ML20091Q586
| ML20091Q586 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 01/27/1992 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9202050019 | |
| Download: ML20091Q586 (10) | |
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BALTIMORE
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GAS AND ELECTRIC 1650 CALVERT CUFFS PARKWAY 1.USBY MARYLAND 20657-4702 GEonor C. CREEL, Vict PRgsIDENT NvcktA4 ENERGY (4 to) ROO-44 5L Janucry 27,1992 U. S. Nuclear Regulstory Commission Washington,DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Cah*ert Cliffs Nuclear Power Plant Unit No.1; Docket No. 50-317 Rearest Relief from ASME Boiler & Pressure Vessel Code Section XI Reduirement IWV-3417(a)
Gentlemen:
Baltimore Gas and Electric Company requests relief from ASME Boiler & Pressure Vessel Sect. XI requirement IWV-3417(r) as allowed under lo CFR 50.55 a(a)(3). We specifically request relief f om monthly full-strok testing of Unit 1 No.12 Main Steam Isosation Valve (MSIV) for the remainder of Unit l's operating cycle. Compliance with thi:: requirement would resuit in hardship without cotnpensatory quality or safety improvement.
I.
Component for Which Reliefis Requested; A.
Main Steam Isolation Valve 1-MS4048-CV (No. 12 MSIV) is a 34-inch, hydraulically-eperated, "Y" pattern globe valve, madc by Rock well-Edward Valve.
B.
The No.12 MSIV design funaion is to c!csc within six seconds from receipt of an L
isolation signal, thereby preventing rapid blowdown of Steam Generator (SG) shell-side water and uncontrolled cooldown of the Reactor Coolant System. The valve also l
closes to prevent contaimnent release cf 3G shell-side contents (both generators) into containment d tring Main Steam Line Break (MSLB).
j2 C.
The applicab!e ASME Sect. III Code Classificetion for this valve is Class 2.
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D. '
Tha applicable ASME Sect. XI Valve Category is B (IW%2200: seat leakage L
inconsequential to fulfillment of valve's function).
E.
Full-stroke test frequt.ncy is every 92 days in Cold Shutdown (Mode 5) conditions.
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Document Control Desk
.lanuary 27,1992 -
Page 2 II.
Code Requirements for Which Relleris Requested:
IWV-3417(A) states:
"[ijf, for power-operated valves, an increase in stroke time of.. 50 percent or more for valves with full-stroke times less than or equal to 10 seconds is observed, test frequency shal; be increased to once per month until corrective action is taken...."
Ill.
Proposed Alternative:
We propose performing a monthly partial-stroke test of No.12 MS!V using each of its two hyd nul9 Jump-valve circuits. This provides appropriate safety assurance until Unit l's next seh :duled outage (currently planned for March 6,1992 ).
IV.
Supportine Information; A.
Sequence of Events:
During an untilanned outage on December 23,1991, our staff performed Surveillance Test Procedure (STP) O-1-1, "MSIV Fud-Stroke Test." whe t Unit I was in Ifot Shutdown (Mode 4) even though the test was not required The No.12 M.c!V full stroke was timed at 4.05 see., less than the Technical Specification aceptance va' sue (5.2 sec.). The test procedure did nat identify the ACME alert value for the valve i
(greater than 3.1 sec.), and therefore the operators evalusted the test as satisfactory.
Test-result review relative to alert value criteria is narmally done by the Functional Surveillance Test Coordinator (FSTC) prior to restarting the unit. Because of the unplanned nature of the test, it was not reviewed by the FSTC prior to startup and the slower than normal stroke time was not recognized until later.
On December 30,1991, the FSTC reviewed the test and determined that No.12 MSIV had tested in the Alert Range. Unit 1 was operating at 30 percent power. An
. Issue Report was written and plant staff notified. STP 047-1, "MSIV Partial-Stroke Test," was performed shortly after. Test results were compared with six previous tests dating ba :k to August 29,1991. No abnormal trends were noted.
B.
MSIV Control-Circuit
Description:
- Attachment (1) is a simpliG.:d MSIV electric / hydraulic wutrol. circuit diagram. The valve closes when either solenoid vah e opens, releasing pilot pressure from under the hydraulic dump valves. When either dump valve opens, hydraulic pressure under the I.
MSIV piston is vented, stroking the valve. The bench-tested maximum closing time is l
five seconds for one open dump valve. The bench-tested ruasimum closing time with both dump valves open is three seconds. Normally, both dump valves function to quickly stroke the valve. During a post. installation test under Mode 5 conditions, the valve closed in-4.5 seconds with only one open dump valve.
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Document Control Desk l
, January 27,1992 -
Page 3 C.
