Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[clancy688]

as much as they posted before , before "converting Bequerel from cesium to Bequerel from iodine equivalent"

Yeah... if I understand correctly, the previous numbers were 0.69 Tbq/h I131 and 0.14 TBq/h C137 (forgive me for mistakes, I'm reciting those numbers from my memory). They just added those two numbers and got 0.83 TBq escaping activity per hour.
That's not wrong... that's the activity you can measure. But if you want to tell people how bad that activity is (for example 1000 TBq Krypton-85 per hour would pose no real threat), you convert it into I131 equivalence.

They didn't do that with those numbers and have done that afterwards - but the number they got the second time wasn't per hour, but per day.

Before conversion:

0.69 TBq/h + 0.14 TBq/h = 0.83 TBq/h
0.83 TBq/h * 24h = 19.92 TBq/d

After conversion:

0.69 TBq/h * 1 + 0.14 TBq/h * 40 = 6.29 TBq/h
6.29 TBq/h * 24h = 150.96 TBq/d

The released activity didn't change at all. They only changed the math. It shows you now, that those 20 TBq of I131 and C137 which are escaping per day are as dangerous as 150 TBq I131.

If the number is stable then that's a radioactivity release on Three Mile Island Scale every four days. And a radioactivity release on Chernobyl scale every 110 years.

 

[triumph61]

Re the image at http://www.panoramio.com/photo/49439865



Which indications do you see, that it is a fake?

The Foto is too small 40kb to see if it is real. It is made before B3 Explosion (no debrid on the Roof) No one says that soneone has made a hole in the Building or an Explosion before B3.
sorry in English ist is difficult to explain.

 

[htf]

At least at Unit 1 they manually operated the hardened vent valve. The worker who performed that task received a significant dose that was reported in TEPCO Press Releases. Since that was well after batteries would have been drained I assume they also vented units 2 and 3 manually.

I am thinking about the security concept. Did I get this right:

- venting of the RPV is possible from a remote location or happens automatically even without power.

- venting of the containment requires electrical power. In case of a station blackout someone has to enter the recator building an manually open a valve?

So the security concept is based on the fact that you find somebody stupid enough to do that? Somebody who knows that he will receive a high dose of radiation and may be torn to pieces by a hydrogen explosion? Guess what I would have done in such a situation...

 

[biffvernon]

No one says that soneone has made a hole in the Building

I guess the building must have a door - even a pretty big door to get equipment in and out. But that 'hole' does seem a long way above ground level and there's no sign of it in the earlier picture:

[PLAIN]http://img.ibtimes.com/www/data/images/full/2011/03/15/74732-tokyo-electric-power-co-s-fukushima-daiichi-nuclear-plant-no-4-reactor.jpg

 

[triumph61]

I guess the building must have a door - even a pretty big door to get equipment in and out.

it is on the other side

 

[MiceAndMen]

On the Tepco hand out page at:
http://www.tepco.co.jp/en/news/110311/index-e.html
there are separate photos of the control rooms of unit 3, and 4, and also the photo you are discussing -- according to Tepco the 'Control room for Unit 3 and 4'.

The three photos can be compared, and it can be verified, that the control panel design in the right part of the photo of the 'control room for unit 3 and 4' perfectly matches the control panel design found shown in the individual photo of the control room of unit 3, and -- despite the darkness of it -- that the control panel design in the left side of the photo appears to match the one shown for the control room of unit 4.

Enhancing the contrast of the "unit 3 and 4" picture reveals details on the left, dark side of the picture. It does appear to be part of a control room. I'll accept that the dark part of the room on the left is for Unit 4.

I don't see that the left or the right of the "unit 3 and 4" picture matches up with anything in the individual control room pics for 3 and 4, however. For instance, in the half-dark "unit 3 and 4" picture, there's a diagram of the drywell and torus at the far right. I don't see that in the individual Unit 3 picture anywhere. Similarly, on the far left there are round dials to the left of the whiteboard. I don't see those anywhere in the Unit 4 by-itself picture.

Are we looking at the same pictures? I could be wrong. It wouldn't be the first time in this thread where people claim pictures show things that I don't see.

 

[biffvernon]

Indeed it is. Just exploring the possibility that the 'hole' is there on purpose. I think it's pretty unlikely. A shame the picture with the 'hole' isn't at a higher resolution. It does seem to be corroborated with the satellite pic. It's at a different angle but even lower resolution.

