Meltdown Likely Under Way At Japan Nuclear Reactor

[Tywais]

Yes... Many, sea water is commonly used for additional cooling...

Not so sure about that, for emergency cooling yes. Not as routine though. The stuff is corrosive and will damage equipment over time....

Agreed, sea water is normally only used in emergencies. Normally the water is pure/de-ionized. Two issues, 1st the seriously corrosive effect it has on metals such as the transfer pipes, 2nd the high intensity radiation can activate the minerals in sea water making them radioactive.

Under what circumstances would a nuclear power plant use seawater to cool its reactors?

Using unpurified water is not a normal practice—it's never done. Plants don't take water from the river or the sea to supplement their own internal water, which is in completely closed-loop systems. Of course, they take in some amount of new water periodically to make up for evaporation and other losses like that, but this water is purified before it is used.

Scientific American

[JulianLS]

More on Japan reactor setback: Radioactive gas will be released to ease pressure/RT@BreakingNews

This is worrying. Last time they vented unit 3, the building exploded soon after....... Let's hope they do it slowly so any hydrogen has chance to disperse.

Nothing much left to explode in #3, outside 'structure' is all but gone, Hydrogen won't have a problem to escape that pile of rubble, even if it ignites.

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

[JulianLS]

TEPCO announces pressure has stabilized inside No3 reactor vessel at #Fukushima N-plant, will not release steam for time being./RT@DailyYomiuri

That I think is very good news!

[Lite Beer]

Japan's government says tsunami-stricken nuclearplant will have to close eventually - AP/RT@BreakingNews

[Lite Beer]

Japan nuclear power operator restores electricity to no 2 reactor at stricken plant - Kyodo/@REUTERSFLASH

[Jdietz]

More on Japan reactor setback: Radioactive gas will be released to ease pressure/RT@BreakingNews

This is worrying. Last time they vented unit 3, the building exploded soon after....... Let's hope they do it slowly so any hydrogen has chance to disperse.

Nothing much left to explode in #3, outside 'structure' is all but gone, Hydrogen won't have a problem to escape that pile of rubble, even if it ignites.

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

Suppression pool is made exactly for that: emergency venting, it has no use during normal reactor operation. Instead of venting to atmosphere, you vent through water, forcing water out the overflow. This way you trap more radioactive isotopes compared to venting directly.

Venting directly through the top escape valve of the reactor is the back-up scenario, when there are troubles with the suppression pool. This will directly release radioactive isotopes in the atmosphere, and increase levels around the plant more, so first option is preferred.

Pool is inside the wetwall, but outside the drywall, containing the steel reactor vat.

Edited March 20, 2011 by Jdietz

[katana]

Yes... Many, sea water is commonly used for additional cooling...

Not so sure about that, for emergency cooling yes. Not as routine though. The stuff is corrosive and will damage equipment over time....

Agreed, sea water is normally only used in emergencies. Normally the water is pure/de-ionized. Two issues, 1st the seriously corrosive effect it has on metals such as the transfer pipes, 2nd the high intensity radiation can activate the minerals in sea water making them radioactive.

Under what circumstances would a nuclear power plant use seawater to cool its reactors?

Using unpurified water is not a normal practice—it's never done. Plants don't take water from the river or the sea to supplement their own internal water, which is in completely closed-loop systems. Of course, they take in some amount of new water periodically to make up for evaporation and other losses like that, but this water is purified before it is used.

Scientific American

I thought they did use seawater:

"nuclear power plants would most likely need to be built on the coast where gigalitres of seawater could be used to cool them...says nuclear power engineer Professor John Price of Monash University in Melbourne.

Price...says "gigantic" amounts of water are required to cool a nuclear power station."

link

[Jdietz]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

[WarpSpeed]

Do you mean, what would happen in a country that got hit by a 9 magnitude earthquake and a 10 metre tsunami?

Do any other countries have nuclear power plants in such high risk locations?

Yes... Many, sea water is commonly used for additional cooling...

Not so sure about that, for emergency cooling yes. Not as routine though. The stuff is corrosive and will damage equipment over time....

Yes routine, it is used to cool the plants condensers, external equipment and heat producing machinery, not directly in the reactors.. There are in essence 2 cooling systems one removes heat from the reactors and rod cooling chambers and the second transfers heat from the condensers and such to cool the water back from steam to water again within the reactor cooling system but the 2 never come into contact with each other, they are separate systems doing separate work.. They all have external cooling sources and why most are located close to some water source or artificial ones are created through reservoirs or wells..