Analysis:
Site mgineering staff analyzed the potential causes of the slower stroke time. This analpis included: i) a ;cview of the valve control circuit, ii) a comparison of STPs O-1 1 and 0-47-1 (Attachment 2) and their results, iii) consultation with the vendor, and iv) a review of No.12 MSIV maintenance history (Attachment 3). This analysis included the MSIV nd its actuator and is summarized on Attachment (4).
Two potential causes for increased MSIV stroke time were identified. These are:
1.
Dump-valve solenoid-poppct-scal mechanical friction.
Valve history indicates a 2.1 +/- 0.1 sce. MSIV etroke time (closing). Actual stroke time was 4.05 sec.. Plant and vendct experience is that a stroke-time of this length is indicative of single dump-valve operation. The vendor has experienced cases where poppet seals became " tacky," resulting in slow poppet shifting. After shifting. the poppets become lubricated and continne to shift normally. This is deemed the most likely cause.
Solenoid dump valves are normally overhauled at each refueling outa,,c.
These valves were iast overhauled in spring of 1989. They will be overhauled again during the spring 1992 refueling outage.
Currently, STP O-47-1 is perfortred monthly rui alternate dump valves. He STP will now be performed on both dump valves monthly. His will ensure the poppet seal temains lubricated. This test will be performed on all four MSIVs for both units.
2.
Intermittent handswitch contacts or loose dump-valve-circuit electrical contacts.
STP O-47-1 tests portions of the control circuit. No apparent circuit discontinuity problems were evident when tested.
UFSAR accident ana' sis allows a single dump-valve failure coincident with an additional ingle-atuve failure. A kiose electrical connection affecting a single dunip-valve solenoid is not,' therefore, safeif significant. Additionally, intermittent handswitch contacts-do not affect - MSIV automatic safety functions.13ecause the handswitch is not part of the automatic safety-signal path, a problem with this component would not affect valve's-. accident-response.
D.
Safety Significance Recurrence of slow MSIV operation n not expected. The proposed compensatory r
action should prevent poppet-scal adherence-Nevertheless, if slow valve -operation like that of December 23 reoccurs, the lL condition is bounded by the UFSAR safety analysis. This analysis assumes a 6 see.
closing time: we would expect to see less than 4.5 sec. for a slow poppet. The MSLB analysis assumes one MSIV fails epen.
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1 Document Control Desk inouary 21 1992 Page 4 E.
Code-Requirement Performante Impact Valve full-stroke testing will result in a hardship (plant shutdown to Hot Standby
[hiode 3]) without compensating increase in the level of quality and safety.
F.
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Conclusion:==
Both possible causes identified in Section C, above, world result in only one hydraulic dump valve to fail to INT quickly. h% thly full-stroke testing offers no advantages t
over modified partial stroke testing in assuring continued Operability. Additionally, failure of both dump valves is bounded by the UFSAR htSI B analysis.
Our analysis demonstrates that the valve remains Operable.
IV.
Compensatory \\ctions:
A.
Perform modified partial-stroke test to increase poppet-cycling frequency.
B.
Perforp' f"It itroke testing (plant conditions perraitting).
C.
Overhaut valve actuator next refueling outage.
VI.
Implementation Schedule:
A.
Modified partial-stroke test -- hionthly begun December 30.1991.
B.
Full-stroke testing -- when conditions permit.
C.
Valve overhaul -- Unit 1 Spring-1992 outage.
Safety Committee Review 4
The proposed relief request has been reviewed by our Plant Operations and Safety Review Committee and they concluded compliance witn IWV-3417(a) would result in hardship without compensatory quality or safety improvement.
Relief is requested through April 1,1992. Your reply is needed by.Tanuary 30, 1992 to avert operational impact. Should you have any questions regarding this matter, we will be pleased to discuss them with you.
