POWER November 2016 - 29

TOP PLANTS
Table 1. Primary vendors involved in the Peach Bottom extended power
uprate project. Source: Exelon Corp.
Company
ABB
Alstom
AZZ | WSI
Barnhart
BHI Energy (WeldTech)
CB&I
Dresser-Rand
EBI (Electrical Builders Inc.)
Enercon
Energy Solutions
Flowserve
GE
Konecranes
Mammoet
Sargent & Lundy
SPX
Westinghouse
Project responsibility
Instrumentation, control, and electrical support
Turbine services, engineering support
Repair and overhaul services
Heavy-load/super-load movers
Welding services
Maintenance craft workers, schedulers, and in-field oversight
Technical support
Electricians and electrical engineering
Engineering support
Onsite contractors
Technical support
Technical support
Crane support for heavy lifts
Feedwater heater project
Engineering support
Heat exchanger support
Technical support
getting approval to implement the upgrades,
sourcing all of the needed parts and materials,
scheduling all of the tasks, carrying out
the plan, and monitoring and verifying the
quality of the work was a massive undertaking.
In the end, it took about six years to complete
the entire process for both units.
" We are fortunate to have so much experience
and expertise in outage planning at
Peach Bottom. We are all working toward the
goal of planning and scheduling a safe, precise,
and efficient outage. The Peach Bottom
team is one of the best in the industry working
tirelessly to make sure all of the puzzle
pieces come together correctly, " said Matt
Retzer, outage manager at Peach Bottom,
as quoted in a booklet detailing some of the
EPU accomplishments.
Not surprisingly, the critical path for the
project included a lot of turbine and generator
work. New high-pressure turbines were
needed to accommodate the higher main
steam flow rates that would result from the
EPU. Cross around relief valves for the turbines
were also replaced.
The generator rotor and stator were re(Figure
1),
wound
and
rotor-monitoring
capabilities were upgraded. In addition, the
automatic voltage regulator, exciter, and rectifier
were replaced. The goal of the changes
was not only to increase component ratings
but also to improve reliability.
The isophase buses, which are the conductors
that carry the very large currents from
the generator to the step-up transformers, required
replacement so that they could safely
handle the current produced when operating
November 2016 | POWER
at the new EPU limits. To ensure adequate
cooling of the bus bars, new ductwork was
also installed. The current transformers, used
to provide a proportional input to the generator
protective relay system, were likewise
upgraded to ensure accurate indication of the
power being generated.
Boiling water reactors (BWRs), such
as those installed at Peach Bottom, have
steam dryers mounted above the fuel assemblies
inside the reactor vessel. Steam
generated in the reactor passes through the
steam dryer to remove entrained moisture
and ensure that only dry steam enters the
steam lines. Some operating BWRs have
experienced vibration fatigue damage in
their steam dryers after steam flow was increased
as part of a power uprate.
To address this concern, Exelon replaced
the steam dryers during Peach Bottom's
EPU project. Westinghouse-designed Nordic
steam dryers were installed. They have an
octagonal shape, with three concentric rings
of panels and symmetric fluid flow paths.
Fabrication details, such as full-penetration
welds, make them well suited to withstand
dynamic loads, and the design efficiently reduces
moisture carryover.
An added benefit of reduced moisture carryover
is that source term spread has been
reduced, that is, less radioactive contamination
passes through the system to the turbines
and condensers, which reduces dose rates
throughout the plant. An acoustic monitoring
system upgrade was also installed so that
vibration and stress levels in the new steam
dryers could be evaluated.
www.powermag.com
POWER POINTS
Winning Attributes
Completed a successful
extended power uprate on both
of the plant's operating units
Operated at greater than 92%
annual capacity factor during the
entire six-year project, including
92.9% in 2015 as upgrades to
Unit 3 were being completed
Increased thermal output from
each reactor by 12.4%, adding
about 270 MW of electrical
generation
New Life for an Aging Plant
Countless other upgrades were made during
the EPU project. They included replacing
reactor feed pump turbine rotors and casings,
changing feedwater heaters, upgrading
condensate pumps and motors, adding main
steam line safety relief valves, modifying main
steam line pipe supports, increasing the boron
enrichment level in standby liquid control
tanks, adjusting hydrogen injection and noble
metals chemical injection systems, adding accelerometers
to measure flow-induced vibration
on piping systems, and implementing
margin improvement modifications to various
motor- and air-operated valves throughout the
plant, among other things.
The station has been a model of excellence
in recent years. Its annual capacity factor never
dipped below 92% during the entire six-year
period that the EPU projects were in progress,
and it reached the 92.9% mark in 2015 as upgrades
to Unit 3 were being completed.
" The successful completion of this project
is the result of years of hard work by Peach
Bottom employees and contractors, " Mike
Massaro, Peach Bottom site vice president,
said in a press release. " As part of EPU, almost
every major component in the plant
has been upgraded or replaced, which makes
Peach Bottom an even safer and more efficient
facility. "
The EPU " pit stop " appears to have left
the plant " firing on all cylinders. " What that
means is that the station is ready to " race "
well into the future. On June 7, 2016, Exelon
announced that it would seek a second 20year
license extension for both units. Peach
Bottom's current operating licenses don't
expire until 2033 and 2034, so if approved,
the reactors could continue operating into the
2050s. ■
-Aaron Larson is a POWER associate
editor.
29
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POWER November 2016

Table of Contents for the Digital Edition of POWER November 2016
