ML19031A533

LER 1978-013-01 for Salem Unit 1 Inoperability of Four Service Water Strainers

ML19031A533
Person / Time
Site:	Salem
Issue date:	03/22/1978
From:	Librizzi F Public Service Electric & Gas Co
To:	Grier B NRC/IE, NRC Region 1
References
LER 1978-013-01
Download: ML19031A533 (7)

Text

0 PS~G Public Service Electric and Gas Company 80 Park Place Newark. N.J. 07101 Phone 201 i430-7000 Ma r ch 2 2 , 19 7 8 Mr. Boyce H. Grier Director of USNRC Office of Inspection and Enforcement Region 1 631 Park Avenue King of Prussia, Pennsylvania 19406 De a r Mr

• Gri e r :

LICENSE NO. DPR-70 DOCKET NO. 50-272 REPORTABLE OCCURRENCE 78-13/0lT Pursuant to the requirements of Salem Generating Station Unit No. 1 Technical Specifications, Section 6.9.1.8.i, we are submitting Licensee Event Report for Reportable Occurrence 78-13/0lT. This report is required within fourteen (14) days of the occurrence, however, i t was in-advertently being reviewed with others that had a thirty day report requirement and as a result, the report is late.

Sincerely yours,

.))u F

• P

• Li::JJ_*"-

General Manager Electric Production CC: Director, Office of Inspection and Enforcement (40 copies)

Director, Office of Management Information and Program Control (3 copies)

/

I The Energy People 7809500:33 95*2C":ll 1400:.11 9.77

Report Number: 78-13/0lT Report Date: 3/22/78 Occurrence Date: 2/28/78 Incident Date: 1/11/78 Facility: Salem Generating Station Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE!

Degradation of Service Water System CONDITIONS PRIOR TO OCCURRENCE:

The unit was taken out of service at 0146 hours0.00169 days <br />0.0406 hours <br />2.414021e-4 weeks <br />5.5553e-5 months <br /> because of cir-culating water problems and the reactor placed in Hot Standby Mode 3. The air temperature was below freezing with 20 to 30 MPH winds and the river contained finely dispersed floating ice (slush or frazil).

DESCRIPTION OF OCCURRENCE:

At the time of the incident, operating problems were experienced*

with the circulating water system due to plugging of the screen by ice and grass in the river. The unit power level was reduced in order to continue operating but was eventually tripped due to loss of circulating water flow. During this period, operating personnel noted a slow decay in Service Water header pressure and a decrease in the Service Water pump motor amperage. In-vestigation revealed high pressure differential across several service water pump strainers and backwash shaft shear pins broken on four strainers. The internals of the failed strainers were inspected and found to be essentially free of ice, grass or foreign matter.

• DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

It was observed that the river was covered with slush and frazil ice at the time of the incident. Due to the natural buoyancy of ice, this mixture is usually confined to the surface of the water.

As the service water pumps take suction from within one and one-half feet of the bottom of the intake structure (which has minimum

13 feet qf water depth at low tide) chances of ingesting surface ice and thereby plugging strainers is normally negligible with the present design. Examination of Figure 1, however, leads to the postulation of possible condition whereby the surface ice was ingested, thereby causing binding of the backwash mechanism.

As can be seen from Table I, river silt had built up in all pump intake bays acting as a weir, causing the pumps to draw ice laden water from the surface.

Table I shows the comparative silt levels and free water depths above the silt "weir", for each of the intake bays. It should be noted that during the event, the four strainers which failed were associated with the bays having the least free water depth above the silt, and thus the higher chances of surface ice ingestiono Conversely, the one pump strainer which was in service but which did not fail, had a significantly deeper free water source, and thus a lower probability of surface ice ingestion.

It is plausible that ice ingestion caused by buildup of siltation in the intake structure, caused binding of the backwash arms and subsequent failure of the shear pins.

ANALYSIS OF OCCURRENCE:

It was determined that the Technical Specifications did not require this incident to be reported, however, an investigation of its safety significance was initiated. The investigation was con-cluded on February 28, 1978, and the findings were determined to be reportable under Section 6.9.1.8.i of the Technical Specifica-tions.

The investigation developed two possible explanations: random chance simultaneous failure of shear pins, or ingestion of en-trained river ice causing binding of the backwash arms as des-cribed earlier. It was concluded that the "random failure" cause was of low probability and not a common mode (or non-random multi-ple) failure.

The ice ingestion theory could have affected all pumps, and i t was concluded that there is a reasonable chance that a failure mechanism exists which ~ould prevent the Service Water system from fulfilling its design basis safety function.

CORRECTIVE ACTION:

Corrective action to eliminate this potential failure mode, involves the elimination of the weir effect by preventing silt accumulation from exceeding 3 feet in depth in any pump bay. Silt removal has been accomplished in all bays and monthly inspections will be per-formed to establish a pattern of silt buildup. This inspection interval will be reviewed based on this experience and as necessary, a new schedule established by December 1, 1978, for implementation during the winter months when freezing river conditions may be ex-pected.