 

[PietKuip]

This photo I believe was taken on the 11th or the 12th of March 2011:
http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

To state the obvious, this is before unit 4 blew up :-)

However, first question:
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Is not this a shadow from the top of one of the venting towers?

 

[MiceAndMen]

Page 117 and following deals with various venting related issues
http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima9April2011.pdf

even more interesting to read:
http://www.osti.gov/bridge/servlets/purl/6980202-feK1wp/6980202.pdf

"THE ROLE OF BWR SECONDARY CONTAINMENTS IN SEVERE ACCIDENT MITIGATION:
ISSUES AND INSIGH1S FROM RECENT ANALYSES"

The second paper linked is one I saw early on. On pp 4-5:

The secondary containments of domestic BWRs were designed and/or constructed
by ten different architect/engineering firms (Table 1) , and vary considerably in basic design characteristics such as volume, number of floors, the arrangement of stairways and elevator shafts, etc.

That was and is the basis for my contention that it's not a good idea to speculate too much on the exact locations of reactor building layouts and positioning of components inside. We know now pretty much where the SFPs are in units 3 and 4, but to my mind it was grossly premature to take the ubiquitous color GE artist's concept sketch of a Mark I reactor building and extrapolate too much information from it, and subsequently treat that speculation as fact.

We still have not seen any diagrams of the refueling floors at Fukushima Dai-ichi. In fact, except for a couple of elevation drawings we haven't seen much of anything regarding the internal arrangement of any building at the site. All we have are guesses; admittedly educated guesses, and on this forum they can be quite good, but there is a lot we don't know.

 

[NUCENG]

Yes but you can't vent only manualy with holes, maybe they open vent valve but this wouldn't remove much hydrogene, there is another system for that but i t need power to work, you can see it on some pictures of bwr reactors for example in usa, but it is like venting system in normal buildings, it need power to pump off hydrogene from reactor hall...

I think you are confusing the hardened vent and vent through the standby gas treatment system SBGT requires power to run, but is a low pressure system and shouldn't have been used on a pressurized containment. The hardened ven simply opens a path to the stack and vents the high pressure to the stack. No power needed it works on differential pressure.

 

[elektrownik]

I think you are confusing the hardened vent and vent through the standby gas treatment system SBGT requires power to run, but is a low pressure system and shouldn't have been used on a pressurized containment. The hardened ven simply opens a path to the stack and vents the high pressure to the stack. No power needed it works on differential pressure.

Yes but it would only decrease pressure and would not remove hydrogene

 

[MadderDoc]

The Foto is too small 40kb to see if it is real. It is made before B3 Explosion (no debrid on the Roof) No one says that soneone has made a hole in the Building or an Explosion before B3.
sorry in English ist is difficult to explain.

You appear to be close to saying that because we think there wasn't a hole in B4 before the explosion in B3, then a photo which appears to show a hole in B4 before that must be a fake.

Consider, though, that independently taken satellite photos from Digitalglobe from the 12th and 13th of March show a quite similar defect of the wall, at the very same spot:

If there indeed was a hole in the east wall of unit4, before the explosions, as these photos appear to be showing, there is no need to hypothesise about an extra explosion to cause it, nor that someone made the hole deliberately. We need no further assumptions because, we know that the building had just before been exposed to an extraordinarily strong earthquake.

 

[Astronuc]

You appear to be close to saying that because we think there wasn't a hole in B4 before the explosion in B3, then a photo which appears to show a hole in B4 before that must be a fake.

Consider, though, that independently taken satellite photos from Digitalglobe from the 12th and 13th of March show a quite similar defect of the wall, at the very same spot:

If there indeed was a hole in the east wall of unit4, before the explosions, as these photos appear to be showing, there is no need to hypothesise about an extra explosion to cause it, nor that someone made the hole deliberately. We need no further assumptions because, we know that the building had just before been exposed to an extraordinarily strong earthquake.

They may have been trying to vent near the SFP. They vented Unit 2 in a similar manner, but they really needed the vent near the roof.

 

[etudiant]

Surely the opening is a door.
There is a flight of steps leading up to that level n the south side and there are what may be 4 heat exchangers on the roof between the reactor and turbine buildings. So it is a routinely accessed site.
It would be expected that the support structure of the reactor building, with a large elevator, would be used to help move large items to the roof of the turbine building, as we have here. That requires a big door.

