ML20012B566
| ML20012B566 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/05/1990 |
| From: | Blosser J, Evans K UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-90-002, LER-90-2, ULNRC-2165, NUDOCS 9003150328 | |
| Download: ML20012B566 (6) | |
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U. S. Nuclear Regulatory Commission Document Control Desk i Washington, DC 20555 L ULNRC-2165 l
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DOCKET NUMBER 50-483 l
' CALLAWAY PLANT UNIT 1 FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 90-002-00 ELECTRICAL PROBLEM IN THE CONTROL ROD SYSTEM LED TO A CONDITION PR0llIBITED BY THE PLANT'S ,
TECHNICAL SPECIFICATIONS AND A TEMPORARY WAIVER OF COMPLIANfd2 The enclosed Licensee Event Report is submitted to describe an. .
electrical problem in the control rod system which led to a condition prohibited by Technical Specification (T/S) 3.1.3.1. This led to a :
temporary waiver of compliance from the plant's T/S per 10CFR50.91 ] '
granted from the Office of Nuclear Reactor Regulation. This event is reportabic per 10CFR50.73(a)(2)(1)(B). ,
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. D. Blo1ser '
Manager. Callaway Plant TfS edum !
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- cc diCtrib:. tion fCr ULNRC-2165 :
Mr. A. Bert Davis Mr. $. V. Athavale '(2 copies)
Regional Administrator Office of Nuclear Reactor Regulation' ,
U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission ,
' Region III Mail Stop 13-E J 799 Roosevelt Road Washington, D.C. 20555 !
Glen Ellyn, IL ~60137
!~ American Nuclear Insurers. Mr. O. Maynard l l1 c/o Dottie Sherman, Library Wolf Creek Nuclear Operating Corp. :j The Exchange Suite 245 P. O. Box 411 >
270 Farmington Avenue Burlington, KS 66839 Farmington, CT 06032 !
Mr. Merlin Williame >
Manager, Electric Department Supt. of Regulatory Quality & I Missouri Public Service Commission Administrative Servicea !
- P. O. Box 360 Wolf Creek Nuclear Operating Corp. [
_ Jefferson City, MO 65102 P. O. Box 411 :
Burlington, KS: 66839 l Records Center Mr. R. L. Hague l Institute of Nuclear Power Operations Chief, Project Section 3C !
Suite 1500 U.S. Nuclear Regulatory Commission }
> 1100 circle 75 Parkway Region III
- Atlanta, GA 30339 799 Roosevelt Road -!
i Glen Ellyn, IL 60137 l
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NRC Resident Inspector !
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' 6 8 i* Electrical Problem in the Control Rod System Led to a condition Frohibited by the Plant's Technical Specifications and a Temporary k'aiver of Compliance tvthi DATIISI tth wueABER 86i A&PDhi Daf t th DTHER 0 ACittit&8 INVOLVID 681 MOttH DAY vt Aft v4Ah H ,1 (a k saa , ppg 3, p,y yggg . a g s p, y g.g,, ppg ,,g , gyy gg ,t y, O I bjol0log i ;
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On 2/2/90, at 1405 CST, a control rod urgent failure alarm was received during the performance of a monthly surveillance on movable control rod assemblies due to an electrical problem. Technical Specification (T/S) 3.1.3.1 Action Statement (b) was entered. The control rods remained trippable. The plant was in Mode 1 - Power Operations at 100 percent Reactor Power.
On 2/2/90, the Resident Inspector and the Office of Nuclear Reactor Regulation (NRR) were contacted and a temporary waiver of compliance per 10CFR50.91 was granted at 1630 until the period ending at 1405 on 2/5/90 This extended the T/S 3.1.3.1.b allowed outage time from 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to allow resolution of the control rod electrical failure. This request was consistent with the Operating License amendment request of 8/2/89.
Troubleshooting revealed one circuit card with a defective chip. The defective slave cycler counter card was replaced and the control rod system declared operable at 0922 on 2/3/90.
An evaluation of slave cycler counter card history at Callaway indicated that this was the only failure since a modification installed additional cooling to the rod drive set room in June, 1987. The licensee concluded this event was a random failure and no further action will be taken.
l The Operating License amendment to T/S 3/4.1.3 was implemented on 3/1/90. !
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0l0 0l2 or 0l4 l 1 Basis for Reportability This Licensee Event Report is submitted as a result of noncompliance from Technical Specification (T/S) 3.1.3.1 Action Statement (b). The licensee i
obtainedatemporaryvag$rofcomplianceper10CFR50.91relatingtomovable control rod assemblies. A control rod urgent failure alarm was received during the performance of monthly surveillance per T/S 4.1.3.1.2 on movable control rod assemblies due to an electrical problem. The control rods remained trippable. This event is reportable per 10CFR50.73(a)(2)(1)(B).
Condition at Time of Event Mode 1 - Power Operations, Reactor Power - 100 percent.
