Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[etudiant]

The monthly change was named with regards to the oil separating part ,not the cesium filters

These oil filters are somehow accumulating radioactivity where they are not supposed to ,

but the oil needs to be filtered out to avoid damaging the cesium filters.

There are 4 parallel installed processing lines

Thank you for the extra insight on the filter changes.
The question remains for me, how do they plan to capture 300PBqs of cesium in cartridges that need to be manually changed. The cesium is about a million curies worth, unless I've dropped a decimal somewhere.

 

[clancy688]

The cesium is about a million curies worth, unless I've dropped a decimal somewhere.

You did. It's ten million. ;)

I'd be interested in how many becquerels one filter is supposed to capture until it's changed. Or does anybody know how to convert "4 mS/v" of C134 and C137 at a 1:1 ratio into becquerel?

 

[Atomfritz]

]Wouldn't an old fashioned moonshine still scaled up to industrial size capture the oil and sludge and most of the contamination too before handing the water to your equipment ?

Perhaps a big prefilter unit...

Hmm, could a lake serve as temporary storage, oil and particle separator all-in-one?

Thank you for the extra insight on the filter changes.
The question remains for me, how do they plan to capture 300PBqs of cesium in cartridges that need to be manually changed. The cesium is about a million curies worth, unless I've dropped a decimal somewhere.

I also don't understand this. Formerly in https://www.physicsforums.com/showpost.php?p=3333806&postcount=8633" I calculated the mass of a megacurie Cs-134 as 773 grams and of Cs-137 as 11.55 kg.
So alone the cesium contamination in the water could be in the magnitude of a hundred kilograms up.

By the way, the Kurion steel/glass things appear to be designed to be handled remotely and instantly vitrified after getting satiated.
But I miss any statements that there a vitrification plant is projected.

Irradiation sources containing only milligrams of Cs are being transported in heavy lead shielding.
And there have been several detailed IAEA reports on the dire medical outcomes of people touching or approaching such very small sources unshielded.
Other uncanny reports tell about the fate of workers in the irradiation business.

So this is maybe just a calculation mistake?
It would not be the first one, and worse even would be the fact that Tepco, Areva and the other parties involved all overlooked that mistake.

 

[jlduh]

Thank you for the extra insight on the filter changes.
The question remains for me, how do they plan to capture 300PBqs of cesium in cartridges that need to be manually changed. The cesium is about a million curies worth, unless I've dropped a decimal somewhere.

Well, again, this is my main question: how can so much radioactivity which is normally contained inside a so big containment system (a reactor building) be contained in cartridges that have to be handled and stored? What kind of shielding in a cartridge can replace the one from a complete reactor? Contamination will be concentrated in these cartridges but how can this all system be run without huge radiation around pipes, cartridges and so on, making it almost unmanageable with the kind of volumes per day we are talking about?

This is a complete mystery for me...

But maybe this sentence from NHK is a beginning of the answer:

TEPCO says the effort will require time. In addition, depending on the situation, it may have to reconsider the working of the entire system and examine the effect of radioactivity emitted from nearby pipes.

By the way, i checked weather forecast and more than 70mm of rain are anticipated in the area in the next week... so new thousands of tons of water from this "natural cooling" will add soon to the current amount contained in the site. The situation is getting critical this time.

http://www.weather-forecast.com/locations/Fukushima/forecasts/latest

 

[razzz]

Grime, oil and don't forget salt all radioactive. Grime can be settled out in a holding pond, oil need detergent to separate it, and salt needs an acid bath.

Passive filtering would be pumping it to the top and let gravity pull it down through filters and trickle out the bottom for further processing.

All these things and mechanical separation like centrifuges besides heat distillation need added materials that become contaminated. Looks like they picked pressure filtering as the main theme which is working, the pre-clean problems can be overcome but has to be done on a massive scale. They should probably irradiate an empty oil tanker while waiting to figure out what to do. Buy some time storing it elsewhere.