A good analogy would be an air conditioner which requires an internal fan in it to remove heat from the condenser and transfers that heat to the atmosphere after the gas is compressed and heats up in the process, that fan also serves the double purpose of cooling the internal components of the A/C such as the compressor both externally from air flow and internally from cooling the freon or R32 that flows through it but it does not come into contact with those gases..

Cooling power plants

Hyperboloid (a.k.a. hyperbolic) cooling towers (Image 1) have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material. The hyperboloid shape also aids in accelerating the upward convective air flow, improving cooling efficiency. They are popularly associated with nuclear power plants. However, this association is misleading, as the same kind of cooling towers are often used at large coal-fired power plants as well. Similarly, not all nuclear power plants have cooling towers, instead cooling their heat exchangers with lake, river or ocean water.

[edit]

I've put up the entire link to Wiki for your perusal because it's too much to post up but I quoted the applicable paragraph for summation and highlighted the pertinent text..

[Tywais]

I thought they did use seawater:

"nuclear power plants would most likely need to be built on the coast where gigalitres of seawater could be used to cool them...says nuclear power engineer Professor John Price of Monash University in Melbourne.

Price...says "gigantic" amounts of water are required to cool a nuclear power station."

link

Reactor cooling is "closed loop". The closed loop portion certainly has to be pure. However, in closed loop systems there is also the heat exchanger process which pulls the heat from the closed loop water system without being in contact with the water itself. Possible this is what he is missing in his statement.

//edit - ah, see Jdietz gave the short version.

[StreetCowboy]

8>< SNIP NESTED QUOTES DELETED ><8

I thought they did use seawater:

"nuclear power plants would most likely need to be built on the coast where gigalitres of seawater could be used to cool them...says nuclear power engineer Professor John Price of Monash University in Melbourne.

Price...says "gigantic" amounts of water are required to cool a nuclear power station."

link

Thermal power stations (coal, oil, nuclear, pig manure, old tyres) reject their heat to one of two ultimate heat sinks - the atmosphere, via cooling towers, or the sea.

However, there is an intermediate sealed circuit, normally pure water with corrosion inhibitors, which takes heat from the boiler (reactor, furnace whatever) to the turbines where the electricity is generated. Remaining waste heat is then dumped to the sea / atmosphere before the coolant gets fed back into the boiler (reactor / whatever). Hence the coastal nature of most power stations. Inland stations, with cooling towers, still use quite a lot of water in the towers to take the heat away by evaporation as well as convection - hence the plumes of condensation above the cooling towers.

SC

[WarpSpeed]

Yes... Many, sea water is commonly used for additional cooling...

Not so sure about that, for emergency cooling yes. Not as routine though. The stuff is corrosive and will damage equipment over time....

Agreed, sea water is normally only used in emergencies. Normally the water is pure/de-ionized. Two issues, 1st the seriously corrosive effect it has on metals such as the transfer pipes, 2nd the high intensity radiation can activate the minerals in sea water making them radioactive.

Under what circumstances would a nuclear power plant use seawater to cool its reactors?

Using unpurified water is not a normal practice—it's never done. Plants don't take water from the river or the sea to supplement their own internal water, which is in completely closed-loop systems. Of course, they take in some amount of new water periodically to make up for evaporation and other losses like that, but this water is purified before it is used.

Scientific American

Sorry..............Incorrect..........

See this picture below of the plant prior to this disaster, in the lower left you see water in motion it is being expelled from the plant through cooling vents for the purposes of what I explained previously..

I've kept mostly quiet until now mostly choosing to make corrections or specific observations as there are enough "experts" here as it is.

Here is the plant my BIL help to engineered and was an integral part of building..

Note the cooling canals on either side, it draws from the ocean on one said and expels into the Intercoastal waterway on the other very warm water and is well known for it's winter manatee migration who use the water to stay warm and the viewing areas expressly set aside for visitors to view. See below..

Couple this with my vast personal experience with my father also being an engineer at the original Bikini Atoll tests and there is far more I have kept private with nothing to prove and I'm well qualified, far more qualified then some have respected.....

Edit: I see now that you need to read back to the original post being answered which you did not quote.. It does not speak to "reactors" it speaks to power plants being located in "high risk" locations..

Edited March 20, 2011 by WarpSpeed

[WarpSpeed]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

Not only can be, but is on all coastal reactors and all power plants..