Description of Evenj Union Electric requested an Operating License amendment from the Nuclect Regulatory Commission (NRC) in letters ULNRC-2055 dated 8/2/89 and ULNRC-2129 dated 12/29/89. These letters requested a change to T/S 3/4.1.3 and its associated Bases to allow continued operation for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with one or more control rod assemblies inoperable due to an electrical problem in the control rod system provided all affected control rods remained trippable.
On 2/2/90, at approximately 1405 CST, a control rod urgent failure alarm was received during the performance of a monthly surveillance on movable control rod assemblies. The failure was determined by utility Instrument and Control (160) department personnel to be electrical, not mechanienl, and the control rods were capable of insertion into the core upon a reactor trip nignal. The control rods were declared inoperable by the licensed Shift Supervisor and T/S 3.1.3.1 Action Statement (b) was entered. This T/S Action Statement states: "With more than one full-length rod inoperable or misa3fgned from the group step counter demand position by more than 212 steps (indicated position), be in 110T STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />."
on 2/2/90, the Resident Inspector and the Office of Nuclear Reactor Regulation (NRR) were contacted to request a temporary waiver of compliance per 10CFR50.91 to extend the T/S 3.1.3.1 Action Statement (b) allowed outage time from 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to allow resolution of the control rod electrical failure. This request was consistent with the Operating License amendment request of 8/2/89.
Upon NRR's review of Callaway's Operating License amendment to T/S 3/4.1.3, the temporary waiver of compliance was granted at 1630 on 2/ /90 until the period ending at 1405 on.2/5/90 to complete the repairs. This was based on the utility's assurance that the control rod's primary safety function would not be impaired. Due to this approval, the licensee was in technical noncompliance with T/S 3.1.3.1 Action Statement (b) at 2005 on 2/2/90.
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0l0 0l3 or 0l4 virica . n. .as w ecs ann wnn The control rod, system was repaired and determined to be operable by T/S surveillance testing. The T/S 3.1.3.1 Limiting Condition of Operation was natisfied at 0922 on 2/3/90.
Root Cause The 1&C department troubleshooting revealed one circuit card ( } with a defective chip. This card was an electronic counter circuit that is part of the slave cycler in the control rod logic cabinet.
Corrective Actions
- 1) The defective slave cycler counter card was replaced. An evaluation of slave cycler counter card history at Callaway indicated that this was the only failure since a modification installed additional cooling to the rod drive set room in June, 1987. The licensee concluded this event was a random failure and no further action will be taken.
- 2) Operating License amendment No. 51 to T/S 3/4.1.3 was impicmented on 3/1/90. This r.mendment allows 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to troubleshoot and repair this type of failure.
Safety Significance The inoperable control rods could have been tripped and therefore were able to perform their safety function. Since the safety function (reactor trip) of the control rod system was not impaired, this event did not adversely affect or endanger the health or safety of the general public or involve a significant safety hazard.
Previous Occurrences LER 85-048-00, 11/29/85, ULNRC-1214 On 11/2/85, a reactor trip occurred as a result of a power range high negative flux rate. A Feedwater Isolation Auxiliary Feedwater Actuation, Steam Generator Blowdown and Sample Isolation, and turbine trip occurred as a result. .
The power range high negative flux rate reactor trip resulted when a control rod bank dropped. The bank dropped due to a logic error resulting from a failed slave cycler. counter card in a control rod power cabinet. The card was replaced.
l-L Due to prior failures of similar cards, an investigation, which included manufacturer assistance was initiated. This investigation concluded that the card failures were random.
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LER 86-024-02, 1/30/87, ULNRC-1439 On 7/1/86, three rod groups were rendered inoperable due to a faulty slave cycler counter card in the control rod logic cabinet. A plant shutdown was initiated in accordance with Technical Specification 3.1.3.1, Movable
' Control Assemblies Group Height. The rod groups were declared operable after replacing the faulty card.
Corrective actions includedt replacing the faulty card and returning it to the vendor. The vendor evaluation indicated that elevated temperatures directly affected the performance of the card. To prevent recurrence, temporary ductwork was installed to the control rod cabinets and a design change was later implemented to increase permanent cooling in the room.
-LER 86-029-00, 9/23/86, ULNRC-1373 On 8/25/86, during a controlled shutdown of the reactor, a turbine runback occurred. During the runback, as rods were stepping in, a control rod system failure occurred.
The control rod system failure was caused by a slave cycler counter card failure. The slave cycler counter card was replaced. Although no common !
cause was identified, Westinghouse attributed similar control rod failures in other plants to elevated ambient temperatures in control rod cabinets.
Measures were initiated to increase cooling to the control rod cabinets. l l
Footnotes j The system and component codes below are from IEEE Standards 805 and 803A, !
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- 1) System - AA, Component - ROD
- 2) System - AA j l' \
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