 

[clancy688]

And there have been several detailed IAEA reports on the dire medical outcomes of people touching or approaching such very small sources unshielded.

The Goiana accident would be a very great example (INES 5, 1987, 93 grams, 50 TBq). The orphan source consisted of C137.

So this is maybe just a calculation mistake?
It would not be the first one, and worse even would be the fact that Tepco, Areva and the other parties involved all overlooked that mistake.

If so, then it would rather be a measuring mistake than a calculation mistake. They got the 720 PBq number by measuring each basement / turbine building / etc. alone and adding up the numbers.
I got the 2 * 140 PBq number for C134 and C137 by taking TEPCOs measurements of each basement / turbine building / etc. and adding up the numbers for each single isotope.

The pdf in question: http://www.tepco.co.jp/cc/press/betu11_j/images/110603a.pdf (page 8)

 

[Atomfritz]

Or does anybody know how to convert "4 mS/v" of C134 and C137 at a 1:1 ratio into becquerel?

Important and difficult question.
This http://www.aristatek.com/Newsletter/05%2002%20February/The%20First%20Responder%20Technically%20Speaking.htm" has a description of how this can be calculated and provides various examples.

Quotes:
"For example, the flux of gamma photons from 1 gram of Cesium 137 at a distance of 10 meters in air is 2.7543 (10)9 photons/m2-s. This converts to a dose of 0.402 rem/hr. There is only one gamma energy level to consider (0.66 MeV) and no neutron emissions."
"At 100 meters away, the rem dose for the cesium 137 example would probably be on the order of 0.004 rem/hour."

(See my last post for conversion becquerel->gram. For other isotopes FAS has a list also http://www.fas.org/programs/ssp/nukes/armscontrol/uraniumdirtybombs.html".)
Hope this helps to convert to Sieverts.

 

[clancy688]

Quotes:
"For example, the flux of gamma photons from 1 gram of Cesium 137 at a distance of 10 meters in air is 2.7543 (10)9 photons/m2-s. This converts to a dose of 0.402 rem/hr. There is only one gamma energy level to consider (0.66 MeV) and no neutron emissions."

That would be about 200 Sv/h at 10 meters for all basement water C137 collected in a bucket. Nice. Or rather... "ouch".

 

[MJRacer]

The monthly change was named with regards to the oil separating part ,not the cesium filters

These oil filters are somehow accumulating radioactivity where they are not supposed to ,

but the oil needs to be filtered out to avoid damaging the cesium filters.

There are 4 parallel installed processing lines

If I am not hallucinating, here is what may be happening:

Interesting things happen at interfaces. They tend to collect impurities. Consequently, one way to purify/refine/decontaminate something is to play with interfaces. Sugar is refined by crystallization. After crystals are grown, many if not most of the impurities will be on the surface of each crystal. By controlling the size of each crystal, it is possible to grow crystals of fairly uniform size that are larger than a given size wire mesh. After growing them, the crystal surfaces can be washed off, thus removing a huge amount of impurities in a single step. 2 crystallization steps suffice to produce almost perfectly pure sugar, by exploiting a liquid/crystal interface. Similarly, IIRC silicon is refined by pushing melt zones through a crystal. The impurities collect at the liquid/crystal interface and are pushed out with the melt zone. Beer can be concentrated by lowering its temperature slowly until water crystals form, which are then removed. The result is Eisbock. These are just some examples.

One would have to ask the NEs, but I suspect that highly radioactive water has, until now, almost never been contaminated with hydrocarbons. At Fukushima, several very large fuel tanks for the diesel generators were displaced by the tsunami. I would suspect that the thousands of gallons of fuel inside of them were also spread around the plant site. In designing the water treatment system, it appears to me that a rather conventional approach was taken by removing each contaminant in a separate step. There was no time for test runs.