 

[MadderDoc]

Is not this a shadow from the top of one of the venting towers?

That's what I thought too until it occurred to me by looking at the light and shadows that this photo must have been taken before noon. So the shadows of the exhaust towers are all on the west side of the buildings.

 

[Caniche]

Yeah... if I understand correctly, the previous numbers were 0.69 Tbq/h I131 and 0.14 TBq/h C137 (forgive me for mistakes, I'm reciting those numbers from my memory). They just added those two numbers and got 0.83 TBq escaping activity per hour.
That's not wrong... that's the activity you can measure. But if you want to tell people how bad that activity is (for example 1000 TBq Krypton-85 per hour would pose no real threat), you convert it into I131 equivalence.

They didn't do that with those numbers and have done that afterwards - but the number they got the second time wasn't per hour, but per day.

Before conversion:

0.69 TBq/h + 0.14 TBq/h = 0.83 TBq/h
0.83 TBq/h * 24h = 19.92 TBq/d

After conversion:

0.69 TBq/h * 1 + 0.14 TBq/h * 40 = 6.29 TBq/h
6.29 TBq/h * 24h = 150.96 TBq/d

The released activity didn't change at all. They only changed the math. It shows you now, that those 20 TBq of I131 and C137 which are escaping per day are as dangerous as 150 TBq I131.

If the number is stable then that's a radioactivity release on Three Mile Island Scale every four days. And a radioactivity release on Chernobyl scale every 110 years.

Now I'm confused . Is that 20TBq daily discharge a combined figure for I131/c137 ?
Anyhow the independent nuclear test ban monitors put the average daily discharge figures for c137 at 5000TBq's per day. So ignoring liquid discharge and overlooking the hygroscopic tendencies of Ce 137 ,after 50 days that puts the total discharge of radioactive Ce137 at roughly 250,000 TBq as compared with the stated fallout of 85,000 TBq from Chernobyl.
I'm probably wrong but from official figures it does appear that we waved goodbye to the chernobyl monster about four weeks ago Tuesday and just keep on growing :-(

 

[MiceAndMen]

Indeed. I found a blueprint of the service floor layout, supposedly of units #2--#5, in this page

http://fukushimafaq.wikispaces.com/3D+and+Autocad+Rendering+%26+Analysis

I have seen that page. He got that floorplan layout from here after I originally posted it here on 15 April . It's from the Oyster Creek blueprint set, and is cropped from the original exactly the way I cropped it before posting it. There is no doubt in my mind he got that diagram from here.

Finally for now an image was posted this evening of a layout of the service floor showing the SFP etc, this I believe is the missing link which should allow me to finish the 3D model for some more interesting analysis, this also supports my view the reactor is off-centre.

The OC floor layout is probably close to the Fukushima Dai-ichi ones, but they are not identical. I'm glad he found it useful

As for buildings 2-4, I think I found a vertical elevation cross-section for Unit 3 in a Japanese-language PDF which I discovered a few days ago. I'll look for the link for you.

 

[Most Curious]

Page 117 and following deals with various venting related issues
http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima9April2011.pdf

even more interesting to read:
http://www.osti.gov/bridge/servlets/purl/6980202-feK1wp/6980202.pdf

"THE ROLE OF BWR SECONDARY CONTAINMENTS IN SEVERE ACCIDENT MITIGATION:
ISSUES AND INSIGH1S FROM RECENT ANALYSES"

The CalTech document is a great collection of pictures and data relating to the Fukushima accident. I read it 10 days ago but glad to see it posted here again for all to consider.

I think it will be determined at some time in the future's investigation that like most of the bad things that happened resulted because of the total station blackout - a beyond design basis event. IOW, they were screwed when the tsunami took out the generators.

The venting system relies on fans and filters to remove particles before discharge up the stack. Apparently, little thought was given to a natural draft type back-up venting plan. Top goal was preventing radioactive release. Being so focused on that primary goal, they designed systems that INCREASED such releases in a severe accident!


