Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[ernal_student]

The meltdown occurred before venting and before the fuel rods got exposed?

It might help to recall the details with this excerpt from the accumulated information on the related wikipedia page:

On 11 March at 14:46 JST, unit 1 scrammed successfully in response to the earthquake though evacuated workers reported violent shaking and burst pipes within the reactor building. All generated electrical power was lost following the tsunami leaving only emergency batteries, able to run some of the monitoring and control systems. At 15:42, TEPCO declared a "Nuclear Emergency Situation" for units 1 and 2 because "reactor water coolant injection could not be confirmed for the emergency core cooling systems." [...]

After the loss of site power, unit 1 initially continued cooling using the isolation condenser system; by midnight water levels in the reactor were falling and TEPCO gave warnings of the possibility of radioactive releases. In the early hours of 12 March, TEPCO reported that radiation levels were rising in the turbine building for unit 1 and that it was considering venting some of the mounting pressure into the atmosphere, which could result in the release of some radioactivity. Chief Cabinet Secretary Yukio Edano stated later in the morning the amount of potential radiation would be small and that the prevailing winds were blowing out to sea. At 02:00 JST, the pressure inside the reactor containment was reported to be 600 kPa (6 bar or 87 psi), 200 kPa higher than under normal conditions. At 05:30 JST, the pressure inside reactor 1 was reported to be 2.1 times the "design capacity", 820 kPa.Isolation cooling ceased to operate between midnight and 11:00 JST 12 March, at which point TEPCO started relieving pressure and injecting water. One employee working inside unit 1 at this time received a radiation dose of 106 mSv and was later sent to a hospital to have his condition assessed.

Rising heat within the containment area led to increasing pressure. Electricity was needed for both the cooling water pumps and ventilation fans used to drive gases through heat exchangers within the containment. Releasing gases from the reactor is necessary if pressure becomes too high and has the benefit of cooling the reactor as water boils off but this also means cooling water is being lost and must be replaced. If there was no damage to the fuel elements, water inside the reactor should be only slightly radioactive.

In a press release at 07:00 JST 12 March, TEPCO stated, "Measurement of radioactive material (iodine, etc.) by monitoring car indicates increasing value compared to normal level. One of the monitoring posts is also indicating higher than normal level." Dose rates recorded on the main gate rose from 69 nGy/h (for gamma radiation, equivalent to 69 nSv/h) at 04:00 JST, 12 March, to 866 nGy/h 40 minutes later, before hitting a peak of 0.3855 mSv/h at 10:30 JST.

At 13:30 JST, workers detected radioactive caesium-137 and iodine-131 near reactor 1, which indicated some of the core's fuel had been damaged. Cooling water levels had fallen so much that parts of the nuclear fuel rods were exposed and partial melting might have occurred. Radiation levels at the site boundary exceeded the regulatory limits. [...]

At 15:36 JST on 12 March, there was an explosion in the reactor building at unit 1.

The press release came out at what is now considered the approximate time of the meltdown - during the period of increased gamma radiation.

 

[intric8]

"Does anyone have any reliable info on the nuclear plants - the reports on the news seem garbled to me."

Weeks ago, someone mentioned the very first message in this thread (above), and how things have changed so little with Tepco that this comment is still very appropriate today.

Ringing truer than ever.

 

[triumph61]

According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB10001424052748703509104576325110776621604.html

 

[clancy688]

According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB10001424052748703509104576325110776621604.html

Did they actually solve the Unit 4 explosion mystery? Sounds to good to be true... hence it can't be true! (just kidding... but what's up with them... suddenly releasing informations)

 

[AntonL]

According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB10001424052748703509104576325110776621604.html

Did they actually solve the Unit 4 explosion mystery? Sounds to good to be true... hence it can't be true! (just kidding... but what's up with them... suddenly releasing informations)

Tepco have been reading this forum for ideas, I postulated this a month ago

But where does the Hydrogen come from for the explosion, forum members here agree that the explosion centre was lower down in the building on the north side, which does make sense because of the observed damage.

