ML18096A882

LER 92-008-01:on 920501 & 0713,main Steamline Isolation Resulted in ESF Signal Actuations & Trip of Low T Bistables. Caused by Design,Mfg,Const/Installation Inadequacy.Mods to Correct Flow Sensing Line Concerns underway.W/920806 Ltr

ML18096A882
Person / Time
Site:	Salem
Issue date:	08/06/1992
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-008, LER-92-8, NUDOCS 9208140159
Download: ML18096A882 (5)

Text

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Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038.

Salem Generating Station August 6, 1992 U. s. Nuclear Regulatory Commission Document control.Desk*

Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 SUPPLEMENTAL LICENSEE EVENT REPORT 92-008-01 TQis Licensee Event Report supplement is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR50.73.

It addresses a second main steamline isolation event with the same causal factors as the previous event (addressed by the original LER). It is being submitted within thirty (30) days of the second event.

• Sincerely yours,

c. A. Vondra General Manager -

Salem.Operations MJP:pc Distribution The Energy PeOple 9208140159 920806 PDR ADOCK 05000311

. -~*.

• NRC FORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-01.04_

(6-89) -*

EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD

• LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 ..

FACILITY NAME (1)

Salem Generating Station - Unit 2 TITLE (4)

Engineered Safety. 'Feature signal actuation: Main Steamli:rie Isolation.*

EVENT DATE (5) LER NUMBER (6) REPORT DATE C7l OTHER FACILITIES INVOLVED CBI MONTH DAY YEAR YEAR - .tt SE~~~~~~AL Jt ~~~~~~ MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISI 01s1010101 I I ol 1 ~ 3 c 2 9 2 - I oI al s - ol 1 d s oI 6 9 I2 OPERATING THIS REPORT IS SUBMITTED PURSUANT TD THE Rl:QUIREMENTS OF 1*0 CFR §: (ChttCk ono or more of th* following} (11)

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50.73(1)(2)(iv)

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50.73(1)(2)(;) 50.73(1)(2)(viiilCAl 366AI iii (Bl IS0.73C1112Hiil 50.73Coll2)Ciiil ---

LICENSEE CONTACT FOR THIS LER 1121 50.73C1l (2) (vi 50.73(1)(211xl NAME TELEPHONE NUMBER AREA.CODE M .T n,...11 ::>t"'k - T.'R'R rnnrni ..,,,.+,....,... 6 IO I 9 31 3 I 9 1- I 2 I 0 12 I 2 COMPLETE ONE LINE FDR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 MANUFAC* MANUFAC*

CAUSE SYSTEM COMPONENT SYSTEM COMPONENT TUR ER TUR ER I I I .I I I I I I I I I I I I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR .

EXPECTED I YES (If Y*S. compl*t* EXPECTED SUBMISSION DATE!

ABSTRACT (Limir ro rxi NO 1400 spaces. i.tJ., approximaretv fifteen single-spacs rypswrirtan lines} 118)

SUBMISSION DATE 1151

.. I I I This LER Supplement addresses a second main steamline isolation (MSI) event. Both events occurred with the plant in Mode 4 (<350°F).durin_g plant heatup on low Tavg (< 543°F) coincident with * . high steamline flow signals. The events occurred on May 1, 1992~ at 0410 hours0.00475 days <br />0.114 hours <br />6.779101e-4 weeks <br />1.56005e-4 months <br /> and July 13, 199i, at 0508 hours0.00588 days <br />0.141 hours <br />8.399471e-4 weeks <br />1.93294e-4 months <br />. Just prior to each event, the plant had entered Mode 4; at 0221 hours0.00256 days <br />0.0614 hours <br />3.654101e-4 weeks <br />8.40905e-5 months <br /> on May 1, 1992 and at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on July 13, 1992, respectively. In Mode 4, Reactor Coolant System T 9 ranges from 200°F to-350°F (act~al temperature was approximately 250°F);

therefore, the low T bistables are tripped providing half of the logic signal require~vior MSI. The high steamline flow logic requires indication of high flow iri 1 out of 2 channels_ per Steam Generator (S/G) in 2 of the 4 S/Gs. Both MSI events occurred when No. 22 S/G's Steamline flow channel 1 a_nd No. 24 S/G Steamline *flow* channel 1 bistables

• tripped. The root cause of these events is "Design, Manufacturing, Construction/Installation inadequacy. With the plant in Mode 4, condensate flashes to steam in the steamline flow reference legs resulting in channel spikes. This apparently occurred_coincidently in the Nos. 22 and 24 S/G channels satisfying the _logic.for MSI. Assessment of this event indicated that the false high flow signals were not caused by failed components. The false signals cleared after a few hours. A study of main ste*amline flow instrumentation concerns was completed prior to this event . . Engineering is developing design modifications to correct main steainline flow sensing line concerns.

NRC Form 366 (6-89)

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET.NUMBER _LER NUMBER PAGE Unit 2 5000311 92-008-01 2 of 4 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse Pressurized Water Reactor Energy Industry Identification System (EIIS)*codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

Engineered Safety Feature signal actuations;*Main Steamline.Isolation Event Date: 5/01/92 and 7/13/92 I Report Date: 8/6/92 This report was initiated by Incident Report Nos.92-288 and 92-433.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 4 (Hot Shutdown)

DESCRIPTION OF OCCURRENCE:

This LER Supplem~nt addresses a second main steamline isolation (MSI)

_event. Both events occurred with the plant in Mode 4 during plant heatup

, on low Tavg* (< 543°F) coincident with high steamline flow signals. .

