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Things may be slowing down a bit here at Clean Energy Insight over the next month or two. Currently, it is outage season for the nuclear power industry. Many of our contributors will be supporting outage work on-site at nuclear power plants.
In the nuclear power industry, an “outage” does not primarily refer to a power outage or blackout. Every Spring and Fall, when power demand is at its lowest, the nuclear industry shuts down some of their plants for maintenance and repair.
This could mean packing up and going to a nuclear power plant for the next three months, or staying at their home office and working the night shift. We will try our best to keep you updated on nuclear news and interesting nuclear power facts. However, all of our focus will be on our work in order to be as safe as possible and as productive as possible during these critical outages. Plus, working on an outage can help an engineer gain priceless experience in the field and in the industry, which will make Clean Energy Insight better equipped to bring you voices of experience. So…
What is an “Outage?”
In the nuclear power industry, an “outage” is a period of time in which a nuclear power plant shuts down (stops producing power) in order to perform routine maintenance, replacements, and/or re-fuel the reactor. During this time, the power utility ramps up power production at other plants, or purchases additional electricity from neighboring utilities to make up for the power production from a reactor that is scheduled for an outage.
Depending on the type of outage, it can last from one and a half to two months. Additionally, outage staff works in 12 hour shifts in order to keep things moving and to provide 24 hour support.
A nuclear plant would be able to tout a 100% capacity factor if it weren’t for these scheduled outages. Because of these necessary outages, nuclear power plants achieved an energy industry best capacity factor of 91.8% in 2008.
Some of the components that are replaced or maintenanced include but are not limited to: reactor heads, steam generators, pumps, motors, turbines and fuel.
Re-Fueling
Re-fueling outages average about 35 days in length, some have been done in 15-20 days, and are done every 18-24 months. This means that a nuclear reactor doesn’t need to be re-fueled but every 18-24 months, setting nuclear power apart from other energy sources such as coal that need to be refueled on a daily basis.
Fuel Rods
Pumps and Motors
Pumps and motors must also be replaced or maintenanced during outages in order to service the plant and lengthen its service-life.
Baby Pump
Reactor coolant pump motors are the largest pump/motor assembly in a nuclear power plant. These can be about 28 feet in height, weigh over 100,000 lbs, roll at 9,000-12,000 horsepower, and spit out 88,000 gallons of water per minute.
Reactor Coolant Pump for the Westinghouse AP-1000 Reactor
Turbines
Here’s a great video from National Geographic on the turbine replacement at Susquehanna Nuclear Power Plant.
Reactor Heads
Reactor vessel closure heads must be replaced at a plant periodically as well. These are pretty heavy components as well. Usually around 200,000 lbs. It’s quite a feat to be able to move an object this heavy so precisely. Here’s a great document from Bechtel on the process they use to replace reactor heads in a safe and efficient manner. Link: Bechtel Detail Design.
Reactor Head
Reactor Head being put into place
Steam Generators
Steam generators are one of the biggest components in a nuclear power plant and can weigh around one million pounds. Moving these things is big business. It is also an art. The coordination and precision of this type of operation is impressive and intricate. The only way to give it justice is to see it in person. Although, I hope these images will help you understand the scope of this type of project.
Steam Generator
Here is a news clip from Lancaster Online showing two steam generators moving through rural Pennsylvania a couple of weeks ago on their way to Three Mile Island for the outage there slated to start October 26th. The generators will be installed and the reactors will be back online by January 1st.
The delivery route must go through multiple levels of planning including coordination with local law enforcement and structural qualification of roads and bridges along the route since the steam generators are so heavy. The steam generators that are currently running at Three Mile Island will be removed and placed in a building called an Original Steam Generator Storage Facility (OSGSF). This facility is designed and rated to prevent the release of low-level radiation to the public and environment.
These aren’t the only activities that are performed during outages. Some include modifications that will increase the life and power output of existing plants. Others may include increasing fire protection safety measures in the plant. There are many different modifications that a utility performs during outages that will increase quality and performance at their nuclear plants. Hopefully, this post provides a high-level overview of a nuclear power industry outage. For more detailed information, feel free to ask any questions in the comment section below.
[...] Carrington Dillon at Clean Energy Insight wrote a very informative piece on the answer. In the nuclear power industry, an “outage” does not primarily refer to a power outage or blackout. Every Spring and Fall, when power demand is at its lowest, the nuclear industry shuts down some of their plants for maintenance and repair. [...]
Great series for helping to dispell myths and “non”-information about nuclear power. I wanted to clarify the “capacity factor”:
“…A nuclear plant would be able to tout a 100% capacity factor if it weren’t for these scheduled outages. Because of these necessary outages, nuclear power plants achieved an energy industry best capacity factor of 91.8% in 2008.”
Capacity factor (in simpler terms) for an electrical production facility is a prediction of how much power the unit will produce for the year. It actually DOES take into account how much outage time the unit will incur (as well as scheduled power reductions for testing, etc). If the unit is able to meet all of its predicted power generation, it meets 100% of its capacity factor. If there is an unplanned outage or power reduction due to an equipment issue (generally performed to place the plant in a safer condition or increase safety margin), then the amount of lost electrical production is subtracted from the “100%”, thus reducing its capacity factor. Overall, if a nuclear unit is scheduled for an outage during that year, it is EXPECTED that the unit capacity factor will be less than 100%. On the plus side, it is possible for a unit to exceed it capacity factor (Calvert Cliffs Unit-2 for 2008, for example, exceeded 102% capacity factor) if more electricity is produced, and planned power reductions are shorter than anticipated. Some margin is put into capacity factor predictions, so if equipment reliability is good (indicative of a plant doing the right maintenance on the right equipment at the right time), then not all of the margin is used, resulting in a higher capacity factor.
Andrew McNeil (Calvert Cliffs - Reactor Operator)
Thanks for the input, Andrew! Always appreciated.
Carrington
[...] back. After a month of outage season it’s time to get back to work. Most of Clean Energy Insight’s contributors are back [...]