[Deeral]

Japan's nuclear industry has had a rather chequered history even in the last decade - so I should repeat - imagine if this sort of stuff happens in a less "organised" country?If Japan which apparently gets 75% of their power from nuclear sources, can't get their shit together you do you expect can????

Do you mean, what would happen in a country that got hit by a 9 magnitude earthquake and a 10 metre tsunami?

Do any other countries have nuclear power plants in such high risk locations?

I would suggest every country sited on the "ring of fire" plus a few more around the world straddling the edges of tectonic plates.Whether they already have or are considering nuclear power

[lannarebirth]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

Not only can be, but is on all coastal reactors and all power plants..

In most marine type applications I am aware of, seawater is only used to cool the freshwater, which is in a closed loop system, and is the direct coolant of the heat source. Maybe you all are just misunderstanding each other.

[Alphonso]

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

Something I've been wondering about. Is the suppression pool supposed to have an igniter to burn off the potentially dangerous hydrogen gas and if so is there no backup way of safely venting should the ignition system fail?

[Tywais]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

Not only can be, but is on all coastal reactors and all power plants..

In most marine type applications I am aware of, seawater is only used to cool the freshwater, which is in a closed loop system, and is the direct coolant of the heat source. Maybe you all are just misunderstanding each other.

Looks to be the case as subsequent posts, including mine, had stated the use of sea water is part of the heat exchange process and not the direct cooling loop of the reactor. Believe that is the source of confusion, but believe it is clear now the distinction.

[WarpSpeed]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

Not only can be, but is on all coastal reactors and all power plants..

In most marine type applications I am aware of, seawater is only used to cool the freshwater, which is in a closed loop system, and is the direct coolant of the heat source. Maybe you all are just misunderstanding each other.

I'm not misunderstanding anything, though you're correct others are. The responders to my post are not reading the original quote I responded to and jumping to incorrect conclusions..

I responded to the post regarding dangerous locations and why plants are located on coastlines etc. for example which was quoted in my original post and suddenly everyone was jumping on the reactor cooling debate saying incorrectly that these plants are not cooled by seawater when they are, though as fully documented now, not the reactors, which was never in contention.. Coastlines around the world are inherently dangerous locations for these plants but unfortunately a pretty much unavoidable one so better redundancy and safety needs to be well built in and over-engineered not just perceivably "adequately" engineered..

This thread is moving at light speed and everyone is overanxious to get their opinions heard and a lot is getting overlooked in the process. I suggest everyone posting, slow down take a deep breath and comprehend the posts they reply to before doing so to avoid a real donnybrook occurring..

Edited March 20, 2011 by WarpSpeed

[katana]

The sea can be used as a heat sink, not the same as pumping seawater directly in the reactor core.

Yes, didn't say it was put in direct contact with the core, just that it's used for cooling, indirectly, hence the raised sea or lake temps around the plant.

[jfchandler]

Actually, I was surprised... The surface levels of Reactor 3 clearly are trashed...

But one thing I was reading indicated that in Reactor 3, the spent fuel cooling pool was 6 or 7 levels below ground... That seemed strange, because in Reactor 4, it's supposedly up in the upper roof levels.

Clearly, there's not much if anything left of the upper levels of 3... So maybe that report is correct.

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

[JulianLS]

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

Something I've been wondering about. Is the suppression pool supposed to have an igniter to burn off the potentially dangerous hydrogen gas and if so is there no backup way of safely venting should the ignition system fail?

No, there is no system to ignite the hydrogen. The idea is not to ignite it! The explosions earlier in the week were accidental ignition, either from an electrical spark or from pyrophoric compounds in the vented gases (uranium itself is pyrophoric when finely divided). The hope is that the hydrogen dissipates naturally without igniting. They have knocked holes in the upper walls of reactors 5 and 6 to facilitate dispersal of any hydrogen gas.

As I understand, the plant does not generate hydrogen in normal operation. They believe the hydrogen came from water (steam) reacting with (accidentally) exposed fuel rods. So there isn't a system in place to dissipate the hydrogen safely that I am aware of. Apart from knocking holes in the wall....

[WarpSpeed]

True at the top of the building..... But bear in mind that the plant is partly underground. And they were considering venting the reactor into the pressure suppression pool. Which is the toroid structure at the bottom. An explosion down there could potentially send the core shooting up into the air like a rocket

Something I've been wondering about. Is the suppression pool supposed to have an igniter to burn off the potentially dangerous hydrogen gas and if so is there no backup way of safely venting should the ignition system fail?

