of some shielding they have installed to protect workers in this area (an issue I touched on recently here in the discussion about what dose workers would actually receive)

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_03-e.pdf

I am sure Tepco are managing the exposure of workers better than this, but the possibility of receiving your annual (emergency) dose in 8 hours puts the task facing those workers in context.
 
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  • #10,183
Bandit127 said:
I can't find a decent link for it, but I do remember reading that they received a whole body dose of around 180 mSv and were released from hospital a few days later.

This was about two other workers, not those from turbine building water...
This is interesting, reactor 2 released biggest amount of radiation (into basement water), ant there is interesting thing, unit 1 which doesn't have such big power like 2,3 increase temperature when they reduced amount of injected water, but it look like it doesn't make difference for unit 2, the temperature is stable, so there is question where core is now, some peoples think that it is in reactor basement, this would explain extream water contamination and no change in temperature...
 
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  • #10,184
elektrownik said:
This was about two other workers, not those from turbine building water...

I think it was those from the turbine building water.

I found a link. Not to the report that they were released from hospital, but it does describe their estimated dose.
http://www.tepco.co.jp/en/press/corp-com/release/11032503-e.html"

It says they ignored their radiation alarms. The mind boggles...
 
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  • #10,185
Crane's back. 21:30 GMT. Nothing on the TEPCO camera.
crane2.jpg
 

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