ML17348A829

LER 89-018-01:on 891212,use of Single Manual SI Block/ Unblock Switch for Both Trains of SI Outside Design Basis. Caused by Inadequate Original Plant Design.Info Re Potential Single Failure Mode Provided to personnel.W/910117 Ltr

ML17348A829
Person / Time
Site:	Turkey Point
Issue date:	01/17/1991
From:	Plunkett T, Dawn Powell FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-002, LER-89-018, NUDOCS 9101230310
Download: ML17348A829 (9)

Text

ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9101230310 DOC.DATE: 91/01/17 NOTARIZED: NO DOCKET FACIL:50-250 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH. NAME AUTHOR AFFILIATION POWELL,D.R. Florida Power & Light. Co.

PLUNKETT,T.F. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 89-018-01:on 891212,use of single manual SI block/

unblock switch for both trains of SI outside design basis.

Caused by inadequate original plant design. Info explaining potential single failure mode provided to personnel.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR i ENCL ( SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 AULUCK,R 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 N RE~~EBS) 1 1

1 1

NRR/DST/SRXB 8E RES/DSIR/EIB 1

1 1

1 RG E 01 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE ii'ASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOivl P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROiiI DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

.. Box 029100, Miami, Fi.,~ 33102-9100

'giN H

~

ib8i L-91-002 10 CFR 50.73 U ~ ST Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Units 3 and 4 Docket No. 50-250 and 50-251 Reportable Event: 89-018-01 Date of Event: December 12, 1989 Plant Operating Outside of it's Design Basis Due to a Desi n Inade uac of the Safet In 'ection Block Switch The attached revision 1 to Licensee Event Report 250-89-018-00 is being provided pursuant to the requirements of 10 CFR 50.73 to provide additional information on the subject event.

Very truly yours, T. F. Plunkett Vice President Turkey Point Nuclear TFP/DPS/ds enclosures cc: Stewart DE Ebneter, Regional Administrator, Region II, USNRC, Senior- Resident Inspector, USNRC, Turkey Point Plant 91012303iO 910117 PDii ADOCK 050002 r0 PDR an FPL Group company

NRC Forth 388 U.S, NUCLEAR REGULATORY COMMISSION (8.83 I APPAOVED OMB NO 31504104 LICENSEE EVENT REPORT (LER) EXPIRES. Sill lee FACILITYNAME (1I DOCKET NUMBER ('1) PA I Turkey Point Unit 3 o s o o o25 0 >oF05 TITLE(~ ) ant perat>ng uts> e s es;gn asks ue o es~gn na equacy Safety Injection Block Switch EVENT DATE I5) LEA NUMBER (81 REPORT DATE (7I O'THER FACILITIES INVOLVED (8)

SBQUeNZIAL R 4 Vts IOrr DAY FACILITYNAMES DOCKET NUMBER(SI MONTH OAY YEAR YEAR NUMoeR NUMBER MolvzH YEAR Turke Point Unit 4 o so o o 251 12 12 89 89 Ill 018 0 1 0 1 1 791 0 5 0 0 0 OPERAT )NO THIS REPORT IS SUBMITTED PURSUANT T 0 THE REOUIREMENTS oF 10 cFR (); rch<<c one o. mo e ol the forlow npl (11 MODE (8) 20.402(8) 20,405(c) S0.7l(cl(2llwl 73.71(5)

POWER 20.40S(e I(Ill)(r(il I I li) 50.38(c)III 50,73(c I (2)(v) 73.7 1(c)

LEUEL 1 0 0 20.405(el(I)(P) 50.38(c)(l) 50,73(el(1) (viiI OTHER ISpecrly rn Aottrett Oerow enp rn TertHRC Form 20.405( ~ 50.73( ~ ILT)lil 50.73(el(2)(villi(AI 3$ SAI 20.405(e ) (Ivl 50.73(c l(1)(ill 50,73(cl(2)(villi(BI cf.r, 20.405 (~ ) (I ) (v) 50.73(c) (2) I BI I 50.73( ~ l(2)(cl LICENSEE CONTACT FOR THIS LER 111l NAME TELEorroNE NUMBER AREA CODE David R. Powe11, Licensing Superintendent 0 5 2 6 - 5 5 9 COMPLETE ONE LINE FOR EACH COMPONENT FAILUAE OESCRISEO IN THIS REPORT (13)

MANVFAC REPORTABLE SYSTEM COMPONENT MANVFAC. REPORTABLE CAUSE SYSTEM COMPONENT TO NPRDS CAUSE TVRER TVRER TO NPRDS n SUPPLEMENTAL REPORT EXPECTED III~ I MONZrr OAY YEAR EXPECTED SUBMISSION DAZE IISr YES Ilfyel, COmPiete EXPECTED S(ISMISSIOH OA TEI X NO ABSTRACT ILimrr to (400 tpeceA l,e.. epptonrmetery Bitten trr p'e tpete typewnNen hnetl (18)

