October 19, 2014
Nuclear Reactor Operators Want Extensions To 80 Years
The plants were built decades ago. If brittle parts can be replaced they could operate for 80 years.
What I wonder: Could new nukes be designed to make it much easier to extend their lives? The most obvious step: make it easier to swap in replacement parts for those parts that get brittle from radiation. Is that practical? Already possible?
The market is going to undervalue designs that can last for 80 years. Bonds sold to build a nuclear power plant will have 10-20-30 year redemptions.
On a related note, The Tennessee Valley Authority's Watts Bar 2 reactor is finally being completed after first being ordered in 1970. If it finishes fuel loading by its expected December 2015 date and then operates for 80 years it will shut down in late 2095.
Randall Parker, 2014 October 19 06:42 PM
If I'm not mistaken, the most crucial part subject to neutron embrittlement is the reactor vessel itself.
Repairing radiation damage requires annealing, which appears to be very hard to do as the plant is not designed for it. Who'd order an annealing system for a unit when it won't be used for half a century? How would you test it? How would you guarantee the quality of the results?
NuScale's approach puts the entire reactor and containment in a vessel that's moved to the spent fuel pool for refueling. This allows full replacement of units that age out or suffer corrosion. Terrestrial Energy plans to replace cores after 7 years of operation. That may be the future. We'll see.
"make it easier to swap in replacement parts for those parts that get brittle from radiation. Is that practical? Already possible?"
This is already built in in most new reactor offerings. Some concepts are more suited to it intrinsically. Boiling Water Reactors (BWRs) for instance, replace their steam generator with each refuelling, because the steam generator is the fuel. Steam separators and dryers are fully replaceable and are in fact removed each refuelling (every 1-2 years). BWRs also have a lower fluence on the reactor vessel so it needn't be replaced.
The media like to make a big fuss about plant lifetime. The truth is you can make the plant last as long as you want, in coal plants for instance the boiler tubing is replaced, the electrostatic/baghouse filters are replaced, scrubbers are replaced, etc etc. At some point very expensive structural repairs have to be done or new technology is available, that then leads the utility to a decision to stop operating the plant.
Because of the negative and hostile business environment that nuclear operates in, small equipment replacement issues such as are routinely done in coal plants without media attention, become massive plant investment risks costing billions to correct or even forcing plant decommissioning, such as in the SONGS nuclear plant.
Technically, nuclear plants age much slower than coal plants. Coal is nasty, nasty corrosive combustion gasses, sulphur, metals, abrasive dust and ash everywhere. Heavily loaded mechanical equipment to transport all that fuel... nuclear is very different. It is clean, controlled.
"If I'm not mistaken, the most crucial part subject to neutron embrittlement is the reactor vessel itself."
True for PWRs. Some new designs such as EPR use a heavy neutron shield within the vessel, that protects it. BWRs don't have a large fluence on the vessel and only have to replace the shroud at some point. This is perfectly possible.
But neutron embrittlement isn't the only issue. More pressing usually are steam generators for PWRs. They are massive monolithic devices entombed in a mausoleum of concrete containment. Not easy to replace, which translates to high cost in the nuclear world. Think >200 million USD for SG replacements in a large plant.
"Repairing radiation damage requires annealing, which appears to be very hard to do as the plant is not designed for it. Who'd order an annealing system for a unit when it won't be used for half a century? How would you test it? How would you guarantee the quality of the results?"
Can't do. Either reduce fluence (neutron shield, lower power density cores) or arrange for replacements. Annealing must be done in a nonradioactive controlled environment and in small pieces for quality control and good results. SMR vessels might be a possible upper bound on the maximum size but not much economic gain here (compared to just recycling it). Graphite annealing and re-use as-is is attractive though, as it isn't easy to recycle.
"Terrestrial Energy plans to replace cores after 7 years of operation. "
We are planning on replacing everything, not just the core but also the reactor vessel, heat exchangers and pumps. It will be a totally sealed unit, like an inkjet printer cartridge, its easy to replace without getting ink on your hands and makes for a good business model (for instance sell modules with margin, plant itself at base cost).
Do you work for Terrestrial Energy?
I am looking to add research reports on nuclear from my side. but can't completed yet, as soon as reports will complete. I will share with you all....
You post such a great article, Thanks for sharing!