Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 84-12
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 27, 1984
Information Notice No. 84-12: FAILURE OF SOFT SEAT VALVE SEALS
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
Purpose:
This information notice is provided as a notification of the failure of soft
seat valve seals to meet the leakage limits of Appendix J of 10 CFR Part 50.
No specific action is required in response to this information notice, but
it is expected that recipients will review the information presented for
applicability to their facilities.
Description of Circumstances:
The Anchor/Darling Valve Company has provided a number of valves to nuclear
power plants that have a combination of soft and hard seats. Prior to
October 1981, Anchor/Darling procured molded ethylene-propylene rubber seals
from the Stillman Rubber Company. After that date, Anchor/Darling procured
extruded-vulcanized soft seals from Stevens Associates. As described in more
detail below, check valves with both types of seals failed to meet 10 CFR
50, Appendix J, requirements at the LaSalle County Nuclear Power Station.
Specifically, on September 29, 1983, the Commonwealth Edison Company
reported (LER 83-107) that the inboard feedwater check valves at LaSalle
Unit 1 had failed to meet the leakage limits of Appendix J of 10 CFR Part
50. When the check valves were opened for inspection, the soft seat showed
damage around the pressure-relieving vent grooves, some wear on the soft
seat face, and slight wear on the body seat.
These check valves had been modified before initial plant operation from a
hard seat valve to a combination soft and hard seat configuration. This was
accomplished by modifying the valve discs to allow the installation of the
soft seat seals. The seals were of molded ethylene-propylene rubber obtained
through the valve manufacturer, Anchor/Darling Valve Company, from the
Stillman Rubber Company.
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IN 84-12
February 27, 1984
Page 2 of 3
The reason these soft seat valve seals failed has not been definitely
determined at this time, but failure is believed ;o be due to one or more of
the following:
1. Sharp edges around the pressure equalizing ports located in the discs
had cut the soft seal material in many locations. The sharp edges
apparently had not been properly removed when the valve discs were
modified. It is possible that local leak rate air bypassed the seal
through these cuts.
2. The machining of the soft seals for proper fit may have affected their
sealing capability.
3. The service conditions encountered by the valves during plant startup
and shutdown may have damaged the soft seals.
The damaged molded seals were replaced in September with new soft seals of
an extruded-vulcanized design obtained through the valve manufacturer from
Stevens Associates. These seals were ground at the site to obtain proper
fit. The valves subsequently passed the local leak rate tests. Since the
cause of the failure of the original molded seals had not definitely been
determined, the licensee agreed to perform a local leak rate test on the
valves during a subsequent outage.
On December 9, 1983, the licensee reported (LER 83-146) that, following
approximately a month of operation, the inboard feedwater check valves again
failed to pass the local leak rate tests. It was determined that the
excessive leakage was a result of gaps on the perimeter of the disc seal
material, one about one-half inch long and the other about one and one-half
inches in length. These gaps appeared at the seam, or "vulcanized," points
of the seal. It was also noticed that one of the seals appeared to be
hardened slightly with multiple minute cracks. In addition, alignment
problems were identified that would have prevented the discs from closing
squarely against the seal.
The utility has replaced the vulcanized seals with molded (one piece) seals
similar to those in the original design. In addition, with the assistance of
a manufacturer's representative, the clearances within the valve have been
adjusted to within the manufacturer's specifications.
In its December 14, 1983, response to a November 28, 1983, Confirmatory
Action Letter, the utility indicated that the molded "seals lasted, as a
minimum, one refueling cycle" when used in similar applications at other
facilities. The utility based this conclusion on telephone conversations
with:
1. Pilgrim Station where the seals were initially installed during the
1976-77 refueling outage. At the first subsequent refueling outage
(1979), two seals were replaced in order to pass the local leak rate
test. The next refueling outage (1981-82) required replacement of four
seals in order to pass the local leak rate test.
2. Brunswick Unit 1 where the seals were initially installed during the
refueling outage in January 1980. The seals passed their local leak
rate tests in August 1982 as well as the tests during the first
subsequent refueling outage (1982-83).
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IN 84-12
February 27, 1984
Page 3 of 3
3. Brunswick Unit 2 where the seals were initially installed during the
refueling outage in June 1980. At the first subsequent refueling outage
(1982) all the seals were changed to pass the local leak rate tests.
Also in accordance with the Confirmatory Action Letter, the licensee is
developing an augmented testing and inspection program and a program for
obtaining and installing soft seals that are fully environmentally
qualified. As a minimum, the augmented testing and inspection program will
include another local leak rate test and an inspection of the accessible
portions of the seals within 90 days of achieving power operation.
Conversations with Anchor/Darling Valve Company, indicated that the company
believes the failure of the extruded-vulcanized seals resulted from improper
vulcanizing of the seal joints. Additionally, the valve manufacturer is of
the opinion that the problem is probably limited to one batch of seals and
only affects the LaSalle County Nuclear Power Station. However,
Anchor/Darling is now recommending the use of the molded ethylene-propylene
rubber seals. Attachment 1 is a chronological listing of those nuclear
plants to which Anchor/Darling provided soft valve seals. The dates of
delivery are also shown. All soft seals, both initial and replacement,
furnished after October 1981 are of the extruded-vulcanized type. At this
time we do not know which of the valves listed in Attachment 1 may have
replaced seals since that date. Also, we do not know which of the valves
have applications that are safety related or important to safety.
