Information Notice 1992-50, Cracking of Valves in the Condensate Return Lines of a BWR Emergency Condenser System
| ML031210758 | |
| Person / Time | |
|---|---|
| Issue date: | 07/02/1992 |
| From: | Rossi C Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| IN-92-050, NUDOCS 9206290237 | |
| Download: ML031210758 (10) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 July 2, 1992 NRC INFORMATION NOTICE 92-50: CRACKING OF VALVES IN THE CONDENSATE RETURN
LINES OF A BWR EMERGENCY CONDENSER SYSTEM
Addressees
All holders of operating licenses or construction permits for boiling water
reactors (BWRs).
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform addressees of cracking found in valves in the condensate
return lines of the emergency condenser system at the Nine Mile Point Nuclear
Station, Unit 1. 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
Following a reactor trip at Nine Mile Point, Unit 1, on May 1, 1992, the
licensee (Niagara Mohawk Power Corporation) inspected the drywell to
investigate the cause of a recent increase of unidentified leakage in the
reactor coolant system. The licensee found a 0.5 gpm leak coming from a
manual gate valve at a 1-inch drain line connection. The leaking gate valve, designated valve 39-02, is located in the condensate return line for the
loop 12 emergency condenser system.
The emergency condenser system has two independent loops (loops 11 and 12).
Figure 1 shows the configuration of the condensate return line in loops 11 and 12. In the condensate return line, a manual gate valve is connected
downstream of a tilting disc check valve. At each of those two valves, two
1-inch drain lines are connected to the bottom part of the valve body with one
drain line at the upstream side and the other one at the downstream side of
the valve. The valve bodies are made of CF8M cast stainless steel.
While investigating the leakage at the manual gate valve 39-02, the licensee
removed the internal components of the adjacent check valve to perform a
visual test (VT), a radiographic test (RT), and an ultrasonic test (UT). The
licensee visually observed cracks on the inside surfaces at both valves in
loop 12. At gate valve 39-02, the licensee found cracks near each of the two
drain holes. At check valve 39-04, the licensee found cracks near a
downs. .,drain hole and found evidence of cracking in the threads of the
9206290237
- -1 IN 92-50
July 2, 1992 upstream drain. These cracks were further examined radiographically
ultrasonically. The licensee found four cracks including and
near the drain hole upstream of'gate valve 39-02. The a throughwall crack
throughwall crack to be about 3.5 inches long and orientedlicensee reported the
from the hole. The other three cracks were all reported radially outward
0.35 inch of passing through the wall (1.25 inch wall to be within 0.15 to
thickness).
licensee found two cracks in the drain hole area downstream The
(39-02), which is the unisolable side of the valve body. of the gate valve
reported the deepest crack to be about 1 inch long and The licensee
passing through the wall. The licensee found four cracks within 0.15 inch of
downstream of check valve 39-04 with the deepest reported near the drain hole
0.1 inch of passing through the wall. The licensee to be within
visually
small indication on the seat ring in manual gate valve observed one
also examined valves 39-01 and 39-03 in the condensate 39-02. The licensee
of the emergency condenser system and found two cracks return line for loop 11 upstream of manual gate valve 39-01. The largest crack near the drain hole
about 1.25 inch long and 1 inch deep. The licensee reported was reported to be
the valve body in loop 11 to be less severe than that the cracking of
in loop 12. The
licensee observed cracking indications on the inside surface
that joins the gate valve to the check valve but did of a butt weld
not
indications by the radiographic examination. The licensee confirm these
examined selected piping welds inboard of the condensate ultrasonically
valves and found no indications. return isolation
The licensee removed a boat sample containing a 0.5-inch
manual gate valve 39-02 in loop 12. The licensee examinedlong crack from
metallographically and fractographically (using a scanning the boat sample
microscope) and found that the crack had propagated electron
little secondary cracking. These features are typicaltransgranularly with very
of
propagation. The licensee noted possible fatigue striations fatigue crack
well-developed. The licensee measured the delta ferrite that were not
sample to be about 15 percent. content of the boat
Discussion
The emergency condensate system at Nine Mile Point, directly to the reactor coolant system, operates by Unit 1, which is connected
acts as a backup for the main condenser to remove thenatural circulation and
following a reactor isolation. The emergency condenserreactor decay heat
Point, Unit 1, as shown in Figure 2, has two loops (loop system at Nine Mile
two condensers in each loop. During normal plant operation, 11 and loop 12) with
return isolation valves (39-05 and 39-06) are closed, the condensate
valves (39-07, 08, 09, and 10) are open in each loop. and the steam isolation
two valves, a manual gate valve and a tilting disc check As shown in Figure 1, horizontal sections of the condensate return line. The valve, are located in
are connected to the suction side of the recirculation horizontal sections
manual gate valves are maintenance valves and are open piping system. The
operation. during normal
The licensee postulated thermal fatigue as the root cause
the valve bodies, upon considering the straight and of the cracking in
transgranular cracking
morphology, the location of the cracks on the bottom surface
near
July 2, 1992 the licensee did
discontinuities, and the orientation of the cracks. However, and cycling
not find the direct causes of the apparent thermal stratification cracking
at the affected valves. The licensee speculated that the observed
condensate
may have been caused by the leaking of the cold water from the tilting disc
and the periodic opening of the
isolation valves (39-05 and 06) of the time and
in the check valve. The licensee provided a limited history return
temperature as evidence of thermal cycling in the loop 12 condensate in loop 11, it
line valve 39-06. Although the licensee also observed crackingline during a
did not observe such thermal cycling on the condensate return return lines
1-week test. The sections of the emergency condenser condensate of
that showed evidence of cracking are classified as American Society its current
Mechanical Engineers (ASME) Code Class 1. The licensee extended of the cracks
outage to complete acceptable code repairs because of the extent the cracks found
in the reactor coolant pressure boundary and, in particular, at the downstream drain line hole for valve 39-02.
