Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[westfield]

However, the twisted metal structure we see here in the foreground appears to be made of steel sheet-ware of an extension which we do not see in any of the structural elements of the roof.

I looked at the video some more and while it does have a funky shape if you "un-origami" it in your head it becomes evident it's just a plain "T" section bent over on itself - the crud collected in the "pocket" at the main bend makes it look like something more complex.

Such are the perils of trying to figure out this stuff, even forgiving the photography limitations, once something is bent and\or burnt even everyday shapes can become difficult to recognise.

 

[GJBRKS]

My question is not so much "why didn't TEPCO act sooner" or in any way political. I'm merely interested in whether or not it is safe from a technical standpoint to let the water come so close to boiling while installing a new pump instead of using already in place emergency systems. Of course, if it's not safe and/or not "by the book", then my question would certainly become "why didn't they act sooner."
Maybe in my lay(wo)man's mind, I just assumed (yes, I know the saying about "assume") that it's pretty much an automatic process: if one cooling system fails or part of it fails, no questions asked, the next one is put in operation. It takes me by surprise that it's apparently up to the ... hm, who? ... to decide when emergency cooling is activated and when not?

To have an amount of liquid water at 99.9 Celsius boil at 100 Celsius ,
it needs an equivalent energy input of around 540x times the energy to raise it 1 degree below boiling point.
And a 1000x times to raise it one degree when it is steam

So to make it boil from 100 degrees ,
you would have to add the same energy as to raise its temperature from -400 to 100 degrees ( roughly speaking as the heat energy changes at lower temperatures) , -400 Celsius however is impossible of course.

Or vice versa : the amount of energy released when condensing is equal to the absorbed heat energy of steam at a temperature of 1100 degrees celsius

So you see that it takes a lot more energy to make it all boil than to make it raise in temperature , thereby making the chance it would drop the waterlevel rather small in such a timeperiod

 

[MadderDoc]

I looked at the video some more and while it does have a funky shape if you "un-origami" it in your head it becomes evident it's just a plain "T" section bent over on itself - the crud collected in the "pocket" at the main bend makes it look like something more complex.

Such are the perils of trying to figure out this stuff, even forgiving the photography limitations, once something is bent and\or burnt even everyday shapes can become difficult to recognise.

I have attached no particular significance to the peculiar hook shape, nor inferred it to indicate anything of a complex shape. Certainly there can be no argument that what we are looking at has been bent severely out of its original shape. I can't see from you markup how you imagine the original shape of such a 'plain "T" section', which you indicate to clearly recognise this piece to have been originally. Also, have you formed an opinion from where it could have originated?

 

[htf]

To have an amount of liquid water at 99.9 Celsius boil at 100 Celsius ,
it needs an equivalent energy input of around 540x times the energy to raise it 1 degree below boiling point.
And a 1000x times to raise it one degree when it is steam

...

Sorry, but this is a rather confusing explanation.

Things are quite simple: when not cooled, some water will evaporate and the pressure will raise and the water temperature will consequently raise beyond 100°C. The normal operation temperature of a BWR is ~280°C at a pressure of ~70 bar. This means that in an intact PRV the temperature and pressure can go up to that values without danger. So a lot of decay energy can easily be absorbed even without cooling for some time: energy for evaporating some water + energy for heating up the water beyond 100°C. This gives a lager buffer. Remember, it took hours to raise the water temperature by ~20°C.

So, there was no immediate danger from that point of view. To aspects are more alarming to me:

1. It seens that unit #5 and #6 are less stable than Tepco claims.

2. There seems to be no working automatic monitoring system in place. To my understanding the pump failure has not been detected for hours.

 

[MiceAndMen]

I have attached no particular significance to the peculiar hook shape, nor inferred it to indicate anything of a complex shape. Certainly there can be no argument that what we are looking at has been bent severely out of its original shape. I can't see from you markup how you imagine the original shape of such a 'plain "T" section', which you indicate to clearly recognise this piece to have been originally. Also, have you formed an opinion from where it could have originated?

