Information Notice 1987-40, Backseating Valves Routinely to Prevent Packing Leakage
SSINS No.:
6835 IN 87-40
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
August 31, 1987
NRC INFORMATION NOTICE NO. 87-40:
BACKSEATING VALVES ROUTINELY TO
PREVENT PACKING LEAKAGE
Addressees
All nuclear power reactor facilities holding an operating license or a con- struction permit.
Purpose
- -
Thislinformation notice is provided to alert recipients to potentially sig- nificant safety problems that could be caused by backseating valves routinely
to prevent packing leakage.
It is expected that recipients will review the
information for appliability to their facilities and consider actions, if
appropriate, to preclude a similar problem.
However, suggestions contained
in this notice do not constitute NRC requirements; therefore, no specific
action or written response is required.
...
Description of Circumstances
On-June 12, 1987, Virginia Electric and Power Company reported (Licensee Event
Report [LER] 87-011-00) that on May 16, 1987,-a low flow reactor trip occurred
at its Surry Power Station, Unit 1. The cause of the low flow was the failure
of the. stem of the A hot leg loop stop valve.
The stem failure permitted the
disk to drop and partially block flow in the A loop.
The licensee is performing
a detailed metallurgical examination to determine the failure mode and mechanism
of the valve stem. The preliminary report indicated that failure was due to
stress or fatigue.
Before this event, the licensee had routinely backseated the loop stop valves
as part of its Containment Checklist Procedure before startup.
In accordance
with this procedure, the valves were manually torqued onto their backseats to
1/16-inch deflection while the unit was in cold shutdown.
This value was
reverified when the unit reached a hot shutdown condition. To reduce the
stress on the valve stem, the licensee is revising the operating procedure
- so that the valves are normally operated off the backseat.
A similar event had occurred with the B hot leg loop stop valve on December 1,
1973.
This failure was evaluated by Westinghouse, and a failure report,'"Surry
Unit No. 1 Reactor Coolant Isolation Valve Stem Failure Report," was issued on
March 7, 1974. In the report, the failure mechanism was identified as a high
878250140
"lit
August 31, 1987 strain, low-cycle failure with little deformation. --
The high strain was at- tributed to the licensee's practice oftroutinely electrically backseating
the valves on torque during plant startup.
In this method, the valve's motor
operator is used to drive the valve open. until the forces resulting from the
disk pressing against the backseat are high enough to cause the open torque
switch to open.
This practice caused the valve stem to be subjected to high
stresses each time the valve-was opened.
Depending on the gearing within the
motor operator, these stresses may have remained until the valve was closed
during the next plant shutdown.
The report recommended that the valves not be electrically backseated on torque.
It further recommended that if backseating became-necessary during maintenance, it should be done manually by the use of the'handwheel with minimum' applied load
and without exceeding the compensating spring pack deflection specified in the
manufacturer's revised instruction manual.
This manual, "Instruction Manual
Motor Operated Reactor Coolant 30" Loop Stop Valves for Reactor Coolant System
Westinghouse WNES 546-CAK-70497B Darling Valve S.O. E-5004," states in a cau- tion that manual backseating is permissible only if the open deflector 'indicator
reading does not exceed 1/16-inch maximum and-that manual backseating may be
used only when the packing needs replacement.
As noted above, contrary -to this
recommendation, it- had been the licensee's recent poliGy to routinely manually
backseat these valves during plant startup.
Before the-1973-value-stem-failureit-hadabeen4,h4 censeei
seszpIactace
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routinely electrically backseat the valves during plant startup.
Although
Virginia Electric and Power Company had stopped this'practice in-1974, the- NRC staff is aware that other licensees routinely electrically backseat valves.
The most common reasonfor this is to stop valve leakage from around the stem
on valves that are not readily accessible during plant operations.
The following inspection reports reflect current practices and problems related
to electrical backseating.-
(1) NRC Inspection Report'50-321/85-34 provides the results of-an inspection
at Edwin I. Hatch Nuclear Plant, Unit 1, performed between November 10 and
December 20, 1985.
In the report, the inspectors noted observing informa- tion tags that'indicated that the reactor-core isolation cooling (RCIC)
system inboard steam line isolatio'n and the' reactor water cleanup- (RWCU)
system inboard-isolation valves had been electrically backseated. The
operating personnel indicated that they were not aware that any testing
had been done to verify that the valves would close within the required
time limits. -A violation was issued when subsequent testing of the RWCU
valve demonstrated that it could -not close within the required time'limits.
Additional testing of the RWCU valve showed that it did meet the closure
time limits'when it was not starting from a backseated condition.
NRC Inspection Report 50-321/86-22 and 50-366/86-22 provides the results- of an inspection performed at Hatch Units 1 and 2 between July 28 and
August 1, 1986., In the report, the inspectors noted that the licensee
routinely electrically backseated containment isolation valves in the high
pressure coolant injection, RCIC, RWCU, and recirculating pump systems.
-
K)
August 31, 1987 'Review of maintenance records Indicated that the'valves had, been electri- cilly backseated as many as 18 times during the previous 2 years.
