OT: Massive 8.9 quake in northern Japan

[Schanilec]

Hope those idiots are consentrated on one site. Easier to keep and eye on them.

[witpqs]

FYI, USGS is now calling it a 9.0 earthquake.

[rtrapasso]

ORIGINAL: witpqs

FYI, USGS is now calling it a 9.0 earthquake.

These things tend to increase over time for technical reasons... originally the Sumatra quake that produced the tsunami was called an 8.7... now up to 9.1+ depending on who you believe. It took a few years to revise the numbers.

i wouldn't be terribly surprised if they end up calling the recent Japanese quake a 9.3 or 9.4 (in about 2 years).

[USSAmerica]

Things are going downhill at the Fukushima Daiichi nuclear plant.  [:(]

[Mynok]

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

[witpqs]

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.

[ChezDaJez]

ORIGINAL: witpqs

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

[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? 

[herwin]

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? 

The secondary loop is also a closed loop.

[Mynok]

Where are they pumping in the seawater then?

[witpqs]

ORIGINAL: ChezDaJez

ORIGINAL: witpqs

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

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.

[Bullwinkle58]

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? 

The secondary loop uses distilled water as well. Seawater is used in the condensate loop through the main condensers to convert used steam back to secondary loop feed water. That seawater is then tossed over the side. As to your last quesiton, the sea is large and cold, and the sub is small and only a little warm. There may be other ways to track subs from environmental effects, but I ain't discussing them here.

[LargeSlowTarget]

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.

If electrical power for the pumps is the problem, then something like this could be a solution? Unfortunately no turbo-electric ships that I know off remain in service - last one seems to have been SSN-685.

[Bullwinkle58]

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.

Press reports that the main Iodine isotope they're worried about has a half-life of eight days. I don't know the decay heat features of these reactors. I've seen elsewhere that the cores are a combo of uranium ond plutonium (about 7% of the latter.) Don't know if that's true.

[JWE]

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? 

Technically, yes, perhaps. But the secondary loop discharge and recirc is periodic. Discharge is often over, or even under the layer, and is so dispersed that it doesn't have a 'trail' as one might suspect.

IR heat detect, on the surface at least, requires a realtively large 'differential' to resolve a source. Dispersion from the sea makes that problematic for surface forces even with the requisite equipment.

Beneath the surface, layering (horizontal and vertical) and current shift makes it practically impossible to track a vessel on the basis of its discharge heat signature. Water temperature and water pressure tend to collapse the discharge stream into a very narrow stream that is rotary and disperses by square law.

Brother Chez may have some more practical things to say, but given what we gots now, there aint no way to get there from here unless you get real lucky.

[Mynok]

Wired on the plant situation

[USSAmerica]

ORIGINAL: Mynok


Wired on the plant situation

That's a very good explanation of the situation.

[ChezDaJez]

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

[herwin]

ORIGINAL: Mynok


Where are they pumping in the seawater then?

Now.

[herwin]

Brother Bullwinkle is doing what he's supposed to do.