Information Notice 1997-84, Rupture in Extraction Steam Piping as a Result of Flow-Accelerated Corrosion
'
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
December 11, 1997
NRC INFORMATION NOTICE 97-84: RUPTURE IN EXTRACTION STEAM PIPING AS A
RESULT OF FLOW-ACCELERATED CORROSION
Addressees
All holders of operating licenses for nuclear power reactors except those who have permanently
ceased operations and have certified that fuel has been permanently removed from the reactor
vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to potential generic problems related to the occurrence and prediction of flow- accelerated corrosion (FAC) in extraction steam systems. 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 April 21, 1997, Omaha Public Power District's Fort Calhoun Station, while operating at 100-
percent power, experienced an approximate 0.56 m2 [6 ftl rupture of a 30.5-centimeter [12- inch]-diameter sweep elbow (radius equal to five times the pipe diameter) in the fourth-stage
extraction steam piping. The operator, upon hearing steam noise and observing steam rising
from the turbine deck, believed that a steam line had broken and manually scrammed the
reactor. As a precaution, emergency boration was initiated. The main turbine tripped
automatically as a result of the reactor trip. The turbine trip had the effect of isolating the
rupture. Plant systems and related parameters responded as expected during the event.
The steam line rupture damaged a nonsafety-related electrical load center in the vicinity of the
pipe break. Additionally, collateral damage was experienced in several cable trays and pipe
hangers, and insulation containing asbestos was blown throughout the turbine building. Certain
portions of the fire protection system actuated in response to fusible links in the sprinkler heads
melting because of high temperature. Because there were no personnel in the immediate
vicinity of the rupture, no one was injured.
120
n +4NT~ES
17-09
9719-11
9712 W ik l a a
K.
IN 97-84 December 11, 1997 The fourth-stage extraction steam system emanates from the outlet of the high-pressure turbine
and preheats the feedwater heaters. The design operating conditions in the piping are
2068 kilopascal gauge [300 psig] and 2180C [4250F], with a steam quality of approximately
92 percent. The piping is fabricated of A-1 06B carbon steel and has a nominal wall thickness of
0.953 centimeter [0.375 inch]. The licensee's root cause assessment attributed the failure to
FAC in the extraction steam piping. Initial indications of degradation in the extraction steam line
at the Fort Calhoun facility were first discovered in 1985, when the furthest upstream long- radius elbow (radius equal to one and a half times the pipe diameter) was replaced because of
a pinhole leak. At that time the next upstream sweep elbow was also replaced.
The fourth-stage extraction steam system had been recognized as a system that was
susceptible to erosion and/or corrosion. It was, therefore, being monitored by the licensee's
erosion and corrosion control program. Part of the licensee program was utilizing the
CHECWORKS computer code to identify high-wear-rate areas to be selected for inspection.
The CHECWORKS model for the fourth-stage extraction steam piping predicted that long- radius elbows would wear at a higher rate than the sweep elbows when exposed to similar
conditions. Using CHECWORKS predictions, the licensee inspected and replaced all four long- radius elbows, but the failed sweep elbow was never inspected.
Part of the licensee's corrective actions following the rupture included inspecting all sweep
elbows that had not been previously inspected. The measured wall thickness (0.112 centimeter
[0.044 inch]) of the furthest downstream sweep elbow in the fourth-stage extraction piping was
also significantly below the minimum wall thickness (0.272 centimeter [0.107 inch]) specified by
code requirements and had to be replaced. Additionally, another sweep elbow in the fourth- stage extraction piping was also replaced because the wear (measured wall thickness of
0.394 centimeter [0.155 inch]) was considered excessive, even though it was not below the
minimum allowable thickness.
The CHECWORKS predictions of the wear in the fourth-stage extraction steam system were
not consistent with the actual observed wear rates as measured on the components, that is, sweep elbows showed substantially greater wear than predicted.
