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First New US Nuclear Reactor In Two Decades Gets Permission To Begin Fueling (ieee.org)
An anonymous reader writes: The Tennessee Valley Authority's Watts Bar nuclear power plant began construction in 1973. The plant's first reactor was completed in 1996, and it began operation. Work on the second reactor paused in 1988, and only resumed in 2007. That reactor is now complete — the first newly-operational Generation II reactor since the 1990s. The new reactor has been granted an operational license, and it will soon begin fueling. While the Gen II reactors aren't unsafe, they're much less safe than the Gen III AP1000s. "Compared to a Westinghouse Gen II PWR, the AP1000 contains 50 percent fewer safety-related valves, 35 percent fewer pumps, 80 percent less safety-related piping, 85 percent less control cabling, and 45 percent less seismic building volume. ... If an accident happens, the AP1000 will shut itself down without needing any human intervention (or even electrical power) within the first 72 hours."
This is what the stupid scaremongering of the media, some politicians and many environmentalists ends up causing: instead of building Gen III or even Gen IV plants, we're finishing ancient Gen II plants because that's all that's been approved, decades ago. They are quite literally the cause for nuclear energy's relative safety concerns.
If the government could make its mind up and stop wasting time, the US could rapidly diminish and even eliminate its reliance on fossil fuels without even having to suffer through energy shortages. Allow breeder reactors on top and you'd also eliminate the whole nuclear waste scare while being that much more efficient and cost-effective.
Have you ever visited a construction site after construction was stopped for any significant amount of time?
I've been to a couple of commercial construction sites (ie, mostly steel and concrete, versus wood for residential) where construction had stalled for a couple of years after the property value collapse, and crews were literally having to break-up concrete because unfinished exposed rebar ends had rusted and that rust expanded the rebar down into the concrete, causing cracks to begin in that concrete.
That was after only a couple of years. Imagine how bad it would get after close to 30 years. Buildings already have enough problems when they're finished if they don't get regular maintenance over the course of decades, but unfinished buildings that are not environmentally sealed will undoubtedly fare far, far worse.
I know that nuclear reactors are supposed to be structurally overengineered simply due to the nature the forces they contain, but starting out with a handicap due to building structural problems doesn't sound like the greatest plan, and that's before account for all of the other technical changes that have been engineered through the decades. We've already seen problems in younger reactors that were finished approximately on their original timetables, this seems like it's asking for more.
Do not look into laser with remaining eye.
My car has two doors, does that make it less safe then a car with 4 doors?
Well yeah, if you had to go through all of them to get out...
“He’s not deformed, he’s just drunk!”
The AP1000 has 72 hours of decay heat removal capability in the event of total loss of onsite power. If no action is taken to replenish cooling water, then decay heat would cause overheating and overpressure of the containment building and require venting of the containment building to the atmosphere. Radioactivity release from such venting is likely to be low unless meltdown or fuel damage has already occurred. Due to the large inventory of water within the containment building, decay heat is unlikely to result in meltdown for many days following the exhaustion of the containment cooling water.
In order to ensure integrity of the containment, additional cold water would need to be pumped into the containment building roof tank within 72 hours. This could be by restoration of the electrical supply, use of diesel powered water pumps held on site, use of portable water pumps held near site, or by use of fire pumps.
The ESBWR which is the main competitor to the AP1000, meets the Gen3+ requirement of 72 hours of decay heat removal without operator intervention. Like the AP1000, no diesel or grid power is necessary to meet this requirement. Like the AP1000, the ESBWR has 2(N+1) redundant UPS systems with 72 hours of battery autonomy for shutdown control and monitoring equipment. However, the ESBWR has a 7 day reserve of cold water for containment cooling. In the event of operator inaction, the UPS batteries will deplete after approximately 72 hours, but passive containment cooling will continue for up to 7 days before water tanks would need to be replenished.
The AP1000 has a number of on-site and internal reserve water tanks, holding close to 1 million gallons of demineralized water.
The plant has several electric pumps capable of transferring water from the bulk tanks to the containment cooling system, which could be connected to portable generators in a serious emergency. The plant also has multiple connection ports for portable pumps allowing water to be transferred into the containment cooling system from the bulk tanks or from fire engines/water tankers.
As the containment cooling tanks are at atmospheric pressure, only low pressure pumps are required, unlike at Fukushima where emergency response teams were trying to use pumps to inject water into the reactors at dozens of atmospheres of pressure.
