in the event of any major disruption of society, most of the nuclear power plants can be expected to melt down
Source? I’m given to understand that they have a lot of fail safes. Wouldn’t they all just turn off? Also, it seems like the disruption would have to be extremely sudden for even that to happen. Otherwise, they’d just turn the power plant off.
Even 1 Chernobyl corresponds to awful lot of nukes.
It may correspond to an awful lot of nukes in terms of fallout, but it corresponds to exactly zero in terms of sending dust into the air and messing with the climate.
1: One does not simply turn the reactor all the way off (picture of Aragorn, err, Boromir, or who ever). There’s the decay heat, several megawatts of it even after months of shutdown (google decay heat), that can’t be turned off, and virtually all reactors require intervention to keep that cooled. Likewise for spent fuel pools, that boil itself out over course of a week or two. That’s what happened in Fukushima—the reactors did shut down correctly but all powered decay heat removal systems failed when tsunami water flooded the basements (in which they kept the switchgear and emergency generators). The spent fuel pools were an immense problem and at least one—in the reactor building #4 where reactor was not loaded with fuel—did boil off to the point of partially uncovering the fuel, at which point they got the concrete pump to pump water in. That’s Japanese, a nation of 127 millions, responding in the tsunami that killed about 16 000 people and displaced perhaps a million (excluding those displaced due to reactor). The spent fuel pool was allowed to boil itself off to the level of fuel.
AP1000 is advanced safe reactor design. It raised the no-intervention time to the whooping 72… hours.
Major safety systems are passive; they require no operator action for 72 hours after an acci-dent, and maintain core and containment cooling for a protracted time without ac power.
Which is typical hard to parse statement which translates to: after 72 hours, the cooling water reserve evaporates off, and you get yourself regular meltdown like in any other design. The protracted time without water is 72 hours. The operator action is getting a lot of water on top of 10 story building somehow. Note that most reactors in use require AC power, that’s why it is so awesome AP-1000 doesn’t need AC power. Also, note risk estimates at one in 10 millions years. WTF are they even doing at NRC, some sort of circle of self delusion wrt what sort of stuff happens in 10 millions years. Mankind survival is unlikely to have that sort of reliability, and that’s counting the recoveries from stone age.
2: Mostly yes, i’m only speaking of radioactive pollution there.
One does not simply turn the reactor all the way off
Perhaps not, but I’d expect you’d flip a switch, and then the automated systems would shut it off, or something to that effect.
Which is typical hard to parse statement which translates to: after 72 hours, the cooling water reserve evaporates off, and you get yourself regular meltdown like in any other design.
So, set it to shut down automatically after 36 hours without operator action, and it will be fine.
can release up to 10 Chernobyls of cs-137 or so
Why didn’t they have that problem at Three Mile Island?
Perhaps not, but I’d expect you’d flip a switch, and then the automated systems would shut it off, or something to that effect.
You expect wrong. Nature isn’t rubber padded, and technology isn’t friendly magic. You flip switch, control rods go in, the chain reaction stops, the decay heat continues.
So, set it to shut down automatically after 36 hours without operator action, and it will be fine.
It is 72 hours after the full shutdown, that it melts itself down. edit: or to be pedantic, gets outside design parameters; the melt may take another couple days.
Why didn’t they have that problem at Three Mile Island?
Because the spent fuel pool didn’t boil itself dry. They had a core meltdown, luckily they had full external power and could keep circulating the coolant.
The Fukushima is the TMI without external power: same reactor types, 3 out of 3 melting. The Tokio being evacuated is Fukushima the other time of the year when wind is blowing inland. Ain’t a safety feature of the reactor design that it failed in the season when wind is mostly blowing to ocean. At least they did consider evacuation.
Source? I’m given to understand that they have a lot of fail safes. Wouldn’t they all just turn off? Also, it seems like the disruption would have to be extremely sudden for even that to happen. Otherwise, they’d just turn the power plant off.
It may correspond to an awful lot of nukes in terms of fallout, but it corresponds to exactly zero in terms of sending dust into the air and messing with the climate.
1: One does not simply turn the reactor all the way off (picture of Aragorn, err, Boromir, or who ever). There’s the decay heat, several megawatts of it even after months of shutdown (google decay heat), that can’t be turned off, and virtually all reactors require intervention to keep that cooled. Likewise for spent fuel pools, that boil itself out over course of a week or two. That’s what happened in Fukushima—the reactors did shut down correctly but all powered decay heat removal systems failed when tsunami water flooded the basements (in which they kept the switchgear and emergency generators). The spent fuel pools were an immense problem and at least one—in the reactor building #4 where reactor was not loaded with fuel—did boil off to the point of partially uncovering the fuel, at which point they got the concrete pump to pump water in. That’s Japanese, a nation of 127 millions, responding in the tsunami that killed about 16 000 people and displaced perhaps a million (excluding those displaced due to reactor). The spent fuel pool was allowed to boil itself off to the level of fuel.
AP1000 is advanced safe reactor design. It raised the no-intervention time to the whooping 72… hours.
http://en.wikipedia.org/wiki/AP1000#Design_specifications
http://www.ne.doe.gov/pdfFiles/AP1000_Plant_Description.pdf
Which is typical hard to parse statement which translates to: after 72 hours, the cooling water reserve evaporates off, and you get yourself regular meltdown like in any other design. The protracted time without water is 72 hours. The operator action is getting a lot of water on top of 10 story building somehow. Note that most reactors in use require AC power, that’s why it is so awesome AP-1000 doesn’t need AC power. Also, note risk estimates at one in 10 millions years. WTF are they even doing at NRC, some sort of circle of self delusion wrt what sort of stuff happens in 10 millions years. Mankind survival is unlikely to have that sort of reliability, and that’s counting the recoveries from stone age.
2: Mostly yes, i’m only speaking of radioactive pollution there.
Boromir. Goodness, what are they teaching in schools these days?
Ahh, right. lol.
Perhaps not, but I’d expect you’d flip a switch, and then the automated systems would shut it off, or something to that effect.
So, set it to shut down automatically after 36 hours without operator action, and it will be fine.
Why didn’t they have that problem at Three Mile Island?
You expect wrong. Nature isn’t rubber padded, and technology isn’t friendly magic. You flip switch, control rods go in, the chain reaction stops, the decay heat continues.
It is 72 hours after the full shutdown, that it melts itself down. edit: or to be pedantic, gets outside design parameters; the melt may take another couple days.
Because the spent fuel pool didn’t boil itself dry. They had a core meltdown, luckily they had full external power and could keep circulating the coolant.
The Fukushima is the TMI without external power: same reactor types, 3 out of 3 melting. The Tokio being evacuated is Fukushima the other time of the year when wind is blowing inland. Ain’t a safety feature of the reactor design that it failed in the season when wind is mostly blowing to ocean. At least they did consider evacuation.