ML20137Q977

Forwards Corrected Evaluation of Plans 1A/1B & 1C Re Root Cause Findings & Corrective Action Repts.Nrc 851030 Evaluation Contained Incorrect Ref to Operator Inability to Reset Auxiliary Feed Pump Turbines

ML20137Q977
Person / Time
Site:	Davis Besse
Issue date:	11/15/1985
From:	Stolz J Office of Nuclear Reactor Regulation
To:	Williams J TOLEDO EDISON CO.
References
NUDOCS 8512050402
Download: ML20137Q977 (4)

Text

November 15.', 1985

.. .~.

Docket No. 50-346 DISTRIBUTTON, ACRS-10 f 6~PDRj, NRC

- Ringram L PDR ADeAgazio Mr. Joe Williams, Jr. ORB #4 Rdg Gray File Senior Vice President, Nuclear HThompson EBrach Toledo Edison Company OELD 40rnstein Edison Plaza - Stop 712 EJordan WPaulson 300 Madison Avenue BGrimes GDick Toledo, Ohio 43652 JPartlow GEdison

SUBJECT:

EVALUA7 ION OF TOLEDO EDIS0N COMPANY PLANS NO. lA/1B AND IC -

CORRECTION By letter dated October 30, 1985, we provided you with evaluations of a number of Toledo Edison Company root cause findings and corrective action reports. The evaluation for plans IA/IB and IC contain an incorrect reference to the operator's inability to reset the AFPTs. Enclosed is a corrected version of the evaluation.

Sincerely,

'oziau x e m = cx Juw r. stuu

• John F. Stolz, Chief Operating Reactors Branch #4 Division of Licensing

Enclosure:

As Stated cc w/ enclosure:

See next page

.  % 4 ADeAga i ;cr J l 11/ /85 11/ 5 8512050402 851115 PDR ADOCK 05000346 P PDR

Mr. J. Williams Davis-Besse Nuclear Power Station Toledo Edison Company Unit No. I cc:

Donald H. Hauser, Esq. Ohio Department of Health The Cleveland Electric ATTN: Radiological Health Illuminating Company Program Director P. O. Box 5000 P. O. Box 118 Cleveland, Ohio 44101 Columbus, Ohio 43216 Mr. Robert F. Peters Attorney General Manager, Nuclear Licensing Department of Attorney Toledo Edison Company General Edison Plaza 30 East Broad Street 300 Madison Avenue Columbus, Ohio 43215 Toledo, Ohio 43652 Mr. James W. Harris, Director Gerald Charnoff, Esq. Division of Power Generation ,

Shaw, Pittman, Potts Ohio Department of Industrial Relations and Trowbridge 2323 West 5th Avenue 1800 M Street, N.W. P. O. Box 825 Washington, D.C. 20036 Columbus, Ohio 43216

Paul M. Smart, Esq. Mr. Harold Kohn, Staff Scientist Fuller & Henry Power Siting' Commission 300 Madison Avenue 361 East Broad Street P. O. Box 2088 Colcabus, Ohio 43216 Taledo, Ohio 43603 -

Mr. Robert B. Borsum President, Board of Babcock & Wilcox Ottawa County Nuclear Power Generation Port Clinton, Ohio 43452 Division Suite 200, 7910 Woodmont Avenue Bethesda, Maryland 20814 Resident inspector U.S. Nuclear Regulatory Commission 5503 N. State Route 2 Oak Harbor, Ohio 43449 Regional Administrator, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

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Enclosure 1 DAVIS-BESSE EVALUATION OF LICENSEE'S REPORT REGARDING OVERSPEED TRIPS OF THE AUXILIARY FEED PUMP TURBINES-TOLEDO EDISON PLANS NO. IA/1B and IC We have reviewed the findings, corrective actions, and generic implications report entitled, "Overspeed Trips Of The Auxiliary Feed Pump Turbines on June 9,1985 at Toledo Edison's Davis-Besse* Nuclear Power Station" concern

[ the problems associated with an overspeed trip of the auxiliary feed pump turbines (AFPT).

The AFPT is a steam driven turbine which drives the auxiliary.

feedwater pump.

Both of the auxiliary feedwater pumps.(AFP), including the .

turbine and overspeed

. -- - trip mechanism (OTN), at Davis-Besse are identical except for the model of the governors. .

Each AFPT is fed from 1.ts respective steam generator (SG), that is SGI feeds AFPT 1 and SG2 feeds AFPT 2..

In addition, there is a cross connection such that each SG can feed the redundant AFPT, i.e., SGI can feed AFPT 2 and SG2 can ,

' feed AFPT 1.

These cross connected lines are normally closed. During the June 9th ever.t. a low SGI level signal opened the steam line to AFPT When 1.

the operator (five seconds later) tripped both channels on low SG pressure, the normal steam lines were isolated and the cross connected steam lines w opened.

The licensee, by analysis, has detennined that a large quantity of condensate connect lines. could have been formed when the steam was admitted to The condensation in the steam lines formed a water slug at the l, AFPTs and could have caused the overspeed of the' AFPTs.

The licensee has .

. wroposed three different scenarios where this water slug could cause the AFPT to trip on overspeed. The first scenario is where the water slug in the

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governor valve causes the valve to open too far in an attempt to maintain

! turbine speed.

When the water clears the valve, the valve admits teemuch steam and the AFPT trips on overspeed. The second scenario is where the water l

flashes as it enters the turbine and thereby accelerates the turbine du 'S sudden expansion until it trips. The third scenario is similar to the scenario except the water slows down the turbine and the governor va'ly to try to, maintain speed. When the water clears the turbine. the gover.

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valve is open too far and the turbine trips on overspeed. In order to support this hypothesis, the licensee also calculated the quantity of condensate which could be fomed in the nomal lines used to power the AFFTs. A comparison of the quantity of condensate fonned in the line from SG1 to AFPT 1 is almo:t as .much as from SG2 to AFPT 1. The licensee could not explain why the AFPT 1 had never tripped on overspeed when fed :from SG 1. In addition, the licensee has not determined how or why the condensate resulted in the overspeed tripping

'of the AFPTs. The identification of the: root cause was done hypothetically and the Itcensee has not proposed to perform any verification tests.

.- - 0 . .

The licensee has proposed maintaining all steam lines from the SGs to the AFPTs at full pressure and temperature up to the turbine inlet isolation valves, which s are approximately 10 hat from the turbines. These turbine inlet isolatio,n '.

valves are to be replaced with pneumatically operated control valves.. Thus, on an initiation signal, only the new valves will be require'd to change -

position'. This valve lineup has been tested by the licensee, as indicated in i

a meeting on September.25, 1985. Each start of the AFPTs resulted in accept-able performance, i.e , no' overspeed trips occurred.

Based on our review of the licensee's findings, corrective actions, and generic implications report and the successful initiations of the AFPTs with hot stear lines, we believe that the licensee has identified the root cause l

j of the overspeed trips of the AFPTs and that the licensee has taken the

! appropriate corrective action.

l l Dated: October 30, 1985 l Retised November 15,'1985 The following NRR personnel contributed to this evaluation: John Ridgely

_ _ _ , _ _ .