IR 05000267/1988006
| ML20151M736 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/25/1988 |
| From: | Ireland R, Norman D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20151M733 | List: |
| References | |
| 50-267-88-06, 50-267-88-6, IEB-85-003, IEB-85-3, NUDOCS 8804250118 | |
| Download: ML20151M736 (8) | |
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a APPENDIX U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
NRCilnspection Report:
50-267/88-06 Operating License:
DPR-34-Docket:- 50-267 Licensee:
Public Service Company of Colorado (PSC)
2420 W. 26th Avenue, Suite 15c Denver, Colorado 80211 Facility Name: Fort St. Vrain Nuclear Generating Station (FSV)
Inspection At: Platteville, Colorado Inspection Conducted:
February 29 through March 4,1988 i
Inspector:
A [ c (. / [o SM'# A m:va D. E. Norman, Reactor Inspector, Plant Systems Date Section, Division of Reactor Safety Approved:
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R. E. Ireland, Acting ChieY, Plant Systems Date Section, Division of Reactor Safety J
Inspection Sumary Inspection Conducted February 29 through March 4, 1988 (Report 50-267/88-06)
Areas Inspected:
Routine, unannounced inspection of licensee's actions related to IE Bulletin 85-03.
Results: Within the areas inspected, no violations or deviations were identified.
880425011e 88041e PDR ADOCK 05000267 O
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-2-a DETAILS
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Persons Contacted
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T. McIntire, Supervisor, Nuclear Site Engineering
- J. Southers Engineer, Nuclear Site Engineering
- N. Snyder, Superintendent, Maintenance
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- P. Tomlinson, Manager, Quality Assurance Division NRC
- P. Michaud, Resident Inspector
- Denotes those present at the exit interview on March 4,1988.
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2.
IE Bulletin (IEB) 85-03 IEB 85-03, "Motor Operated Valve Common Mode Failure During Plant
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Transients Due to Improper Switch Settings," expressed concerns about the proper setting of switches that control the operation of motor operated i
valves (MOV). Action Item (a) of the bulletin requires that the design
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basis for the operation of each high pressure coolant injection / core spray i
t and emergency feedwater systems (RCIC for BWRs) that are required to be i
tested for operational readiness be reviewed and documented; Item (b)
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requires that correct switch settings be established; Item (c) requires differential pressure testing, preferably, or other justification to
demonstrate operability with settings from Item (b);-Item (d) requires plant procedures that wil? assure the maintenance of correct switch i
settings throughout plant life; Item (e) requires a written report from accomplish Items (b) ports results of Item (a) and contains the prcgram to the licensee that re
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and (d), including a schedule for completion of the
items; and Item (f) requires a written report of the completed program.
The status of each item is discussed below:
a.
Items (a) and (e) - The valves covered by the bulletin, and their
design basis, were provided by the licensee by letter dated May 14, 1986. The bulletin addressed specific systems for PWR and BWR I
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reactors which required valve testing.
The licensee selected systems from the high temperature gas cooled reactor which were considered i
analogous to the PWR and BWR systems addressed by the bulletin.
The rationale for the systems selected was presented in Attachment 2 to the submittal.
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Results of a staff review of the submittal will be included in a j
subsequent NRC inspection report.
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Item (b) - Licensees were required to establish switch settings to assure valta operability at the pressure differentials presented in Item (a).
Based on data from the M0 VATS Corporation data bank, settings for most valves at FSV were determined by calculating minimum thrusts required to open or close valves at maximum. expected differential pressures. This value, with added-conservatism, was then compared to the operator and valve design limits to ensure'that limits had not been exceeded.
Torque switches were adjusted so that the operators would deliver the target thrust values during the valve tests.
Several stop-check valves driven by SMB-4T operators could not be set by the above method, since absolute thrust values could not be measured with the test equipment.
For those valves specific values for torque switch scale settings were provided by Limitorque.
c.
Item (c) - Typically, valves included within the scope of the bulletin are rising-stem gate or globe valves with Limitorque operators. At FSV several Limitorque operated stop-check valves are also installed in systems which the licensee deems to be covered by the bulletin.
The valves were all tested by the M0 VATS Corporation signature analysis system. While the system is capable of doing a comprehensive analysis of most valves, it could not ieliably measure thrust for certain SMB-4T/stop-check valve combinations, and the torque switches could not be set to specified thrust values.
A discussion of each switch which controls operation of Limitorque valve operators follows:
(1) Thermal Overload Relay - These relays are used primarily to protect continuous duty motors while running rather than during starting.
