Information Notice 1995-11, Failure of Condensate Piping Because of Erosion/Corrosion at Flow-Straightening Device
,
, -- --
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
February 24, 1995
FAILURE OF CONDENSATE PIPING BECAUSE OF
EROSION/CORROSION AT A FLOW-STRAIGHTENING
DEVICE
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to possible piping failures caused by flow
disturbances that are not accounted for in erosion/corrosion programs.
It is
expected that recipients will review the information for applicability to
their facilities and consider actions, as appropriate, to avoid similar
problems.
However, suggestions contained in this information notice are not
NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances
On November 29, 1994, the Sequoyah Unit 1 reactor tripped from 100-percent
power. Approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after the plant trip, Tennessee Valley Authority
(TVA, the licensee) observed water pouring from a 16 inch nominal size
diameter condensate line between the 1B4 and 1B3 feedwater heaters. A
licensee investigation found , 180 degree circumferential crack in the reduced
section of a nominal 14 inch pipe. This pipe section was part of a
Westinghouse flow-metering device that had been installed during the first
refueling cycle to test turbine performance.
The metering device consisted of three flanged sections of pipe: the first
section reduced the pipe diameter from 16 inch to 14 inch; the last section
expanded the diameter back to 16 inch; and the middle section contained a
flow-straightening device, a nozzle, and flow taps. The flow straightener
device consisted of three 0.95 cm [0.375 inch] thick, circular plates with
drilled flow holes. The plates were spaced about 0.3 meter [1 foot] apart and
held together by four 1.27 cm [0.5 inch] rods.
The first circular plate fit
the pipe flange face and held the fixture in place.
The other two plates fit
the machined, inside surface of the 14 inch diameter pipe section.
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February 24, 1995 Discussion
TVA found that the pipe failure occurred at the interface of the edge of the
middle plate and the inner surface of the pipe wall.
The failure resulted
from bypass flow around the edge of the plate, which caused very localized
erosion along a narrow band, approximately 1.27 cm [0.5 in] wide and
360 degrees around the pipe wall. A 7.6 cm [3 inch] wide, 0.32 cm
[0.125 inch] deep machined surface, 360 degrees, on the outer surface of the
pipe in the same area of the internal erosion may have contributed to the pipe
failure.
This surface had been machined to serve as a reference surface and
the inner surface was machined to ensure a snug fit of the flow straightener
inside the pipe. At the failure area, erosion had further thinned the pipe
wall to approximately 0.127 cm [0.05 inch].
The condensate line containing the flow-metering device was in the
erosion/corrosion program and modeled with CHECMATE, but it was modeled as a
straight 16 inch pipe section without any diameter or thickness change.
CHECMATE is a program used by a majority of licensees that predicts
erosion/corrosion rates in piping components, ranks the components in order of
damage potential, and calculates the time remaining before reaching a user
defined acceptable wall thickness. The licensee personnel responsible for
operations and engineering were aware that the flow-metering device was
installed; however, ambiguities in drawings prompted the personnel responsible
for the erosion/corrosion program to assume that these sections had been
removed. The pipe configuration had not been visually inspected and it had
been modelled as a straight section.
After the pipe failure, the CHECMATE model, including the condensate line with
the flow-metering devices, was re-analyzed. The CHECMATE program did not
include a model for the flow straightener; the closest model for this device
was a straight pipe section. The CHECMATE model would have indicated a high
rank for erosion downstream of the nozzle, which would have been modelled as
an orifice.
Therefore, knowledge that the metering device was installed still
may not have prompted an inspection of the area of piping that failed (the
area of the flow straightener).
Even if the area had been inspected, the band
of erosion was so localized that it could have been missed since only grid
intersections are inspected.
The licensee determined that the parallel condensate lines still had the
temporary metering devices installed and replaced those sections with straight
16 inch sections of pipe.
The licensee also determined that the heater drain
system had two of these temporary metering sections but decided to leave the
lines in service because the flow straighteners had been removed in an outage
and present thickness measurements indicated no unacceptable erosion.
The root cause of the failure was the bypass flow around the middle plate of
the flow straightener. This bypass flow was not anticipated and the NRC staff
is not aware of any previous industry experience that would have demonstrated
a need to have the CHECMATE program indicate a high rank for flow
straighteners. This example is an indication of how flow disturbances not
accounted for by modelling tools can affect the reliability of licensee
erosion/corrosion programs.
February 24, 1995 Related Generic Communications
In NRC Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants,"
July 9, 1987, the staff requested licensees and applicants to inform NRC about
their programs for monitoring the wall thickness of carbon steel piping.
By NRC Generic
Thinning," May
implement long
Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall
2, 1989, the staff requested licensees and applicants to
term erosion/corrosion monitoring programs.
The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
1
.ran
. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts:
B. R. Crowley, RII
(404) 331-5579
N. Economos, RII
(404) 331-5580
K. I. Parczewski,
(301) 415-2705 NRR
Attachment:
List of Recently Issued NRC Information Notices
'-Attachment
February 24, 1995 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
95-10
Supp. 1
95-10
95-09
95-08
95-07
95-06
Potential for Loss of
Automatic Engineered
Safety Features
Actuation
Potential for Loss of
Automatic Engineered
Safety Features
Actuation
Use of Inappropriate
Guidelines and Criteria
for Nuclear Piping and
Pipe Support Evaluation
and Design
Inaccurate Data Obtained
with Clamp-On Ultrasonic
Flow Measurement Instruments
Radiopharmaceutical Vial
Breakage during Preparation
Potential Blockage of
Safety-Related Strainers
by Material Brought Inside
Containment
02/10/95
02/03/95
01/31/95
01/30/95
01/27/95
01/25/95
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All holders of OLs or CPs
for nuclear power reactors.
