ML20040D763
| ML20040D763 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/21/1982 |
| From: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8202020229 | |
| Download: ML20040D763 (4) | |
Text
y Docket No. 50-362 a
50 55(e) Report TICOVa t: n Southern California Edison Company gE G2 JAN 25 % D p
,. o.,0, oo 2244 WALNUT GROVE AVENUE ROSEMEAD, CALWORNIA 91770 vtCE P.tSsDisef
$13 572 -1474 January 21, 1982 C
Y Mr. R. H. Fn ge lken, Dire cto r iiEC'mlED Of fice o f In spection and En forcement t'
U. S. Nuclear Pe gulatory (bmmission 9_1 FEB 11992> J2 Re gion V n t::u tcrm m a '/
1450 Maria Lane, Suite 210 c'-
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Walnu t Cree k, Califo rn la 94596-5368 N
De ar Mr. En gelken:
03 Subje c t:
Ib cke t No. 50-36 2 San Onofre Nuclear Generating Station, Unit 3 In a le tte r to your office dated January 8,1982 we identified a condition which was considered to be potentially reportable in accordance with 10CFR50.5 5(e).
The condition involves the failure o f a coupling in the actuator o f the LPSI Flow (bn tro1 Valve in thit 2.
Evaluation o f the condition indicates that it meets the reportability criteria o f 10CF R5 0.5 5 (e ).
At tache d are twen ty-five '2 5) co pie s o f a r e por t entitled " REPORT ON SHUTDOWN COOLING FLOW CONTROL VALVE COUPLING FAILURE."
If you have any questions regarding this report, we muld be please d to discus s this matte r with you a t your conven ien ce.
Ve r y tr uly yo ur s,
Fn clo sure s cc:
Vi. to r S tello (NRC, Director I&E)
A. E. Cha ffe e (NRC, San 01o f re thits 2 & 3) lE O m25t2agicamjk sg s
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4 REPORT ON SHUTDORN COOLING SYSTEM
/
FLOJ CONTROL VALVE COUPLING FAILURE San Onofre Nuclear Generating Station, Units 2 and 3 INTRODUCTION This report is submitted pursuant to 10C FR5 0. 55(e ).
It describes a condition involving the failure o f the coupling whiu connects the valve stem to the pneumatic valve operator on shutdown coolin g system flow (SDCS) control valve FV-030 6 installed in San Onofre Unit 2.
By letter dated January 8,1982, Southern California Edison confirmed notification to the NRC of this condition which was considere d patentially reportable in accordance with 10C FR5 0.5 5(e ).
This report is presented to record the results o f tne investigation an d analysis and the corrective action s which are being taken or are under consideration BACKGROUN D In order to comply with the recent NRC requirements for remote controlability o f the shutdown coolin g system certain valve s must be modified.
One such change calls for changing the design o f tne air operated FV-0306 shutdown cooling flow control valve from f ail closed to fail to a nominal 30% open po sitio n.
This change mean t the return spring o f the actuator wo uld cause the valve to open.
In the previous design the air pressure on the diaphram o f the operator acte d to open the va lve.
In order to restrict valve opening to the 30% open position, a lug was welded to the coupling which connects the air operator to the valve stem.
this lug comes in contact with a _stop and thus prevents furthe r rotary motion o f the couplin g, limitin g the valve o pening to 30% o f full open.
Gaupling failure was cause d by an impact between lub an d sto p which occurre d during a test which was performed to investigate the capability o f the valve to open under high differential pressure.
DESCRIPTION OF DEFICIENCY Several problems have been encountered previously with the lug /sto p design modification.
These were due to manufacturing errors which have been corrected.
The condition which is the subject o f this repor t was r
e n co un te re d o n _ De cembe r 7, 1981 while the FV-0306 valve was be in g te s te d fo r it s a b ilit y to o pe n a ga in s t a differential pressure o f 220 psi.
Air was being bled from the air operator but the actuato r sprin g was no t able to open the valve.
The
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REPORT ON SHUTDOWN COOLING FLOW CONTROL VALVE... S0/2 Page 2 differential pressure across the valve was then lowered gradually until the valve o pened.
This opening was sudden since there was no air on the operator diaphram.
The sto p lug on the coupling absorbed the full energy and stopped the valve opening at the 30% position.
This te s t wa s re pe ate d a se con d time.
Since this was a severe test and not representative o f normal valve operation, the possibility o f damage to the valve wa s r e co gn ize d.