For that scenario I can also give a very imaginative explanation. When unit 3 was vented, could unit 4 have pumped hydrogen steam into unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure, Furthemore, we do not know if there are any dampers in the system and if installed I would imagine they fail open when power is lost.

Lets assume unit 3 pumped unit 4 full of steam and hydrogen, this would then be into the suppression chamber, then H2 will leak into the primary containment chamber, it would not immediately escape to the roof, as there is a seal between the reactor vessel and PCV so that PCV is not flooded during fuel transfer. The Hydrogen could have leaked out through the access hatch which would not have been sealed due to the maintenance taking place, This access hatch is on the ground floor, which is the right level for a lower explosion centre. The only question why the long delay between units 3 and 4 exploding.

and again later

this new underwater video of SFP4 certainly seems to rule out that SFP4 boiled dry and Hydrogen produced by overheating fuel rods and, so how did the Hydrogen get into reactor 4 building? In my opinion, only two possibilities remain:
1. Hydrogen being pumped into the building during venting of unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure.
2. Radiolysis of water as perhttps://www.physicsforums.com/showpost.php?p=3287847&postcount=6068"

Do you have any other ideas?

 

[PietKuip]

One question for the physicists: core temperature began rising very fast, but once it reached 2900 degrees it suddenly stopped rising. Why? I'd expect a temperature graph resembling a function of ln(x), not such a sudden stop.

It stops at the boiling point of corium. The boiling point of iron is 2750 ºC.

 

[StrangeBeauty]

(just kidding... but what's up with them... suddenly releasing informations)

The cynic in me says the answer is "Please don't look at #3 too closely right now! Oh look! #1 melted down 16 in hrs two months ago! #4 was blown up by #3!" The "shiny object distraction technique" in action. I hope I'm very wrong. :)

 

[clancy688]

It stops at the boiling point of corium. The boiling point of iron is 2750 ºC.

Thanks. And how could they measure those numbers?And another question: Where do I get up to date sensor data of Unit 3?

 

[PietKuip]

Thanks. And how could they measure those numbers?

These are calculations. The timing is made to fit the measured temperatures at different places.

 

[clancy688]

These are calculations. The timing is made to fit the measured temperatures at different places.

I meant, where did they get the numbers to build their graphs in the TEPCO press release regarding the melt down. The graphs shown there don't look as if they were done with calculation data.

 

[|Fred]

Then you should've watched german tv... quite the opposite.

As far as the opinion given in this board was concerned, the exact expertise was (if I recall corectly) " if there is water in the RCV then meltdown is unlikely ". The available data indicated there was some watter.

I do believe that the given statement still stand

 

[GJBRKS]

obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11

i am not sure, where the other data set, that stolfi et al are using originates from.

'On the other hand, as the temperature of the RPV of Unit 1 is in the range of 100°C - 120°C, stable cooling is being achieved'

looking at the #3 data, this is a little scary...

Wow , that link finally makes it clear where to find the D/W HVH temperature sensor :

http://img220.imageshack.us/img220/1281/tempsensors.jpg

And if its BELOW the RPV , then the increasing temperature reading for Unit 3 ( up to 197 Celsius from 125 Celsius within 24 hours) could mean that corium has breached into the containment just now ...

 

[Astronuc]

obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11

i am not sure, where the other data set, that stolfi et al are using originates from.

'On the other hand, as the temperature of the RPV of Unit 1 is in the range of 100°C - 120°C, stable cooling is being achieved'

looking at the #3 data, this is a little scary...

I should point out that the 110515e10.pdf is an analysis - a model - and may not reflect physical reality, which is often the case in licensing/safety analysis. Effectively, to get to fuel pellet melting, they would have to assume near adiabatic conditions.

They also claim to have water in the bottom of the RPV, but not the core. The progression seems somewhat unreal.