The article goes on for quite a bit about how much less "safety related hardware" newer plant designs have but I highly doubt that that says anything about how safe a reactor is or not. What DOES make a difference is fail safes, regular inspections, backups, emergency response plans, all with a design double checked by someone with a high school level of common sense. What has caused most of the major nuclear disasters? Rank stupidity. Fukushima was caused by the idiotic placement of backup generators and associated control hardware, in a basement and the subsequent failure of plant operators to call for necessary resources. Chernobyl was caused by them futzing with the reactor outside of normal operating procedures and then activating an emergency system that was not designed to handle those modifications. Three Mile Island was caused by a lack of appropriate sensors to recognize a lack of coolant in the reactor caused by a faulty relief valve. Knowing the reactor coolant level/pressure/temperature with certainty, having the ability to shutdown the reaction, and the ability to keep the reactor cool are the only things you need to prevent 99% of nuclear disasters. I'm not saying that designing a nuclear plant is easy, but keeping your backup cooling systems above water, not experimenting with a full sized nuclear reactor & knowing if your coolant is pouring out of a relief valve would seem to be no brainers that shouldn't have been missed.
Could they use the heated containment water to drive a Stirling engine which would pump more water?
I'm not a nuclear scientist (let alone a rocket scientist), but somehow it seems like there's a way to (relatively simply) use the heat from containment cooling to pump water.
And is there a reason the containment water couldn't be a loop with a cooling stage so it could be self-replenishing? It seems to make more sense if you consider the idea of the containment heat being used to drive pumps which circulated the water.
I'm sure there are good reasons why this is a Rube Goldberg perpetual motion kind of an idea, but it seems like a way where as long as it generates heat it could pump its own cooling.
To be fair, the 42 year delay was so that they could convince the people of Tennessee that electricity wasn't the work of the devil.
You are welcome on my lawn.
There is a loop but it's the massive cooling tower. If however though the piping between the containment vessel and the cooling tower is destroyed you want a means of cooling outside of the intended infrastructure.
The backup cooling is a gravity fed system, once-through. The goal is simplicity for an emergency operation.
Anything more complex is really just duplicating the primary cooling system.
Pedant Mode...ON.
More properly, the failure rate of two doors in your example would be 1 - (999/1000)^2. For four doors, it would be 1 - (999/1000)^4.
Which gives you numbers pretty close to the 1/500 and 1/250 you mentioned. The divergence increases as the number of doors increases....
"I do not agree with what you say, but I will defend to the death your right to say it"
Here are full details, with appropriate references, about the idea ending the reliance on fossil fuels in the US requires nuclear to be a significant part of the energy mix:
https://docs.google.com/docume...
The summary is that solar, wind, hydro, and geothermal can make an important contribution, providing a significant portion of our energy needs. A very significant portion cannot be solved by those four choices - for reliable, steady power in huge amounts the choices are fossil fuels or nuclear.
As I understand it the US has about 18GW of solar PV installed capacity with about a 28% capacity factor - so roughly 5 GW of actual power generation.
These two reactors together will generate about 2.2GW with a 90% factor, or around 2 GW.
One power plant, 40% of the capacity of all PV in the country.
I think that no new nuclear reactors have been built in the United States, because no one wants a beta gen III+ nuclear reactor. In the West, there were 3 different nuclear reactors, Areva's EPR reactor, Westinghouse's AP1000 reactor, and GE's ESBWR reactor. GE decided to exit the nuclear reactor business. Several AP1000s, and EPRs have been under construction in Europe and China since the late 2000s. The EPR reactor in Finland is considered a screw up, and is getting major design changes. China hasn't been reporting many problems. Maybe China is better at building stuff, they haven't found the problems, or the problems have been kept secret. The UK thinks China is better at building stuff. None of the EPR, or AP1000 reactors has started commercial electricity generation, so the waiting game is a smart one for now.
"To be fair, the 42 year delay was so that they could convince the people of Tennessee that electricity wasn't the work of the devil."
No, the time was spent vainly trying to convince liberals of that fact.
Considering how long it takes to get turbine rotors for coal fired units of a smaller size (~ 5 years) a lot of it was probably waiting for parts. There's a bit of a queue for rarely produced items.
What about folks from Bucksnort? Or folks from Lynchburg bearing delicious gifts?
No, that's a message from Bruce Dickinson.
That was the regulatory regime beforehand, and it resulted in the most colossal waste of money ever: Shoreham
The combined (construction & operating) license regulatory regime is intended specifically to prevent such wasteful endevours, The design, construction, and operation of the facility is approved largely upfront to ensure the plant can actually be operated when it's built.
Alcohol, Tobacco and Firearms should be the name of a store, not a government agency.
A couple of comments. I worked at Watts Bar for 6 years - from just before they restarted construction until 2013. I now work out at one of the new reactors under construction at VC Summer.
