That makes almost no sense at all. I'll do your google search but as far as I can tell there's not reason to shut down a nuke plant when the grid goes down.
I normally agree with a lot of your points, but I can't for the life of me figure out why you would think it wise to keep a nuclear plant online when there's no grid to send the energy to.
Can the electricity generated be stored? I guess it's a question of how much storage they might have -- enough for the odd surplus here or there, or a more substantial system.
Electricity cannot be stored in any meaningful amount, which is why the plant shutdowns took place.
Just for your info, while the U.S. is back up and running as usual, Ontario is still in crisis mode. Our problems should be resolved by the weekend, but we depend on the Gov't run nukes a whole lot.
New York and the other jurisdictions can tap into cheap power from the Northeast, a luxury we don't have. Quebec can supply hydro-electric power, but the cost appears to be prohibitive.
Torontonians are still being asked not to run a/c, not to turn on washers or dishwashers before 8pm, not use car washes or other 'frivolous' electric indulgences and turn off as many lights as possible.
So, as you can imagine, we're demanding to be kept informed on the how and why.
always-on, and this stuff becomes "outlet valve" for always-on power
< there are certain types of nuclear plant (such as some in Ontario) whose SCRAM shutdowns produce rare reaction-inhibiting isotopes that take time to decay/dissipate, delaying restart of said reactor by days or weeks. in such cases, it might be preferable to keep the thing running. >
premium customers (Universities/Labs, Local Govt, Communications, etc)
businesses or public services outside of the critical list for whom steady provision of power is worth every penny
regular shmoes
once basic services work, extra power can be shared among you. buy a bigger UPS and/or conserve
i'd vote for the big Tesla lightning, personally. Free Aurora show.
That makes almost no sense at all. I'll do your google search but as far as I can tell there's not reason to shut down a nuke plant when the grid goes down.
As I said, I'm speculating because I do not know the condition of the particular power plants.
Given that a nuclear reactor has a specific fuel load and that it is normally run at high power/high load for efficiency:
The power produced by the nuclear reactor is proportional to the neutron flux produced by fission. As the nuclear fuel is depleted, the control rods, which are made of neutron absorbing material, have to be withdrawn more and more to produce the same amount of power.
The amount of fission product waste produced is also proportional to the neutron flux. One particular isotope absorbs neutrons well.
If the reactor goes from producing a high load, say 80% power, to a self-sustaining load, say 8-12%, there is a significant amount of xenon. Because the xenon takes a while to produce (from the decay of iodine), the relative amount can increase. Since more neutrons are being absorbed by the xenon (i.e., not producing power), the control rods must be withdrawn more in order to keep the nuclear power plant running within its specified parameters (pressure and temperature). If the reactor plant is old (is due for a refueling), the control rods may be near their limit of travel, and then when they can no longer be withdrawn, the reactor will begin to shut itself down.
In this case, it would seem that a controlled shutdown would make more sense.
This does not even address the fuel load. While naval ships are designed to operate for up to 20 years without refueling (probably 8 to 12 years on the average), as far as I have heard, civilian plants are refueled every 18 to 24 months. Since the electrical grid cannot be restored instantaneously (as implied by previous comment by Paul, but we could discuss that if someone wants), the utility might not want to run the nuclear reactor until the integrity of the grid has been verified and (I am assuming again since I am not a power engineer) the grid has been partitioned so that when the generators are brought on line, they don't have to supply more than their capacity.
I assume the generators produce alternating currrent.
This must be first converted into direct current and then stored in batteries. Battery technology is not at a state where we can do this in large amounts.
If we had large reservoirs, we could pump water into the reservoirs and use hydroelectric generators. Environmentalists would be very concerned if we were to plan such reservoirs.
In France, where they are up to 80% dependent on nuclear power, I hear they are experimenting with hydrogen generation during off peak hours. Right now, nuclear power might be the only practical way of producing the large amounts of hydrogen for a "hydrogen" economy.
I'm sure there is a concern in the United States with using nuclear reactors to produce hydrogen because the environmental opposition is such that we have not built a nuclear power plant in 20 years. (Someone could argue with me on this since I'm writing off the top of my head.) The plants are getting old and are not being replaced. Any plan of what to do with the nuclear waste (said to be the volume of a shoebox for each family per year) has been met with "not in our backyard". So, there might be a concern with reserving the power production for commercial electrical usage unless we can modernize the plants, build new ones, and store the waste products.
Edit: I guess the good thing is that while we cannot store the electricity in any meaningful quantity, when the plants are offline, they just are not producing any electrical power, and so there is no great loss or potential loss (except perhaps in the hydroelectric plants, solar, or wind plants).