They chose to remove oil via "dissolved air flotation," thus creating an air/oil/water emulsion with three interfaces: oil/water, air/oil and air/water. Furthermore, there is another interface involving the different viscosities of oil and water. As I said before, impurities tend to collect at interfaces. In this case, after concentrating impurities at the three interfaces, I would suggest that the impurities were trapped within the oil due to the large difference in viscosity between oil and water. Consequently, when the first Kurion ISM (oil and technetium) trapped the remaining oil droplets, it may also have trapped a good bit of all radioactive particulates and not just technetium. Hence, the large and rapid rise in radioactivity of the first cartridge.

They may have just discovered a novel way to remove large amounts of radioactive contamination from water in just three steps: (1) pour bucket of diesel fuel into contaminated water, (2) form air/oil/water emulsion, (3) filter through Kurion oil+technetium cartridge and Bob's your uncle! By trapping the oil droplets in the Kurion cartridge, the hot particles are also trapped. If this is happening, then one should be able to take a sample of what was collected in the first oil+technetium cartridge and see if large quantities of cesium and perhaps iodine are being trapped. They shouldn't be, as the next two cartridges are where the cesium and iodine, respectivelly, are supposed to be trapped.

If my theory is shown to be valid, then no flocculation step is necessary. The system will have shown itself to be effective at trapping hot particles in only 3 steps. However, the operational difficulties of dealing with hot cartridges may be very challenging.

Either that or I am totally wrong.

 

[joewein]

They got the 720 PBq number by measuring each basement / turbine building / etc. alone and adding up the numbers.
I got the 2 * 140 PBq number for C134 and C137 by taking TEPCOs measurements of each basement / turbine building / etc. and adding up the numbers for each single isotope.

The pdf in question: http://www.tepco.co.jp/cc/press/betu11_j/images/110603a.pdf (page 8)

I can confirm your calculations.

From the same data I also get a total of 3 kg of Cs-134 and 44 kg of Cs-137 in 105,100 t of water in units 1-4 and the central rad waste building.

 

[intric8]

Also, if filters reach capacity every 5 hours (assuming that is the worst case scenario), they will be going through roughly 3600 cartridges per month. I wonder if our friends at Kurion have planned for the possible eventuality of supplying many thousands of cartridges over the next year or two? And as clancy pointed out-

That would be about 200 Sv/h at 10 meters for all basement water C137 collected in a bucket. Nice. Or rather... "ouch".

That figure underscores how daunting of a task this recycling idea really is, making it difficult for me to feel optimistic about its long term sustainability.

At this juncture, the ball seems squarely in Kurion's court. Areva hangs around trying to be useful somehow, and Tepco is forced to find other means to store or dispose of the water.

 

[etudiant]

None of the process problems would matter if there were adequate storage for the contaminated water.
Yet 100,000 tons is the capacity of a small tanker. Presumably TEPCO could afford to buy a couple of double hulled tankers for use as a temporary storage depot. The tankers might need to be scrapped after use, but they are cheap, maybe $50mm tops.
In fact, if the water could be transported elsewhere, it would allow a much better shot at setting up and running a decent purification facility, something impossible in this small site where everything has to be shoehorned to fit.
Is there some fatal objection to such an approach?

 

[joewein]

Is there some fatal objection to such an approach?

Using an unmanned tanker anchored within the harbour basin of the plant, it seems like a no brainer to me: There is nothing to lose compared to letting the water drain directly into the ocean.

As for using the tanker to ship out the water however, I suspect the tanker idea becomes more viable only *after* the water has been processed. It was my impression that this was the idea with the floating platform too: Decontaminate the water as much as possible, pump it into the "megafloat" and tow it to Rokkasho-mura for final cleanup.

The radiation on a vessel filled with that much cesium solution should be a serious hazard to any crew and I can't see much political acceptance from any prefecture near the plant to let this pass their coast, let alone dock in a port.

 

[Orcas George]

Here are some objections that I can think of:

1) You are giving the radiation more "legs"; disabled radioactive tanker drifting off of Tokyo would be a Tom Clancy novel, nothing you want in real life.