 

[Godzilla1985]

Eh, come on. Given TEPCO's own statements concerning #1 in that WSJ article, do you really think any of those gauges can be trusted? #3 probably had a full meltdown after 16 hours as well, and the corium dropped through some time around the 21st of March when that thick black smoke appeared...

 

[~kujala~]

Nice work, Anton!
(BTW: I remember there were some counterarguments against your theory. Now that TEPCO has adopted your theory is there any more validity in these counterarguments? TEPCO engineers must know their plants so their evaluations about possible theories have a certain level of assertiveness, which the outsiders lack.)

 

[triumph61]

The work to install a supporting structure for the floor of the
Spent Fuel Pool of Unit 4 was started. (From May 9.)


http://www.nisa.meti.go.jp/english/files/en20110510-1-1.pdf

Has someone checked the Situation IN Unit 4??

 

[AntonL]

looking at the #3 data, this is a little scary...

[PLAIN]http://k.min.us/iNbS.JPG

 

[GJBRKS]

Eh, come on. Given TEPCO's own statements concerning #1 in that WSJ article, do you really think any of those gauges can be trusted? #3 probably had a full meltdown after 16 hours as well, and the corium dropped through some time around the 21st of March when that thick black smoke appeared...

You talking to me ? ...

 

[jim hardy]

Somebody mentioned that 3 & 4 shared a vent stack.
If that's so,

unit 4 with its substantial heat source in the spent fuel pool should have established a "draft" up its tall stack just from the warm humid air coming off the pool.
No different than your fireplace chimney just lots taller.
Natural circulation, warm light moist air rises. Moist air is lighter than dry air even at same temperature.

That would cause a natural draft from 3 to 4 through whatever remained of 3's ventilation systems so long as the dampers stayed open.

 

[elektrownik]

Interesting that unit 3 temperature going down after boron injection...

 

[SteveElbows]

Interesting that unit 3 temperature going down after boron injection...

The information I've seen says that they only started adding boron to the water this afternoon, and the temperature data we have ends at 11:00 so we don't know what effect the boron has yet.

 

[mscharisma]

obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11

i am not sure, where the other data set, that stolfi et al are using originates from.

'On the other hand, as the temperature of the RPV of Unit 1 is in the range of 100°C - 120°C, stable cooling is being achieved'

looking at the #3 data, this is a little scary...

As Tepco states: "On the other hand, as the temperature of the RPV of Unit1 is in the range of 100-120 degrees Celcius, stable cooling is being achieved."

I recall vividly that in the early days of this disaster, "stable cooling" meant cooling sufficient to prevent uncovering of the core, meltdown, and subsequent breaching of the reactor by corium. Interesting for me as a layperson so see how "stable" - whether relating to cooling directly or to reactor condition as a whole - gets redefined as we go along, and not for the better either.

While I'm reading here and elsewhere diligently, I lack the ability to fully comprehend all of your discussions. So just tell me this, please, you folks who understand physics, reactors, etc.: Maybe while our tolerance level for bad news is being consistently expanded, this situation, regardless of which reactor or SFP, is not getting better, but progressively worse, correct?

(Clarification to be on the safe side: "folks" above not meant derogatory in any way! Appreciate this forum more than you all can ever imagine.)

 

[tsutsuji]

The cynic in me says the answer is "Please don't look at #3 too closely right now! Oh look! #1 melted down 16 in hrs two months ago! #4 was blown up by #3!" The "shiny object distraction technique" in action. I hope I'm very wrong. :)

Special advisor to Prime Minister Goshi Hosono said "Unit 1 is to some extent being appropriately cooled, but what worries me is rather unit 3 which is not necessarily being satisfactorily cooled. How to respond to this is a comparatively heavy weight in my head." http://www.yomiuri.co.jp/politics/news/20110515-OYT1T00446.htm

 

[clancy688]

Okay, another question:

So TEPCO said that Unit 1 suffered a total core meltdown after 16 hours, but most of the core is still contained inside the RPV. Let's assume that's in fact how the situation inside Unit 1 really is.

