Information Notice 1988-01, Safety Injection Pipe Failure
A
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
January 27, 1988
NRC INFORMATION NOTICE NO. 88-01:
SAFETY INJECTION PIPE FAILURE
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This information notice is to alert addressees to a potentially generic problem
concerning the reliability of piping in safety-related systems-due to valve
leakage which results in thermal cycling of the piping.
Recipients are expected
to review the information for applicability to their facilities and consider
actions, if appropriate, to preclude similar problems from occurring at their
facilities.
However, suggestions contained in this information notice do not
constitute NRC requirements; therefore, no specific action or written response
is required.
Description of Circumstances
On December 9, 1987, while restarting Farley Unit 2 after a refueling outage, the licensee noted increased moisture and radioactivity within containment.
The unidentified leak rate for the RCS was determined to be 0.7 gpm.
After
entering containment to identify the location of the leak, licensee personnel
determined that the leak could not be isolated. The reactor, which was at
33 percent power, was shut down to facilitate repair.
By ultrasonic testing, the licensee found an indication of a crack on the
interior surface of the 6-inch ECCS piping connected to the cold leg of RCS
Loop B. The indication was located at a weld connecting an elbow and a hori- zontal spool, as shown in Attachment 1. Further, the indication was on the
underside of the pipe and extended circumferentially 60 degrees in both direc- tions from the bottom of the pipe.
The crack extended through the wall for
approximately 1 inch at the center of the indication.
Visual and metallo- graphic examinations showed that the weld had failed as a result of fatigue
after roughly one million stress cycles. The licensee examined the operating
records and determined that the number of stress cycles imposed by starting up
and shutting down and by safety injections was significantly less than the
relevant design criteria.
8801210097
IN 88-01 January 27, 1988 On the basis of this information, the licensee postulated that the stress
loads were (1) thermal and created by valve leakage or convective flow cells
or (2) mechanical and created by flow-induced vibrations.
To test these postu- lations, the licensee replaced the failed piping and installed sensors for
temperature and acceleration near the location of the failed weld and at a
location 25 to 30 inches upstream from the failed weld, that is, on the other
side of the check valve.
The licensee also installed sensors at similar loca- tions on the ECCS pipe connected to Loop C. At each location the sensors
were distributed circumferentially around the pipe.
Data from the sensors demonstrated that there was an adverse temperature distri- bution in the Loop B ECCS piping as shown in Attachment 1. The circumferential
temperature difference at the location of the failed weld was 2150 F. Further, the temperature at the bottom of the pipe fluctuated as much as 300 F in 30
seconds.
This spatial and temporal distribution was caused by failure of the
valve in the bypass pipe around the boron injection tank (BIT) to seat properly.
The valve, which is shown in Attachment 2, is believed to be the cause of
failure of the weld.
Leakage through the valve apparently caused the check
valves in the Loop B ECCS pipe to partially open, or chatter, admitting rela- tively cold coolant to the unisolable portion of the pipe between the nozzle
and the first check valve.
Temporarily redirecting the valve leakage away
from the ECCS manifold changed the temperature distribution, as shown in
Attachment 1. It should be noted that there may be other safety-related piping
in both PWRs and BWRs which could experience similar fatigue due to thermal
cycling.
Data from the temperature sensors for Loop C indicated that the check valves
in that pipe were not chattering and that the temperature distribution was
normal.
Further, none of the accelerometers indicated adverse mechanical
stress cycling.
Examination of the analysis of record for the small-break, loss-of-coolant
accident indicated that double-ended failure of the unisolable ECCS pipe may
not have been enveloped.
Discussion:
A generic safety question may exist for those plants having dual purpose pumps
that are used for charging the RCS with coolant during normal operation and
injecting emergency core coolant at high pressure following an accident.
During
normal operation, with one of the pumps providing charging flow to the RCS via
the normal charging piping and with a leaking valve allowing coolant to flow to
the ECCS manifold, pressure in the manifold will exceed RCS pressure and check
valves in the ECCS piping will open admitting relatively cold coolant to the RCS.
The flow rate via this additional path or paths is determined by the throttling
that occurs in the leaking valve.
If the check valves in more than one ECCS
pipe open, then more than one unisolable ECCS failure may occur.
Subjecting
the flawed piping to excessive stresses induced by a seismic event, water hammer, or some other cause conceivably could result in simultaneous double-ended failure
of more than one ECCS pipe.
IN 88-01 January 27, 1988 Corrective action for this common-mode failure would include redesigning the
piping, instrumenting unisolable and adjacent portions of the piping to detect
cyclic or abnormal thermal stresses, instrumenting the ECCS manifold to detect
pressure resulting from valve leakage, or providing additional surveillance.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.
Ch
.El:.
Ros
Dfrector
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Roger Woodruff, NRR
(301) 492-7096 Attachments:
1. Farley 2 Temperature Data
2. Farley 2 ECCS
3. List of Recently Issued NRC Information Notices
t.1A
.
