05000346/LER-1981-012-03, /03L-0:on 810212,control Rod 1-3 Absolute Position Indication Declared Inoperable Due to Fluctuating Signals Causing Asymmetric Rod Alarms.Exact Cause Undetermined,But Absolute Position Indication Leads Picking Up Noise
| ML19350A920 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/13/1981 |
| From: | Werner J TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML19350A919 | List: |
| References | |
| LER-81-012-03L, LER-81-12-3L, NUDOCS 8103170493 | |
| Download: ML19350A920 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| 3461981012R03 - NRC Website | |
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U. S. MUCLEAR REGULATORY COMMISSION NRC FORM 366 (7 77)
LICENSEE EVENT REPORT
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bJ ENENT DATE 74 75 REPORT C AT E 80 EVENT DESCRIPTION AND PROBABLE CONSEOUENCES h o 2 l (NP-33-81-11) On February 12, 1981 at 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br />, Control Rod 1-3 Absolute Position I
l o l3 l l Indication (API) was declared inoperable due to fluctuating signals which caused num - l l o i 4 l l erous " asymmetric rod" alarms. The station entered the action statement of Technical 1 l Specification 3.1.3.3.
There was no danger to the health and safety of the public or I o s lo is l l station personnel. The position of the control rod was verified by actuating one of l 10171 l its zone references. The rod was not varying from its intended position, only the l
I loisl l API was faulty.
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l Ylh l A [g l Al 3l 8l Og 33 34 34 36 31 40 4l 42 43 44 47 CAUSE DESCR'PTION AND CORRECTIVE ACTIONS h the I QJO_J IThe problem was isolated to the API signal between the +5 VDC into containment at I
l outer containment electrical penetration terminal board and the return API sinnal at i i i 2 ] the same location.
It appears noise is being picked up in the electrical penetration l l'TTTl l module. FCR 79-401'was written to obtain spare penetration nodules. At the next out-j 1 age, Rod 1-3's API signals will be brought through installed spare wires in its present i 4 enetration7 7
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DVR 81-025
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TOLEDO EPISON COMPANY DAVIS-BESSE NUCLEAR JWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-81-11
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.DATE OF EVENT: Februar, 12, 1981 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Control Rod 1-3 Absolute Position Indication (API)
Fluctuations Conditions Prior to Occurrence: The unit was in Mode 1, with Pcwer (MWT) = 2761 cod Load (Gross MRE) = 920 Description of Occurrence: On February 12, 1981 at about 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br />, Control Rod 1-3 API was declared inoperable due to fluctuating signals which caused nu=erous
" asymmetric rod" alarms. Also the API would not indicate movement when the rod was moved out in relation to the group. This placed the unit in the action statement of Technical Specification 3.1.3.3 which required the position of the control rod to be verified by actuating one of its zone reference indicators. The rod position was verified at its 100% withdrawn position, and the rod position indication was placed in asymmetric bypass.
Designation of Appareni e nae of Occurrence: The exact cause of this occurrence is undetermined. The problem has been isolated to the API signal between the +5 VDC into containment at the outer containment electrical penetration terminal board, and the returr..I' signals at the same location. During the 1980 Refueling, Facility Change Request 79-413 changed the position indication (PI) assemblics and PI cables on the reactor head. Because of this and information from previous troubleshooting of similar API problems, it appears the API signal leads are picking up noise in the electrical penetration modules.
Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The rod did not vary frcs its intended position, only the API was faulty.
Corrective Action
Work Request IC-55-04-81 was written to place a brush recorder on the signal leads at the outer containment electrical penetration terminal board.
Because of information gathered at this point and information gathered from other rods with similar problems, using test connections inside of containment (see Licensee Event Reports NP-33-79-141 (79-116), NP-33-80-07 (80-004), NP-33-80-21 (80-015) and NP-33-80-35 (80-025) it was felt noise was being picked up within the electrical penetration. Facility Change Request 79-401 has been written to obtain cpare penetration modules for use in replacing defective modules. Until this faci-lity change request has obtained final approval and spare modules are purchased, c. facility change request has been written to bring rod 1-3 API signal through installed spare wires in its present penetration. This will be done at the next cutage.
LER #81-012
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TOLEDO EDIS0!; COMPATI DAVIS-BESSE !!UCLEAR PO',iER STATIO!; U'iIT O!iE SUPPLE'T::TAL II; FORMATIO!; FOR LER ::P-33-81-11 PAGE 2 Failure Data: There were numerous previous failures of control rod API prior to the 1930 refueling cutage and the i=ple entation of Facility Change Request 79 '.13 as noted above. This is the first reported failure of an ASI since then.
LER i81-012 O
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