I normally agree with a lot of your points, but I can't for the life of me figure out why you would think it wise to keep a nuclear plant online when there's no grid to send the energy to.
Unless you enjoy a really good fireworks show.
Did I say that? No. What I am saying is that I don't believe that it takes so long to bring it up after a relatively short down time on the grid. What were they thinking, "Oh gosh our crystal ball tells us this will take days so let's push the rods in and take the pile all the way down." No. Does anyone even know what they did to the pile? I'm guessing no. Also for people who don't know you don't have to shut down the pile to stop making electricity.
I don't know what you all are debating about, but up here in Rochester our RG&E Ginna Nuclear Power Plant was completely shut down during the black out. Even several days after power was restored, the media was saying that Ginna was only running at half of its normal capacity, and it would still take a little more time to get it back to 100%.
Did I say that? No. What I am saying is that I don't believe that it takes so long to bring it up after a relatively short down time on the grid. What were they thinking, "Oh gosh our crystal ball tells us this will take days so let's push the rods in and take the pile all the way down." No. Does anyone even know what they did to the pile? I'm guessing no. Also for people who don't know you don't have to shut down the pile to stop making electricity.
Okay, my mistake. The answer to that is simple though. The nuke plants are quite old and poorly maintained. The engineers felt it was unsafe to keep them going without the grid up and running.
Perhaps those who have been whining about deregulation and insisting that the private sector doesn't invest in maintenance and upkeep can explain to me why Ontario's publicly owned nuclear facilities seem to be in such extremely poor shape.
I don't know what you all are debating about, but up here in Rochester our RG&E Ginna Nuclear Power Plant was completely shut down during the black out. Even several days after power was restored, the media was saying that Ginna was only running at half of its normal capacity, and it would still take a little more time to get it back to 100%.
Also for people who don't know you don't have to shut down the pile to stop making electricity.
OK, I'll try one last time. I'm not a Ph.D in physics, so I'm not going to try to talk at a highly technical level.
In a power generating reactor, it is more dangerous to keep the reactor running without producing power. Control of a pressurized water reactor relies on negative feedback, which takes the form of the power (electrical) demand.
It is probably a safety issue to run the reactor without producing power.
With no demand and with the reactor critical, it will still produce heat. Running the reactor hotter will tend to shut down the reactor because the water density would go down. Lower density means fewer neutrons are themalized. Thermal neutrons are the ones that cause fissions in this design of reactor. To keep the reactor running, the control rods would have to be withdrawn further. Added to the effect discussed earlier (xenon poisoning), in the event of an accident, it would take longer to do an emergency shutdown of the reactor (by driving in the control rods or dropping the control rods) increasing the possibility of damage to the reactor core.
In low power operations, the reactor core is not the only source of heat. The pumps can generate a significant amount of heat.
A nuclear reactor is often controlled my monitoring the neutron flux level. At low powers, this level is significantly less than during normal operation. The behavior of the reactor at this level is affected by the rate of change in the (thermal) neutron level. So, because we only need a relatively small change in neutron level to create a large change in power and because the instruments are monitoring at the low end of their detection capability, there is an increased possibility of damaging the reactor in the event of an accident. An accident could be the lifting of a relief valve that sticks open or the rupture of a steam pipe. (As mentioned above, the reactor is likely to be operating at the high end of the temperature band. Also, the steam side - assuming that the power plant uses steam turbine generators - is at the highest pressure with no electrical demand. So, the mechanical stresses under these conditions would be the highest.) When a relief valve lifts or a pipe ruptures, this results in a slug of cold water entering the reactor. The increased density results in a greater thermalization of neutrons, and the power would spike.
Whether or not any actual reactor damage would occur cannot be predicted by the basic facts mentioned above. However, if the opeators noted a power spike or (more likely) an automatic shutdown of the reactor occurred, the subsequent restart of the reactor would be delayed until the extent of reactor damage (if any) was determined. I do not know this for a fact, but given the amount of regulation of nuclear power plant operation, I would guess that the rules would keep the reactor shut down for a significant period of time.
Furthermore, I speculate that the regulations prohibit the opeation of a power producing reactor when it is not producing power (except for highly regulated testing), for the reasons mentioned above as well as others which I haven't thought of.
Given the discussion of nuclear power that I've seen in another thread, I'm sure there is a more knowledgable person who could explain this better.
Comments
I normally agree with a lot of your points, but I can't for the life of me figure out why you would think it wise to keep a nuclear plant online when there's no grid to send the energy to.