If not properly sized, the effects of successive starts and high loads during valve seating or unseating could cause an undesired interruption of power to the motor and prevent proper operation of the actuator, _ Regulatory Guide (RG) 1.106, Revision 1, dated March 1977, addresses this potential problem and presents a choice of two regulatory positions to be implemented.
By Change Notice (CN) 2119, dated October 13, 1986, the licensee implemented the position stated in Section C, paragraph 1(b) of the RG, which states, "Those thermal overload protection devices that are normally in force during plant operation should be bypassed under accident conditions."
The licensee's actions regarding M0V thennal overloads appear to be acceptable.
(2) Torque Switch 0)en (TS0) - The TSO is used to limit mechanical thrust applied >y an operator to a valve during the opening stroke in order to prevent damage to the operator or valve,
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-4-These switches are usually bypassed to prevent interruption of a safety function in the event-the torque switch should actuate.
Torque switchec had been replaced as part of the operator EQ upgrade program; therefore, as-found data which would have shown the operability status of the operators / valves was not available.
The switches were reset during testing at either the target thrust or the torque switch scale setting determined as described above.
Valves were then stroked during startup, when a high system pressure was available, to verify operability under valve differential pressure conditions.
Because of limitations imposed by systems configurations, the maximum design basis differential pressures could not be duplicated during testing; however, a simulated load was applied to the valves to represent the maximum expected differential pressures needed for switch adjustment.-
It was also found during the inspection that valves HV-2237 and HV-2238 had not been tested with a differential pressure, and operability had been established by comparison to HV-3108 which had been tested.
The valve operators are the same model; however, the valves are different, and the basis for comparisor.
was not established. HV-2237 and HV-2238 are Walworth Model P-418313, 8-inch globe valves, and HV-3108 is a Rockwell Edward Model 5906MY, 10-inch stop-check valve. This stop-check valve is a boiler feed pump isolation valve which must open or
close under a design differential pressure of 4500 psi. This capability was established by the tests performed. On the other
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hand HV-2237 and HV-2238 are emergency condensate valves which l
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must open or close with a design differential pressure of i
450 psi.
Since all three of these valves use SMB-4T operators, it is clear that the condensate valves have sufficient thrust.
Torque switches have been set to protect the valves and the operators from damage.
In order to complete the test records, the licensee should provide a comparability analysis of these globe and stop-check valves in association with valve operator thrust requirements.
Pending review of this analysis, this is consideredanopenitem(267/8806-01).
(3) Torcue Switch Close (TSC) - The clo:e torque switch is normally usec to limit valve closure thrust; howeve'
closure uf butterfly valves and some globe and gate valves is centrolled by the close limit switch. Since the TSC provides a normal control function and is exercised on every closure stroke, setting requires more careful consideration than for the open torque switch.
The limiting requirement is at the end of travel when the thrust requirements are highest, the effect on flow control is most significant, and the switch is not bypassed.
It is, j
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envelope the most limiting thrust requirement and that margin be available to allow for valve and operator degradation. Also to be considered at the upper setting limit are valve and operator design limits and available operator' motor torque at reduced
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voltage input.
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As stated in paragraph 2.C.2, as-found data were not availa91e.
i Switches were set to the target values and tested in the same
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manner as the TSO were tested.
The licensee's actions concerning the TSC settings appear to be acceptable.
(4) Open Limit Switch - The open limit switch provides control for the upper limit of valve stem travel in the open direction and stops the valve operator motor at the proper time to assure proper valve stroke and to prevent inadvertent valve backseating. Undesired backseating has caused valve stem
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shearing, stem thread twisting, or valve bonnet metal working
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which could result in stem scoring and packing blowout.
It is necessary to set the open limit switch away from the backseat, with margin to allow for motor contactor dropout time and inertia.
Independent verification should be done to assure that the switch has been properly set.
The open limit switch should
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not be used for adjusting the stroke time since this could stop i
the valve prior to being fully opened.
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It could not be determined from the data reviewed at what i
position open limit switches were set.
There were also no requirements in the maintenance procedures for setting the
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switches and for independently verifying that the valves had not backseated.
It was stated that training instructions covered limit switch setting and that proper setting to prevent
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i backwating had been verified from the M0 VATS thrust signature,
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During the inspection, the maintenance procedures were revised to include open limit switch settings. Also included in the
revised procedures was the requirement to verify that valves had t
stopped at 1 1/2 handwheel turns away frem the backseat.
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revisions to the maintenance program appear to be adequate to demonstrate control of valves at the open position.
(5) Close Limit Switch - Close limit switches are not used on the
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valve operatcrs at FSV.