I wondered about that thing since the video first came out. The embedded "teardrop" - or "airfoil" - shaped void is very odd. I have not a clue nor a guess as to where it came from. To me, it doesn't look like an "L" or a "T" piece at all. It resembles most of all a metal pastry stuffed with concrete rubble or stone pebbles. It doesn't look like anything has folded over, because then how would the rocky stuffing get inside? It almost looks like whatever it was originally, it was already filled with concrete/rocks/grout/whatever and has been broken off of a larger thing. (Sorry for the extreme non-technical descriptions, but I have no better way to describe the thing.)

Does anyone have a good size estimate for it?

 

[intric8]

New at this, first post. Thinking; so far weather patterns have saved the situation. Weather is changing, any comments for the next few months? Seasonal patterns?

Everyone is concerned about how the typhoon would detrimentally effect operations at the plants, well it seems to have obliterated in-air readings around Iitate. Much lower, for now.

http://www.falloutphilippines.blogspot.com/

On seasonal Japan wind changes and precipitation, just basic info -

http://falloutphilippines.blogspot.com/2011/04/japan-summer-weather-is-nigh-and-heres.html

 

[Jorge Stolfi]

That reminds me. How many floors does reactor 3 building have? And how many were destroyed? Is building four the same design?

http://giappopazzie.blogspot.com/2011/05/post-tecnico-4-approfondimento-sulla.html

 

[tsutsuji]

Two nuclear power plant operators may have exceeded the 250 mSv limit : http://www.euronews.net/newswires/947269-two-fukushima-workers-may-have-exceeded-radiation-limit/

 

[swl]

Seawater Levels of Iodine at unit 2 Iodine-131: 24,000 becquerels/liter on may 28 (was only 5,200 becquerels/liter at the same place the day before) : is this rising significant and can be related to RVP/corium state ?

What is the source far that data? Do you know if there was an equal increase in the Cesium levels?

If ONLY the Iodine-131 increased, I would wonder about criticality. If not, I wonder if it is just a matter of the rainwater runoff.

 

[elektrownik]

Reactor 5 temperature increase again ??
90.5
92.2
93.7
83.0
76.5 <-pump replaced and on
70.0
64.9
60.8
56.5
52.8
50.5
50.0
50.9 <-temperature start increasing again
53.1
55.3
57.5
59.6
61.5
64.0
66.0
68.1

 

[swl]

At some time on May 28th somebody or something has removed several treetops south of the plant: Tepco's webcam facing the south wall of unit 4 now has a considerably better view to it:

It has been quite windy, so I wonder if the trees are not simply bowing from the wind. It's still quite windy now, but we should know in a day or two if the view of the unit 4 building is once again obscured.

On another point, while I'm usually bothered by the rain, I'm glad for the rinsing we've had over that past could days; there was this grey dust coating everything and I'm glad it's gone for now. Wish I had access to a GM counter.

According to the news here, the rainy season has officially started. If I remember the news correctly, the start is 17 days earlier than usual and one of the earliest starts ever. But to be honest, from what I can tell, the meteorologists have no clue about the rain beyond a week or two into the future.

 

[rowmag]

I wondered about that thing since the video first came out. The embedded "teardrop" - or "airfoil" - shaped void is very odd. I have not a clue nor a guess as to where it came from. To me, it doesn't look like an "L" or a "T" piece at all. It resembles most of all a metal pastry stuffed with concrete rubble or stone pebbles. It doesn't look like anything has folded over, because then how would the rocky stuffing get inside? It almost looks like whatever it was originally, it was already filled with concrete/rocks/grout/whatever and has been broken off of a larger thing. (Sorry for the extreme non-technical descriptions, but I have no better way to describe the thing.)

Does anyone have a good size estimate for it?

The red and white Thermo Label attached to the sampling tube is, I believe, about 3 cm long, so that gives a scale. The twisted metal thing is probably about the size of one's hand, or maybe a bit smaller, barring some trick of perspective.

 

[Bandit127]

Two nuclear power plant operators may have exceeded the 250 mSv limit : http://www.euronews.net/newswires/947269-two-fukushima-workers-may-have-exceeded-radiation-limit/

Looks like they ingested some iodine 131 somehow.

Regarding the two TEPCO male employees, we were informed that levels of
internal radioactivity (iodine 131) present in their thyroids is higher
than normal according to the Japan Atomic Energy Agency (Independent
Administrative Corporation), which is cooperating with us in the
conducting of the examinations and evaluations.

