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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