Then I'm still wondering, if something similar could've happened to Units 2 and 3, or could've not happened for several reasons. I see two big differences between Unit 1 and Units 2 and 3:

First difference would be the emergency cooling system. Unit 1 used an Isolation Condenser. It was probably not effective at all. But Unit 2 and 3 are using a different system, a RCIC. And according to TEPCO, RCIC in Units 2 and 3 worked longer as the Isolation Condenser (if it worked at all). So Units 2 and 3 were after the shutdown probably better cooled than Unit 1.

The second different is the produced heat. Unit 1 is at 1400 MWt, Units 2 and 3 at 2400 MWt. As far as I've seen on the blue prints, Units 1-3 are similar in dimensions, but nearly twice in thermal power.
So in Unit 1's case we've seen that the RPV was able to withstand the decay heat of a molten 1400 MWt core. But that doesn't mean that the RPV will withstand the decay heat of a 2400 MWt molten core.

What I'm trying to say is that what happened to Unit 1 (total core melt down) doesn't necessarily happened to Units 2 and 3. Furthermore that Unit 1's RPV withstood the corium doesn't necessarily mean that the RPVs of Units 2 and 3 will withstand the Corium as well. Or am I wrong?

 

[razzz]

Tepco have been reading this forum for ideas, I postulated this a month ago and again later

That was a bit of nice deductive reasoning there AntonL, even lacking the details of the plumbing. With small self extinguishing fires rumored in Unit 4, I wasn't sure how hydrogen could build up. Looks like the hydrogen was migrating its way to the upper floors but ignited before it could pressurize the entire interior. Doors and passageways were probably left open during the re-construction.

Deciding if your valves should fail open or fail closed must be tough in a nuke plant.

Fallout nearby and around the world had to becoming from somewhere out of this plant, the latest information should be of no surprise. When they recently revised down a 70% loss of a core to 55%, does that mean they lost 15% of a core to vaporization? If the corium is gaining mass, how big can a corium get?

 

[Rive]

According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB10001424052748703509104576325110776621604.html

Well, this has a secondary meaning too: the explosion in U3 was most likely 'just' a hydrogen explosion. IMO, of course.

Ps.: third meaning: the fuel in SFP#4 might be OK.

Unit 3 temperature plots
IMG

Well, it's tempting to apply the graphs on the drawing to produce a film - maybe we would know where is the 'core' :-)

No problem. I wasn't aware of anything like an equipment weight movement list.

It was https://www.physicsforums.com/showpost.php?p=3294820&postcount=6534". Check attachment, second page.

What's interesting is that the referred equipment has much less weight than the other 'covers' of its kind, so it must be small - not enough to cover the main SFP.

Or am I wrong?

You are right. The isolation condenser has a relatively small heat capacity: the RCIC has the whole capacity of the torus as a heat sinker, AFAIK.

 

[razzz]

As Tepco states: "On the other hand, as the temperature of the RPV of Unit1 is in the range of 100-120 degrees Celcius, stable cooling is being achieved."

I recall vividly that in the early days of this disaster, "stable cooling" meant cooling sufficient to prevent uncovering of the core, meltdown, and subsequent breaching of the reactor by corium. Interesting for me as a layperson so see how "stable" - whether relating to cooling directly or to reactor condition as a whole - gets redefined as we go along, and not for the better either.

While I'm reading here and elsewhere diligently, I lack the ability to fully comprehend all of your discussions. So just tell me this, please, you folks who understand physics, reactors, etc.: Maybe while our tolerance level for bad news is being consistently expanded, this situation, regardless of which reactor or SFP, is not getting better, but progressively worse, correct?

(Clarification to be on the safe side: "folks" above not meant derogatory in any way! Appreciate this forum more than you all can ever imagine.)

You have it right, they move the goal posts at a whim. If something is 600 degrees and doesn't rise to 610 degrees then the situation is stable in TEPCO line of thinking.