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(6) Open Torque Switch Bypass - When an open torque switch is used, bypassing the switch during the initial portion of the open stroke is required so that the switch will not prematurely stop valve travel because of the high torque condition required for initial valve movement.
There is no specific requirement for the amount of valve travel during which the torque switch should
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i be bypassed so long as the initial high torque requirement has been bypassed.
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i Procedures at F3V require torque switches to be bypassed for a
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minimum 20 percent of the opening stroke, beginning from the l
time that the operator starts to develop thrust. Data reviewed
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showed that the open torque switches had been bypassed from
20.3 percent to 24 percent of the valve stroke.
This part of the switch setting program appears to demonstrate i
acceptable setting of the open torque switch bypass.
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(7) Close Torque Switch Bypass - Torque switches are not bypassed
ouring the closing stroke at FSV.
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Item (d) - This item requires that the licensee prepare or revise procedures to ensure that correct switch settings are determined and maintained throughout the life of the plant. The following documents
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which contained switch setting procedures were reviewed during the
inspection:
PEP-9, Issue 1, dated January 6, 1988, "Motor Operated Valve
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Program"; and
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HPE-1675-EQ Issue 3, dated August 19,1987, "Testing of Motor
Operated Valves Using MOVATS-2100/2150 Signature Analysis System j
with Baseline Signatures."
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valve operators, were not included in the procedures.
This was considered a weakness in the procedures.
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There were no instructions for setting the open limit switches.
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Reduced voltage operation was not considered in determining the i
thrust available from cperators and in selecting torque switch targets, j
Acceptance criteria were not presented for motor running
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current.
During procedures review, it was observed that no requirement existed
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for torque switch limiter plates to be installed and it appeared from the valve testing data that the limiter plates were not in place.
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The limiter plates were originally installed by Limitorque to prevent i
adjustment of torque switches to values which could exceed operator i
design limits, and may have been removed when operators were environmentally qualified. The limiter plate is especially significant for those operators for which thrust values could not be
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reliably measured.
During this inspection, the licensee obtained maximum allowable torque switch settings from Limitorque for the questionable operators; based on those values, no switches had been
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set above the allowable limits. However, since torque switches hed
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accuracy of the maximum allowable settings is questionable.
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Pending resolution of this question, this item is considered unresolved (267/8806-02).
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Item (f) - The required report was submitted by the licensee on l
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January 14, 1988, and will be reviewed by the staff.
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observations were made concerning the submittal:
r (1) The explanation was incomplete for the techniques used to set i
torque switches.
For instance, the M0 VATS system was used to t
set most switches at a desired target thrust; however, certain
operator / valve combinations could not use the M0 VATS method, and t
the switches were set to a desired TS scale reading.
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(2) No explanation of switch control schemes was made.
For example, s
the following aspects should be made clear:
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Valve opening and closing is controlled by torque switches.
Valve open position is controlled by a limit switch which j
is adjusted to prevent backseating.
Closed limit switches
are not used.
r Open torque switches are bypassed for 20 percent of the l
valve stroke to prevent premature tripping.
Bypassing of j
close torque switches is-not used.
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Bases are needed for sizing and operation of thermal overloads during testing, normal operation, and emergency
situations.
3.
(0 pen) Open Item 267/8636-01:
During the EQ outage, the licensee performed a walkdown inspection of all EQ equipment at which time numerous I
problems were identified. As a result of the problems, a two-phase program was identified in CAR 86-105, which required inspection of all non-EQ safety-related equipment. Phase I of the program, which had to be
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completed prior to reactor power operation, determined whether repairs were needed to establish the operability of electrical and I&C equipment.
Phase II was begun shortly after completion of Phase I and involved a systematic review and walkdown of plant systems and components to verify as-built configurations and nameplate data.
Phase II was expected to
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require from 1 to 2 years to complete.
The status of Phase II was reviewed by the NRC inspector and is shown below:
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30 systems identified to be walked down
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4 system walkdowns in progress 13 systems have not been started b.
Program completion delayed by the fire and by the check valve walkdown(SOER83-06)
c.
Typical problems identified by walkdown 44 components had missing model number and/or manufacturer identification 16 components had cescription problems
4 components had wrong model number
3 safety-related maintenance deficiencies identified (These subsequently could not be substantiated.)
This item will remain open pending completion of the Phase 11 program.
4.
Unresolved Item 3 Unresolved items are matters about which more information is required in order to ascertain whether they are acceptable items, items of noncompliance, or deviations.
One unresolved item is discussed in paragraph 2.d.
5.
Exit Interview An exit interview was conducted on March 4, 1988, during which time results of the inspection were reviewed with members of the FSV staff.
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