Timeline for Can Average Joe reboot the nuclear power plant?
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| Nov 17, 2015 at 1:28 | comment | added | J... | @SeanBoddy Reading back, I guess I could have been more clear. If anything, this just makes more strongly the point that Joe would have a hell of a task ahead of him. Maybe he could run the reactor at 0.05% power... hacking in smaller turbines, re-routing steam, adding load resistors in the cooling tower, reprogramming control algorithms to deal with xenon oscillations at such crazy low power levels...hopefully without radiating himself to death and breaking critical equipment for which spares are scarce. Hey, why not, eh? ;) | |
| Nov 17, 2015 at 0:20 | comment | added | user8827 | Mea culpa, and apologies. I genuinely thought you believed the thermal output of the reactor was a set value regardless of demand. I shall hang my head in shame at the earliest opportunity. :) | |
| Nov 17, 2015 at 0:17 | comment | added | J... | @SeanBoddy Is that where we're crossing wires? Yes, it's absolutely a limitation imposed (partly) by the turbines, but generally by the system as a whole. The turbines need the reactor to be running at a sufficient power output to turn them at the required speed. At that speed, they necessarily generate a large minimum amount of power. Below some minimum operating point, which is a measurable fraction of the rated power, things just don't work - as a system. The entire design of the plant is predicated on at least some minimum operating level that is much higher than Joe can deal with. | |
| Nov 17, 2015 at 0:04 | comment | added | user8827 | So long as you understand that that is a limitation of the turbines and not the reactor. | |
| Nov 17, 2015 at 0:00 | comment | added | J... | @SeanBoddy I understand completely what you are saying. Still, 500 people would need, on average, maybe 600kW of generating capacity. Even running at a minimum of 15% output, a 1.1GW Westinghouse is putting out 165MW. Yes, reactors are variable. Can you run a massive nuclear plant at 0.05% of its rated output? No - sorry, you cannot. It was never designed to work that way. It cannot sustainably work that way. There are additional problems for average Joe to solve here. | |
| Nov 16, 2015 at 23:10 | comment | added | user8827 | Load following, in the industry, describes the control mode used to govern how the station turbines respond to large scale changes in grid loading, which is a coordinated effort. That has no bearing on the physics inside the core, which will output only what is asked from it. You have completely misunderstood what being a base load station means in this context. | |
| Nov 16, 2015 at 22:57 | comment | added | J... | @SeanBoddy See : powermag.com/managing-minimum-load , and on load-following : oecd-nea.org/ndd/reports/2011/load-following-npp.pdf -- although a normal plant like an AP-1000 would simply not be equipped for load-following in the ways described in the latter document. | |
| Nov 16, 2015 at 21:40 | comment | added | J... | @SeanBoddy Keep in mind this is very different from a nuclear plant in a sub, for example, where you're immersed in the largest cooling tank the world could possibly provide. Infinite free cooling is not available to a large land-based plant. The challenge of regulation rather more difficult. | |
| Nov 16, 2015 at 21:37 | comment | added | J... | @SeanBoddy I'm still sceptical. The nuclear reaction can only be moderated so much before it just doesn't go anymore, and nuclear plants are generally really slow in changing their power output levels. Some plants are designed to be load-followers, but this is mostly not true of (big) nuclear plants. The cooling tower can theoretically be used to soak up excess heat that is not converted to electricity, but it is only really designed to absorb continuously the thermal load remaining after the generators have taken away their share. I really think the plant needs a minimum load to work. | |
| Nov 16, 2015 at 21:10 | comment | added | user8827 | And there is the conceptual error I'm talking about. Reactors exist in balance with the amount of power drawn from them due largely to a negative temperature coefficient of reactivity. A reactor will, in fact, only produce the quantity of power that is demanded of it. It just so happens that commercial nuke plants are more efficient as base-load stations - meaning when they come online, they are intentionally loaded to near maximum for reasons of cost effectiveness, not because they physically must. They do have to shed heat, but that's different. | |
| Nov 16, 2015 at 12:55 | comment | added | J... | @SeanBoddy Consider that the nuclear plant will be generating 1+GW (or whatever) of power when the reaction is going - a nuclear power plant is essentially a giant heatsink that is designed to remove that energy from the plant by converting it to electricity and pushing it through the thousands of devices plugged into the grid. Without that energy sink to remove the energy from the plant it has nowhere to go and that is definitely a big problem. For the system to work it must be able to shed the energy it generates. | |
| Nov 16, 2015 at 12:53 | comment | added | J... | @SeanBoddy The physical load on the turbines is proportional to the load being drawn by the grid. Without a sufficient electrical load attached to the plant the turbine will not have sufficient resistance to turning and will accelerate beyond its rated rotational speed. Removing the expected load from the generators would cause all types of protection systems to kick in, probably ending up with the plant in some sort of emergency shutdown mode. | |
| Nov 15, 2015 at 16:40 | comment | added | user8827 | But the "too much power" scenario only happens at high speed, when there is a big shift in where power is being delivered dynamically across the grid. The station by itself isn't going to make any more or less power than you ask it to by turning things on. | |
| Nov 15, 2015 at 16:37 | comment | added | user8827 | There is a slight conceptual error here, but only very slight. The generating station does, in fact, need to put out some small amount of power or else the turbines themselves could have trouble regulating speed. And load sharing would be a tremendous problem, except if this was actually going to work, they need to island the nuke plant (isolate a portion of the grid just for it) and black start. I never ran a commercial reactor so I don't know if the local loads on the station are sufficient to stabilize the turbines. | |
| Nov 9, 2015 at 9:28 | comment | added | DevSolar | ...and trying to just run the reactor at a "low" setting isn't a good idea either. Fission reactors have a minimum "safe" operating level, and trying to work around that gives you all kinds of problems... ask the Chernobyl operators, who were so confused by the core's behaviour that they eventually blew it up -- and they were trained operators. | |
| Nov 7, 2015 at 10:54 | history | edited | J... | CC BY-SA 3.0 |
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| Nov 2, 2015 at 13:50 | history | edited | J... | CC BY-SA 3.0 |
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| Nov 2, 2015 at 13:36 | history | edited | J... | CC BY-SA 3.0 |
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| Nov 2, 2015 at 13:28 | review | First posts | |||
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| Nov 2, 2015 at 13:26 | history | answered | J... | CC BY-SA 3.0 |