ML20085G263

AO BFAO-7325W:on 731005,inner Rupture Diaphragm of HPCI Sys Failed.Caused by Several Vacuum Cycles Inside Turbine Discharge Piping.Replacement Rupture Diaphragm Installed & Design Investigation Initiated

ML20085G263
Person / Time
Site:	Browns Ferry
Issue date:	10/15/1973
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G265	List: ML20085G263 ML20085G274
References
AO-BFAO-7325W, BFAO-7325W, NUDOCS 8308240734
Download: ML20085G263 (2)

Text

O remmessee vaAsy nursOmi>v c-- m CHATTANCOGA, tennessee i /6 3 , 374Q1 L u / .- .

flJy fM

• 1 Cetober 15, 1973 sN'kh@N

- PARTNPnUHIP Mr. Joh t F. O'Icary I j Directorate of Licensing q g Office of Regulation p O g i

U.S. Atomic Ener6y Co=ission M t Washington, DC 205f+5 'g s M I >

Dear Mr. O'Icary:

O TE:l:TisSSEE VALISY NJTHORITY - BROWNS FERRY NUCLEAR PIl.:iT UNIT 1 -

l DOChl:T !!O. 50-259 - FACILITY OPERATING LICENSE DPR ABNOM1 l CCCUR3E:!CE ?JCET EFAO-7325W The purpose of this report is to provide details concerning failure of the inner rupture diaphrap of the High Presrure Coolant Injection Syctem o.1 unit 1 at Erowns Ferry Nuclear Plant. This condition was j reported to the Region II Director of Regulatory Operations on

) October 5,1973 I

Dascrintion of the Incident l

Cn Cetcher 5,1?73, during the performace of 3tartup Tect Inctruction 15, l

High Preccure Coolant Injectica Syctem, tne HPCI system was isolated l i automatically by }he preccure switches tetscen the inner and outer l rupture diaphragm on the turbine exhcust. Surveillance tests of ,

, redundant core cooling systems were begun immediately.

Investigation and Corrective Action The High Pressure Coolant Injection System turbine dischar6e piping has an inner and outer rupture diaphrop to prevent overpressurizing the t

turbine casing. Pressure switches between the two diaphragms vill

isolate the turbine chould the inner diaphra p fail or rupture.

The inner ntpture diaphre6a was removed and examined. It was determined from the appearance of the diaphragm that the failure of the scaling membrane in the diaphrap vas cauced by a vacuum inside the turbine dicchard.: piping cul casing and not overpreccure. The turbine cacing and discharge piping vere not up to operating temperature when icolation occurred and cteam in the turbine cacing and diccharge piping condenced at cuch a rate that air leakage in and around shaft seals could not take up the void created by the condencation. It is sucpected that l several vacuum cycles were rec,uir'ed to cause failure.

8308240734 731015

• PDR ADOCK 05000259 J S PDR ' " t'h COPY SENT REGION ((i g l

a

]

, em 1

2

- i+ Mr. John F. O'Icary Cetober 15, 1973 TEIINESSEE VALI17 AUTHORITY - EROWIIS FERRY NUCLEAR PLANT U'iIT 1 -

DOCKET NO. 50-259 - FACILITY OPERATING LICENSE DPR ALIiOEMAL GCCURRCNCE REPO.Tf EFAC-7325U A replacement rupture diaphrag:a was installed. Surveillance Instruction 1+.5.E.2, EPCI Functional Test, was catisfactorily perfomed following diaparaga replacement and the HPCI was returned to service.

To prevent recurrence for the lonc tem, a design investigation has been initiated to eencider replacing the present rupture disc with one decicned with a vacuum support. The vacuum cupport would prevent covement of the rapture dice ucmbrane if it vere subjected to a vacuum.

Very truly yours, TENUESSEE VALiff A'JTHORITY I l

p '. g . .

E ' '. -Th ./~.NI '

[%" director of Power Production o

(

CC: Mr. Noman C. Moceley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street, IiW.

Atlanta, Georgia 30303 l

l I

l '

l i