A Field Action Request was filed on December 9,1981 indicatin g that the FV-0306 valve should continue to be used for system testing on an interim basis while the probalem o f valve stickin g was re solve d by the supplie r.
Coupling damage was confirmed on January 6,1982 when the coupling cracke d durin g continue d use o f the valve in shutdown cooling system testing.
An e xamination o f the coupling revealed a classic brittle fracture.
An aly sis o f Sa fe ty Implications The couplin g failure that occurre d on FV-0306 was pro duce d during testing conducted using differential pressures across the valve far in excess o f those expecte d durin g normal or accident o peration.
Howe ve r, the following analysis is provided to describe the condition s that would exist were such a f ailed coupling to have gone unde tected.
The FV-0306 valve is located in a section o f piping that is commo n to bo th low pressure safety injection (LPSI) p ump s.
The valve is used in ba th emergen cy core coolin g an d shutdown coolin g function s.
Dur in g a s hutdown coo lin g p ro ce s s FV- 0306 i s r e mo te ly o pe ra te d to con tro l flow thro ugh the shutdown coolin g hea t exchanger s.
Should the FV-0306 coupling fail while in the shutdown cooling made o f operation, total system flow control can be achieved by u s f.n g e ithe r t he LPS I He a de r va lve s in a t hro ttle mo de o r by iso latin g FV-0306 an d thro ttlin g flow with it s bypas s valve.
During normal plant o peration FV-0306 is maintained in its emergen cy core coolin g position.
The trave l sto p limits the wide o pen position o f the valve to the 30 percent open position require d fo r emergen cy core coolin g flow o f a single LPSI pump.
This fixed ma ximum o pen po sition also serves to preven t pump runout flow.
In the even t o f a lo ss o f powe r following a Sa fety Injection Actuation Signal resulting in o pe ra tio n wi t h o n e LPS I p ump an d fo ur LPS I he ade r va lve s o pen.. The 30 percent o pen position is maintained by the actuato r re turn sprin g.
Operatin g procedure s require that the air supply to the actuator be removed and locked out during powe r ope ration.
Durin g shutdown coolin g, the air supply to t he a c tua to r i s r e s to re d to a llow t he o pe r a to r to r e mo te ly control / limit shutdown cooling heat exchanger bypass flow.
If the coupling were to fail when FV-0306 is required to be in the 30 % o pe n pa sitio n, the ball o f the valve could rotate to a position where ECCS flow wo uld be less than required, o r to a
A REPORT ON SHUTDOWN COOLING FLOJ CONTROL VALVE...SO/2 Page 3
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4; position where LPSI pump runout flow could exceed the It should be no te d, howeve r, tha t the capability o f the pump.
initiator o f coupling failure, i.e., cracking, wo uld have to have been cause d by prio r operation o f FV-0306 usin g the air operator under high differential pressures not expected to be encountere d durin g plan t operation.
It is no ted that, with the exception o f the travel stop, shutdown cooling heat exchanger flow control valve HV-9316 is similar to FV-0306.
Valve HV-9316 is common to bo th shutdown cooling heat exchanger s and is designed to fail to its wide The open position upon loss o f power or loss o f air.
possibility o f a couplin g failure is considere d remote bacause, unlike FV-0306, the HV-9316 coupling is not subject to the stresse s impose d by an intermediate position travel the failure o f the HV-9316 coupling would s to p.
In any e ven t, have no effect on ECCS operation as the valve is no t in the ECCS flow path and it does not have an isolation function.
In a shutdown coolin g mode, the consequence s o f an HV-9316 coupling failure could be either an increase or decrease in shutdown coolin g hea t exchange r flow.
Durin g a shutdown cooling process, a reduction in shutdown cooling heat exchanger flow could be corrected by opening a locally actuated valve that bypasses HV-9316; total flow could then be controlle d with the LPSI header valve s.
An increase in flow could also be corrected by throttling the header valves.
CORRECTIVE ACTION A replacement coupling o f the same construction as the one exhibiting the last failure has been installed on FV-0306.
De tailed instructions for coupling assembly and inspection o f the valve for damage were pr;vided by the supplier o f the valve.
Fo r first cycle operation o f Unit 2, Valve FV-0306 will be operated manually in the SDCS made, and the air supply to the actuator will remain removed and locked out.
A program o f testing to mare fully investigate cause s o f the coupling f ailure and appropriate long term action is underway l
at the valve manufacture r 's facility.
i i
LS:fm 0639Q 21JAN82 l
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