What I have not seen discussed (and in 300 pages I may well have missed it!) is service water. Was service water (sea water for cooling) available after the EQ? Would it have been available after the tsunami IF electrical power had remained available? Once the suppression pools reached 100 degrees C even the steam driven pumps would have become useless. Just how long does it take to heat the SC to 100C without service water cooling available? Did high SC temperature fail the steam driven pumps or did loss of battery power cause that?

 

[clancy688]

Now I'm confused . Is that 20TBq daily discharge a combined figure for I131/c137 ?

Bingo. http://www-pub.iaea.org/MTCD/publications/PDF/INES-2009_web.pdf" page 15 for further informations.

Anyhow the independent nuclear test ban monitors put the average daily discharge figures for c137 at 5000TBq's per day. So ignoring liquid discharge and overlooking the hygroscopic tendencies of Ce 137 ,after 50 days that puts the total discharge of radioactive Ce137 at roughly 250,000 TBq as compared with the stated fallout of 85,000 TBq from Chernobyl.

Source please? The austrian meteorological agency ZAMG http://www.zamg.ac.at/aktuell/index.php?seite=2&artikel=ZAMG_2011-04-02GMT09:28" the C137 releases from March 12th - 19th at 1000 - 70.000 TBq. Initial estimates were afaik up to 5000 TBq C137 per day. And they are using the nuclear test ban network (CTBTO).

But that doesn't count for ALL days. Watch http://fukushima.grs.de/sites/default/files/Messwerte_ODL_Fukushima_Daiichi_110421-1230_Gesamt.pdf"chart. You can see that there were big radioactivity releases between March 12th and 19th. And afterwards practically nothing.
The reactors were releasing up to 10.000 TBq per hour at one time, but only for a short period. Now it's at the 20 TBq per day, or 150 TBq converted.

 

[MadderDoc]

Surely the opening is a door.
There is a flight of steps leading up to that level n the south side and there are what may be 4 heat exchangers on the roof between the reactor and turbine buildings. So it is a routinely accessed site.
It would be expected that the support structure of the reactor building, with a large elevator, would be used to help move large items to the roof of the turbine building, as we have here. That requires a big door.

Consider the position of the apparent hole, and where this assumed door would lead into below the service floor. What use would a big door be of there? For lifting large items to the roof floor, it should be above the service floor.

But indeed the building appears to have had such a opening, however at the wall panel at row 2, column 4.

Note the distinctly different way this panel has been blown off, with remaining sharp edges and paint deco along those edges. We see the same phenomenon at unit 3, the exact same position, row 2, column 4. The opening that has been made in the east wall of unit 2 is also in this position.

 

[rowmag]

Here is a Picture of the Map

Here are some easier to read versions of the map, from the morning papers:

From Asahi Shimbun:
[URL]http://www.asahi.com/special/10005/images/TKY201104240165.jpg[/URL]

From Yomiuri Shimbun:
[PLAIN]http://www.yomiuri.co.jp/photo/20110424-585450-1-L.jpg

The numbers are all in mSv/h.

There is a notable accumulation of hot material around the NW corner of the Unit 1 reactor building. Is Unit 1's SFP on the north side of the building?

Unit 4 does not appear to have scattered much radioactive material onto the ground.

Unit 3's stuff went all over the place.

 

[clancy688]

Interesting, the 300 and 900 mSv/h chunks were found where the big debris from the Unit 3 explosion must have gone down.

 

[MiceAndMen]

This photo I believe was taken on the 11th or the 12th of March 2011:
http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

To state the obvious, this is before unit 4 blew up :-)

However, first question:
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Hard to tell what the sun angle is, but it looks to me like the shadow of the top of the south vent stack.

 

[Dmytry]

Ok, seriously, why convert it to I-131 equivalent? It is so meaningless. The Cs-137 is a long term hazard, accumulates in muscle tissue. The I-131 is a short term hazard, it accumulates in thyroid, it is preventable with iodine tablets. I will refrain from telling what I think about this conversion of everything to "I-131 equivalent".

 

[TCups]

That's what I thought too until it occurred to me by looking at the light and shadows that this photo must have been taken before noon. So the shadows of the exhaust towers are all on the west side of the buildings.

Unit 4 was down for service. There is a flight of stairs, yes, but it accesses the roof adjacent to the open panel. More likely it is a door or a removable service panel to allow equipment to be moved onto or off of the roof. Low resolution, but at magnification, it does not look to be damage due to an explosion or fire. There is no corresponding debris on the adjacent roof either.

