United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-81: Broken Inner-External Closure Springs on Atwood & Morrill Main Steam Isolation Valves

                                                            SSINS No.: 6835 
                                                            IN 86-81       
                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                             September 15, 1986

Information Notice No. 86-81:   BROKEN INNER-EXTERNAL CLOSURE SPRINGS ON 
                                   ATWOOD & MORRILL MAIN STEAM ISOLATION 
                                   VALVES 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit. 

Purpose: 

This notice is provided to inform recipients of a potentially significant 
safety problem that could result from broken inner-external closure springs 
on main steam isolation valves (MSIVs) manufactured by Atwood & Morrill Co.,
Inc. The springs that failed were manufactured by Duer Spring and 
Manufacturing Co. Quench cracks, which apparently developed during the 
manufacturing process, caused the springs to fail. 

It is expected that the recipients review the information for applicability 
to their facilities and consider actions, if appropriate, to preclude a 
similar problem 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: 

During an inspection of MSIVs following low-pressure seat leakage tests at 
Enrico Fermi Unit 2 in May 1986, the licensee observed that four 
inner-external closure springs were broken into two-to-seven pieces. The 
licensee analyzed two of the broken springs and determined the failure to be
quench cracking caused by the heat treatment process during manufacturing. 
There are eight MSIVs with eight inner-external and eight outer-external 
closure springs per valve. All outer-external closure springs were found 
intact and undamaged. All 64 external springs were from the same heat number
(#8067703). The external closure-spring assemblies (inner and outer) perform
a safety function to close the MSIVs. 

Discussion: 

Springs from Duer Spring and Manufacturing Co. were supplied to PWR and BWR 
nuclear power plants on MSIVs manufactured by Atwood & Morrill. The external
closing springs that failed at Fermi 2 were the inner springs around the 
valve yoke rods. The following effects on valve operation could occur with 
one or more springs failing: 


8607110318 
.

                                                       IN 86-81          
                                                       September 12, 1986 
                                                       Page 2 of 2       

1.   Slower closing time with steam in the normal forward flow direction. 
     For BWRs, General Electric estimates the closure time would increase 
     from the Technical Specification requirements of 3 to 5 seconds but 
     will remain under 10 seconds. 

2.   Increased difficulty in meeting low-pressure seat leakage test, 
     requirements in BWR units. 

3.   Valve closure with steam in the reverse flow direction in PWR units 
     could be adversely affected since the springs provide the only external
     closing assistance. Internal closing assistance is provided by the use 
     of a pilot poppet design in these valves. 

The spring manufacturer also performed laboratory metallographic examination
of the failed springs and verified that the failure was the result of quench
cracking. Atwood & Morrill and Duer Spring have recommended that at the 
first available opportunity all the external closing springs on all MSIVs be
cleaned and magnetic particle testing be performed. Duer has provided an 
inspection procedure. 

Atwood & Morrill is issuing a letter to all affected customers concerning 
this event which recommends that the above actions be taken. The Atwood & 
Morrill list of affected units is attached. In addition, General Electric 
has issued a service information letter, SIL No. 442 dated July 18, 1986, to
owners of affected BWRs recommending a visual inspection and, in some cases,
load tests. The NRC has reviewed the two procedures and has determined that 
either recommendation is adequate for BWRs. For PWRs, only the Atwood & 
Morrill recommendations are appropriate. However, consideration should be 
given to visual inspections of the springs following any cycling of the 
valve until completion of the Atwood & Morrill recommended inspection. 

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. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  J. C. Stone, IE
                    (301) 492-9044

Attachments:
1.   List of affected plants as identified by Atwood & Morrill
2.   List of Recently Issued IE Information Notices
.

                                                        Attachment 1      
                                                        IN 86-81          
                                                        September 15, 1986 
                                                        Page 1 of 3        

                        ATWOOD & MORRILL CO., INC.

                        Main Steam Isolation Valves
                  Furnished With External Closing Springs
                 Manufactured by Duer Spring & Manuf. Co. 

                                 PWR UNITS

Utility             Station             Quantity and Valve Size 

Duke Power Co.      Catawba 1 & 2       8 34-inch 

Duke Power Co.      McGuire 1 & 2       8 32-inch

Duke Power Co.      Perkins 1, 2, & 3   12 32-inch Units Cancelled 

Duke Power Co.      Cherokee 1, 2, & 3  12 32-inch Units Cancelled 

Houston Lighting    South Texas         8 32-inch 
  & Power             Project 1 & 2     

South Carolina      Virgil Summer 1     3 32-inch 
  Elec & Gas 

TVA                 Bellefonte 1 & 2    8 32-inch 

TVA                 Sequoyah 1 & 2      8 32-inch 

TVA                 Watts Bar 1 & 2     8 32-inch 
.

                                                        Attachment 1      
                                                        IN 86-81          
                                                        September 15, 1986 
                                                        Page 2 of 3       

                        ATWOOD & MORRILL CO., INC.

                        Main Steam Isolation Valves
                  Furnished With External Closing Springs
                 Manufactured by Duer Spring & Manuf. Co.

                                 BWR UNITS 

Utility             Station             Quantity & Valve Size 

Boston Edison       Pilgrim 1           8 20-inch 

Cleveland Elec.     Perry 1 & 2         16 26-inch Illuminating 

Detroit Edison      Enrico Fermi 2      8 26-inch 

Georgia Power       Hatch 1             8 24-inch 

Gulf States Util.   River Bend 1        8 24-inch 

Houston Lighting    Allens Creek 1      8 24-inch Unit cancelled 
& Power 

Illinois Power      Clinton 1           8 24-inch 

Jersey Central      Oyster Creek 1      4 24-inch 
Power & Light 

Mississippi Power   Grand Gulf 1 & 2    16 28-inch 
& Light 

Niagara Mohawk      Nine Mile Point 1   2 24-inch 
Power Corp. 

Northern States     Monticello          8 18-inch 
Power Co. 

Pennsylvania        Susquehanna 1 & 2   16 26-inch 
Power & Light 

Philadelphia        Limerick 1 & 2      16 26-inch 
Electric 

Philadelphia        Peach Bottom 2 & 3  16 26-inch 
Electric 

Public Service      Hope Creek 1 & 2    16 26-inch Unit 2 cancelled 
Elec & Gas 
.

                                                        Attachment 1      
                                                        IN 86-81          
                                                        September 15, 1986 
                                                        Page 3 of 3       

                        ATWOOD & MORRILL CO., INC.

                        Main Steam Isolation Valves
                  Furnished With External Closing Springs
                 Manufactured by Duer Spring & Manuf. Co.

                                 BWR UNITS

Utility             Station             Quantity & Valve Size TVA                 
Browns Ferry 1, 2,  24 26-inch 
                      & 3 

TVA                 Hartsville A1, A2,  32 26-inch Units B1 & B2 
                      B1 & B2                          Cancelled 

TVA                 Phipps Bend 1 & 2   16 26-inch Units cancelled 
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