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The New Oconee Digital Reactor Protection System and Engineered Safeguards System

Issue 4 and Volume 4.

By Nick Negoescu, I&C Procedure Writer for RPS/ES Upgrade, Oconee Nuclear Generating Plant

Duke Energy has always had the future of its customer’s needs in mind. Duke’s progressive attitude, especially for safety, transcends the entire corporation. Duke’s commitment to safety also involves replacing old equipment under its life cycle management program. Plants have their equipment replaced after reaching end of life use.

The 2,538 MW Oconee Nuclear Station in South Carolina. Photo courtesy of Duke Energy.

“The systems in the plants right now, they are doing an excellent job. The plants are very safe, they’ve been doing their jobs for years,” said Joe Naser, technical executive with the Electric Power Research Institute.

The goal of going digital is commitment to safety. All nuclear owners commit to the Nuclear Regulatory Commission (NRC) to replace critical components after end of life is reached.

The youngest nuclear plant in the U.S. went online with analog controls in 1996, the same year DVDs were introduced in Japan. More than half of the nation’s nuclear power plants are at least 30 years old, and only three have come on since 1990.

“It’s to the point where you can’t replace that equipment anymore,” said Jere Jenkins, director of Radiation Labs at Purdue University.

The 2,538 MW Oconee Nuclear Station has three reactor units. Unit 1 was commissioned in July 1973, Unit 2 in September 1974 and Unit 3 in December 1974. Oconee Nuclear Station put out bids for a new digital reactor protection system (RPS) and engineered safeguards (ES) system in 2001. Areva won the bid and began the road to certification by the Nuclear Regulatory Commission (NRC) for the most critical safety systems in a nuclear power plant.

It has taken nuclear power plants so long to go digital because the NRC wanted assurances the new safety control systems would be as reliable as the old ones and could not be compromised by hackers.

As a result, the U.S. has been on the sidelines while digital control of nuclear plants is widespread in Europe and Asia.

The digital revolution has brought Americans iPods for their music, movies that stream to their cell phones over the Internet and computers connected to satellites to help them find retail stores that sells those items.

The nuclear plant digital systems will provide operators with much more data about plant operations and a level of precision impossible with an analog system, which often requires moving components to get things done.

One of the biggest concerns of regulators was worries the software used to run the new controls might be hacked from outside the plant.

Documents given to the NRC show Duke Energy’s software provider designed a system with no external network connections. Any communication between the reactor operators and the system is heavily restricted and must be authorized by plant operators.

Installation

Approval from the NRC and delivery for testing to Oconee happened in late 2009. Site procedures, planning and testing readied the Unit 1 RPS/ES system for installation. Starting with the spring outage of 2011, approval was granted to install the RPS/ES system. This outage was to take between 65 to 70 days.

If a nuclear plant sits idle for a day, it can cost a utility company more than $2 million. So a 70-day outage could cost $140 million, plus the cost of new fuel ($60 million) and labor and parts to be changed ($90 million). That isn’t spare change, even for a company like Duke Energy.

“Those utilities need to keep those plants running. To have unplanned outages as a result of an analog system isn’t doing what we need it to do; that’s a financial risk,” said Jenkins.

NRC Commissioner Ostendorff and inspectors discuss the refueling outage and installation of a digital control system prior to installation at the Oconee station. Photo courtesy of the NRC

The new control system at reactor 1 is part of $2 billion in upgrades that Duke Energy is making to keep its three reactors at the station running safely for the next 30 years. The control panel installation coincides with a planned refueling outage. Reactor 3 will get its new digital panel during next year’s refueling and the RPS/ES upgrade at reactor 2 is scheduled for 2013. The new panels alone for all three reactors cost $250 million.

Oconee Nuclear Station’s reactor operators have spent months training on an exact replica of what the new control panel will look like. And it looks a lot like the old system.

“One of the goals is to make operators’ life, I won’t say easy, but to make operators more focused on the primary aspects of the job,” said Jeff Hekking, a senior reactor operator who helped test the new system. “Just like an airline pilot, you want him to focus on flying the airplane. You don’t want him spending all day trying to get the cabin pressure right.”

During a recent training simulation, Hekking and two other operators dealt with a problem with the water that cools the reactor and keeps the nuclear reaction in check. Dinging bells, similar to what someone would use in old movies to summon a hotel bellhop, mark when things first go off kilter. The engineers stay back and let the situation get worse.

Dozens of tiny red rectangular lights turn green as the control rods of nuclear material are removed from the reactor core. Warning sirens sound, but they are subdued wails, not shrieking claxons.

The engineers then start to control the situation, pushing buttons and pulling levers. Commands are double-checked and repeated to make sure everyone is on the same page.

Duke Energy said it made sure its engineers can manually take over all digital processes in case there are any problems.

Reactor operators work on 12-hour shifts. At least three are in the control room of each reactor at all times, even eating their lunches at the gray desks behind flat-screen monitors. Others are doing maintenance, checking components or other tasks, but can be brought into the control room if needed.

Hekking has been a reactor operator for 19 years and is used to working with components that were manufactured around the same time he was born, alongside some of the latest technology, like the control panels being put into place at Oconee.

The Oconee Nuclear Station reactor is one of the first of the 104 reactors in the United States not controlled with the same analog technology that brought the world cassette tapes and slide rules. Technicians have finished installing and testing digital controls for the reactor protection system and engineered safeguards safety systems of the Oconee Nuclear Station, a move closely watched by other nuclear complexes.

“The RPS/ES digital upgrade is one modification of which we should be particularly proud,” said Scott Batson, Oconee station manager. “This is the first digital RPS/ES upgrade to receive regulatory approval and be installed in the United States, and has gained a lot of attention in the industry.”

More importantly, he said, the successful installation of the RPS/ES system in the unit 1 control room provides operators with an even more reliable system to ensure the safety features of the plant will function should they ever be called upon.

The installation problems incurred were typical of other equipment upgrades. Old wiring replacements, cable labels missing or degraded, basic wiring installation errors and every device needing to be thoroughly tested for functionality and operability.

The cross-discipline team assembled for this project performed extraordinarily. The teams involved were plant management, project management, outage control, operations, engineering, procedures, schedulers, planners, supervision, instrumentation, mechanical, fire protection, civil and security. Additionally, Areva personnel manned the war room for all needs including operations, engineering, design and field supervision.

The outage successfully came to an end at 68 days 17 hours.

It’s not often when we get to be part of something that changes an industry and that is needed since Japan’s Fukushima Daiichi problems. This installation will change the U.S. nuclear fleet’s perspective for the better.

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