AI Used in Nuclear Unit Outage Planning
Wed, April 21, 2021

AI Used in Nuclear Unit Outage Planning

Nuclear power plants run almost all the time and refuel only once every two years. / Photo by: Rebel Werner via 123rf


Nuclear unit outage planning or scheduling is an important factor for an economic and safe nuclear power plant performance. It is a complex task, which involves the coordination of technical, regulatory, and safety requirements, available resources, and all work and activities before and during the outage. Each utility or plant has a strategy for long term, middle term, and short term outage planning.

Ontario Power Generation 

Ontario-based generator Ontario Power Generation, which has a portfolio of more than 16GW capacity, has been using artificial intelligence in its nuclear unit outage scheduling to ease the process. It currently produces half of the electricity that people in Ontario, Canada rely on every day. They have century-old hydro stations and some of the best run nuclear stations in the world.

Power generation news provider Power Engineering has reported that it has been a yearly occurrence in OPG nuclear facilities to have a planned maintenance outage that lasts for two to three months. For every outage, the scheduling requires around 20,000 to 25,000 individual tasks and most of the said tasks are the same as previous outages. This means that the company’s outage personnel are manually populating and searching for tasks from the previous schedules and reviewing the procedures as well.

Their current outage scheduling process comprises more than 40 major milestones that begin over two years prior to the start of the nuclear unit outage. The electric generation company then set its outage milestones based on the best practices of the industry related to duration, scope, and reliability. They also take into consideration the individual nuclear facility requirements.


Ontario Power Generation has been using artificial intelligence in its nuclear unit outage scheduling to ease the process. / Photo by: alexandersikov via 123rf


Outage AI solution

Using artificial intelligence called Outage AI solution, it helped them predict the “logic ties” for tasks that are a part of their outage window and create the first part of their schedule with all tasks already populated. Such a kind of approach lessens the manual effort but also maintains oversight contingency all throughout the development of every nuclear outage plan. It helped them mitigate the possible duration extensions and risk in the process.

The company shares that their AI solution is a cloud-hosted and custom-built application that combines with their existing information technology infrastructure. The technology has also leveraged the elements of intelligent automation, natural language processing, machine learning, and artificial intelligence.

The objective of the system is to predict the breakdown structure of the thousands of tasks, including their logical ties (successors) and their predecessors. Then it will automatically schedule the 20,000 to 25,000 tasks to the upcoming unit outage as part of the Revision B schedule.

Presently, the AI solution of OPG uses 8 years worth of previous outage data to help create the predictions. It was likewise developed to gather upcoming nuclear unit outage plans so the company can use it for future preventative maintenance outages. So, the more data is processed and consumed by the Outage AI Solution, the more inteligent the technology becomes.

Three pillars of the technology

There are three pillars that have been developed to address the technical and functional requirements set by the company’s skilled outage team. One is the making of dummy tasks to determine the missing tasks from the historical outage schedule. Second is automated scheduling of unscheduled tasks, and the third foundational pillar is erasing the logic ties that may otherwise create schedule loops. The first two pillars are centered on an NLP-based algorithm and the third pillar utilizes a loop detection kind of algorithm to find the culprit logic ties as well as quality control the output.

Nuclear refueling outage days

Since nuclear power plants run almost all the time and refuel only once every two years or so, shutting down the plant is a significant event but is often done in a season when electricity demand is the lowest, opined scientist James  Conca, who specializes in geologic disposal of nuclear waste and other energy-related research. Yet, the nuclear power plant should be refueled as infrequently as possible to produce the most energy at the lowest cost.

In 2011 and 2012, the average length of refueling in the US was 44.5 outage days. The figure decreased in 2013 at 40.5 outage days, 36.5 days in 2014, 35.5 days in 2015, and stood out at 33.5 outage days in 2016 to September 2018. Database company Statista details that the electricity needs in the US are met by various energy carriers, including oil and natural gas, renewable energy sources, nuclear fuel, and coal.

While there are a variety of fuels that the country can use, their power generation structure is primarily composed of nuclear power and coal to provide its citizens with around the clock supply of electricity. This is why it is an important element in their country’s power generation mix. 

The top 15 nuclear generation countries in 2018, according to the Nuclear Energy Institute, are the United States (807,078 nuclear electricity supplied in gw-hr), France (395,908), China (277,056), Russia (191,340), South Korea (127,077), Canada (94,450), Ukraine (79,532), Germany (71,866), Sweden (65,868), United Kingdom (59,112), Spain (53,364), Japan (49,330), India (35,389), Czech Republic (28,256), and Belgium (27,251).