No written response to this information notice is required. If you have any
questions regarding this matter, please contact the Regional Administrator
of the appropriate NRC Regional Office, or this office.
Edward L. Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contacts: D. R. Hunter, Region III
(312) 790-5555
R. J. Kiessel, IE
(301) 492-8119
Attachments:
1. Anchor/Darling Check Valves with Dual Seat Design
2. List of Recently Issued IE Information Notices
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Attachment 1
IN 84-12
February 27, 1984
Page 1 of 4
ANCHOR/DARLING CHECK VALVES WITH DUAL SEAT DESIGN
VALVE DESCRIPTION
ANSI
UTILITY, DATE, PRESSURE
AND FACILITY QUANTITY SIZE CLASS (NO.) DESIGN
BOSTON EDISON
3-77, Pilgrim 1 4 18" 900 Tilting
Disc Check
CAROLINA POWER & LIGHT
9-79, Brunswick 1 & 2 2 18" 900 Tilting
Disc Check
3-80, Brunswick 1 & 2 2 18" 900 Tilting
Disc Check
COMMONWEALTH EDISON
8-80, LaSalle 1 & 2 4 24" 1500 Tilting
Disc Check
NORTHEAST UTILITIES
9-80, Millstone 1 4 18" 1500 Swing Check
NEBRASKA PUBLIC POWER
1-81, Cooper Nuclear 4 18" 900 Tilting
Disc Check
FLORIDA POWER & LIGHT
1-81, Turkey Point 2 2 1/2" 150 Swing Check
DUKE POWER
6-81, Oconee 6 24" 900 Tilting
Disc Check
PENNSYLVANIA POWER & LIGHT
6-81, Susquehanna 4 24" 900 Tilting
Disc Check
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Attachment 1
IN 84-12
February 27, 1984
Page 2 of 4
ANCHOR/DARLING CHECK VALVES WITH DUAL SEAT DESIGN
VALVE DESCRIPTION
ANSI
UTILITY, DATE, PRESSURE
AND FACILITY QUANTITY SIZE CLASS (NO.) DESIGN
COMMONWEALTH EDISON
6-81, LaSalle 1 & 2 2 10" 150 T-Globe
VERMONT YANKEE NUCLEAR POWER
8-81, Vermont Yankee 4 16" 900 Swing Check
TVA
10-81, Sequoyah 1 & 2 4 8" 150 Tilting
Disc Check
4 6" 150 Tilting
Disc Check
10-81, Watts Bar 1 & 2 4 8" 150 Tilting
Disc Check
4 6" 150 Tilting
Disc Check
ILLINOIS POWER
7-82, Clinton 2 18" 1500 Tilting
Disc Check
CAROLINA POWER & LIGHT
7-82, Brunswick 1 & 2 2 8" 150 Angle Globe
GEORGIA POWER
9-82, Hatch 1 & 2 2 20" x 16" x 20" 150 Y-Globe
2 10" x 8" x 10" 150 Y-Globe
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Attachment 1
IN 84-12
February 27, 1984
Page 3 of 4
ANCHOR/DARLING CHECK VALVES WITH DUAL SEAT DESIGN
VALVE DESCRIPTION
ANSI
UTILITY, DATE, PRESSURE
AND FACILITY QUANTITY SIZE CLASS (NO.) DESIGN
BOSTON EDISON
9-82, Pilgrim 1 1 20" 150 Y-Globe
Stop
1 8" 150 Y-Globe
Stop
SOUTHERN CALIFORNIA EDISON
9-82, San Onofre 1 2 1/2" 150 T-Globe
ARKANSAS POWER & LIGHT
11-82, Arkansas Nuclear 2 4" 600 T-Globe
One
PENNSYLVANIA POWER & LIGHT
12-82, Susquehanna 1 20" 150 T-Globe
1 10" 150 T-Globe
LONG ISLAND LIGHTING
1-83, Shoreham 2 18" 150 Y-Globe
2 8" 150 Y-Globe
WASHINGTON PUBLIC POWER SUPPLY SYSTEM
1-83, WNP-2 4 24" 900 Swing Check
CONSUMERS POWER
1-83, Big Rock Point 1 10" 1500 Swing Check
DETROIT EDISON
2-83, Enrico Fermi 2 1 20" 150 Y-Globe
1 10" 150 Y-Globe
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Attachment 1
IN 84-12
February 27, 1984
Page 4 of 4
ANCHOR/DARLING CHECK VALVES WITH DUAL SEAT DESIGN
VALVE DESCRIPTION
ANSI
UTILITY, DATE, PRESSURE
AND FACILITY QUANTITY SIZE CLASS (NO.) DESIGN
DUKE POWER
2-83, Oconee 3 6" 630 Swing Check
TVA
3-83, Browns Ferry 12 3/4" 1500 Swing Check
WASHINGTON PUBLIC POWER SUPPLY SYSTEM
4-83, WNP-2 1 10" 150 T-Globe
DETROIT EDISON
5-83, Enrico Fermi 2 2 24" 900 Swing Check
4 20" 900 Swing Check
2 12" 900 Swing Check
CINCINNATI GAS & ELECTRIC
6-83, W. H. Zimmer 1 8" 150 T-Globe
6-83, W. H. Zimmer 1 6" 1500 Tilting
Disc Check
DETROIT EDISON 10-83, Enrico Fermi 2 1 4" 900
Swing Check
2 1 1/2" 900 Swing Check
2 6" 150 Swing Check