2) Tankers are not designed to be leakproof, so you could easily have a spill during the filling process -- and that would mean you now have an unapproachable tanker full of radioactive crud. This could be mitigated if we started a couple of months ago, perhaps somebody has and we don't know about it.

3) If another tsunami hits while the tanker is being filled?

4) Fukushima harbor is apparently shallow (they call it the "shallow draft quay") so getting the stuff out to the tanker may be as complicated as the decontamination process, and just as risky. You are going to have long tubes with radioactive water going out to a ship bobbing at anchor, and you cannot allow any of it to spill.

5) I do not know if the bridge of a tanker will be sufficiently isolated from the hold for the crew to be able to operate it if the hold is highly radioactive. The last thing you want is a Mary Celeste situation.

I think railway cars might be a solution, or tanker trucks. (They have a pretty cool radio-controlled excavator, why not a truck cab?) One thing to avoid is all of the radioactive eggs in one basket, as tempting as it sounds. We know how to deal with things like leaking tank cars, leaking tankers are a different matter. (Break out the poly wrap!)

 

[MadderDoc]

It is not plausible that the exhauster after having done relatively little to lower the air contamination over a 5 day operation period, then suddenly over a 12 hour period appears to have decimated it. It is also not plausible that it is due to a measurement or graphing error.

But Tepco could plausibly have opened the door, letting in fresh air. Yesterdays press article reported that taking this step had been authorized.

I wrote this with reference to measurements published in
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110617_01-e.pdf

I shall have to eat my words, seeing this document:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110619e2.pdf

According to this latter document, the radioactive content in unit 2 air on June 18th was back up where it was before and during the first 5 days of exhauster operation -- iow it appears to have had no real effect -- and there is reason to think that the drastic drop displayed by the former document was a fluke and may well not have reflected reality in unit 2. Nonetheless Tepco says it will commence gradually opening the doors to unit 2 starting today (March 19th) -- only now not with reference to any strong effect of the exhauster, but rather with reference to the expectation that opening doors will not significantly change the radioactive content in air at the boundary of the plant.

 

[tsutsuji]

Thank you for the extra insight on the filter changes.
The question remains for me, how do they plan to capture 300PBqs of cesium in cartridges that need to be manually changed. The cesium is about a million curies worth, unless I've dropped a decimal somewhere.

According to http://www.meti.go.jp/press/2011/06/20110609006/20110609006-2.pdf the purifying facility is supposed to produce, over one year :

2,000 m³ of radioactive sludge will be produced. 400 caesium absorption towers will be spent.

I have no idea how the petabecquerels are distributed between the towers/cartridges and the sludge, but the fact that cooling is mentioned only in connection with the sludge made me imagine that the sludge was hotter than the cartridges.

You did. It's ten million. ;)

I'd be interested in how many becquerels one filter is supposed to capture until it's changed. Or does anybody know how to convert "4 mS/v" of C134 and C137 at a 1:1 ratio into becquerel?

My understanding is that the 4 mSv/h

* were measured in the air outside the vessel
* dropped to 1 mSv/h or lower after flushing

So you cannot consider these 4 mSv/h as something measuring directly the radiations inside the cartridge/tower.

 

[GJBRKS]

They may have just discovered a novel way to remove large amounts of radioactive contamination from water in just three steps: (1) pour bucket of diesel fuel into contaminated water, (2) form air/oil/water emulsion, (3) filter through Kurion oil+technetium cartridge and Bob's your uncle! By trapping the oil droplets in the Kurion cartridge, the hot particles are also trapped. If this is happening, then one should be able to take a sample of what was collected in the first oil+technetium cartridge and see if large quantities of cesium and perhaps iodine are being trapped. They shouldn't be, as the next two cartridges are where the cesium and iodine, respectivelly, are supposed to be trapped.

If my theory is shown to be valid, then no flocculation step is necessary. The system will have shown itself to be effective at trapping hot particles in only 3 steps. However, the operational difficulties of dealing with hot cartridges may be very challenging.

The system is an unexpected over-performer.
Perhaps something good will come out of it sooner than expected.