From: http://www.tepco.co.jp/en/press/corp-com/release/11053003-e.html"

 

[Jorge Stolfi]

I have began to update my plots of main variables (temperature, pressure, water leve, water input and CAMS) for Fukushima Daiichi units #1-#3:

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

The previous version stopped at NISA press release 128. The new version includes NISA releases 145--152. Releases 129--144 will be entered next time.

The new version also adds many data points of pressure, water level, and CAMS for the earlier days, from consolidated and supposedly revised tables posted by TEPCO:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_1u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_2u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf

Other data sources out there may be merged later if time allows.

In light of this new data, several data points were corrected or removed from the plots. However this process may have added many new errors, watch out.

TEPCO is now posting a dozen or so temperature readings from each reactor. Since other eople have been plotting this data, I have no plans to include it in my plots.

The latest NISA releases show two numbers for the water pumping in #3. Presumably one is the fire extinguishing line, the other the main water inflow line. Which is which?

All the best, --stolfi

 

[tsutsuji]

Reactor 5 temperature increase again ??
90.5
92.2
93.7
83.0
76.5 <-pump replaced and on
70.0
64.9
60.8
56.5
52.8
50.5
50.0
50.9 <-temperature start increasing again
53.1
55.3
57.5
59.6
61.5
64.0
66.0
68.1

If you look at the plot at the top of http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11053006_temp_data_56u-e.pdf you can see that it is a regular pattern everyday. Apparently the cooling system doesn't start until the temperature rises above 70°C or so. It seems that they can't cool the reactor and the pool at the same time. While the pool is cooling, the reactor is heating up, and vice-versa.

 

[westfield]

I have attached no particular significance to the peculiar hook shape, nor inferred it to indicate anything of a complex shape. Certainly there can be no argument that what we are looking at has been bent severely out of its original shape. I can't see from you markup how you imagine the original shape of such a 'plain "T" section', which you indicate to clearly recognise this piece to have been originally. Also, have you formed an opinion from where it could have originated?

yes the markup on the still frame is not helping really is it - I stepped through the video frames. then I folded a bit of paper into an angle shape and "bent" it to visualise how it might fold. I think the crud is hiding the edges continuing from the teardrop bending point.

But if it's not a "T" it won't be the last time I'm wrong;)



And are you kidding? It might have come from R4 for all anyone knows.

 

[DSamsom]

Temperatures in RPV reactor 3 are on the rise again after they lowered the rate of cooling water. That decission was most likely taken to limit the amount of radioactive waste water (problems with full tanks and/or leaking tank). Wonder whether they can afford to pump more water in the reactor again, given the fact that most tanks are full.

http://www.tepco.co.jp/nu/fukushima-np/f1/images/11053013_temp_data_3u-j.pdf

 

[SteveElbows]

The latest NISA releases show two numbers for the water pumping in #3. Presumably one is the fire extinguishing line, the other the main water inflow line. Which is which?

What release are you reading? The ones I've looked at have tended to state which is which, and for reactor 3 the fire line rate has been 0 for a few days now. But the same thing is being done at reactor 2 now, so you should see 2 readings for that one at the moment.

 

[SteveElbows]

Looks like we are going to get a new live video feed from the site starting on Tuesday:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110530_02-e.pdf

 

[joewein]

The latest NISA releases show two numbers for the water pumping in #3. Presumably one is the fire extinguishing line, the other the main water inflow line. Which is which?

All the best, --stolfi

Feeding via the fire extinguishing line was completely stopped on May 28 at 20:54. 13.5 m3/h is being fed via the feedwater pipe alone now.

 

[NUCENG]

"That just doesn't happen" under normal circumstance when the pool is cooled,
and H2 and O in solution quickly recombine, but
[PLAIN]http://k.min.us/invwtS.JPG

https://www.physicsforums.com/attachment.php?attachmentid=35318&d=1304876672" Light Water Reactor Hydrogen Manual by Allen L Camp

In https://www.physicsforums.com/showpost.php?p=3287847&postcount=6068" , using above paper I worked out that some 120 to 150kg of Hydrogen could have been developed in SFP-4



Conspiracy believers would quickly prove that the http://en.wikipedia.org/wiki/High_Frequency_Active_Auroral_Research_Program"

I have followed up on the potential for radiolysis and believe it is a plausible explanation for the Unit 4 explosion and damage. I am still looking at the possible scenario of Hydrogen gas from unit 3 through the SBGT system ducting.

