05000000/LER-1986-052, Partially Withheld LER 86-052-01:on 860926,security Data Mgt Sys Computer Terminals Became Inoperable (Ref 10CFR73.21). Caused by Overload of Alarms & Sys Instability.Sys Restored by Placing Sys Multiplexers Online

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Partially Withheld LER 86-052-01:on 860926,security Data Mgt Sys Computer Terminals Became Inoperable (Ref 10CFR73.21). Caused by Overload of Alarms & Sys Instability.Sys Restored by Placing Sys Multiplexers Online
ML20238F824
Person / Time
Site: Wolf Creek, 05000000
Issue date: 11/13/1986
From: Mike Williams
KANSAS GAS & ELECTRIC CO.
To:
Shared Package
ML20238F760 List:
References
FOIA-87-512 LER-86-052, LER-86-52, NUDOCS 8709160371
Download: ML20238F824 (3)
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LER-2086-052, Partially Withheld LER 86-052-01:on 860926,security Data Mgt Sys Computer Terminals Became Inoperable (Ref 10CFR73.21). Caused by Overload of Alarms & Sys Instability.Sys Restored by Placing Sys Multiplexers Online
Event date:
Report date:
0002086052R00 - NRC Website
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.nrnac,so ,.w <... r.i.- ,no on September 26, 1986, at approximately acticns to establish full compensatory measures were initiated in anticipation a Security Data mgement System camputer f ure. At approximately both computer terminals became inoperable.

'these events were most ikely caused by an of alarms and system instability. Extensive troubleshooting activities were performed as a result of several unsuccessful attempts to restore the system. At approximately j the system was restored by individually placing system multiplexer on line anc manually configuring the system data loop.

Follcuing verification of p r s stem o ration, compensatory measures were terminated at approximately )

In accordance with 19CFR 73.71(c), this event has been classified as a major loss j of physical security effectiveness properly compensated, and thus is considered to be a moderate loss. Previous cmputer malfunctions are discussed in Licensee Event Reprts 86-945-90 and 86-049-00, 8709160371 870914 l PDR FOIA l GORDONB7-512 PDR

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On September 26. 1986, at approximately actions to establish full j compensatory measures were initiated in Anticipation of a Security Data ,

Management System computer [IA-CPU) malfunction because of numerous computer i system reconfi urat and fault board failure alarms being generated. At approximately both terminals of the ocaputer system became inoperable.

Shortly therea ter, a reed switdbover to Central Processi Unit (CPU) 'B' as master wa initiated. j The switchover to CPU 'B' as master  ;

did not complete sat isf actorily as evidene by an absence of alarm processing. l It is believed that the terminal inoperability and subsequent unsuccessful switchover were caused by an overload of alarms and the instability of the system.

1 Following these attempts,  !

diagnostics were performed cn the disk drives, the  !

controller boards, and the data loop. E:xtensive data was tained following each CPU malfunction for detailed analysis.

In an ef fort to restore the system and to prcmote identification of the problem area, the system multiplexer were taken off line ard individually brought back on line. When the last multiplexer was restored to service, the system aJain became unstable. We system data loop was manually configured in a manner which ellcwed full locp connunication and restored stable system operation at approximately Device testing was subsequently performed to verify proper system operation. Following completion of this testing, the compensatory measures were terminated at approximate 1M During subsequent investigations, it was determined that the alarm overload and system instability were most likely induced by increased signal attenuation in one section of the communication imp. As discussed in Licensee Event Report 86-054-00, a vendor evaluation of the ccanunications signal strength around the data In mid-October,1986, f lowing de ed diagnostic testing faulty interface baards were discovered, whicti was discussed in]

Special Report 86-004. %ese board ve been replaced. It appears that this replaconent has at least partially resolved the unsuccessful switchover problems. Between mid-October and mid-November, there have been fourteen successful switchovers, emmunilemIW' M

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0J1 0!3 Since completion of t'.ese corrective actions, there has been one computer l

l malfunction on October 24, 1986, which is discussed in Special Report 86-006. The occurrences discussed in that report are dissimilar to the events I discussed herein and are currently considered to be unrelated.

In accordance with 197R 73.71(c), this event has been classified as a major loss .

of physical security effectiveness properly compensated, and thus is considered I to be a rtoderate loss. Previous computer malfunctions are discussed in Licensee Event Reports 86-045-30 and 86-049-00.

