Slitherine

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ORIGINAL: witpqs

FYI, USGS is now calling it a 9.0 earthquake.

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ORIGINAL: Mynok

They need to get some power generation there ASAP so they can shut those reactors down. I fear the worst.

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ORIGINAL: witpqs

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ORIGINAL: Mynok

They need to get some power generation there ASAP so they can shut those reactors down. I fear the worst.

The reactors shut down at the first warning of the quake. Apparently the whole thing has been dealing with residual heat.

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ORIGINAL: bradfordkay

Steve, I always wondered about the secondary loop in submarines. Is it seawater being pumped through? Can the trail of warmer water be used to find the sub? 

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ORIGINAL: ChezDaJez

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ORIGINAL: witpqs

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ORIGINAL: Mynok

They need to get some power generation there ASAP so they can shut those reactors down. I fear the worst.

The reactors shut down at the first warning of the quake. Apparently the whole thing has been dealing with residual heat.

The residual heat from the reactor core is the problem. I'm no expert and most of my nuclear reactor knowledge comes from submarine type reactors but the underlying principle is the same though the execution may be somewhat different.

A reactor is basically nothing more than a huge pressure cooker. Within this pressure cooker, you have a primary loop that contains water under high pressure. The reactor's sole purpose is to generate the heat to turn this water into the steam that drives a turbine. It is a closed loop system and has no access to the environment unless damaged. The water in this loop is radioactive.

To recondense the steam back into water, the primary loop passes through a secondary loop that receives water from a lake, river, ocean or huge cooling ponds. This secondary loop is entirely seperate from the primary loop and is open to the environment. This water is not radioactive. The water in the secondary loop is circulated by means of huge main cooling pumps. These pumps require considerable electrical power to function. It is the loss of electrical power to these pumps that is causing all the problems at Fukushima Dai-ichi.

The electrical generation plant failed because the reactors scrammed after the quake as they are supposed to causing the turbines to stop. The backup diesel generators then took over. All was fine until the tsunami swamped the backup generators causing them to fail. Emergency battery back up then took over until they were depleted after about 6-8 hours.

With the loss of the secondary loop, the reactors had no way to stay cool so the water inside the primary loop continued to evaporate and build up heat and pressure within the containment vessel. Think of it as a tea kettle sitting on a hot stove with no way to turn off the stove. With no operational secondary loop to cool the steam back into water, the water level in the core began to drop exposing more and more of the uranium rods. As more uranium is exposed, the temperature climbs. Uranium rods exposed to air can generate about 2200 degrees celsius but uranium begins melting at about 2100 degrees celsius. When the rods reach this temperature, you now have meltdown occuring.

Hope this helps those who aren't familiar with reactor design and hopefully I don't look like to much of an idiot to those that are!

Chez

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ORIGINAL: bradfordkay

Steve, I always wondered about the secondary loop in submarines. Is it seawater being pumped through? Can the trail of warmer water be used to find the sub? 

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ORIGINAL: ChezDaJez

The electrical generation plant failed because the reactors scrammed after the quake as they are supposed to causing the turbines to stop. The backup diesel generators then took over. All was fine until the tsunami swamped the backup generators causing them to fail. Emergency battery back up then took over until they were depleted after about 6-8 hours.

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ORIGINAL: witpqs

I also forgot to mention that much of the heat is coming from the products of the fission reaction. They are short-lived to fairly short-lived radioactive isotopes. As they decay they release heat. The amount of them present decreases as they decay, and therefore the amount of heat they release also decreases. Still, it is a lot of heat at first, then decreases fairly rapidly over hours/days/weeks. The uranium itself will be putting out some heat from its decay too, but at first the big heat producer is those short-lived isotopes.

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ORIGINAL: bradfordkay
Steve, I always wondered about the secondary loop in submarines. Is it seawater being pumped through? Can the trail of warmer water be used to find the sub? 

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ORIGINAL: Mynok


Wired on the plant situation

Mike

"Good times will set you free" - Jimmy Buffett

"They need more rum punch" - Me


Artwork by The Amazing Dixie

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ORIGINAL: bradfordkay

Steve, I always wondered about the secondary loop in submarines. Is it seawater being pumped through? Can the trail of warmer water be used to find the sub? 

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ORIGINAL: Mynok


Where are they pumping in the seawater then?

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ORIGINAL: ChezDaJez

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ORIGINAL: bradfordkay

Steve, I always wondered about the secondary loop in submarines. Is it seawater being pumped through? Can the trail of warmer water be used to find the sub? 

I think Bullwinkle used to be a nuke so he understands the shipboard systems far better than I do. As he says the secondary system on newer submarines is a closed loop system. On early generation Soviet nuculear submarines the secondary loop was cooled by seawater.

I know several countries including the Soviets/Russians and the US have all experiemented with ways to detect submarine heat trails using IR and blue/green laser systems over the past few decades. What progress has been made I don't know.