First off, WBN2 and WBN1 share structures. Actually, all the structures except for the reactor building itself is shared. The units are what is considered an "opposite hand" configuration, which means that essentially a piece of equipment, piping, or valve on the far west side of the plant for U1 would be on the far east side, at the same northing, for U2 with everything matching up in the middle. The units also share many systems, and in order for them to start up U1, they had to have those systems (and many of the U2 pumps, valves and other support equipment) in service. The units also share a control room, spent fuel pool, diesel generators, and more. The only completely independent structure is the reactor building, which was structurally complete when they halted construction. Most everything inside was complete (major equipment set, piped in, etc). Most of what was lacking were control systems, instrumentation, and some valves. Also, all of this equipment was under temperature and humidity controls during the layup period.
One other thing - all of these structures are reinforced concrete. The unique thing about concrete is they get stronger with age unless you have something like saltwater causing problems. They're also *very thick* and *heavily reinforced* concrete - as in, the age isn't a handicap at all.
I hate sigs...
So what? A coal plant burns *3000 tons* of fuel every day. THAT'S LIKE A MILLION TASR BOMBAS!
Please think of the stray dogs.
Did you notice it was delivered at twelve minutes to midnight? Ten minutes early.
As the other guy said, you're confusing environmentalists with NIMBYs, but also, you're confusing two groups of environmentalists. The smart environmentalists are pro-nuclear, or at least, anti-coal and anti-fossil-fuel and in favor of nuclear as an alternative to those for the time being until better sources can be made more economical.
Yeah, unfortunately there's a bunch of dumb anti-nuclear people out there who don't want any nuclear power, but don't have any suggestions at all about what to do to make the electricity needed, and strangely seem to have little to say about fossil fuel (esp. coal) power, which has horrible environmental effects. Not all environmentalists are like this.
IMO, we as a nation should be moving to eliminate most if not all fossil fuel electricity generation, and only use nuclear and renewables (solar, wind, etc.). Solar power is getting cheaper all the time, and is highly versatile: you can put panels over parking lots, on commercial rooftops, etc., which is also very close to the point-of-use which greatly reduces transmission losses (unlike nuclear where the plant is generally far from where the power is consumed). However, solar of course doesn't work too well at night so it requires a storage method, such as hydroelectric (pump water uphill during the daytime when you have surplus capacity, run it downhill through the dam at night to generate power). But realistically, we probably can't generate all we need with renewables just yet, so nuclear is a good solution for generating large baseline loads. This will be even more important as we move towards more EVs on the road, which will mostly be recharging at night.
Emergency core cooling, formally known as the passive residual heat removal system (PRHR) is provided by a gravity pumped heat exchanger which transmits heat from the reactor coolant into a 1 million litre refuelling water tank in the containment building. To initiate passive cooling, there are 2 parallel valves which hold the circuit closed, each capable of providing 100% of necessary flow. The valves are dual-activated (DC electrical and pneumatic). They fail open under spring tension in the event of failure of the control signal.
In the event that both PRHR valves fail to open, then the reactor circuit will be vented into the containment building (simulating a pipe break). This will cause the reactor circuit to lose coolant and trigger the emergency cold coolant injection systems. A series of gas-charged hydraulic accumulator tanks discharge in sequence into the reactor to ensure it remains full of water, while steam is allowed to vent through pressure relief valves. Each stage of coolant injection has two fully independent dual redundant trains, with the key valves being dual redundant, dual-activated and fail-open within each train. This culminates with valves connecting the reactor coolant system and the refuelling tank together opening, providing 1 million litres of additional coolant capacity.
After about 24 hours (or sooner in the event of a large pipe break) coolant injection is complete, the reactor is fully de-pressurised and the circuit is fully open to the containment building. The refuelling tank will have been drained, either through a pipe break (or manually) and the water will completely submerge the reactor and its associated piping. The decay heat from the core can then escape via the reactor vessel walls and pipes into the water flooding the containment.
The core injection systems are sufficiently powerful that clean rupture of a 25 mm diameter pipe will not result water level dropping below the top of the core at any time. In the event of a large pipe break (e.g. a clean rupture of a 350 mm PRHR pipe), then temporary uncovering of the reactor core is possible, and this may result in overheating and damage to the fuel, however, because of the very high capacity of the coolant pressurizer and coolant injection tanks/accumulators, and temperature rise is brief and below the level at which the fuel rod cladding is expected to fail or produce hydrogen. As is conventional for nuclear pipework, the pipes are built in such a way that they are intended to leak long before rupture, so a clean rupture would be a rare event.