Unless you enjoy a really good fireworks show.
Electricity cannot be stored in any meaningful amount, which is why the plant shutdowns took place.
Just for your info, while the U.S. is back up and running as usual, Ontario is still in crisis mode. Our problems should be resolved by the weekend, but we depend on the Gov't run nukes a whole lot.
New York and the other jurisdictions can tap into cheap power from the Northeast, a luxury we don't have. Quebec can supply hydro-electric power, but the cost appears to be prohibitive.
Torontonians are still being asked not to run a/c, not to turn on washers or dishwashers before 8pm, not use car washes or other 'frivolous' electric indulgences and turn off as many lights as possible.
So, as you can imagine, we're demanding to be kept informed on the how and why.
power plants and refineries regularly flare some of their "excess" gases
dams can dump water in flood times
if the juice gotta go, it gotta go.
pipe it to some NASA projects and leave the plasma throttles open,
or some gigantic Tesla coils to test lightning-powered flying cars.
my bet? a priority-tiered grid (might mean upgrading new layers) with:
- critical infrastructure (EMS, Fed Govt/Mil/Security, Airports, etc)
- premium customers (Universities/Labs, Local Govt, Communications, etc)
- regular shmoes
i'd vote for the big Tesla lightning, personally. Free Aurora show.always-on, and this stuff becomes "outlet valve" for always-on power
< there are certain types of nuclear plant (such as some in Ontario) whose SCRAM shutdowns produce rare reaction-inhibiting isotopes that take time to decay/dissipate, delaying restart of said reactor by days or weeks. in such cases, it might be preferable to keep the thing running. >
businesses or public services outside of the critical list for whom steady provision of power is worth every penny
once basic services work, extra power can be shared among you. buy a bigger UPS and/or conserve
Originally posted by Scott
That makes almost no sense at all. I'll do your google search but as far as I can tell there's not reason to shut down a nuke plant when the grid goes down.
As I said, I'm speculating because I do not know the condition of the particular power plants.
Given that a nuclear reactor has a specific fuel load and that it is normally run at high power/high load for efficiency:
The power produced by the nuclear reactor is proportional to the neutron flux produced by fission. As the nuclear fuel is depleted, the control rods, which are made of neutron absorbing material, have to be withdrawn more and more to produce the same amount of power.
The amount of fission product waste produced is also proportional to the neutron flux. One particular isotope absorbs neutrons well.
If the reactor goes from producing a high load, say 80% power, to a self-sustaining load, say 8-12%, there is a significant amount of xenon. Because the xenon takes a while to produce (from the decay of iodine), the relative amount can increase. Since more neutrons are being absorbed by the xenon (i.e., not producing power), the control rods must be withdrawn more in order to keep the nuclear power plant running within its specified parameters (pressure and temperature). If the reactor plant is old (is due for a refueling), the control rods may be near their limit of travel, and then when they can no longer be withdrawn, the reactor will begin to shut itself down.
In this case, it would seem that a controlled shutdown would make more sense.
This does not even address the fuel load. While naval ships are designed to operate for up to 20 years without refueling (probably 8 to 12 years on the average), as far as I have heard, civilian plants are refueled every 18 to 24 months. Since the electrical grid cannot be restored instantaneously (as implied by previous comment by Paul, but we could discuss that if someone wants), the utility might not want to run the nuclear reactor until the integrity of the grid has been verified and (I am assuming again since I am not a power engineer) the grid has been partitioned so that when the generators are brought on line, they don't have to supply more than their capacity.
Originally posted by BuonRotto
Can the electricity generated be stored?
Not with our present technology.
I assume the generators produce alternating currrent.
This must be first converted into direct current and then stored in batteries. Battery technology is not at a state where we can do this in large amounts.
If we had large reservoirs, we could pump water into the reservoirs and use hydroelectric generators. Environmentalists would be very concerned if we were to plan such reservoirs.
In France, where they are up to 80% dependent on nuclear power, I hear they are experimenting with hydrogen generation during off peak hours. Right now, nuclear power might be the only practical way of producing the large amounts of hydrogen for a "hydrogen" economy.
I'm sure there is a concern in the United States with using nuclear reactors to produce hydrogen because the environmental opposition is such that we have not built a nuclear power plant in 20 years. (Someone could argue with me on this since I'm writing off the top of my head.) The plants are getting old and are not being replaced. Any plan of what to do with the nuclear waste (said to be the volume of a shoebox for each family per year) has been met with "not in our backyard". So, there might be a concern with reserving the power production for commercial electrical usage unless we can modernize the plants, build new ones, and store the waste products.