IN 97-84 December 11, 1997 Subsequent investigations by the licensee determined that the inconsistencies between
predicted and actual wear were due to two factors. First, the "line correction factor" calculated
by CHECWORKS for the fourth-stage extraction steamline was not within the acceptable range
specified in the CHECWORKS users' manual. The line correction factor in CHECWORKS is
used to adjust wear rate predictions in a given line to account for plant operating conditions that
may vary with time. It is determined by comparing predicted wear to measured wear at
locations in the line which have been inspected.
In order for the CHECWORKS predicted wear rate for a location to be valid, the line correction
factor must be between 0.5 and 2.5. For the line containing the sweep elbow that failed, the
wear rates calculated by CHECWORKS used a line correction factor that was outside this
range. Therefore, as specified in the CHECWORKS users' manual, the predicted wear rates
for this line were not valid.
Second, the line correction factor was biased and thus underpredicted the wear rates. In 1987, the licensee updated the parameters used by CHECWORKS to include the wear measured in a
long-radius elbow. One of the inputs in CHECWORKS is the length of time the component has
been In service. The licensee assumed that this elbow had been in service since initial
operation of the plant In 1973; however, the elbow had been replaced in 1985. Therefore, the
actual wear occurred over 2 years rather than the presumed 14 years. Thus, the period of time
that was assumed for the wear to have occurred caused CHECWORKS to calculate a line
correction factor that underestimated the wear rates for sites in the line.
This event revealed the importance of understanding the limitation of methodologies used in
computer programs and of incorporating accurate plant-specific data from nondestructive
examination programs.
Related Generic Communications
In NRC Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants," July 9, 1987, the staff
asked licensees and applicants to inform the NRC about their programs for monitoring the wall
thickness of carbon steel piping (Accession No. 8707020018).
In NRC Generic Letter 89-08, "Erosion/Corrosion Induced Pipe Wall Thinning," May 2,1989, the staff asked licensees and applicants to Implement long-term erosion/corrosion monitoring
programs (Accession No. 8905040276).
IN 97-84 December 11, 1997 Additionally, the following NRC information notices (INs) provide information about similar
events related to FAC:
IN 82-22, "Failures in Turbine Exhaust Lines," July 9, 1982 (Accession No. 8204210392).
IN 86-106, nFeedwater Line Break," December 16, 1986 (Accession No. 8612160250).
IN 87-36, "Significant Unexpected Erosion of Feedwater Lines," August 4, 1987 (Accession
No. 8707290264).
IN 88-17, "Summary of Responses to NRC Bulletin 87-01, 'Thinning of Pipe Walls In Nuclear
Power Plants," April 22, 1988 (Accession No. 8804180039).
IN 89-53, "Rupture of Extraction Steam Line on High Pressure Turbine," June 13, 1989 (Accession No. 8906070273).
IN 91-18, "High Energy Pipe Failures Caused by Wall Thinning," March 12, 1991 (Accession No. 9103060153).
IN 91 -18, Supplement 1, "High Energy Pipe Failures Caused by Wall Thinning," December 18,
1991 (Accession No. 9112120218).
IN 93-21, "Summary of NRC Staff Observations Compiled During Engineering Audits or
Inspections of Licensee Erosion/Corrosion Programs," March 25, 1993 (Accession
No. 9303190051).
IN 95-11, "Failure of Condensate Piping Because of Erosion/Corrosion at a Flow-Straightening
Device," February 24, 1995 (Accession No. 9502210050).
IN 97-84 December 11, 1997 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under Section 50.65, Requirement for monitoring the effectiveness of maintenance at nuclear
power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any
questions about the information in this notice, please contact the technical contact listed below
or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
J.).
