Duke Energy’s
Oconee Nuclear Station, located near Seneca, SC, achieved a milestone in the
early part of this decade by becoming the first American nuclear power plant exploiting
a fully digital safety system across all three of its reactors. The new digital control panels cost
approximately $250 million, part of a $2 billion overall infrastructure
investment (Wheeler, 2012).
As with any progressive initiative, a major concern
focused on attaining approval by overcoming conservative opinion, specifically
that of the Nuclear Regulatory Commission (NRC), regarding the digital
conversion of the analog
reactor protection systems (RPS) as well as the engineered safeguard protection
systems. In order to overcome the skepticism of the NRC, Duke Energy had to
demonstrate via an all digital operating
system the ability to “ensure
that the principle of “defense-in-depth” is maintained, not only for the
new hardware but for the accompanying software” (Nuclear
Entergy Institute, 2016) as well as prevent cyber intrusions.
Duke Energy
opted to pursue approval of the field-tested, and globally-employed, Areva
Teleperm XS (TXS) system as it promised “high reliability through
fail-safe design, fault tolerance, integrated self-checking, structural
simplicity, and robustness, including resistance to temperature swings,
vibration, seismic loads and electromagnetic radiation” (Hashemian, 2011). With its approval “the NRC confirmed
the new system’s ability to meet safety requirements as well as federal cyber
security requirements to isolate the system from cyber-attacks (sic)…data flow
from the plant’s safety-related systems remains isolated from the Internet” (Nuclear Entergy Institute, 2011).
After surmounting this obstacle, Duke Energy moved
forward with its digital conversion. A primary focus of this transfiguration
revolved around Oconee’s aging analog safety systems such as the RPS. In any
nuclear power station, the function of the RPS remains “to protect the integrity of the plant’s nuclear fuel by monitoring
inputs from the reactor core” (Hashemian, 2011). According to Areva’s documentation, the TXS software
possessed such capabilities due to its redundant architecture in design,
self-monitoring capabilities, employed logic via deterministic system behavior,
engaged diversity and handling of common-cause failures, and upheld system
security measures (Areva).
The
implementation of a fully digital system provided plant operators with greater
operational control by integrating the capabilities of “monitoring plant
systems, trending analyses and component malfunction predictions…which, in
turn, increases plant safety above the high levels already being achieved” (Nuclear Entergy Institute, 2016). Additionally,
“digital instruments by comparison are more precise, less liable to break down
than their electro-mechanical counterparts, and can monitor themselves as well
as a wider array of plant systems” (Nuclear
Entergy Institute, 2016). This inherent reliability “reduces maintenance
downtime and makes for greater operational efficiency and cost-effectiveness”. (Nuclear Entergy Institute, 2016). Although analog systems remained in place as
back-up protocol mechanism, the Oconee’s new digital RPS possessed “four
redundant protection channels that monitor safety-related plant parameters and
generate reactor trip signals to protect the fuel and fuel cladding, the
reactor coolant system and the reactor building from damage” (Hashemian, 2011).
Reference List
Areva. (n.d.). Teleperm XS System Overview.
Retrieved from Areva:
http://www.areva.com/mediatheque/liblocal/docs/activites/reacteurs-services/reacteurs/pdf-teleperm-xs-feat.pdf
Hashemian, H. M. (2011). USA's first fully digital
station. Retrieved from Nuclear Engineering International:
http://www.neimagazine.com/features/featureusa-s-first-fully-digital-station/
Nuclear Entergy Institute. (2011). Duke's Oconee
Reactor Goes Digital. Retrieved from NEI:
http://www.nei.org/News-Media/News/News-Archives/dukes-oconee-reactor-goes-digital
Nuclear Entergy Institute. (2016). Digital: The New
Word in Nuclear Power Plant Control Rooms. Retrieved from NEI:
http://www.nei.org/News-Media/News/News-Archives/Digital-The-New-Word-in-Nuclear-Power-Plant-Contro
Wheeler, B. (2012). Entering the Digital Age: Upgrading
I&C Systems at U.S. Nuclear Plants. Power Engineering, 116(9).
Retrieved from Power Engineering:
http://www.power-eng.com/articles/print/volume-116/issue-9/features/entering-the-digital-age.html
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