.

The events occurred on May 1, 1992, at *0410 hou'rs and July 13, 1992, at 0508 hour0.00588 days <br />0.141 hours <br />8.399471e-4 weeks <br />1.93294e-4 months <br />s~ Just prior to each event, the plant had entered Mode

• 4; at 0221 hours0.00256 days <br />0.0614 hours <br />3.654101e-4 weeks <br />8.40905e-5 months <br /> on May 1, 1992 and at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on July 13, 1~92, respectively.

In Mode 4, Reactor Coolant System T 9 ranges from 200°F to 350°F (actual temperature was approximately 250°F); therefore; the low T bistables are tripped providing half the logic signal required foravg MSI. The high steamline flow logic requires *indication of high flow in one (1) of two (2) **channels per steam Generator (S/G)

• in two (2) of the four (4) S/Gs. In both events, the MSt occurred when the No.

22 Steam Generator's (S/G) steamline flow channel No. 1 and No.-24 S/G's steamline flow channel No. *1 bistables tripped.

MSI is an Engineered Safety Feature (ESF). on May 1, i992; at 0536 hours0.0062 days <br />0.149 hours <br />8.862434e-4 weeks <br />2.03948e-4 months <br /> and July 13, 1992, at 0734 hours0.0085 days <br />0.204 hours <br />0.00121 weeks <br />2.79287e-4 months <br />, these events were reported to the Nuclear- Regulatory Commission (NRC) in accordance with Code of Feder~l Regulations 10CFR 50.72(b) (2) (ii).

APPARENT CAUSE OF OCCURRENCE:

The root cause of these events is "Design, Manufacturing,

• construction/ Installation inadequacy~ With the plant in Mode 4, condensate flashes to steam in the steamline flow reference legs

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating station DOCKET NUMBER LER NUMBER PAGE.

Unit 2 5000311 92-008-01* 3 of 4 APPARENT CAUSE OF OCCURRENCE: {cont'd)

• resulting in channel spikes. This apparently occurred coincidently in the Nos. 22 and 24 S/G channels satisfying the logic for MSI. Salem Unit 1 has experienced similar MSI actuations (e.g., September 23, 19~1; reference LER 272/91-031-00).

• Assessment of these. events, by Maintenance personnel, concluded.that the false high steam flow signals were not caused by failed components. The false signals cleared on their own after a few hours.*

The Salem design arrangement for main steamline flow differential pr~ssure measurement includes two (2) taps (to provide redundancy) on the high and low pressure side of the main steamline venturi.

Attached to the taps are 1" manual globe valves. Steam is directed through 1 11 pipe to condensate pots locate<] near the high pressure tap. Condensate is then.directed to a Rosemount model 1153HD5 differential pressure transmitter via a 3/8" line.

ANALYSIS OF OCCURRENCE:

MSI protection is applicable in Mode 1 (Power Operation), .Mode 2 (startup) , and Mode 3 (Hot standby)

• It is provided to mitigate the consequences of various design base accidents including main steamline rupture and steam generator primary to secondary tube rupture.

In Mode 4, the reactor is subcritical with T v 9 *between

.200°F and 350°F. Decay heat is removed eith~r by the Residual Heat

. Removal (RHR) System {BP} or steaming from the steam generators.

Makeup water to the S/Gs can be supplied by either a Condensate Pump or an Auxiliary Feedwater Puinp. *

• I At the time of the actuat1on, decay heat removal'was being accomplished using the RHR System. During the first event, all valves which close on an MSI signal were already closed~ At the time I.

of the second event, the MS7 valves (Steam Generator Drain Valves).

were open. They closed_per design. The other valves were already closed. In both events, the plant responded per design.

• Since the actuations did not result from an actual plant need for Main Steam Isolation, these events did not affect the health or safety of the public. However, since Main Steam Isolation is an ESF

• system, they are reportable to the Nuclear* Regulatory Commission in accordance with Code of Federal Regulations 10CFR50.73(a) (2) (iv).

After initiation of the first MSI signal, Nos~ 23 and 24 S/G main steamline isolation bezel and overhead alarm indications were not received. Investigation revealed that one of the. redundant position I

indication limit switches for the 23MS167 and 24MS167 valves required minor adjustment. The 23MS167 and 24MS167 valves were closed at the time of the event. All four MS167 valves were successfully functionally tested (i.e., stroked) after the first event. This

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. ' LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit *2 . 5000311 92-008-01 4 of 4 ANALYSIS OF OCCURRENCE: (cont'd) concern did not recur during the second MSI.

CORRECTIVE ACTION:

As identified by Salem Unit 1 LER 272/91-031-00, main steamline flow instrumentation was being assessed. An in-depth study was completed prior to the subject events. Engineering is developing design r modifications.to correct main steamline flow sensing line concerns.

The _23MS167 and 24MS167 valves limit switches were adjusteq and the valves were functionally tested (i.e., stroked).

General Manager~ -

Salem Operations

• MJP:pc SORC Mtg.92-089