United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-12: Failure of Soft Seat Valve Seals

                                                          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. 
.

                                                        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). 
.

                                                        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  
.

                                                        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 
.

                                                        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 
.

                                                        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 
.

                                                         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

Page Last Reviewed/Updated Tuesday, November 12, 2013