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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."
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.
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.
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.
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.
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...