 

[intric8]

Is there some fatal objection to such an approach?

No, though we hope the above statement doesn't turn out to be a real life eventuality with any of the tepco staff.

The long term viability of storing water is also in question, and though i am not professionally in a position to field any recommendations, it sometimes helps to hear observations presented out loud.

 

[clancy688]

If my theory is shown to be valid, then no flocculation step is necessary. The system will have shown itself to be effective at trapping hot particles in only 3 steps. However, the operational difficulties of dealing with hot cartridges may be very challenging.

Well, in that case you'd not only have highly radioactive waste, but highly flammable radioactive waste.

 

[GJBRKS]

Well, in that case you'd not only have highly radioactive waste, but highly flammable radioactive waste.

As I understand it , when diesel , it is not as flammable as gasoline :

http://en.wikipedia.org/wiki/Flammability

http://en.wikipedia.org/wiki/Flash_point

diesel fuel rated 2 as material that must be moderately heated or exposed to relatively high ambient temperatures before they will ignite

 

[Borek]

This can be probably further moderated by additives. Whether it makes sense (that is, doesn't pose additional problems with increased amount of waste) is another question.

However, if the idea is viable, it should work with other oily substances as well, some of them are much less flammable.

 

[tsutsuji]

From NISA's 174th press release http://www.meti.go.jp/press/2011/06/20110619001/20110619001.html (Japanese), there is this figure http://www.meti.go.jp/press/2011/06/20110619001/20110619001-8.pdf provided with the announcement that the water level in the reactor of unit 4 is going to be raised by injecting water from below.

See also the diagram in http://www.47news.jp/CN/201106/CN2011061901000328.html explaining that the water level being too low, the radiations from the shroud and dryers are no longer shielded.

 

[etudiant]

According to http://www.meti.go.jp/press/2011/06/20110609006/20110609006-2.pdf the purifying facility is supposed to produce, over one year :



I have no idea how the petabecquerels are distributed between the towers/cartridges and the sludge, but the fact that cooling is mentioned only in connection with the sludge made me imagine that the sludge was hotter than the cartridges.



My understanding is that the 4 mSv/h

* were measured in the air outside the vessel
* dropped to 1 mSv/h or lower after flushing

So you cannot consider these 4 mSv/h as something measuring directly the radiations inside the cartridge/tower.

Thank you, tsutsuji, for this incremental information.

It does leave me confused.
The Kurion modules were stated to be cesium specific and able to pick up all but 0.1-0.01% of it. Given the close to 50 kg cesium in the water, as joewein calculated in post 10035, there will be a kilogram of cesium per train per month, using all 4 trains and assuming a 1 year operations. That suggests very hot cartridges, excellent from the perspective of the cleanup if the vitrification works, but very hard to reconcile with a 4 mSv/h radiation measure in the vicinity of the cartridge.

 

[tsutsuji]

An Asahi article provides the figures for the radiation measurement after flushing :

Slightly past 3 a.m. on June 18, TEPCO began the purifying operation by pumping in low-level radioactive water, which lowered the radiation levels to 1.76 and 0.95 millisieverts per hour, respectively.
http://www.asahi.com/english/TKY201106180163.html

I previously wrote that the flushing was made with "clean water". That was a bit wrong. Actually it seems that the flushing is performed using the above mentioned "low-level radioactive water".

The Kurion modules were stated to be cesium specific

If you look at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110617_04-e.pdf only the red modules (chabazite ?) are cesium specific. The green modules (where the high radiation problem is occurring) are technetium specific and the yellow modules are iodine specific.

In the June 19th press conference ( http://www.ustream.tv/recorded/15480184 ), if my understanding is correct, the NISA people say that the 4 cesium specific red modules are rotated from time to time so that the first module, which bears the biggest burden is not always the same one. Using this rotation system, the facility was supposed to be able to run over an extended time without any cartridge change.

 

[~kujala~]

See also the diagram in http://www.47news.jp/CN/201106/CN2011061901000328.html explaining that the water level being too low, the radiations from the shroud and dryers are no longer shielded.