 

[clancy688]

You have it right, they move the goal posts at a whim. If something is 600 degrees and doesn't rise to 610 degrees then the situation is stable in TEPCO line of thinking.

A big german news site commented on the situation as "stable on the brink". I think that's what comes closest to the actual events.

 

[MadderDoc]

REGARDING THE VISIBILITY OF THE FIREBALL AND IGNITION OUTSIDE OF BLDG 3 CONTAINMENT
IMO, I believe I could see ignition occurring outside of Bldg 3.

OK, so you claim to have seen the ignition, I should have suspected someone would :-) But at least I can ask you to reconsider. It is not easy, I know. As the old sage said, 'the subtlest act is to set another before you'. But, I am presenting you with new evidence, so that would be a good reason to reconsider.

See the prior images I posted some time back.

I have looked at those images and the preceding discussion. The video used to produce these frames are, excuse me, crappy. No wonder Jorge protested! I would too, if I had found this site earlier. But, fortunately much better video sources are available, and for your convenience frames from such a video is at gyldengrisgaard.dk/fuku_expl3/

The source video for those frames, unlike the one you have been looking at, comes in HD, and it comes prezoomed to the interesting parts. Consequently you can see the same as you can in the poor video, but also -- sans comparison -- more.

Here is a side by side mount of the first frame showing a flash of fire from the two sources, sticking with your numbering, this is frame number 2:

And here is a side by side mount of the frame immediately _preceding_ the first frame with a flash of fire, frame number 1:

From both sources it is clear that an explosive event is ongoing in frame 2.
From the better source it is clear that an explosive event is ongoing in frame 1, too.

Now we can say, these were two separate events. In frame 2 we could then be seeing the ignition of event 2, and this is undoubtedly outside the building. In frame 1 we see the effects of another event, but we cannot say where that one ignited.

Alternatively we can say that the two frames show the same explosive event at two different points in time, separated by 0.03 seconds. In frame 1 the flash of fire from the event is not yet visible behind the building. In frame 2 it has grown to become now visible over the building. Neither of the two frames are able to show us the ignition.

I am sure it is well known what Ockham would have to say about this. Ockhams principle is more of a philosophical nature, than a scientific one, admittedly. Still, it seems to be a sound principle also in science, that we consider the simpler explanation first, and only adds further assumptions as needed.

<..>my simple explanation would be that the oxygen available for the initial explosion in the primary containment (if that is what had occurred) had been consumed, that very hot steam and hydrogen gas were being jetted, and that contact with air outside of the building with a higher concentration of oxygen outside of the building allowed ignition (re-ignition?) of the ejected gas. Someone earlier posted a video of a similar effect observed in a fireball exiting a mine explosion, I believe.

Yes OK, that's, er, quite simple, -- at least it could've been more complex.

However, a simpler explanation exists: A single explosion with a flash of fire coming from youguesswhere shooting out through the eastern wall, the flash of fire becoming visible to us 0.03 seconds later.

 

[etudiant]

As Tepco states: "On the other hand, as the temperature of the RPV of Unit1 is in the range of 100-120 degrees Celcius, stable cooling is being achieved."

I recall vividly that in the early days of this disaster, "stable cooling" meant cooling sufficient to prevent uncovering of the core, meltdown, and subsequent breaching of the reactor by corium. Interesting for me as a layperson so see how "stable" - whether relating to cooling directly or to reactor condition as a whole - gets redefined as we go along, and not for the better either.

While I'm reading here and elsewhere diligently, I lack the ability to fully comprehend all of your discussions. So just tell me this, please, you folks who understand physics, reactors, etc.: Maybe while our tolerance level for bad news is being consistently expanded, this situation, regardless of which reactor or SFP, is not getting better, but progressively worse, correct?

(Clarification to be on the safe side: "folks" above not meant derogatory in any way! Appreciate this blog more than you all can ever imagine.)

