How do you refurbish a nuclear reactor? The short answer: carefully.
When Ontario Power Generation decided that the Darlington Nuclear Power station outside Toronto needed to be overhauled to extend its lifespan by 25 years, it set out for itself a significant challenge. Building a nuclear plant from scratch is a massive undertaking on its own, but refurbishing an active plant harbouring radioactive material while it’s still operational is a colossal task.
Darlington is made up of countless components ranging from tiny bolts and bearings to 960 feeder tubes (that can weigh hundreds of pounds per section). As part of the restoration, each component is being analyzed to see whether or not it needs to be replaced.
It’s literally everything
“It’s literally everything,” says Mark Arnone, vice-president of refurbishment execution at OPG. “We’re looking at all of our computers, all of our codes that operate the computers. We’re looking at piping, valves; we’re looking at electrical components, cables (we take pieces of cable out and do specific testing on them).”
The process digs so deep down that it will even analyze the material longevity of the springs that separate the inner and outer calandria tubes. That may sound arduous (if not tedious) but it’s only a fraction of the process OPG has been going through for the past few years. The more significant undertaking has been the development of an 85,000 square-foot mock of the Darlington reactor (designed to scale) to serve as a training ground for the construction crew that will execute the refurbishment — a crew that could total as many as 4,000 people.
The $30-million mock facility — set for completion in the spring of 2014 — sits adjacent to a 70,000 square-foot warehouse where the reactor’s new components (designed and built off site) will be stored until the renovation is underway, as well as a 175,000 square-foot office building.
The mock-up will allow those involved in refurbishing Darlington’s four reactor units to get a realistic sense of the spatial and environmental constraints that exist within the plant and account for these constraints when developing the plan to replace components. The facility includes not only realistic dimensions for entrance ways but also accounts for the position of almost 500 distinct tools (i.e. custom-engineered machinery required to move and place components) of which there will be between two and five replicas on site.
Some of those tools will be controlled remotely using advanced computers systems connected to closed-circuit cameras in the facility. Those systems will allow heavy and cumbersome items such as the feeder tubes that connect to the face of the reactor to be removed and replaced with enhanced precision.
“To get people qualified; to get them to work efficiently and effectively, there has to be the right training environment, especially with adults,” says Mr. Arnone. “It’s very important that we allow them to visualize, to see, to test, to practice and ultimately to provide opportunities for improvement in the process.”
The mock facility was designed with insights from the overseers of previous nuclear refurbishment projects, including the Bruce reactor in southern Ontario, New Brunswick Power’s Point Lepreau facility and the Wolsong plant in South Korea. Perhaps one of the most valuable insights was that the mock needed to be built to scale to allow for accurate rehearsal of the refurbishment process — estimated to take 30 million field hours — and to avoid unexpected delays.
If something has happened, we’ll have a lot more diagnostics that will reduce the probability… of any kind of failure, let alone a catastrophic failure
In addition to the replacement of the facility’s hardware, Darlington’s outdated analogue monitoring system is being replaced with a more modern digital diagnostics network that will allow OPG to monitor the efficacy of even the most minute operational components. Of critical importance will be the sensors that track the rotation, vibration and temperature of the tubes.
The digital system will also be used to look out for the degradation of components as small as bearings, giving Darlington’s maintenance crew the opportunity to replace such parts before they break down and disrupt operations.
“If something has happened, we’ll have a lot more diagnostics that will reduce the probability… of any kind of failure, let alone a catastrophic failure,” says Mr. Arnone.
When the mock facility becomes operational next year, it will function around the clock and throughout the week, training crew members on specific components and tasks associated with the refurbishment. Once the refurbishment is well underway, the site will continue to serve as a training facility for Darlington workers over the plant’s expected 25- to 30-year extended lifespan.
CORRECTION: A previous version of this story incorrectly noted that the calandria tubes at the refurbished Darlington reactor will rotate at 1,800 RPM. It is the turbine that will rotate at 1,800 RPM. The calandria tubes are stationary. The Post regrets the error.