In the drawing there is an arrow going from the RPV area into the SFP area.

Does this mean that they now have confirmed that there is a (small) leak from the RPV area into the SFP area?

From NISA's 174th press release http://www.meti.go.jp/press/2011/06/20110619001/20110619001.html (Japanese), there is this figure http://www.meti.go.jp/press/2011/06/20110619001/20110619001-8.pdf provided with the announcement that the water level in the reactor of unit 4 is going to be raised by injecting water from below.

I think this was something rmattila suggested a long time ago also as a possibility for the units #1 - #3. The idea was that this route would perhaps better guarantee that the core area would be cooled.

Now this confirms that it is at least technically possible.

 

[etudiant]

According to http://www.meti.go.jp/press/2011/06/20110609006/20110609006-2.pdf the purifying facility is supposed to produce, over one year :



I have no idea how the petabecquerels are distributed between the towers/cartridges and the sludge, but the fact that cooling is mentioned only in connection with the sludge made me imagine that the sludge was hotter than the cartridges.



My understanding is that the 4 mSv/h

* were measured in the air outside the vessel
* dropped to 1 mSv/h or lower after flushing

So you cannot consider these 4 mSv/h as something measuring directly the radiations inside the cartridge/tower.

An Asahi article provides the figures for the radiation measurement after flushing :



I previously wrote that the flushing was made with "clean water". That was a bit wrong. Actually it seems that the flushing is performed using the above mentioned "low-level radioactive water".



If you look at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110617_04-e.pdf only the red modules (chabazite ?) are cesium specific. The green modules (where the high radiation problem is occurring) are technetium specific and the yellow modules are iodine specific.

In the June 19th press conference ( http://www.ustream.tv/recorded/15480184 ), if my understanding is correct, the NISA people say that the 4 cesium specific red modules are rotated from time to time so that the first module, which bears the biggest burden is not always the same one. Using this rotation system, the facility was supposed to be able to run over an extended time without any cartridge change.

Thanks for the added input.
This makes the design much clearer. It appears to reflect a sensible set of choices, which would also allow the entire set of skids to be changed out monthly. Consequently, there would be no need either for workers to manhandle each cartridge individually, which had been my perception before. So the cartridges might be fairly hot, but still within acceptable range.
Still, current reality is that the system has not yet really been run and time is short. Any further comments on possible fallbacks?

 

[tsutsuji]

In the drawing there is an arrow going from the RPV area into the SFP area.

Does this mean that they now have confirmed that there is a (small) leak from the RPV area into the SFP area?

The drawing's caption ピットの水がプールに流入　means "the water in the pit flows into the pool".

The article text says プールにつながるピットの水位も低下した : "the pit being connected with the pool, the water level in the pit dropped too".

Further explanations are provided in http://www.asahi.com/national/jiji/JJT201106190076.html : between March 15th and March 20th the water level in the spent fuel pool was so low that the difference of pressure between the pit and the pool allowed water to leak from the pit to the pool. After March 20th the water rose in the pool and the gate between the two became watertight again.

 

[Orcas George]

Has anybody seen a report on how long it takes to replace the filter skid, and how many filter skids they have? It is a modular unit that is designed to be replaced.

I hope the issue isn't that since Kurion is a start up, they don't have the resources to manufacture filter units very quickly. That would have been a bad choice of supplier.

From the media reports, it doesn't seem like this first filter unit is anything very special. It seems to be a carbon filter with zeolite instead of carbon. (Oh, excuse me, "surfacant treated zeolite (STZ)" which means that they sprayed soap on it.)


There is surely a plant in China that can stamp out a few of these per day. Given the urgency to the world, a phone call from the Japanese government to one of the big manufacturers would get an expidited response.

If that is the issue start looking for a bunch of DHL trucks to appear on the webcam soon.

 

[SteveElbows]

The drawing's caption ピットの水がプールに流入　means "the water in the pit flows into the pool".