You highlight vividly how the spin is corrupting the message. Then Japan's government wonders about the emergence of 'rumors' in other countries.
Afaik, the likelihood of another major blast is much smaller now, although reactor 3 could still experience a steam explosion if/when the core remains believed to be still in the reactor pressure vessel melt through and fall into the now flooded dry well. The only question is how much more damage is likely to come, hopefully relatively little, as the bulk of the volatile radioactives have already been boiled off.

Beyond that small comfort, the situation will remain as is for the rest of the year and perhaps much longer,
a shattered site littered with intensely radioactive debris, flooded with a lake of water 100x300x3 meters deep, so radioactive that it can only be approached briefly. That will make cleaning up the spent fuel pools a very long term proposition, so airborne emissions are also likely to continue for a long while.
If the readings from sewage plants near Tokyo and beyond are correct, the accident has already contaminated the larger part of Honshu to the point that the government will have to raise the allowable radiation contamination standards. Seafood and seaweed products are likely at risk for a very long time.

 

[NUCENG]

Did they actually solve the Unit 4 explosion mystery? Sounds to good to be true... hence it can't be true! (just kidding... but what's up with them... suddenly releasing informations)

When I look at the site overhead pictures I see large ventilation pipes to the two offgas stacks located between Units 1 and 2 and between units 3 and 4. The third stack on the Daiichi site is south of unit 4 and has 4 pipes opening at the top. If you look between the reactor buildings and the turbine buildings you can trace 4 large ventilation pipes to the building next to that stack that appear to be from the 4 turbine buildings. I am guessing that this tower is receiving the offgas from the turbine building steam jet air ejectors from all 4 plants. This would then mean that the two stacks between reactor buildings are probably the release points for the hardened containment vent systems and Standby Gas Treatment Systems.

The third tower south of unit 4 with pipes from the 4 turbine buildings is not a likely path because it connects turbine buildings not reactor buildings. Now look at the piping south of the Unit 3 reactor building. It is broken and the end of the pipe is open to air right at the RB for unit 3. I am looking for pictures that show this pipe after the explosion at unit 3 but before the damage to unit 4. If it was broken before the explosion at unit 4 how did the hydrogen get to Unit 4? If it was intact then it is possible this was the pathe for hydrogen to get from one RB to the other.

 

[mscharisma]

A big german news site commented on the situation as "stable on the brink". I think that's what comes closest to the actual events.

Could you please tell me which one and when?
And as I recall, "on the brink" was previously equivalent the risk of fuel melting. So we're pretty much past that now (or now we know about it), making "on the brink" yet another term whose definition gets adjusted for the worse.

 

[clancy688]

Could you please tell me which one and when?
And as I recall, "on the brink" was previously equivalent the risk of fuel melting. So we're pretty much past that now (or now we know about it), making "on the brink" yet another term whose definition gets adjusted for the worse.

http://www.spiegel.de/wissenschaft/technik/0,1518,751818,00.html

 

[tsutsuji]

New Komeito representative Mr Saito said "temperature is rising in Fukushima NPP's unit 3. Because the conditions are not met where nitrogen can be injected to prevent hydrogen explosion, because if a hydrogen explosion occurs everything becomes impossible, a solution is urgently needed" : http://www3.nhk.or.jp/news/html/20110515/t10015898941000.html

 

[SteveElbows]

The third tower south of unit 4 with pipes from the 4 turbine buildings is not a likely path because it connects turbine buildings not reactor buildings. Now look at the piping south of the Unit 3 reactor building. It is broken and the end of the pipe is open to air right at the RB for unit 3. I am looking for pictures that show this pipe after the explosion at unit 3 but before the damage to unit 4. If it was broken before the explosion at unit 4 how did the hydrogen get to Unit 4? If it was intact then it is possible this was the pathe for hydrogen to get from one RB to the other.

There are only a few images from the period after 3 blew but before 4 went up.

I don't think the resolution is high enough to be 100% sure, but it looks to me like there was already debris fallen onto the pipe in the place where it is later shown to be broken. And I think its always been a pretty likely bet that it was falling walls of reactor 3 that caused the damage.