ML20085L861

Ro:On 710705,during Attempt to Perform HPCI Functional Tests,Turbine Could Not Be Rolled Off Turning Gear Due to Failure of Admission Control Valves to Open.Caused by Sticking oil-actuated Interlock Valve in Feedback Loop

ML20085L861
Person / Time
Site:	Dresden
Issue date:	07/14/1971
From:	Hoyt H COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085L870	List: ML20085L861
References
NUDOCS 8311030327
Download: ML20085L861 (2)

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& Commonwealth Edison Company ONE FtRsT NATRONAL PLAZA

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Dresden Nucicar Power Station  ; k ;r[ , I R.R.#1 'I-llorris, Illinois 60450  ; 'JUL19197%

July 14, 1971 h-m Es. mw. c:nr umat

. t:v . :a Dr. Peter A. Morris , Director 4- knsne /. .

Division of Reacter Licensing N

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U.S. Atomic Energy Comission  %/

Uashington, D.C. 20545 l

SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEA11 POJER STATION UNIT #3, SECTIONS 6.6. A.1 AND 6.6.B.2 0F Tile TECHNICAL SPECIFICATIONS

Dear Dr. Morris:

This is to report a condition relating to the operation of the station wherein, during initial 10^ to 150 psig plant retrtup testing, the steam admission control valves to the Hirt . ssure Coolant IvW ion (IIPCI) System failed to open during IIPCI testing. Fair' of the control valves to open rendered the system incapable of providing coolant eiection as required by Section 3.5.C.1 of the Dresden Unit 3 Technical Specifications.

Problem and Investination

/ Planned HPCI startup testing was initiated at a ranctor pressure 'of

/ 150 psig on July 4,1971. At 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on July 5, during a. *tc:upt to perform

/,llPCIfunctionaltests,theturbinocouldnotberolledofftheturninggeardue to failure of the admission control valves to open to allow steam b, the turbine.

This rendered the HPCI inoperable as required by the Technical Specifications.

Insertion of control rods was immediately initiated to reduce pressure below 90 psi and allow an evaluation of the condition with the HPCI system not required to be operabic.

Investigationofthesystemrevealedastickingoil-actuatedinterlock valve in the flow-sensing feedback loop that controls the turbine motor gear unit and control valves during IIPCI operation. Cycling of the motor speed changer (MSC) from the control room, which operates as the automatic speed controller of the turbine when at speed, evidently freed the interlock velve and allowed the control valves to open normally.- Cycling of the control valves several times afteu the interlock valve was free did not repeat the sticking of the valve.

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Dr. Peter !! orris July 14, 1971 At this tiine the hPCI turbine had not been actuated since completion of the pre-operational tests in Noveuber, 1970. It is felt that t he diti tculty was due to the extended idle time between the prcep tests and the present startup tese_s, requiring a cycling pressure to be applied to the hydrsulic pistoa instead of the gradual increase in the initial operation of the I;SC. It in further felt that the valves would have opened as required upon an automatic initiation, due to the suJden surge of oil to the interlock valve which would overco::,e the friction holding the valve closed.

Concluston Monthly surveillance testing of the llPCI systen requires exercisity; of the !!PCI valves. This testing will assure that the valves are properly lubricated and free to move. Also, during extended refueling outages when couti v Inont hly llPCI tests are postponed , and prior te nortup, the llPCI valves which c.1 oe exercised will be exercised to verify tha' i i.e valves are properly lubricated una free to move.

Sincerci ,

i,\. es-

.s who H.K.lloyt O Superintendent itKil:rh 3213

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