On December 12, 1989, with Turkey Point Unit 3 in Mode 1 (power operation) at 100 percent power and Unit 4 in Mode 1 at 40 percent 'ower, the Plant Nuclear Safety Committee (PNSC) determined that the use of a single manual Safety Injection

'(SI) block/unblock switch (Westinghouse OT2 switch using a stack of four OT2A contact blocks) for both trains of SI was outside the design basis for both units. During a control room design review concerning placement of controls on the control room control boards at the Point Beach Nuclear Plant, the use of a single manual SI block/unblock switch for both safety injection trains was questioned. A subsequent review by Wisconsin Electric engineering determined that a single mechanical failure of this switch could block both trains of SI. On September 16, 1988, Point Beach issued Licensee Event Report 88-07 describing in detail their review and conclusions.

After being contacted by the NRC, Westinghouse notified Turkey Point and other applicable Westinghouse facilities. Turkey Point Units 3 and 4 are currently shut down for the 1991 dual unit outage. A separate SI block switch will be installed for each train of SI during this dual unit outage.

NRC Form 355 rB 83r

I NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (9.83)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMS NO. 3150-0106 EXPIRES: 8/31/88 FACILITY NAME (11 DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YE*" SSGUENTIAL REV IS IQ N NUMSSR NVMSSA Turkey Point Unit 3 o s o o o 50 89 018 01 OP. OF 0 5 TEXT /llmoro SPooo /6 /or/olid, voo odd/I/ooo///l)C FINm 3NA3/ (17)

DESCRIPTION OF THE EVENT

~

On September 16, 1988, Point Beach Nuclear Plant submitted a, Licensee Event Report (LER) to the NRC addressing a design deficiency with their control room Safety Injection (SI) block circuit. In a letter dated October 26, 1989, FPL was notified by Westinghouse relating that the SI block circuit concern was potentially applicable to Turkey Point Units 3 and 4. On December 12, 1989, it was determined that this condition resulted in Units 3 and 4 being outside their design basis as described in the Final Safety Analysis Report (FSAR) . At this time, Unit 3 was running at 100 percent power while Unit 4 was at 40 percent power. At 1459 EST, December. 12, 1989, the NRC was notified of this event in accordance with the requirements of 10CFR50.72 (b) (1) (ii) (B) .

The SI block circuit mentioned above is part of the Safety Injection System (EIIS:BQ). Each Unit is provided with two redundant trains of safety injection designed to protect the core from various postulated loss of coolant accidents. Two trains are provided so that a single failure will not cause a loss of SI function.

Manual blocking of both trains of safety injection is achieved using a single Westinghouse OT2 control switch located on the control board. This switch is a three position cam (Block, Neutral, Unblocked) spring return'o neutral switch. 'our Westinghouse OT2A contact blocks are stacked together and operated by a single selector switch. Each block provides a normally closed set of contacts on one side (unblocked) of the contact block and a normally open set of contacts (blocked) on the other side of the contact block.

A failure of the SI block switch "block" (normally open) contacts in the closed position would result in a loss of some SI actuations whenever RCS pressure drops to, less than 2000 psig and Tavg is less than 543 degrees F. High containment pressure SI or'anual SI initiation are not affected by the block circuit. This condition does not meet the requirement of the plant's instrumentation and control section of the FSAR as described in Chapter 7.

On November 6, 1990, FPL Quality Assurance personnel discovered that Off-Normal Operating Procedures 3/4-0NOP-049, "Re-energizing Safeguard Racks After Loss of Single Power Supply,"

require the SI block switch to be held in the "block" position while re-energizing safeguard racks above the permissive setpoint of 2000 psig. This action would be taken to prevent NRCFORM 366A IE 831

NRC Form 3ddA U.S. NUCLEAR REGULATORY COMMISSION (94))

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO. 3150W104 EXPIRES: B/31/EB FACILITY NAME (I) OOCKET NUMBER (2) LER NUMBER Ld) PACE (3)

SEOUENTIAL REVISION NUMBER rEPrr NUMEER Tur.ke Point Unit 3 o s o o o 250 8 9 0 1 8 01 03 OF 0 5 TEXT /I/ mare epeoe ls /er/a/red, Iree edd/dorre/ NRC Farm 3/)//AB/ (17) an inadvertent SI due to relay chatter. Provisions do not exist for testing the SI block switch after this manipulation to ensure that the switch has returned to the neutral position.