They have knocked holes in the upper walls of reactors 5 and 6 to facilitate dispersal of any hydrogen gas.

Another simple feature one would think would be a given in design, emergency venting .....

Edited March 20, 2011 by WarpSpeed

[jfchandler]

Ohh... I've been saving a couple nice things to pass along... So now seems an opportune time...

An info box on the dates of construction, firms involved and various other stuff...

And a nice map of the area around Fukushima, for those planning upcoming vacations there...

PS - I thought the white waters from the aerial photo of the plant posted above were from the plant jacuzzi...

Edited March 20, 2011 by jfchandler

[WarpSpeed]

PS - I thought the white waters from the aerial photo of the plant posted above were from the plant jacuzzi...

Yes serious massage that one gives and with nuclear heating to boot ..

[Alphonso]

No, there is no system to ignite the hydrogen. The idea is not to ignite it! The explosions earlier in the week were accidental ignition, either from an electrical spark or from pyrophoric compounds in the vented gases (uranium itself is pyrophoric when finely divided). The hope is that the hydrogen dissipates naturally without igniting. They have knocked holes in the upper walls of reactors 5 and 6 to facilitate dispersal of any hydrogen gas.

As I understand, the plant does not generate hydrogen in normal operation. They believe the hydrogen came from water (steam) reacting with (accidentally) exposed fuel rods. So there isn't a system in place to dissipate the hydrogen safely that I am aware of. Apart from knocking holes in the wall....

The reason I ask is from this document https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Containment%20Structures.pdf which shows

and mentions recombiners. Just wondering if this is applicable to these reactors. I can not help think there would be some contingency to get rid of the hydrogen in a safe manner although in the case of Fukushima that may not have been possible due to the nature of failures caused by the tsunami.

[brahmburgers]

excerpt from article written during the BP oil spill in the Gulf of Mexico:

"(Watchdog groups) are warning about the BP oil spill's potential damage to Gulf and Atlantic coast nuclear power plants that use seawater to cool pumps and other safety equipment. While seawater is not used to cool the reactors themselves, it's used in the plants' secondary cooling systems. There are concerns that contamination could damage those systems."

full article: Texas Observer

Note: the planned sites for all but one of Thailand's 5 future nuclear plants are along sea shores. The 5th is by a large lake. All are upwind from neighboring countries, particularly Cambodia.

[jfchandler]

Photo via NHK of the protective radiation suits being worn by workers at the Fukushima plant.

Photo via NHK of evacuated residents being checked for radiation.

[unblocktheplanet]

My understanding is that all four 40-year old reactors were about to be decommissioned so no financial loss from using seawater directly for emergency cooling.

What a boondoggle!

[Crushdepth]

My money's on the cement option.

[JulianLS]

No, there is no system to ignite the hydrogen. The idea is not to ignite it! The explosions earlier in the week were accidental ignition, either from an electrical spark or from pyrophoric compounds in the vented gases (uranium itself is pyrophoric when finely divided). The hope is that the hydrogen dissipates naturally without igniting. They have knocked holes in the upper walls of reactors 5 and 6 to facilitate dispersal of any hydrogen gas.

As I understand, the plant does not generate hydrogen in normal operation. They believe the hydrogen came from water (steam) reacting with (accidentally) exposed fuel rods. So there isn't a system in place to dissipate the hydrogen safely that I am aware of. Apart from knocking holes in the wall....

The reason I ask is from this document https://netfiles.uiu...0Structures.pdf which shows and mentions recombiners. Just wondering if this is applicable to these reactors. I can not help think there would be some contingency to get rid of the hydrogen in a safe manner although in the case of Fukushima that may not have been possible due to the nature of failures caused by the tsunami.

The Fukushima unit #3 was constructed in 1970, and went online in 1974. I dont think hydrogen release in a low coolant situation was even considered prior to TMI accident in 1979. Which is why I think it's unlikely that they have any hydrogen flaring systems (as well as the fact that earlier, they vented a number of reactors which subsequently led to hydrogen explosions in Units 1, 2 and 3. And unit 4, but there the source must have been the storage pool not the reactor)

I don't really have a view of how many reactors in the world have such a system, but at a guess, I would say very few. Some of the experts here might have a much better idea than me....