All USNRC medical licensees
authorized to use byproduct
material for diagnostic
procedures.
All holders of OLs or CPs
for nuclear power reactors.
95-05
95-04
Undervoltage Protection
Relay Settings Out of
Tolerance Due to Test
Equipment Harmonics
Excessive Cooldown and
Depressurization of the
Reactor Coolant System
Following a Loss of
Offsite Power
01/20/95
01/19/95 All holders
Permits for
reactors.
of Construction
nuclear power
All holders of OLs or CPs
for nuclear power reactors.
OL = Operating License
CP -
Construction Permit
IN 95-11 February 24, 1995 In NRC Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants,"
July 9, 1987, the staff requested licensees and applicants to inform NRC about
their programs for monitoring the wall thickness of carbon steel piping.
By NRC Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall
Thinning," May 2, 1989, the staff requested licensees and applicants to
implement long term erosion/corrosion monitoring programs.
The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response.
If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Original signed by
Brian K. Grimes
Brian K. Grimes, Director
-
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: B. R. Crowley, RII
(404) 331-5579
N. Economos, RII
(404) 331-5580
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-11.IN
- See previous concurrence
OFC
OECB:DOPS
TECH ED
SC/OECB:DOPS
EMCB:DE
NAME
SKoenick*
JMain*
EGoodwin*
KParczewski*l
DATE
12/14/94
12/19/94
12/19/94
12/21/94 i
OFC
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C/OECB:DOPS
D
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NAME
JStrosnider*
RKiessel*
AChaffee/RLD*
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DATE
12/21/94
01/17/95
01/19/95
02/2, //95
OFFICIAL RECORD COPY
IN 95-XX
January XX, 1995 In NRC Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants,"
July 9, 1987, the staff requested licensees and applicants to inform NRC about
their programs for monitoring the wall thickness of carbon steel piping.
By NRC Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall
Thinning," May 2, 1989, the staff requested licensees and applicants to
implement long term erosion/corrosion monitoring programs.
The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: B. R. Crowley, RII
(404) 331-5579
N. Economos, RII
(404) 331-5580
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: S:\\DOPSSEC\\SEQUOYAH.IN
- See previous concurrence
OFC
l OECB:DOPS
l TECH ED
SC/OECB:DOPS
EMCB:DE
NAME
SKoenick*
JMain*
EGoodwin*
KParczewski*
DATE 1 12/14/94
12/19/94
12/19/94
12/21/94 OFC
C/EMCB:DE
OECB:DOPS
C/OECB:DOPS
D/DOPS
l NAME
JStrosnider*
RKiessel*
I AChaffee/RLD*
BGrimes
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DATE
12/21/94
-1
01/17/95
01/19/95
/
/95
___-OFFICIAL
RECORD COPY
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IN 95-XX
January XX, 1995 NRC Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning,'
May 2, 1989. The staff requested licensees and applicants to implement long
term erosion/corrosion monitoring programs.
The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts:
B. R. Crowley, RII
(404) 331-5579
N. Economos, RII
(404) 331-5580
K. I.
(301)
Parczewski, NRR
504-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
G:\\SSK2\\SEQUOYAH.IN
- See previous concurrence
OFC l OECB:DOPS
TECH ED
lSC/OECB:DOPS
EMCB:DE
NAME
SKoenick*
JMain*
EGoodwin*
KParczewski*
DATE
12/14/94
12/19/94
12/19/94
12/21/94 OFC
C/EMCB:DE
OECB:DOPS
C/OECB:DOPS
D/DOPS
l
NAME
JStrosnider*
RKiessel*
AChaffee/RLD*
BGrimes V98 DATE
12/21/94
01/17/95
01/19/95
/
/95 1
OFFICIAL RECORD COPY
' -ok
IN 95-XX
January XX, 1995
NRC Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning,"
May 2, 1989. The staff requested licensees and applicants to implement long
term erosion/corrosion monitoring programs.
8 The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts:
B. R. Crowley, RII
(404) 331-5579
N. Economos, RII
(404) 331-5580
K. I. Parczewski, NRR
(301) 504-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\SSK2\\SEQUOYAH.IN
- See previous concurrence
OFC
OECB:DOPS
TECH ED
SC/OECB:DOPS
EMCB:DE
NAME
SKoenick*
JMain*
EGoodwin*
KParczewski*
DATE 1 12/14/94
12/19/94
12/19/94
12/21/94
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NAME
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DATE
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1/1 1/95
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OFFICIAL RECORD COPY
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IN 95-XX
January XX, 1995 NRC Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning,"
May 2, 1989.
The staff requested licensees and applicants to implement long
term erosion/corrosion monitoring programs.
8 The NRC also issued several information notices on erosion and corrosion.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts:
B. R. Crowley, RII/DRS
(404) 331-5579 N. Economos, RII/DRS
(404) 331-5580
K. I. Parczewski, NRR/DE
(301) 504-2705 Attachment:
List of Recently Issued NRC Information Notices
OFC }
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TECH ED
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EMCB: g IC
NAME
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[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:\\SSK2\\SEQUOYAH.IN