The article text says プールにつながるピットの水位も低下した : "the pit being connected with the pool, the water level in the pit dropped too".

Further explanations are provided in http://www.asahi.com/national/jiji/JJT201106190076.html : between March 15th and March 20th the water level in the spent fuel pool was so low that the difference of pressure between the pit and the pool allowed water to leak from the pit to the pool. After March 20th the water rose in the pool and the gate between the two became watertight again.

Thanks very much for the translation.

Is Unit 5 mentioned anywhere? Because the latest TEPCO status update seems to suggest this work has now ben done at 4 & 5:

- From 9:14 am to 11:57 am on June 19, we injected fresh water to the
reactor wells and pools for setting temporary equipment of Unit 4 and
Unit 5, in order to improve the working environment (to reduce radiation
dose) in the 5th floor of the reactor building of Unit 4 and Unit 5.

From http://www.tepco.co.jp/en/press/corp-com/release/11061907-e.html

 

[elektrownik]

Thanks very much for the translation.

Is Unit 5 mentioned anywhere? Because the latest TEPCO status update seems to suggest this work has now ben done at 4 & 5:



From http://www.tepco.co.jp/en/press/corp-com/release/11061907-e.html

This must be mistake, according to tepco unit 5 is perfect fine, reactor is loaded with fuel and closed

 

[MadderDoc]

<..>After March 20th the water rose in the pool and the gate between the two became watertight again.

Ouch. There goes the only decent explanation we had of the hot water in the reactor cavity.

 

[SteveElbows]

This must be mistake, according to tepco unit 5 is perfect fine, reactor is loaded with fuel and closed

I looked at the Japanese version of this TEPCO info and I think it only mentions 5th floor, not reactor 5. Perhaps someone could confirm, in which case it is indeed an error with the English version.

http://www.tepco.co.jp/nu/f1-np/press_f1/2011/htmldata/bi1574-j.pdf

 

[MiceAndMen]

From NISA's 174th press release http://www.meti.go.jp/press/2011/06/20110619001/20110619001.html (Japanese), there is this figure http://www.meti.go.jp/press/2011/06/20110619001/20110619001-8.pdf provided with the announcement that the water level in the reactor of unit 4 is going to be raised by injecting water from below.

See also the diagram in http://www.47news.jp/CN/201106/CN2011061901000328.html explaining that the water level being too low, the radiations from the shroud and dryers are no longer shielded.

Does this relate to the need to keep the contents of the equipment pool (e.g. the steam dryer and the steam separators) covered? Going in through the bottom of the reactor would be taking the long way around, and implies that debris on the refueling floor will prevent access to the top of the equipment pool for quite a while yet.

 

[MadderDoc]

<..> Going in through the bottom of the reactor would be taking the long way around, and implies that debris on the refueling floor will prevent access to the top of the equipment pool for quite a while yet.

The chosen route for feeding the water also puzzled me, but I can't see how it implies that access to the equipment pool is prevented by debris and will be so prevented for quite a while yet. There could be many other reasons why this route has been chosen.

 

[joewein]

I looked at the Japanese version of this TEPCO info and I think it only mentions 5th floor, not reactor 5. Perhaps someone could confirm, in which case it is indeed an error with the English version.

http://www.tepco.co.jp/nu/f1-np/press_f1/2011/htmldata/bi1574-j.pdf

Your reading is correct, it mentions only the 5th floor of unit 4, but not unit 5:

６月 19 日午前９時 14 分から午前 11 時 57 分まで、４号機原子炉建屋５階の環境改善（線
量低減）のため、同号機原子炉ウェルおよび機器仮置きプールに淡水の注水を行いまし
た。

This confirms the leak between the reactor pit and the pool between March 15 and 20, which is assumed to have saved the fuel in the pool from worse damage.

I am wondering how much of the temperature of the water in the reactor pit can be explained by heat conduction through the gate separating them. The reactor well itself sits insulated inside the containment, so not that much heat should flow via its walls.