However, no evidence has been located which would confirm that this switch manipulation has been performed above the .

permissive setpoint since our corrective actions for the SI block switch were implemented on January 31, 1990 evaluating possible methods to test the SI block switch 'hile above the permissive setpoint of 2000 psig, two concerns related to previously performed SI block switch operability testing were identified. First, in LER 50-250/89-018-0/ FPL committed to revise procedure O=OSP-200.2, "Plant Startup Surveillances/U by January 31, 1990. This revision was to include a requirement for performing an electrical test of the SI block switch prior to exceeding 2000 psig or exceeding 543 degrees F. Procedure O-OSP-200.2 was revised on January 31, 1990. However, the SI block switch electrical testing was identified as a Mode 2 (Startup) entry constraint. Plant parameters of 2000 psig and 543 degrees F are attained in Mode 3 (Hot Standby) . The SI block switch electrical testing was being performed after exceeding 2000 psig and 543 degrees F.

Second, FPL determined that electrical testing does not fully demonstrate SI block switch operability unless the SI circuit is in the "unblocked" condition under the permissive setpoint of 2000 psig. During normal shutdowns, the SI circuit is blocked while below the permissive setpoint of 2000 psig.

Personnel responsible for developing the electrical test did not recognize this operational constraint. Since the SI block switch electrical test originally committed to did not demonstrate SI block switch operability, a visual inspection test was implemented in its place. On November 15, 1990, the Unit 3 and Unit 4 SI block switch contacts were visually verified to be in the correct position.

CAUSE OF THE EVENT The cause of this condition was an inadequate original plant design. During the construction phase of Turkey Point Nuclear Power Plant, the SI block circuit design did not consider the effect of a potential switch -failure on the design redundancy requirements'RC FORM SEEA (933)

NRC FBNR 366a U.S. NUCLEAR REOULATORY COMMISSION (94)3)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO, 3150M(04 EXPIRES: B/31/EB FACILITY NAME (II DOCKFT NUMBER (2) LER NUMBER (6), PACE (3)

YEAR SEQVENTIAL REVISION NUMBER NVMBER Turkey Point Unit 3 o s o o o2 50 89 0 1 8 01 04 OF 0 5 TEXT ilfmoIS SOsco is Ioqvood, vss sdd o'oosl NRC FontI 8664 sl (13)

ANALYSIS OF THE EVENT The loss of redundancy being reported in this LER involves a postulated mechanical failure of the SI blocking switch. A safety evaluation of the SI block switch indicated an extremely low probability of failing in the postulated manner.

The SI block switch does not affect the operability of the Safety Injection System when above the permissive setpoint of 2000 psig. However, if the block switch were to experience the postulated failure after being manipulated, then three -of the four automatic SI actuation signals would be blocked when pressure decreased below the permissive setpoint of 2000 psig.

The three conditions that automatically initiate SI which could be affected by the switch failure are Low Pressurizer Pressure, High Steam Line differential pressure between any steam generator and the main steam header, and high steam flow coincident with either low steam generator pressure or low Tavg. Phase A Containment Pressure High SI and manual SI initiation are not affected by the postulated switch failure.

Additionally, if valid SI signals were automatically blocked, plant Emergency Operating Procedure procedures direct the operator to manually initiate SI.

CORRECTIVE ACTIONS A. Immediate Corrective Actions

1) Information explaining the potential single failure mode of the SI block switch was provided to operations personnel.

2) A visual inspection of the Unit 3 and 4 SI block switches verified, that the switch contacts were in the correct position.

B. Corrective Actions to Prevent Recurrence Turkey Point Units 3 and 4 are currently shut down for the 1991 dual unit outage. Separate SI block switches will be installed for each train of SI during this dual unit outage.

NRC FORM 366A (94) 3)

NRC Form,36dA U.S. NUCLEAR REOULATORY COMMISSION (94$ )

LICENSEE EVENT'REPORT ILER) TEXT CONTINUATION APPROVED OMB NO,3160M)04 EXPIRES: 6/31/BB FACILITYNAME (1) OOCKET NUMBER (2) LER NUMBER (6) PACE (3)

YEAR ~krj SEQUENTrAL N REVISION NUMBER NUM ER Turkey Point Unit 3 o s o o o 2 5 0 8 9 0 1 8 01 05 OF 0 5 TEXT /// more 6/reoe /e reqrrlred, rree edd/dorre/ NRC Form 36643) (I7)

ADDITIONAL INFORMATION Licensee Event Report 250/87-016-0, issued June 25, 1987, reported an inadvertent actuation of the Unit 3 Train A Safety Injection System.

NRC FORM 366A

$ 43)

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