The
procedure used by the licensee to electrically'backseat the valves con- sisted of bypassing the open limit switch and then driving the valve disk
onto the backseat until the locked motor current of the motor was ap- proached.
(2) NRC Inspection Report 50-277/86-25 provides the results of an inspection
at Peach.Bottom Atomic Power Station, Unit 2, performed between December 8 and 19, 1986. In the report, the inspectors noted the licensee's practice
of electrically backseating valves suspected of having excessive packing
leakage.
The procedure used by the licensee involved an operator manually
closing the motor contacts at the motor control center. The contacts were
held closed until the operator noticed an increase'in the motor current
shown on a clamp-on amp meter.
Discussion:
General Electric Company's Service Information Letter (SIL) 385 issued November
1982-discusses potential valve damage and provides recommendations for motor- operated valves that are normally backseated or are subjected to excessive
backseating torque. This describes the types of damage that could be the
result of backseating as valve stem failure, valve stem elongation, backseat
damage, .cracking of the-stem nut, and-other-re'lted compornent distress.-- It -
also notes that most damage progresses slowly to the point where valve oper- ability is uncertain or valve failure occurs, before the damage is apparent.
Among the recommendations were:
(1) identification of the valves that are normally backseated or that may have
had excessive backseating torque applied and establishment of a program
for evaluation, inspection, and repair of these valves
-(2) consultation with valve and motor operator vendors to establish any
procedures or modifications that could minimize damage, including the
use of torque switches or other vendor-recommended alternatives to
backseating motor-operated valves.
The inspectors also indicated that the licensees for the Hatch and Peach Bottom
plants are taking actions to prevent recurring packing leaks. 'Georgia Power
Company is instituting a program at the Hatch units to replace the packing on
these valves at regular intervals and also plans to live load the packing to
help prevent packing leakage. At Peach Bottom, Philadelphia Electric Company
is modifying the packing gland area, replacing the existing asbestos-based
packing with graphite packing, installing carbon bushings, and live loading
the packing.
The information herein is!being provided as an early notification of a possibly
significant matter that is still under consideration by the NRC staff. If NRC
evaluation so indicates, further licensee action may be requested.
August 31, 1987 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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
George A. Schnebli, Region II
(404) 331-5582
Larry E. Nicholson, RI, Surry Power Station
(804) 357-2102
Keith Poertner, RI, Edwin E. Hatch Nuclear Plant
(615) 842-8001
Richard J. Kiessel, NRR
=_
301) 492-9605 Attachment:
List of Recently Issued Information Notices
UNITEO STATES
NUCLEAR REGULATORY COMMISSI0N
WASHINGTON. D.C. 255
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IUSURCI
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OFFICIAL sUSINESS
PENALTY FOR PRIVATE USE. SM
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August 31, 1987 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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
George A. Schnebli,
(404) 331-5582 Region II
Larry E. Nicholson,
(804) 357-2102 Keith Poertner, RI,
(615) 842-8001
RI, Surry Power Station
Edwin E. Hatch Nuclear Plant
Richard J. Kiessel, NRR
(301) 492-9605 Attachment:
List of Recently Issued Information Notices
- SEE PREVIOUS CONCURRENCES
ERoss
08/2187
- PPMB:ARM *C/OGCB:DOEA:NRR
TechEd
CHBerlinger
08/21/87 08/24/87
- OGCB:DOEA:NRR
RJKiessel
08/17/87
- RII
GASchnebli
08/19/87
- RII
FJape
08/19/87
- RII
ARHerdt
08/19/87
- RII
LReyes
08/19/87
IN 87-XX
August xx, 1987 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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
George A. Schnebl1, Region II
(404) 331-5582
Larry E. Nicholson, RI, Surry Power Station
(804) 357-2102
Keith Poertner, RI, Edwin E. Hatch Nuclear Plant
(615) 842-8001
Richard J. Kiessel, NRR
(301) 492-9605 Attachment:
List of Recently Issued Information Notices
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA:NRR
RJKlessel
08/17/87
- RII
GASchnebli
08/19/87
- RII
FJape
08/19/87
- RII
ARHerdt
08/19/87
- RII
LReyes
08/19/87
- PPMB:ARM
TechEd
08/21/87 D/DOEA:NRR
CERossi
08/ /87 C/OGCB:DOE
NRB
CHBerlinge&4 4 -1Y
08t/q/87
-
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'bin.-
IN 87-XX
August xx, 1987 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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
George A. Schnebli, Region II
(404)331-5582 Larry E. Nicholson,
(804) 357-2102 Keith Poertner, RI,
(615) 842-8001
RI, Surry Power Station
Edwin E. Hatch Nuclear Plant
Richard J. Kiessel, NRR
(301) 492-9605 Attachment:
List of Recently Issued Information Notices
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RJKiessel
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08/g7/87
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CJ?
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kSchnebli
3/J4/87 RuI
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08/lq/87 RH J
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08/if/87 D/DOEA:NRR
CERossi
08/ /87 PPMB:AR FC/OGCB:DOEANRR
TechEdW4 CHBerlinger
08/jl/87 08/ /87