1. I calculated decay heat for Unit 4 based on a full core offload 102 days before 3/11/2011 using rated thermal power of 2381 MWt and three batches of spent fuel aged 1 year (204 bundles), 2 years (204 bundles) and 3 years (171 bundles). I used the methodology of ANSI/ANS-5.1-1979. This calculation estimated decay heat in the Unit 4 SFP as 3.05 MW.
2. Using the various plant drawings posted on the forum I estimated spent fuel pool water volume of 1170 m^3 or 1.17E6 kg.
3. Assuming adiabatic heating and an initial temperature of 25 degC at the time of Loss of Spent Fuel Pool Cooling (15:45 3/11/2011) the estimated time to boiling was 33.5 hours or 3/13/2011 13:12 hr.
4. Using the ORIGEN2 analysis I have referenced before and the same core/batch assumptions used in #1 above I estimated total ionizing radiation in the spent fuel pool as 6.18E24 eV/sec. I determined that alpha and neutrons interactions are several orders of magnitude less than Beta and Gamma so these were ignored. The total used includes Bremsstrahlung radiation and x-rays.
5. Then assuming a production rate of 44 molecules of H2 per 1E4 eV of radiation from the Hydrogen Manual AntonL has referenced, I come up with a production rate of .0903 g of H2/sec. The method used in the Hydrogen Manual indicated it was probably a significant over-estimate of hydrogen generation and this calculation is about one tenth of that estimate. One note in the calculation used by AntonL is that the rates in the table he used are average rates over the entire production time, and need to be converted to instantaneous production reates which will also lower the production rate. I assumed that once pool boiling starts the H2 gas will be released from the pool at the production rate.
6. TEPCO does not know exactly when the damage to Unit 4 occurred, but damage was observed about 3/15/2011 at 06:00. This gives a maximum duration of boiling and hydrogen production.
7. Again using the calculated decay heat rate and latent heat of vaporization of water I calculated a boil-off rate of 1.35 kg/sec from the pool. It would have taken until 3/18/2011 to boil off half the pool volume. Therefore there was no fuel uncovered.
8. Using the discovery time of the Unit 4 building damage, a maximum of 16.9% of the pool volume could have boiled off.
9. In this same time a maximum hydrogen production of 13.25 kg was possible.
10. If we ignore steaming rate and other contributions that could have caused dilution of hydrogen in the refueling floor, a simple linear first order differential equation model would result in a LEL of Hydrogen (4% by volume) in about 15.8 hr or 3/14/2011 05:00. By the time damage was discovered the concentration could have been as high as 65%. This ignores significant dilution due to approximately 20 m^3 of steam entering the refueling floor every second. That steam could have explained why the blowout panels were open on Unit 4 since they would relieve at a low (inches of water) pressure. There was no ventilation assumed due to lass of power, however there could have been some airflow through the blowout panels due to steaming, condensation and buoyancy driven flow.
11. Assuming that all of the generated hydrogen remained in the building, I used an spreadsheet (Estimating Pressure Increase and Explosive Energy Release Associated with Explosions, Version 1805.0), from the NRC website to estimate the explosive power of the hydrogen. This spreadsheet calculated an equivalent TNT weight of 385 kg. Using the perimeter of damage calculation method from US NRC RG 1.91 the radius for overpressure of 1 psi where structural damage could occur is about 130 m.

The intent of these calculations was to determine if the times and sources of heat and radiation would permit explosive concentrations of hydrogen to exist with only radiolysis and fuel pool boiling. More detailed modeling of the interplay between air flow, steam, and hydrogen or use of thermal-hydraulic analysis codes could refine this picture. , but as of now it looks like this scenario is plausible. Thanks AntonL.