response. If
This information notice requires no specific action or writtenplease contact
you have any questions about the information in this notice, Office of
one of the technical contacts listed below or the appropriate
Nuclear Reactor Regulation (NRR) project manager.
4es4re
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts: William H. Koo, NRR
(301) 504-2706 Robert A. Hermann, NRR
(301) 504-2768 Attachments:
1. Figure 1, NMP-1 Emergency Condenser System Condensate Return
Line Configuration Inside Drywell
2. Figure 2, Nine Mile Point Unit One Emergency Condenser System
Simplified Diagram
3. List of Recently Issued NRC Information Notices
AIR OPERATED-,,
SECTION A-A 39-06(LOOP 12$
REACTOR MANUAL GATE VALVE
RECIRCULATION 39-01 (LOOP 11 DRYWELL
FLOW FROM 39-02 (LOOP 12) SHELL
VESSEL ANNULUS '
DISC CHECK VALVE
' 1 \TILTING
39-03
39-04 LOOP 11)
LOOP 12)
I I -/ 0
TO hi
RECIRCULATION ,n
PUMP SUCTION o a
FIGURE 1 NMP-1 EMERGENCY CONDENSER SYSTEM
CONDENSATE RETURN LINE
CONFIGURATION INSIDE DRYWELL
- X
- )I
AttC3achmnt 2 IN !92-50
Jul' .y 2, 1992 Page e 1 of 1
? CONDENSER EMERGENCY C
UP TANK MAKEUP
00 G.- (40.000
EDMERGi
GENCY
ENSERS
39-07 39-09 RPV 39-10 39-08
39-04
39-02
\ ~RECIRCULATION/
\ ~PUMPS (2 OF 5)/
FIGURE 2 NINE MILE POINT UNIT ONE
EMERGENCY CONDENSER SYSTEM
SIMPLIFIED DIAGRAM
A . - &
Attachment 3 IN 92-50
July 2, 1992 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information Date of
Notice No. Subject Issuance Issued to
92-49 Recent Loss or Severe 07/02/92 All holders of OLs or CPs
Degradation of Service for nuclear power reactors
Water Systems
92-48 Failure of Exide Batteries 07/02/92 All holders of OLs or CPs
for nuclear power reactors
92-47
Intent
ional Bypassing 06/29/92 All holders of OLs or CPs
of Automatic Actuation for nuclear power reactors
of Plant Protective
Features
92-46 Thermo-Lag Fire Barrier 06/23/92 All holders of OLs or CPs
Material Special Review for nuclear power reactors.
Team Final Report Findings, Current Fire Endurance
Tests, and Ampacity Cal- culation Errors
92-45 Incorrect Relay Used in 06/22/92 All holders of OLs or CPs
Emergency Diesel Generator for nuclear power reactors.
Output Breaker Control
Circuitry
92-44 Problems with Westing- 06/18/92 All holders of OLs or CPs
house DS-206 and DSL-206 for nuclear power reactors.
Type Circuit Breakers
92-43 Defective Molded Phen- 06/09/92 All holders of OLs or CPs
olic Armature Carriers for nuclear power reactors.
Found on Elmwood Con- tactors
92-42 Fraudulent Bolts in 06/01/92 All holders of OLs or CPs
Seismically Designed for nuclear power reactors.
Walls
OL = Operating License
CP = Construction Permit
. l {
July 2, 1992 discontinuities, and the orientation of the cracks. However, the licensee did
not find the direct causes of the apparent thermal stratification and cycling
at the affected valves. The licensee speculated that the observed cracking
may have been caused by the leaking of the cold water from the condensate
isolation valves (39-05 and 06) and the periodic opening of the tilting disc
in the check valve. The licensee provided a limited history of the time and
temperature as evidence of thermal cycling in the loop 12 condensate return
line valve 39-06. Although the licensee also observed cracking in loop 11, it
did not observe such thermal cycling on the condensate return line during a
1-week test. The sections of the emergency condenser condensate return lines
that showed evidence of cracking are classified as American Society of
Mechanical Engineers (ASME) Code Class 1. The licensee extended its current
outage to complete acceptable code repairs because of the extent of the cracks
in the reactor coolant pressure boundary and, in particular, the cracks found
at the downstream drain line hole for valve 39-02.