'NVery truly yocrs, 1
f W
1 I
for Vice President - Nuclear Energy GCC/JMO/REF/dtm
Document Coi.irol Desk January 27,1992 Page 5 -
Attachments: (1)
Simplified MSIV Hydraulic Diagram (2)
Description of Tests (3)
Valve History (4)
Root Cause Analysis cc:
D. A. Brune, Esquire
- 1. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald. Jr., NRC T. T. Martin, NRC P. R. Wilson, N RC R. I. McLean, DNR J. II. Walter, PSC
SIMPLIFIED MSIV
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HYDRA.ULIC DIAGRAM i
3 C:Q Cs r
/ VALVE '
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ACTUATOR TO RESERVOIR --f'
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'l TEST FLOW OUMP MANUAL ORIFICE CONTROL VALVE ISOLATION i
VALVE I
l CHANNEL B FROM PUMP
>05 R
7, H
^
0--
Ddd 2
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i l
(*
TO RESEh0IR
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TEST FLOW DUMP MANUAL ORIFICE LvNTROL VALVE ISOLATION VALVE iANNEL. A
NITACIIMENT (2)
DESCRIPTION OF TESTS Full Stroke Test (STP O 1)
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Both channels actuate simultaneously, Dump-valve solenoid energizes to reposition dump valve, flybaulic fluid vents to reservoir, o
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Valve rapidly strokes shut, r_artial Stroke Test (STP O 17)
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Each channel tested independently,
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Test-orifice solcnoid energizes to insert test orifice in dump path,
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Damp-valve solenoid energizes to reposition dump valve,
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11ydraulic fluid vents to reservoir, Valve slowly stroker, to 90% open, Dump-valve solenoid de-energizes and dump valve repositions to isolate dump path,
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Test-orifice solenoid de-energizes to remove test orifice from dump path, n pump operates to return valve to 100% open.
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Y O
ATTACl!%1ENT (3)
' VALVE I11 STORY SPRING 1990:
Valve failed tr. full open due to oversized rider ring in conjunction with foreign material in valve.
Replaced upper rider ring. Also replaced actuator with actuator from No. 22 MSIV. Replacement actuator last overhaul < 4 spring 1989. Valve stroke time did i. it exceed the Technical Specilication value during as-found testing.
SPRING 1990:
With valve stuck in intermediate position, valve would not close using control-room handswitch.
Neither dump solenoid energii.ed when handswitch was placed in SilUT. Replaced handswitch.
FAI,1,1990:
With unit at power and valve full open, received intermittent test-valve closure alarms. Replaced timer module in test-valve closure circuit.
I)ECEMilEll 1991:
Routine oil analysis indicated higher than normal acid content. Foam visible on oil surface in reservoir. Replaced hyd.. ulic fluid with unit at power, valve in full open position.
12 MSIV Full-Stroke Test Results (seconds) 04/02M) 2.18 09/15M) 2.16 12/16NO 2.20 05/20S 0 2.09 07/04SO 2.10 12 MSIV Partial-Stroke Test 1)ates Dump Circuit A Dump Circuit B 09/1031 08/29Si 11/05N1 10/24Si 12/31h1 12/01 S1 12/31 S 1 t
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i birACIIMENT (4)
ROOT CAUSE ANALYSIS POSSilllE CAUSES OllSElWATIONS 1.
MSli stroke problem.
a.
Packing / stem friction.
Discounted - nothing noted during STP O-47-1.
b.
Piston ring friction.
Discounted - nothing noted during STP O-47-1.
c.
Check va've assembly friction.
Discounted - nothing noted during STP O-471.
NOTE: STP O-47-1 only moves valve -
stem apptoximately 21/2 inches. An Operations Shift Supervisor locally witnessed the fnll-stroke test of Nos.11 & 12 MSIV on 12/23f>1. Both valves were observed to operate as expected.
2.
Dump valve did not shift.
a.
Probicm wi:h dump solenoid coil.
Discounted - functioned correctly during STP O-47-1.
b.
Handswitch contact problem.
c.
Dump valve solenoid circuit loose Portions tested during STF O-47-1 connection.
functioned correctly, d.
Dump valve and seat adherence.
Discounted - functioned correctly during STP O-47-1. Vendor assessment not a likely occurrence, c.
Solenoid poppet and seat adherence.
Functioned correctly during STP 047-1.
Vendor assessment - possil'le cause based experience with similar actuators.
3.
Hydraulic-fluid-flow-path obstruction.
a.
Fluid quality problem.
Discounted ruled out by oil analysis.
Higher acidity was noted but it would not catee response time to slow, b.
Flow-; ith test orifice.
Discounted - verified correct position.
- c.
Valve misalignment Discounted - valve line-up s crified correct. Flow control valve assumed correct. No evidence to suggest flow control valve misaligned.
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ATTACilMENT (4)-
'i ROOT CAUSE ANALYSIS
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POSSill! E CAUSES OllSERVATIONS 4.
Actuator stroke problem.
a.
Piston ring friction.
Discounted - no leakage observed.
STP O-47-1 we normal.
b.
Scal friction.
No leakage observed. STP O-47-1 was normal.
5.
Valve limit-switch problem Discounted - functioned during -
STP O-1 1 on 12/24St. Operated satisfactorily using manual actuation on ISN2.
6.
Timer problem.
Discounted timer was within calibration dates. Same timer operated properly on No.11 MSIV. Timer calibration verified on 1/#12. Timer and limit switch circuit tested in place on 1992.
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