WITH
WiTHOUT
LEAKAGE LEAKAGE
TOP OF PiPE
40F
495F
BOTTOM OF PIPE
225F
490F
TOP OF PIPE
BOTTOM OF P11
' WITH
LEAKAGE
245F
117F
WiTHOUT
LEAKAGE
I200F
- 115F
cI
FAILED WI
la
A~~
wC
I
! r
I
8 Eccs
COLD LEG iB
mz-I
A
FARLEY 2 TEMPERATURE DATA
r1
COLD LEGS
NbRMAL CHARGiNG
TO RCS COLD LEG B
(
CHARGiNG/HiGH
PRESSURE SAFETY
INJECTION PUMPS
30
x
m
2 I
h3
FARLEY 2 ECCS
,.
.
I
Attachment 3- IN 88-01
January 27, 1988 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
86-81, Supp. 1
87-67
87-66
87-28, Supp. 1
87-65
87-64
87-35, Supp. 1
87-63
87-62
Broken External Closure
Springs on Atwood & Morrill
Main Steam Isolation Valves
Lessons Learned from
Regional Inspections of
Licensee Actions in Response
Inappropriate Application
of Commercial-Grade
Components
Air Systems Problems at
U.S. Light Water Reactors
Plant Operation Beyond
Analyzed Conditions
Conviction for Falsification
of Security Training Records
Reactor Trip Breaker
Westinghouse Model DS-416,
Failed to Open on Manual
Initiation From the Control
Room
Inadequate Net Positive
Suction Head in Low Pressure
Safety Systems
Mechanical Failure of
Indicating-Type Fuses
1/11/88
12/31/87
12/31/87
12/28/87
12/23/87
12/22/87
12/16/87
12/9/87
12/8/87
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 holders of OLs
or CPs for nuclear
power reactors.
All nuclear power
reactor facilities
and all major fuel
facility licensees.
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.
OL = Operating License
CP = Construction Permit
IN 88-01 January 27, 1988 Corrective action for this common-mode failure would include redesigning the
piping, instrumenting unisolable and adjacent portions of the piping to detect
cyclic or abnormal thermal stresses, instrumenting the ECCS manifold to detect
pressure resulting from valve leakage, or providing additional surveillance.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Roger Woodruff, NRR
(301) 492-7096 Attachments:
1. Farley 2 Temperature Data
2. Farley 2 ECCS
3. List of Recently Issued NRC Information Notices
See previous Concurrence
OFC
- EAB:NRR
- EAB:NRR
- C:EAB:NRR :*D:DEST
- XC:GCB
- D:DOEA
NAME :RWoodruff*
RLobel*
- WLanning*
- LShao*
- CBerlinger
.
DATE :1/11/88
- 1/11/88
- 1/12/88
- 1/13/88
- 1/15/88
- 1L2//88
OFFICIAL RECORD COPY
3 Corrective action for this common-mode failure would include redesigning the
piping. instrumenting unisolable and adjacent portions of the piping to detect
cyclic or abnormal thermal stresses, instrumenting the ECCS manifold to detect
pressure resulting from valve leakage. or providing additional surveillance.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the Regional
Administrator of the appropriate regional office or this office.
Charles E. Rossi. Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Roger Woodruff. NRR
(301) 492-7096 Attachments:
1. Farley 2 Temperature Data
2. Farley 2 ECCS
3. List of Recently Issued Information Notices
DISTRIBUTION
EAB R/F
WLANNING
RWOODRUFF R/F
RLOBEL
CROSSI
CBERLINGER
LSHAO
TECH:ED:
AThomas
/ /88
See previous Concurrence
OFC :EAB:NRA
- EAB:NRR
- C:EAB:NRR
- D:DEST
- C:GCQ__ 4 <
D:DOEA:
NAME :RWoodruff*
RLobel*
- WLanning*
- LShao*
- CBerlinger :CERossi
- :
DATE : / /88
- / /88
- / /88
- / /88
1/Ir78
- / /88
OFFICIAL RECORD COPY
I t- K-1d
3 Assurance that this common mode failure does not occur could be provided by
redesign of the piping, instrumenting unisolable and adjacent portions of the
piping to detect cyclic or abnormal thermal stresses, instrumenting the ECCS
manifold to detect pressure resulting from valve leakage, or providing
additional surveillance.
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the
Regional Administrator of the appropriate regional office or this office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact:
Roger Woodruff, NRR
(301) 492-7096 Attachments:
1. Farley 2 Temperature Data.
2. Farley 2 ECCS.
3. List of Recently Issued Information Notices.
DISTRIBUTION
EAB R/F
WLANNING
RWOODRUFF R/F
RLOBEL
CROSSI
CBERLINGER
LSHAO
TECH:EDa
AThomas V
/ //y/88 OFC
- EAB
yR
- EAB:NRR:
- D S
- C:GCB
MDUDEA:
NAME :RW o un :'db RLobel
- anni g
- Lhao
- CBerlinger :CERossi
- :
DATE : I/\\/88
- I/l /88
- I/l /88
- 1/13/88
- / /88
- / /88
OFFICIAL RECORD COPY
DATE: LmI6._l%
TO: RECORD SERVICES BRANCH
FROM: TI
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