 

[elektrownik]

@NUCENG but if fuel wasnt uncovered then what could be source of ignition ? There was no power supply.
I have another question about fuel damage in #4 sfp, after tepco report about unit 1 core melt I think that damage to fuel should start not in upper part of fuel racks in sfp, but in center (inside rack), so maybe fuel upper part looks good, but it is damaged where we can't see...

 

[NUCENG]

One followup on my last post. Based on the calculations and the fact that Unit #4 fuel pool heat sources aere so much larger than at units 1, 2, and 3. Only significant leakage from the spent fuel pools could have produced enough inventory loss to uncover fuel in those pools.

 

[etudiant]

I have followed up on the potential for radiolysis and believe it is a plausible explanation for the Unit 4 explosion and damage. I am still looking at the possible scenario of Hydrogen gas from unit 3 through the SBGT system ducting.

1. I calculated decay heat for Unit 4 based on a full core offload 102 days before 3/11/2011 using rated thermal power of 2381 MWt and three batches of spent fuel aged 1 year (204 bundles), 2 years (204 bundles) and 3 years (171 bundles). I used the methodology of ANSI/ANS-5.1-1979. This calculation estimated decay heat in the Unit 4 SFP as 3.05 MW.
2. Using the various plant drawings posted on the forum I estimated spent fuel pool water volume of 1170 m^3 or 1.17E6 kg.
3. Assuming adiabatic heating and an initial temperature of 25 degC at the time of Loss of Spent Fuel Pool Cooling (15:45 3/11/2011) the estimated time to boiling was 33.5 hours or 3/13/2011 13:12 hr.
4. Using the ORIGEN2 analysis I have referenced before and the same core/batch assumptions used in #1 above I estimated total ionizing radiation in the spent fuel pool as 6.18E24 eV/sec. I determined that alpha and neutrons interactions are several orders of magnitude less than Beta and Gamma so these were ignored. The total used includes Bremsstrahlung radiation and x-rays.
5. Then assuming a production rate of 44 molecules of H2 per 1E4 eV of radiation from the Hydrogen Manual AntonL has referenced, I come up with a production rate of .0903 g of H2/sec. The method used in the Hydrogen Manual indicated it was probably a significant over-estimate of hydrogen generation and this calculation is about one tenth of that estimate. One note in the calculation used by AntonL is that the rates in the table he used are average rates over the entire production time, and need to be converted to instantaneous production reates which will also lower the production rate. I assumed that once pool boiling starts the H2 gas will be released from the pool at the production rate.
6. TEPCO does not know exactly when the damage to Unit 4 occurred, but damage was observed about 3/15/2011 at 06:00. This gives a maximum duration of boiling and hydrogen production.
7. Again using the calculated decay heat rate and latent heat of vaporization of water I calculated a boil-off rate of 1.35 kg/sec from the pool. It would have taken until 3/18/2011 to boil off half the pool volume. Therefore there was no fuel uncovered.
8. Using the discovery time of the Unit 4 building damage, a maximum of 16.9% of the pool volume could have boiled off.
9. In this same time a maximum hydrogen production of 13.25 kg was possible.
10. If we ignore steaming rate and other contributions that could have caused dilution of hydrogen in the refueling floor, a simple linear first order differential equation model would result in a LEL of Hydrogen (4% by volume) in about 15.8 hr or 3/14/2011 05:00. By the time damage was discovered the concentration could have been as high as 65%. This ignores significant dilution due to approximately 20 m^3 of steam entering the refueling floor every second. That steam could have explained why the blowout panels were open on Unit 4 since they would relieve at a low (inches of water) pressure. There was no ventilation assumed due to lass of power, however there could have been some airflow through the blowout panels due to steaming, condensation and buoyancy driven flow.
11. Assuming that all of the generated hydrogen remained in the building, I used an spreadsheet (Estimating Pressure Increase and Explosive Energy Release Associated with Explosions, Version 1805.0), from the NRC website to estimate the explosive power of the hydrogen. This spreadsheet calculated an equivalent TNT weight of 385 kg. Using the perimeter of damage calculation method from US NRC RG 1.91 the radius for overpressure of 1 psi where structural damage could occur is about 130 m.

The intent of these calculations was to determine if the times and sources of heat and radiation would permit explosive concentrations of hydrogen to exist with only radiolysis and fuel pool boiling. More detailed modeling of the interplay between air flow, steam, and hydrogen or use of thermal-hydraulic analysis codes could refine this picture. , but as of now it looks like this scenario is plausible. Thanks AntonL.