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
Charles E. Rossi
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts: William H. Koo, NRR
(301) 504-2706 Robert A. Hermann, NRR
(301) 504-2768 Attachments:
1. Figure 1, NMP-1 Emergency Condenser System Condensate Return
Line Configuration Inside Drywell
2. Figure 2, Nine Mile Point Unit One Emergency Condenser System
Simplified Diagram
3. List of Recently Issued NRC Information Notices
Document Name: CRACKCON.IN
- SEE PREVIOUS CONCURRENCES
D/ *C/OGCB:DOEA:NRR*RPB:ADM
C osJ ' CHBerlinger TechEd
0t15d92 06/22/92 06/10/92
- OGCB:DOEA:NRR *EMCB:DET:NRR *EMCB :DET:NRR *C/EMCB:DET:NRR *D/DET:NRR
DCKirkpatrick WKoo RHermann JWiggins JRichardson
06/12/92 05/29/92 05/29/92 05/29/92 06/18/92
IN 92-XX
June xx, 1992 discontinuities, and the orientation of the cracks toward the hoop. However, the licensee did not find the direct causes of the thermal stratification and
cycling at the affected valves. The licensee speculated that the observed
cracking may have been caused by the leaking of the cold water from the
condensate isolation valves (39-05 and 06) and the periodic opening of the
tilting disc in the check valve. The licensee provided a limited history of
the time and temperature as evidence of thermal cycling in the loop 12 condensate return line valve 39-06. Although the licensee also observed
cracking in loop 11, it did not observe such thermal cycling on the condensate
return line during a 1-week test. The sections of the emergency condenser
condensate return lines that showed evidence of cracking are classified as
American Society of Mechanical Engineers (ASME) Code Class 1. The licensee
extended its current outage to complete acceptable code repairs because of the
extent of the cracks in the reactor coolant pressure boundary, and in
particular the cracks found at the downstream drain line hole for valve 39-02.
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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts: William H. Koo, NRR
(301) 504-2706 Robert A. Hermann, NRR
(301) 504-2768 Attachment: List of Recently Issued NRC Information Notices
Document Name: CRACKCON.IN
- SEE PREVIOUS CONCURRENCES
D/DOEA:NRR CIL% EA:NRR*RPB:ADM
CERossi COi CHBerlinger TechEd
06/ /92 06/r./92 06/10/92 -f
OGCB:DOEA:NRR *EMCB:DET:NRR *EMCB:DET:NRR *C/EMCB:DET:NRR D/DET:NRkj
DCKirkpaty. WKoo RHermann JWiggins JRich rdsn
06/ /2,/92 Al-* 05/29/92 05/29/92 05/29/92 06/t?/92
you have any question `about the information in this nbtice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts: William H. Koo, NRR
(301) 504-2706 Robert A. Hermann, NRR
(301) 504-2768 Attachment: List of Recently Issued NRC Information Notices
Document Name: CRACKCON.IN
- SEE PREVIOUS CONCURRENCES
D/DOEA:NRR C/OGCB:DOEA:NRR
CERossi CHBerlinger
06/ /92 06/ /92
- EMCB:DET:NRR *EMCB:DET:NRR *C/EMCB:DET:NRR D/DET:NRR RPB:ADM
WKoo RHermann JWiggins JRichardson TechEd TMainpT
05/29/92 05/29/92 05/29/92 06/ /92 06/10/92 /
A.
-4-.
of the observed cracking in the valve bodies. However, the direct causes that
created the thermal stratification and cycling at the affected valves were not
specifically identified. The licensee speculated that the observed cracking
may have resulted from the leaking of the cold water from the condensate
isolation valves (39-05, 06) coupled with the periodic opening of the tilting
disc in the check valve. The licensee provided some evidence of thermal
cycling in the loop 12 condensate return line valve 39-06 based on some
limited temperature time history data. Although cracking was also observed in
loop 11, such thermal cycling was not observed on the condensate return line
during a one week test. The sections of the emergency condenser condensate
return lines that showed evidence of cracking are classified as ASME Code
Class 1. Because of the extent of cracking in the reactor coolant pressure
boundary, in particular that found at the downstream drain line hole for valve
39-02, the licensee extended its current outage to complete acceptable code
repairs.
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 project manager
in the Office of Nuclear Reactor Regulation (NRR).
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: William H. Koo, NRR
(301) 504-2706 Robert A. Hermann, NRR
(301) 504-2768 Attachment: List of Recently Issued NRC Information Notices
DISTRIBUTION:
Central Files CBerlinger
EMCB RF CRossi
WKoo
RHermann
JWiggins
DET RF
DET:EMCB DET , B DE *CB TechEd DET:D NRR:OGCB NRR:OGCB
WKoo RHeahn 0 JWggins JMain JRichardson CBerlinger CRossi
s7179 2 '/;5/92 y W//92 /1O /92 / /92 / /92 / /92 OFFICIAL RECORD COPY WP FILENAME: g:\INOTE92 .WKK