ML20085H007
| ML20085H007 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/25/1974 |
| From: | Eric Thomas TENNESSEE VALLEY AUTHORITY |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8308300056 | |
| Download: ML20085H007 (2) | |
Text
r TENNESSEE VALLTW AUTHORITY t'~nin.97 f\\
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- n. p s 1'r. Edson G. Case n m,,,
Acting Director of Licensira Office of Regulation U.S. Atomic Energy Cornission
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Washington, DC 20545
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Dear Mr. Case:
TENNESSEE VMLEY AUTHORITY - BROTCS FERRY HUCLEAR PLANT UNIT 2 -
DOCKET NO. 50-260 - FACILITY OPERATING LICENSE DPR AB:iOR!&L OCCURRE:iCEREPORT3FAO-50-260/7413W The enclosed report is to provide details concerning Average Power Range l'onitor (APRM) channels A, B, and D LPR!! input count circuit sotpoint drift end is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973 This event occurred on Browns. Ferry Nuclear Plant unit 2 on September 15, 1974.
Very truly yours, CESSEE VALLEY AUTHORI1Y
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,Er; 11o=as Di ector of Power Production Enclosure CC (Enclosure):
Mr. Hornan C. 15ccley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street, IIW., Suite 818 Atlanta, Georgia 30303 1g 8308300056 740925 PDR ADOCK 05000260 S
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Report I!o.: BFAO-50-200/71413W Report Date: September 25, 1974
' Occurrence Date:
September 15, 1974 Facility:
Browns Ferry I!uclear Plant unit 2 i
Identification of Occurrence Average Power Range Monitor (AFPJ4) channals A, B,'and D LPRM input count circuit setpoint dM ft.
Conditions Prior to Occurrence The reactor nas operating at approximately 35-percent th'emal power.
Descrintion of Occurrence i
During routine surveillence test,ing at appro+,tely 2!400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on September 15, 1974, the LPR'4 count /incperative trip settin;c:for APRM channels A, B, and D vere found to operate at less than 13 operable LPPld's. Technical specifications require a trip setpoint of less than 14 operable LPPJ4's.
Desinnation of Anparent Cause The LPRM count / inoperative circuitry for APR'4 channels A, B, and D was found to trip at one less operable LPFCI than requircd by the technical specifications, i
This setpoint error is attributed to thermal crift. Also, APRM channel A LPE4 g
averaging card had a bad solder connection.
Analysis of Occurrence The LPPJ4 count / inoperative circuitry functions to count the number of bypassed LPRM's.
Wnen the number of operable LPPll's to a particular APE 4 channel decreasesbelowitsadjustedsetpoint,thecount/inoperativecircuitryinitiates an inoperative trip resulting in a reactor half-screm condition. At the time of this occurrence, only one LPR'4 was bypassed in all three of the APPJ4 channels involved.
Each APR'4 channel has either 21 or 22 LPRM inputs.
Equipment configuration requires exposure of the LPRM count / inoperative circuitry to lower control room tc=ceratu c when adjusting the trip setpoint.
Subsecuent testing confirme,d that such exposure was sufficient to cause the trip cetpoint to function at one less operable LPR'1 then calibrated for during exposed' conditions.
' There ucre no adverse effects on the health or safety of the public as n result of this failure.
I Corrective Action Irrediately unon discovery, the affected channels were readjusted cr.d checked.
Tne other chennels ;ucre tested and found within l'inita. The surven ' ance instruction will be' revised to adjust the count /insacrative circuit to trip at less then 15 cperable L7E4 inputs which,is one tore than required by the tcchnical specifications. This conservative cetpoint should prevent pimilar occurrences.
T~m Failurc Data
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