One of the problems with detecting the heat trail from nuclear subs is just what JWE said. The warmer water is rapidly cooled by the surrounding ocean and by the time it reaches the surface it should be about the same temperature. Also the sea surface temperature is quite variably even over short distances. Currents and wind/wave action will also help to reduce its detectability.

Chez

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ORIGINAL: USS America


That's a very good explanation of the situation.

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ORIGINAL: ChezDaJez


I think Bullwinkle used to be a nuke so he understands the shipboard systems far better than I do. As he says the secondary system on newer submarines is a closed loop system. On early generation Soviet nuculear submarines the secondary loop was cooled by seawater.

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ORIGINAL: Bullwinkle58

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ORIGINAL: USS America


That's a very good explanation of the situation.

It is, but the situation is fast-moving and things have moved along since it was written. I see on TV that there was a fire in a spent rod continament pool in the past twelve hours, and that radioactive readings in Tokyo are elevated, but not yet dangerous.

The French, apparently with no more info than us here, are yelling that the accident is a '6', not a '5' (thanks, France, for that.) Gemrany has shut down a whole bunch of its reactors, but the story didn't say why (inspections I suspect.) And solar-related stocks are soaring, while nuclear-power-related stocks are tanking.

It does seem as if the Japanese govt and the international atomic agency guys aren't on the same sheet of music, and that there is a lot of confusion over who is giving the straight scoop to the world, let alone the Japanese public. I suspect again that there is very imperfect kowledge as a lot of instrumentation is probably wiped, and nobody is going near the containment vessels to use eyeballs.

Now is the time to have invented very good robots. We need a Wayback Machine.

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ORIGINAL: Bullwinkle58

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ORIGINAL: USS America


That's a very good explanation of the situation.

It is, but the situation is fast-moving and things have moved along since it was written. I see on TV that there was a fire in a spent rod continament pool in the past twelve hours, and that radioactive readings in Tokyo are elevated, but not yet dangerous.

The French, apparently with no more info than us here, are yelling that the accident is a '6', not a '5' (thanks, France, for that.) Gemrany has shut down a whole bunch of its reactors, but the story didn't say why (inspections I suspect.) And solar-related stocks are soaring, while nuclear-power-related stocks are tanking.

It does seem as if the Japanese govt and the international atomic agency guys aren't on the same sheet of music, and that there is a lot of confusion over who is giving the straight scoop to the world, let alone the Japanese public. I suspect again that there is very imperfect kowledge as a lot of instrumentation is probably wiped, and nobody is going near the containment vessels to use eyeballs.

Now is the time to have invented very good robots. We need a Wayback Machine.

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On the international scale used by experts to rank nuclear incidents, Chernobyl ranked as a “major accident” or 7, the highest on the scale. Three Mile Island was a 5, an “accident with wider consequences.” Japanese officials have said they regard the Fukushima incident as a 4, an “accident with local consequences.”

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ORIGINAL: spence

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On the international scale used by experts to rank nuclear incidents, Chernobyl ranked as a “major accident” or 7, the highest on the scale. Three Mile Island was a 5, an “accident with wider consequences.” Japanese officials have said they regard the Fukushima incident as a 4, an “accident with local consequences.”

I just got done watching a news/opinion show on TV which attempted to get an expert to say what threat the problems at the reactors in Japan might pose to the U.S. The answers given were not particularly useful to anyone not actually equipped to measure radiation. The problems with the reactors were compared (as in the article) in the segment to Chernobyl and Three Mile Island. A couple of questions not asked were:

1) How does the amount of radiation leaked from the worst case "meltdown scenario" compare to the radiation created by the Hiroshima and Nagasaki atomic bombs?

2) I don't imagine the isotopes of radiative fallout from the atomic bombs were the same as might be created by one or more meltdowns at Fukushima (but perhaps they were). In any case such radiation as was created drifted across the Pacific to the U.S. much the way the "firebomb balloons" launched by the Japanese in 1944-45 did. Was it ever detected here?

3) How long did it take for those balloons to cross the Pacific and how does that time compare to the half-life of Iodine-131 which seems to be the radiation threat mentioned most often?

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ORIGINAL: Chickenboy

Dunno about a large scale nuclear explosion from a nuke plant by comparison.

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ORIGINAL: Mynok

Where are they pumping in the seawater then?

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ORIGINAL: witpqs

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ORIGINAL: Chickenboy

Dunno about a large scale nuclear explosion from a nuke plant by comparison.

Don't worry about that. That's called a nuclear bomb, and that ain't happening. The worst potential problems involve radioactive material being made airborne by means of fire, and any explosions would come from that. The fires so far have not been nuclear materials themselves but in the outer containment (those Hydrogen gas explosions for example) and other parts of the plant.