 

[NUCENG]

Yes but it would only decrease pressure and would not remove hydrogene

The theory of operation of the hardened wetwell vent starts with a containment inerted with nitrogen. The accident releases steam and hydrogen into the containment via the SRVs to the suppression pool where the steam is condensed. As the suppression pool heats up and containment pressure rises torus to drywell vacuum breakers will equalize pressure venting some of the hydrogen back into the drywell. The venting via the hardened vent is done from the airspace at the top of the airspace in the suppression chamber/torus. The venting will remove some of the hydrogen along with stteam and other non-condensible gases. As pressure in the torus drops the differental pressure in the drywell will displace water in the downcomers allowing noncondensiblesm hydrogen and steam from the drywell to vent to the torus and out the vent as well. You are right that it does not remove all of the hydrogen. It is only designed to reduce pressure and prevent containment failure from over-pressurization.

 

[NUCENG]

Surely the opening is a door.
There is a flight of steps leading up to that level n the south side and there are what may be 4 heat exchangers on the roof between the reactor and turbine buildings. So it is a routinely accessed site.
It would be expected that the support structure of the reactor building, with a large elevator, would be used to help move large items to the roof of the turbine building, as we have here. That requires a big door.

BWRs have doors at the other side of the building in the area where casks are loaded or onladed onto transporters. I have never seen a door in that location at a BWR.

 

[etudiant]

The theory of operation of the hardened wetwell vent starts with a containment inerted with nitrogen. The accident releases steam and hydrogen into the containment via the SRVs to the suppression pool where the steam is condensed. As the suppression pool heats up and containment pressure rises torus to drywell vacuum breakers will equalize pressure venting some of the hydrogen back into the drywell. The venting via the hardened vent is done from the airspace at the top of the airspace in the suppression chamber/torus. The venting will remove some of the hydrogen along with stteam and other non-condensible gases. As pressure in the torus drops the differental pressure in the drywell will displace water in the downcomers allowing noncondensiblesm hydrogen and steam from the drywell to vent to the torus and out the vent as well. You are right that it does not remove all of the hydrogen. It is only designed to reduce pressure and prevent containment failure from over-pressurization.

Hydrogen/air mixtures are explosive over a very wide range, from 5%-40% if memory serves. So having the hydrogen diluted but more widely spread may actually increase the hazard.
Was this risk given serious study or is it just another unexpected issue that cropped up as operations became more frequent?

 

[MadderDoc]

<..>
I don't see that the left or the right of the "unit 3 and 4" picture matches up with anything in the individual control room pics for 3 and 4, however. For instance, in the half-dark "unit 3 and 4" picture, there's a diagram of the drywell and torus at the far right. I don't see that in the individual Unit 3 picture anywhere. Similarly, on the far left there are round dials to the left of the whiteboard. I don't see those anywhere in the Unit 4 by-itself picture.
<..>

That is true, you don't see that. My take on it is that the two 'by itself' photos of unit 3 and 4 are pointed in such disparate directions in the room, that they do not overlap with any part of the combination photo taken at the boundary between the two. However, consider the designs of the control panels, in particular the hand railings along them, and the cupboards below (see attachments). This is of course not proof, but it is a strong indication that we are looking at two parts of the same unit 3 control board, and two parts of the same unit 4 controlboard

 

[NUCENG]

Hydrogen/air mixtures are explosive over a very wide range, from 5%-40% if memory serves. So having the hydrogen diluted but more widely spread may actually increase the hazard.
Was this risk given serious study or is it just another unexpected issue that cropped up as operations became more frequent?

As long as the containment is pressurized above atmosphere the amount of oxygen inside containment should remain low. The elevated release point would allow any hydrogen deflagration or detonation to occur away from the vital equipment. Of course if they delayed venting until it caused leaks in the containment or in the vent piping, then you get hydrogen where you don't want it. Good questions!

 

[MadderDoc]

Hard to tell what the sun angle is, but it looks to me like the shadow of the top of the south vent stack.

It is clear from the shadows that this photo has been taken well before noon, (the sun is towards the seaside). The shadow of the south vent stack does not hit the south east corner of the unit 4 building until after noon.

 

[Caniche]

Bingo. http://www-pub.iaea.org/MTCD/publications/PDF/INES-2009_web.pdf" page 15 for further informations.



