ML18018B232

LER 77-019-00 for Dresden Unit 2 Regarding Discovery of the Aprm/Rbm Flow-Bias Indication Exceeding 100% on Both Channels a and B with Core Flow at 100%

ML18018B232
Person / Time
Site:	Dresden
Issue date:	05/09/1977
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS Ltr. #77-419 LER 77-019-00
Download: ML18018B232 (8)

Text

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U.S. NUCLEAR REGULATORY C 'AIIISSION DOCKET NUMBER

'i'JRC'FO?IM 195 .

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I2.7SI Q.'3 FILE NUMBER NRC DISTRIBUTIOPI Foe PART 50 DOCKET MATERIAL INCIDENT REPORT FROM: DATE OF DOCUMENT.

TO:

Commonwealth Edison Company 5/9/77 Mr. James G. Keppler ~ Morris, Illinois DATE REf f)V/D B. B Stephenson gfLETTE R ONOTORIZEO PROP INPUT FORM NUMBER OF COPIES RECEIVED ORIGINAL DCOP Y gtUNC LASS IF I E D

('/6PPD DESCRIPTION ENCLOSURE Licensee Event Report (RO 50-237/1977-19) on 4/25/77 concerning the.APRM/RBM flow-'ias indi@ation exceeding 100% on both "DO NOT REMQVB, channels. A 8 Bo ~ ~ ~ '

'A ELAET EARS: %V<gDND (2-P)

Dresden Uni.t No. 2 RJL NOTE: IP PERSONNEL EXPOSURE IS INVOLVED SEND DIRECTLY TO KREGER/J COLLINS FOR ACTION/INFO RMATI ON BRANCH CHIEF:

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&.E 2 SCHROEDER/IPPOLITO HOUSTON NOVAK/CHECK GRIMES BUTLER HANAUER TEDESCO/MACCARY EISENHUT BAER

-SHAO VOLLMER/BUNCH KREGER/ J ~ COLLINS EXTERNAL DISTRIBUTION CONTROL NUMBER LPDR'0 TIC:

N 771430052 NRC FORM 19d I2.76)

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Commonwe Edison Dresden Nuclear Power Station R.R. g1 Morris, Illinois 60450 Telephone 8151942-2920 BBS Ltr. los77-419 May,9, 19 t

Qc' Mr. James G. Keppler, Regional Director Mg 831977~

us Directorate of Regulatory Operations - Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road

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I'lQ'ganlr Enclosed please find Reportable Occurrence r'eport -nu@84550-237/1977-19.

This report is being submitted to your office in accordance with the Dresden Nuclear Power St:ation Technical Specif.ications, Section 6.6.B.

B. tephe son Station Superintendent Dresden Nuclear Power Station

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Enclosure cc; Director of Inspection 5 Enforcement Director of Management Information 6 Program Control File/NRC nq g s

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2 LICENSEE EVENT REPORT CONTROL BLOCK 1'PLEASE PRINT ALL REQUIRED INFORIYIATION) 6 ucENsEE ucENBE EVENT NAME UCENSE NUMBER TYPE TYPE QoHLI L D RIS 2 0 0 0 0 0 0 0 0 0 4 I I I I ~DI 89

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7 14 15 25 26 30 31 32 REPORT REPOAT CATEGORY TYPE SOUACF OOCKET NUMBER EVENT DATE AEPOAT OATE

~01 ooN'T T L 0 5 0 0 2 3 7 0 4 2 5 7 7 0 5 0 9 7 7 7 8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION During normal operation it was discovered that with core flow at 1000, the APRM/RBM 7 8 9 80 flow-bias indication exceeded

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10010 on both channels A and B. At 10040 core flow, the

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7 8 9 80

~04 APRM scram setpo i nt ( 1 1 74 reactor power) wou d 1 not have been exceeded; however, at 7 89 80 reduced flow rates, the flow-biased scram setpoint would have been non-conservative by approximately 3F. The flow bias flow indication has exceeded. 1000 in the past

[oat 7 8 9 FAME 80 SYSTEM CAUSE COMPONENT COMPONENT (continued)

COBE COBE COMPONENT COOE SUPPUER MANUFACTURER VCIATKIN

[002I ~IA ~0 I N s T R 0 N G 0 8 0 Y 7 8 9 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION During the recent outage, the recirculation drive flow instruments and the APRM/RBM 7 8 9 80

[>g flow converters which receive their input from the instruments were calibrated to 7 8 9

~10 appropriate or ig ina 1. speci f i cat i ons ~ The procedure which was fo1 lowed, however, did 80 7 89 METHOD OF continued 80 FACIUTY STATUS  % POWEA OTHER STATUS OISCOVEAY OISCOVEAY OESCRIPTION

[1111 ~E ~08 3 NA B NA 7 8 9 10 12 13 44 45 46 80 FORM OF ACTIVITY COATENT RELEASEO OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE t11g Z Z NA NA 7 8 9 10 11 44 45 PERSONNEL EXPOSURES NUMBER TYPE OESCRIPTION

~so ~00 0 2 NA 7 89 11 12 13 80 PERSONNEL INJURIES NUMBER DESCRIPTION

[gin] 0 0 0 NA 7 8 9 11 12 80 OFFSITE CONSEQUENCES 1 5 NA CG 2 7 89 LOSS OR DAMAGE TO FACILITY TYPE OESCAIPTION.

~z NA 7 89 10 30 PUBLICITY NA 7 89 ADOIIIONAL FACTORS

+0 NA PHONE'0

[119J 7 89 NAME T. Rausch GPO bbl ~ CbT

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EVENT DESCRIPTION (continued)

(50-237/1977-2) as a result of calibration of the total core flow indication.

The safety implications of this event were minimal because safety and transient analyses do not assume a flow-biased scram function (50-237/1977-19).

CAUSE DESCRIPTION continued) not take into account the present correlation between recirculation drive flow and total core flow (to which the APRM/RBM flow converter readings are referenced). As a result the APRM/RBM scram trip levels could have been non-conservative at core flow rates of less than 1004.

On April 25, 1977, the ALARM/RBM flow converters were readjusted to read 1004 at 1004 total core flow. To prevent a reoccurrence of this event, the appropriate instrument calibration procedure will be revised to include the present correlation between recirculation drive flow and total core flow.

RECEIVED DQCUgEtIT PRQCESSIRC Ut(IT Slf MAY 24 N 8 2l