Edit: I guess the good thing is that while we cannot store the electricity in any meaningful quantity, when the plants are offline, they just are not producing any electrical power, and so there is no great loss or potential loss (except perhaps in the hydroelectric plants, solar, or wind plants).
Originally posted by Frank777
Uh, Scott...
I normally agree with a lot of your points, but I can't for the life of me figure out why you would think it wise to keep a nuclear plant online when there's no grid to send the energy to.
Unless you enjoy a really good fireworks show.
Did I say that? No. What I am saying is that I don't believe that it takes so long to bring it up after a relatively short down time on the grid. What were they thinking, "Oh gosh our crystal ball tells us this will take days so let's push the rods in and take the pile all the way down." No. Does anyone even know what they did to the pile? I'm guessing no. Also for people who don't know you don't have to shut down the pile to stop making electricity.
Did I say that? No. What I am saying is that I don't believe that it takes so long to bring it up after a relatively short down time on the grid. What were they thinking, "Oh gosh our crystal ball tells us this will take days so let's push the rods in and take the pile all the way down." No. Does anyone even know what they did to the pile? I'm guessing no. Also for people who don't know you don't have to shut down the pile to stop making electricity.
Okay, my mistake. The answer to that is simple though. The nuke plants are quite old and poorly maintained. The engineers felt it was unsafe to keep them going without the grid up and running.
Perhaps those who have been whining about deregulation and insisting that the private sector doesn't invest in maintenance and upkeep can explain to me why Ontario's publicly owned nuclear facilities seem to be in such extremely poor shape.
Originally posted by Mac Man 020581
I don't know what you all are debating about, but up here in Rochester our RG&E Ginna Nuclear Power Plant was completely shut down during the black out. Even several days after power was restored, the media was saying that Ginna was only running at half of its normal capacity, and it would still take a little more time to get it back to 100%.
Define "completely shut down".
Originally posted by Scott
Also for people who don't know you don't have to shut down the pile to stop making electricity.
OK, I'll try one last time. I'm not a Ph.D in physics, so I'm not going to try to talk at a highly technical level.
In a power generating reactor, it is more dangerous to keep the reactor running without producing power. Control of a pressurized water reactor relies on negative feedback, which takes the form of the power (electrical) demand.
It is probably a safety issue to run the reactor without producing power.
With no demand and with the reactor critical, it will still produce heat. Running the reactor hotter will tend to shut down the reactor because the water density would go down. Lower density means fewer neutrons are themalized. Thermal neutrons are the ones that cause fissions in this design of reactor. To keep the reactor running, the control rods would have to be withdrawn further. Added to the effect discussed earlier (xenon poisoning), in the event of an accident, it would take longer to do an emergency shutdown of the reactor (by driving in the control rods or dropping the control rods) increasing the possibility of damage to the reactor core.
In low power operations, the reactor core is not the only source of heat. The pumps can generate a significant amount of heat.
A nuclear reactor is often controlled my monitoring the neutron flux level. At low powers, this level is significantly less than during normal operation. The behavior of the reactor at this level is affected by the rate of change in the (thermal) neutron level. So, because we only need a relatively small change in neutron level to create a large change in power and because the instruments are monitoring at the low end of their detection capability, there is an increased possibility of damaging the reactor in the event of an accident. An accident could be the lifting of a relief valve that sticks open or the rupture of a steam pipe. (As mentioned above, the reactor is likely to be operating at the high end of the temperature band. Also, the steam side - assuming that the power plant uses steam turbine generators - is at the highest pressure with no electrical demand. So, the mechanical stresses under these conditions would be the highest.) When a relief valve lifts or a pipe ruptures, this results in a slug of cold water entering the reactor. The increased density results in a greater thermalization of neutrons, and the power would spike.
Whether or not any actual reactor damage would occur cannot be predicted by the basic facts mentioned above. However, if the opeators noted a power spike or (more likely) an automatic shutdown of the reactor occurred, the subsequent restart of the reactor would be delayed until the extent of reactor damage (if any) was determined. I do not know this for a fact, but given the amount of regulation of nuclear power plant operation, I would guess that the rules would keep the reactor shut down for a significant period of time.
Furthermore, I speculate that the regulations prohibit the opeation of a power producing reactor when it is not producing power (except for highly regulated testing), for the reasons mentioned above as well as others which I haven't thought of.
Given the discussion of nuclear power that I've seen in another thread, I'm sure there is a more knowledgable person who could explain this better.