Thank you for this lucid evaluation and analysis.
It indicates that the hydrogen made the inside of building 4 into a fuel/air explosive package of stunning efficiency. I am amazed that less than 15kg of hydrogen could do so much damage, particularly as some of the hydrogen would have escaped through the open blow out panels. But unless there was another source of hydrogen, such as the postulated leakage from reactor 3, this is what we have.

 

[elektrownik]

I also don't understand why unit 4 sfp water temperature is always 84C and 62C for unit 3 sfp, this is not possible that there is no change... also why water level in unit 2 is so low, it looks like they can't fill it with water like in unit 4... it is ~4000 max, but usualy 2000-3000 and unit 4 is 6500 after injection

 

[Astronuc]

I also don't understand why unit 4 sfp water temperature is always 84C and 62C for unit 3 sfp, this is not possible that there is no change... also why water level in unit 2 is so low, it looks like they can't fill it with water like in unit 4... it is ~4000 max, but usualy 2000-3000 and unit 4 is 6500 after injection

Unit 4 SFP had a full core offload, so there was some fuel with a fair amount of decay heat. Unit 4 also had 1331 assemblies in it. Unit 3 SFP had fewer assemblies, and they were only discharged assemblies from last year and previous cycles with 1, 2, 3, . . . years of cooling. The number of assemblies in the SFPs is posted early in this thread.

There could also be structural damage in any of the SPFs, including cracks in the stainless steel liner and concrete structure.

 

[jlduh]

Looks like they ingested some iodine 131 somehow.


From: http://www.tepco.co.jp/en/press/corp-com/release/11053003-e.html"

Again, and as was already discussed it in other threads, this raises the question of the accuracy and the meaning of the measurements in mS/h by dosimeters. In this case again, the difference seems to come from ingested particulates (so this is internal contamination and not external irradiation).

 

[NUCENG]

@NUCENG but if fuel wasnt uncovered then what could be source of ignition ? There was no power supply.
I have another question about fuel damage in #4 sfp, after tepco report about unit 1 core melt I think that damage to fuel should start not in upper part of fuel racks in sfp, but in center (inside rack), so maybe fuel upper part looks good, but it is damaged where we can't see...

Let's just list a couple ignition sources that might have been present:

• Emergency lighting batteries giving out,
• Sparks due to metal on metal shifting in rubble in aftershocks
• Static Electrical Discharge

In the fuel racks in the spent fuel pool cooling is done by buoyancy driven natural circulation. As water heats around the fuel rods it rises and is replaced by cooler water from below. Thus the hotest temperatures are at the tops of fuel assemblies, even if in a spent fuel pool.

In addition, remember that control rods are pulled from the top down out the bottom of the vessel. This is pretty simplistic, but in general the fuel is burned out from the top down and that results in higher decay heat at the top of fuel. Fuel loading in rods is adjusted and rod patterns are used to try to even the heat generation rate over the length of the rod during normal operation, but in general the simple picture works as an adequate approximation.

 

[elektrownik]

Thanks for explanations, in case of ignition
Emergency lighting batteries giving out - I think that we can exclude this because batteries die 8 hours after blackout (if I remember correct from reports)


@Astronuc yes I understand there is more fuel (and not so old) in 4 than in others, but for example they were able to fill unit 1 sfp more than 2, and also no change in temperature in sfp 3 and 4 suggest sensor failure

 

[NUCENG]

Thank you for this lucid evaluation and analysis.
It indicates that the hydrogen made the inside of building 4 into a fuel/air explosive package of stunning efficiency. I am amazed that less than 15kg of hydrogen could do so much damage, particularly as some of the hydrogen would have escaped through the open blow out panels. But unless there was another source of hydrogen, such as the postulated leakage from reactor 3, this is what we have.

Yes, I was surprised at the number until I watched a newreel of the Hindenberg fire. I had previouslt done some TNT equivalencies based on gasoline, fuel oil and propane, but was shocked by the number for hydrogen. I;m not so sure I like the ideas of automobiles running around banging into each other and powered by hydrogen.