FAILURE DATE:

N/A Prepared By R. S. Salvesen Manager - '._~3dem Generating :Sta1:.ion SORG Meeting No. 16-78

~~~~~~~~

NoT~: Vt:'ic:TIL,\L D1H.

ONLY ro .ScA LE".

J j ...SH011JS /i-CTLJA ~ Pe.or=1U:

((,

> I AT No 1.3 HJl-IP 011.)

3i IU

~ UJ 90

2 ~~

3~

J £, JAt /..) 78 Q e

~ lU

r:l ti.L ~

fl.

i u "'

~

~

I I

.. * ' .l ...

FLOATING,

.1-......-~---'

/Ct u

y i

. J

~

~o- " \.'

0 LEAR.. . '

4 r

'k c

e

(.

(

J

' \)

Fie::?. i PosrLJLATt::D /CE ll\JGc:ST101u HECliANlSM SEt=.vicE \tJ1trr=r<_ Sv-sr-cf--1 5 A Lt;"/..-1

TABLE I Comparison of Siltation Levels, Free Water Depths,

& Strainer Failures on 11 January 1978 Service Water System No. 1 Unit Salem Nuclear Generating Station B* C*

Water Depth Water Depth Above Silt Min. Wtr.

Service Max. Silt Above Silt Max. Silt Between . Depth Water Height At At Wall Height Bet. Scrn & Pump Above Silt Failed Pump Curtain Wall At Tide=82' Screen & Pump At Tide=82' Min (B,C) Strainer 11 7.0 ft. 4.0 ft. 10.0 ft. 2.0 2.0 Note (a) 12 8.5 2.5 6.0 6. 0 2.5 x 13 7.5 3.5 10.5 1. 5 1.5 x 14 2.7 8.3 9.5 2.5 2.5 x 15 7.5 3.5 5.5 6.5 3.5 Note (b) 16 7.0 4.0 10.5 1. 5 1. 5 x Note (a) No. 11 pump not in service (b) No. 15 pump strainer was in service - had deepest suction water - did not fail.

~RC (7*771 FORM 366 CONTROL BLOCK: ~I_

LICENSEE EVENT REPORT

_...__...._.....__.___.___,I G)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

U.S. NUCLEAR REGULATORY COMMISSION 1 6

~

7 8 I NI J I s I G I s I 1 1410115 o[ o ! -! of o ! o I of o I -Io! ofG)I 9 LICENSEE CODE LICENSE NUMBER 25 26 41 i I i111 1101 I LICENSE TYPE JO 57 CAT 58 10 CON'T

~

7 8 REPORT SOURCE I

60 T it:\]

Lk..J\..V 61 Q I 5 IQ I Q I QI 2 DOCKET NUMBER I 71 2 10)1 0 68 69 I 21 2 I Bl EVENT DATE 7 Bl@I 74 75 01 3 I 21 REPORT DATE 2 I7 I 8 80 10 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@

[IIIJ I On 1/11/78 four service water strainers became inoperative. T,S.- LCO

[TI)) was not effected. Investigation revealed need for long term ITTIJ corrective action. Ingestion of ice found to cause strainer shear key

[2TIJ failure.

[Ifil 02]

[§JIJ 7 8 9 80 SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUB CODE SUBCODE ITTIJ IWI Al@ !£J@ w@ I x I xi x I XI x I x18 ~@ ~@

8 9 10 . 11 12 . 13 18 19 . 20 SEQUENTIAL OCCURRENCE REPORT REVISION

(,"":;\ LER 'ROCVENT YEi>.R f1EPORT NO. CODE TYPE NC.

'0 REPORT NUMBER f7 I8I I I lo I 113 I 1..,....1 lo! ll l1.J l::::J LQJ 21 22 23 24 26 27 28 29 30 31 32 ACTION *FUTURE ... - *EFFECT SHUTDOWN r::::;.. ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS ~ SUBMITTED FORM ~UB. SUPPLIER MANUFACTURER W@W@

33 34 LLl@

35 W *-1 36 37 01 o I ll 6 40 I* W@41 LBJ@

42 W@ I z I z I z I z I@

43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @*

• I The cause has been determined to be silt level in combination with frazil ice. Inspection program started to maintain silt deoths less than three feet.

o::m 7 8 9 80 FACILITY STATUS  % POWER OTHER STATUS f:iQ\

v::;:J METHOD OF DISCOVERY DISCOVERY DESCRIPTION

~

(SI

[iliJ ~@ I 01,0 I 01@ I. . . .___N_/A_ _ __. ~@ .!. __E=n'-g""'i:;;_*n:. :. .: e;. .;:e; .;:r; ,.;1: ;.*;:.:n'-g'---'I:;;_n;;,;;.. ;.v. . ;;e;;..;s;;_t..;;..;;;;i'-a""'a'. -t=i;...;:o"""n______,

8 9 10 12 11 44 45 46 80 ACTIVITY CONTENT Q\

RELEASED OF RELEASE AMOUNT OF ACTIVITY~ LOCATION DF RELEASE @

CiEJ &J@ LI.JC§)! N/A N A 7 8 9 10 PERSONNEL EXPOSURES NUMBER 0.

11 TYPE DESCRIPTION 39 JP 44 45 80 82] I 01 0 I 010~@ .... l __N.....:...-_ _ _ _ _ _ _ _ _ _ _ _ _ _N~/_A_ _ _ _ _ ___,

8 9 11 12 13 80 PERSONNEL INJURIES c,\

NUMBER DESCRIPTION6

~ 01 0 I 01@ N/A 8 9 11 ~12~----~--'~-~--~-~----~-~-------------~----'BO LOSS OF OR DAMAGE TO FACILITY t;j3' TYPE DESCRIPTION '-::'./

~a 9~@ N/A

~10------,...-------"'----------------~-----------~----------------~so PUBLICITY (.';\ R SE ISSUEDf.:\ DESCRIPTION~ N C U ON Ly .,

rI:IT) ~6.....,__ _ _ _ _ _ _ N..__/A

_ _ _ _ _ _ _ _ _ _ _ _ _ ___, I I I II II II II I I ~

8 9 10 68 69 80 ;;

NAMEOFPREPARER----....;;T.;....;....*_;:;:L~*~~S~p_e~n__;;c_e~r __________~ PHONE: ( 609) 365- 7000 Salem Ext. ~

"