RoActing Director
Pi ision of Reactor Program Management
ice of Nuclear Reactor Regulation
Technical contact: J. Shackelford, RIV
(817) 860-8144 E-mail: jIs2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
Attachment
December 11, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
95-49, Seismic Adequacy of
12/10/97
All holders of OLs for nuclear
Sup. 1 Thermo-Lag Panels
power reactors
97-83 Recent Events Involving
12/05/97 All holders of OLs for pressurized- Reactor Coolant System
water reactors, except those
Inventory Control During
licensees who have permanently
Shutdown
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel
97-82 Inadvertent Control Room
11/28/97
All holders of OLs for nuclear
Halon Actuation Due to a
power reactors
Camera Flash
97-81 Deficiencies in Failure
11/24197
All holders of OLs for nuclear
Modes and Effects Analyses
power reactors except those
for Instrumentation and Control
who have ceased operations
Systems
and have certified that fuel
has been permanently removed
from the vessel
97-80
Licensee Technical
11/21197
All holders of OLs for
Specifications
nuclear power reactors
Interpretations
OL = Operating License
CP = Construction Permit
e
e
e
i'
,E'
KY
IN 97-84 December 11, 1997 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under Section 50.65, "Requirement for monitoring the effectiveness of maintenance at nuclear
power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any
questions about the information in this notice, please contact the technical contact listed below
or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: J. Shackelford, RIV
(817) 860-8144 E-mail: jls2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
TECH EDITOR*
RIV/DRS*by email
RIV/DRS*by email
PECB:DRPM*
NAME
R. Sanders
J. Shackelford
D. Chamberlain
T. Greene
l DATE
09/11/97
09/16/97
109/16/97
09/20/97 OFC
EMCB:DE*
C(A)/EMCB:DE*
D:DE*
SUPECB:DRPM*
NAME
K. Parczewski
E. Sullivan
B. Sheron
R. Dennig
DATE
9/23/97
9/23/97
9/23/97
11/21/97 I
OFC
I C/PECB:DRPM*
l(AED9RPM
NAME
S. Richards
J. &
DATE
11/26/97
12/6197 j
- See previous concurrence
[OFFICIAL RECORD COPY]
DOCUMENT NAME: 97-84.IN
I
IN 97-XX
November XX, 1997 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under Section 50.65, "Requirement for monitoring the effectiveness of maintenance at nuclear
power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any
questions about the information in this notice, please contact the technical contact listed below
or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: J. Shackelford, RIV
(817) 860-8144 E-mail: jis2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
l TECH EDITOR*
RlV/DRS*by email
RIV/DRS*by email
PECB:DRPM*
NAME
R. Sanders
J. Shackelford
D. Chamberlain
T. Greene
DATE
j 09/11/97
09/16/97
09/16/97
09/20/97 OFC
EMCB:DE*
C(A)/EMCB:DE*
D:DE*
SL/PECB:DRPM*
NAME
K. Parczewski
E. Sullivan
B. Sheron
R. Dennig
DATE __9/23/97
9/23/97 j_9/23/97 j_11/21/971
, 1^_
AN
I/,b(7 OFC
lC/PECB:DRPM*1 (A)D/DF3PM
NAME
S. Richards
J.