Source please? The austrian meteorological agency ZAMG http://www.zamg.ac.at/aktuell/index.php?seite=2&artikel=ZAMG_2011-04-02GMT09:28" the C137 releases from March 12th - 19th at 1000 - 70.000 TBq. Initial estimates were afaik up to 5000 TBq C137 per day. And they are using the nuclear test ban network (CTBTO).

But that doesn't count for ALL days. Watch http://fukushima.grs.de/sites/default/files/Messwerte_ODL_Fukushima_Daiichi_110421-1230_Gesamt.pdf"chart. You can see that there were big radioactivity releases between March 12th and 19th. And afterwards practically nothing.
The reactors were releasing up to 10.000 TBq per hour at one time, but only for a short period. Now it's at the 20 TBq per day, or 150 TBq converted.

Yes I see the chart ,thank you ,most reassuring. Still confused though because even if the data was accurate only up to the date of issue ,12/4/2011 that still gives 30 x5,000TBqs of Ce137 average daily emission or 2 x chernobyl in one month as opposed to i x every 100 years.
Any idea what happened after the 19th to reduce discharge to ripe banana levels? Did the containment barriers heal up ? Did the damaged fuel rods (up to 70%) get better, or did the water bombs water cannon and 'concrete pumps' get enough liquid on to prevent most airborne discharge?

 

[gmax137]

What I have not seen discussed (and in 300 pages I may well have missed it!) is service water. Was service water (sea water for cooling) available after the EQ? Would it have been available after the tsunami IF electrical power had remained available? Once the suppression pools reached 100 degrees C even the steam driven pumps would have become useless. Just how long does it take to heat the SC to 100C without service water cooling available? Did high SC temperature fail the steam driven pumps or did loss of battery power cause that?

I too have wondered about the service water pumps, and did they survive the EQ & tsunami. I'm pretty sure I asked about that somewhere way up the thread, but I never got an answer. Looking at the photos of the intake area, the damage looked pretty severe to me, and that's where one usually finds the service water pumps. I'm not sure what they're called in a BWR, so I don't know how to ask more directly.

I had my doubts that the steam-driven cooling would fail on loss of DC; seems like the valves (steam to the turbine & water from the pump to the reactor) would either fail-as-is on loss of power, or have handwheels for local manual operation. Along with procedures, communications, emergency lighting, and accessabilty to take such action. That's what I'm used to seeing in PWR designs.

 

[MadderDoc]

<..> it does not look to be damage due to an explosion or fire. There is no corresponding debris on the adjacent roof either.

True it doesn't look like the result of an explosion or a fire, but we cannot deny that it could be the result of the shaking of the building and its internals during the earthquake. We have indications that the FHM4 may have collided with the east wall (the bent hockey stick), and we cannot say whether that damage happened during the unit 4 explosion, or before it.

Debris from a putative before-explosion hole would be expected to be covered up by the debris of the explosion.

 

[etudiant]

Yes I see the chart ,thank you ,most reassuring. Still confused though because even if the data was accurate only up to the date of issue ,12/4/2011 that still gives 30 x5,000TBqs of Ce137 average daily emission or 2 x chernobyl in one month as opposed to i x every 100 years.
Any idea what happened after the 19th to reduce discharge to ripe banana levels? Did the containment barriers heal up ? Did the damaged fuel rods (up to 70%) get better, or did the water bombs water cannon and 'concrete pumps' get enough liquid on to prevent most airborne discharge?

You raise the same question that has bothered me for some time.
ZAMG was the only source that provided overall emission estimates from an early period. They initially estimated about 1/10th Chernobyl output daily, measured in bequerels and claimed that the levels found after several days by the CTBT network were within a factor of two of the measures generated by their model using those assumptions.
Since then, they have added that their estimates represent an upper bound and might be high by as much as a factor of 1000, but the evacuation zone in Japan is growing and in some dimensions now rivals that at Chernobyl, so there is concern.
Perhaps ZAMGs more positive recent estimates will prove correct.
However, it would be very useful to have a credible and comprehensive assessment of the scale of the airborne emissions.
Of course, the summer winds and rains will provide ground truth on the scale of these emissions by their contamination of central Japan. It would be useful though to have some specific idea of the damage to be expected.