Page 46 - Nuclear Plant Journal - March April 2013
Basic HTML Version
A Solution
for Aging
BWR
Plants: Jet
Pump Anti-
Vibration
Solution
By Bret Nelson, GE Hitachi Nuclear
Energy.
Bret Nelson
Bret Nelson has over 25 years’
experience working in nuclear power,
including construction, testing, and
engineering operations support at the
Perry Nuclear Power Plant in northeast
Ohio, and as a consultant to the nuclear
industry. He has been with GE Hitachi
for seven years, serving the past three
years as manager of the Reactor
Services Hardware Design team. Bret
holds a BSME from Cleveland State
University and a JD from the Capital
University School of Law in Ohio.
Jet Pump related issues, such as
wear and vibration, have increased in
frequency and severity since the 1980s
due to component aging and increased
plant operational performance challenges.
As a result, BWR-4 and BWR-5 Jet
Pump assemblies are increasingly prone
to developing gaps between the restrainer
bracket set screws and the inlet mixer,
excessive wear of the main wedge and
rod, restrainer bracket damage, and slip
joint flow-induced vibrations.
During the spring 2013 refueling
outage season, GE Hitachi Nuclear
Energy (GEH) has begun installing its
innovative Jet Pump Anti-Vibration
Solution (JP AVS) that has been tested by
the Electrical Power Research Institute
(EPRI) to fix these difficult problems
and provide upgrades for BWR 4 and 5
plants. The JP AVS, coupled with GEH
Slip Joint Clamps, will offer a complete
solution to all Jet Pump vibration
problems by addressing the cause rather
than the symptoms of flow induced
vibration (FIV).
GE Hitachi is the first to market
this innovative product, following a
comprehensive and concerted effort,
through causal analysis and testing, to
find a robust and effective solution to
increasing wear among jet pumps in the
BWR fleet.
As a result of the increasing FIV,
the existing set screw and main wedge
system for maintaining the required three-
point contact at the Jet Pump restrainer
bracket was found to be insufficient for
susceptible Jet Pumps. To eliminate this
problem, the new anti-vibration upgrade
at the restrainer bracket takes advantage
of hydraulic loads, while positively
maintaining the required three-point
contact.
The new anti-vibration upgrade at
the restrainer bracket has undergone
successful full-scale testing at the new
EPRI facility in Princeton, New Jersey as
well as thorough vibration testing at Wyle
Labs in Huntsville, Alabama.
As a result of the EPRI testing, the
new GEH anti-vibration upgrade at the
restrainer bracket was demonstrated to
preclude slip joint leakage instability for
most plant operating conditions, even
with a severe slip joint gap. Test results
by EPRI show that with application of the
restrainer bracket upgrade and slip joint
clamp, initiation of slip joint leakage
instability could only occur in areas
that are well outside any plant operating
region. “We are pleased to offer this
innovative and tested solution to our
customers,” said Manny Klein, Jet Pump
Modifications Product Line Leader with
GE Hitachi.
Contact: Emanuel (Manny) Klein,
GE Hitachi Nuclear Energy, telephone:
(910) 819-6427, email: Emanual1.
, and Bret Nelson, GE
Hitachi Nuclear Energy, email:
JP AVS installed on the Jet Pump
Restrainer Bracket.
JP AVS Installed on Jet Pump
Restrainer Bracket showing 3 Point
Contact (Top-Down View).
46
Nuclear Plant Journal, March-April 2013