DATE
%I
tZ697
<1/897U7
- See previous concurrence
[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:\\TAG\\INFAC
IJ
I
A
o
IN 97-XX
November XX, 1997 This information notice requires no specific action or written response. However, recipients
are reminded that they are required to consider industry-wide operating experience (including
NRC information notices) where practical, when setting goals and performing periodic
evaluations under Section 50.65, "Requirement for monitoring the effectiveness of
maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal
Regulations. If you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation
(NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: J. Shackelford, RIV
(817) 860-8144 E-mail: jIs2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
TECH EDITOR*
RIV/DRS*by email
RIVIDRS*by email
PECB:DRPM*
NAME
R. Sanders
J. Shackelford
D. Chamberlain
T. Greene
DATE
09/11197
09/16/97
09116197
09/20/97 OFC
EMCB:DE*
C(A)/EMCB:DE*
D:DE*
SUPECB:DRPM
NAME
K. Parczewski
E. Sullivan
B. Sheron
R. DennigI
DATE
9/23/97
9/23/97
9/23/97
11/21/97 IOFC
C/PECB:DRPM*
(A)D/DRPM
NAME
S. Richards f
J. Roe
DATE
I /97
[__
/97
- See previous cocrence/
[OFFICIAL RECORD COPY]a Y/y7/
DOCUMENT NAME: G:\\TAG\\INFAC
IN 97-XX
November XX, 1997 This information notice requires no specific action or written response. However, recipients
are reminded that they are required to consider industry-wide operating experience (including
NRC information notices) where practical, when setting goals and performing periodic
evaluations under Section 50.65, "Requirement for monitoring the effectiveness of
maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal
Regulations. If you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation
(NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: J. Shackelford, RIV
817-860-8144 E-mail: jls2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
TECH EDITOR*
RIV/DRS*by email
RIV/DRS*by email
PECB:DRPM*
NAME
R. Sanders
J. Shackelford
D. Chamberlain
T. Greene
D
09/11/97
09/16/97
09/16/97
09/17/97 111,0111 OFC
EMCB:DE*
j
C(A)IEMCB:DE*
D:DE*
NAME
K. Parczewski
E. Sullivan
B. Sheron
.FLenn/ig
lDATE
9/23/97
9/23/97
9123197 n
197 OFC
C/PECB:DRPM
(A)D/DRPM
NAME
S. Richards
J. Roe
DATE
/ /97
/ /97 lj
See previous concurrence
[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:NTAGIINFAC
e
4 t
IN 97-XX
October XX, 1997 This information notice requires no specific action or written response. However, recipients
are reminded that they are required to consider industry-wide operating experience (including
NRC information notices) where practical, when setting goals and performing periodic
evaluations under Section 50.65, "Requirement for monitoring the effectiveness of.
maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal
Regulations. If you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation
(NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
J. Shackelford, RIV
817-8604144 E-mail: jls2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
TECH EDITOR
RIVIDRS
a
s
- /:$Aq PECB:DRPM
NAME
R. Sanders*
J. Shackelford
i
D. ChamberlainO)T. Greene (i
)
DATE
09111/97
09/16/97
09/16/97
09/17/97 OFC
EMCB:DE
C(A)/EMCB:DE
- DE
Si.
SLIPECB:DRPM
NAME
K. Parczewski
E. Sullivan
_. Dennig
DATE
/S3197
19 4A7(97;)J41
110/974J31;};3
1/97l
lOFC
C(A)/PECB:DRPM
D/DRPYA
NAME
E. Goodwin
J. Roe
DATE
/ /97
1
/97
- See previous concurrence
[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:\\TAG\\INFAC
W
.
I
a .
I
K)
IN 97-XX
September XX, 1997 This information notice requires no specifi action or written response. However, recipients
are reminded that they are required to
industry-wide operating experience (including
NRC information notices)
where practical, when setting goals and
performing periodic evaluations under Section 50.65, "Requirement for monitoring the
effectiveness of maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of
Federal Regulations. If you have any questions about the information in this notice, please
contact the technical contact listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
J. Shackelford, RIV
(7817-860-8144
_
E-mail: jls2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFC
TECH EDITOR
RIV/DRS
RIV/DRS
l PECB:DRPM
NAME
R. Sanders 0
J. Shackelford
D. Chamberlain
T. Greene
l DATE
ljul11/97
//97
1 //97
1
/97 OFC
C/EMCB:DE
D:DE
SL(A)/PECB:DRPM
C(A)/PECB:DRPM
NAME
J. Strosnider
B. Sheron
C. Petrone
R. Dennig
DATE
I
_
/97 I /197
//97
1
/97 I
OFC
DIDRPM
NAME
J. Roe
DATE
l
/97
[OFFICIAL RECORD COPY]
DOCUMENT NAME: G:%TAGINFAC