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October 7, 1986 9 I@E0VE V I U. S. Nuclear Regulatory Commission b Document Control Desk .b Washington, D.C. 20555 I

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Mr. E. H. Johnson, Director ~~

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t U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 KMLNRC 86-183 Re: Docket No. STN 50-482 Subj: Licensee Event Report 86-054-00 Gentlemen:

The attached Licensee Event Report is submitted pursuant to 10 CFR 73 71 (c) concerning a physical security event at Wolf Creek Generating Station.

The attachment to this letter contains Safeguards Information in accordance withThis disclosure. 10 CFR 73 21 and therefore should be withheld from public letter when separated f: om the attachment, does not contain Safeguards Information and should be '2andled as decontrolled.

Acknowledgement of receipt of this letter, sia the enclosed form would be appreciated. Information In this record W3C delebj in accordance with the Free &m cf ir,f:rm:.- !

Act, exemptions 4 i Lrs very trygg, 2"J-S/4L EN G & \

g Glenn L. Koester '

Vice President - Nuclear GLK:see Attachment 2

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On October 2,1986, at approximately terminals of the Security Data Management System computer became inoperable. At this time, it was discovered that the system had ceased alars processing and actions to establish the required compensatory measures were promptly initiated. A forced switchover to the slave Central Processing Unit (CPU) was accomplished, although proper system operation did not resume. 'Ihese events were likely caused by an overload of incasing alarms. At ap3roximately CPU 'B' was successfully rebooted. By approximately Qstable stem operation had been c6tained by an orderly method of pl sys;em multiplexer on line and manually configuring the system data loop. Following verification of proper em operation, the compensatory measures were terminated at approximately A design change has been initiated to replace certain links of data lcop connunications cable with a type of cable that should minimize loop signal loss.

As stated in Licensee Event Report 86-952-99, which describes a similar event, root cause investigations are continuing, and the results of these investigations along with any identified co-rective measures will be provided in a supplement to that report.

In accordance with 10CFR 73.71(c), this event has been classified as major loss of physical security effectiveness properly ocupensated, ard thus is considered

to be a ncderate loss. Other previous canputer ma? functions are discussed in I,1censee Event Reports 86-045-90 and 86-049-99. ,

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On Octobe: 2. 19:C. n approximately termina a af the Security Data Management Sn-c Computer [IA-CedJ became i pcrable. At this time, it was discovered that the system had ceased alarm processing and actions to establish the required compeustory measures were promptly initiated.

Shortly thereaf ter, a forced switchover to Central Processi.N Unit (CPU) 'D' was initiated.

Although t e switc over to CPU 'B' appeared to ccrnp e norma y, proper stem operation did not restrne. It is believed that the terminal inoperability and subsequent unsatisfactory system operation af ter switchover were caused by an overload of incming alarms induced by noise in the conrnunication loop.

At approximately was taking successfully rebooted,system and stable multiplexer system operation was ob{tained by selected ine and offC placing them back on line in an orderly fashion. At approximately a system instability developed, ich was corrected by a manual configuration of the data loop at approximately , Device testing was subsequently performed to verify proper system operation. Following successful completio this testing, the ccupensatory measures were terminated at approximately%n of u@

A vendor evaluation of the communications signal strength around the data loop has been performed. We results of this evaluation indicated that a significant signal loss was occurring through the loop, most likely due to the type of ccmnunications cable being utilized.

In accordance with the vendor reccmnendations, a design change has been initiated to replace certain links of cable with a type that should minimize loop signal loss. It is believed that this replacement should allow for note stable system operation which will in turn allow for nere ef Mve troubleshooting of any remaining problems.

This event is similar to the occurrence discussed in Licensee Event Report 86-052-00. As stated in that report, investigations concerning the root cause of these events are being actively pursued. The results of these investigations and a description of any identified corrective action will be provided in a supplement to that report.

In accordance with 1KTR 73.71(c), this event has been classified as a major loss of physical security effectiveness properly ccrnpensated, and thus is considered to be a noderate loss. Other previous computer malfunctions are discussed in Licensee Event Reports 86-045-00 and 86-049-00.

Wroughout the time period of this event, the unit was operating in ib$e 1, Power Ooeration, at approximately 100 percent Reactor power. Wis event had no significant effect on the continued safe operation of the plant.

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