ML20198C164
| ML20198C164 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/21/1991 |
| From: | Kovach T COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9106280162 | |
| Download: ML20198C164 (3) | |
Text
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Ccmmenw:alth Edison 37 1400 Opus Place Downers Grove, Illinois 60515 June 21,1991 f
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
]
Subject:
Zion Nuclear Power Station, Unit 2 Response to NRC Augmented Inspection Team (AIT) Report inspection Report No. 50 304/91006 NBC_Docke1 Nom 50-301
References:
(1) Licensee Event Report 91-002 00, Docket No.
50-304/DPR 48 (2) E.G. Greenman letter to Cordell Reed dated April 17,1991 transmitting NRC Inspection Report 50 304/91006 The Augmented Inspection Team report included a list of eight recommendations t
based upon the team's observations. Six of these recommendations were previously addressed in reference (1), which was issued as a result of the event that precipltated formation of the AIT. Although the subject inspection Report did not specifically request a response regarding these recommendations, CECO has determined a response is appropriate for the two previously unaddressed AIT recommendations.
Commonwealth Edison Company's (CECO) response is contained in the attachment to t
this letter.
The security weaknesses discussed in the AIT Report are being addressed in response to Security inspection Report No. 50-295/91005; 50 304/91005.
if your staff has any questions or comments concerning this letter, please refer them to Annette Denenberg, Compliance Engineer at (708) 515-7352.
Very ruly Yours,
/ omas J. 4, ac W
Th Nuclear Licensins M& nager Enclosure cc: A.B. Davis, Regional Administrator - Rill J.D. Gmlth, Senior Resident inspector GAD:TJK:ch l!
ZNI.D/1020/1 -
<0'L 9106280162 910621
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Attachment A IR 50 304/91006 The first of the two AIT recommendations not addressed in previous correspondence was that an evaluation of methods for more widespread use of the 1980 Zion PRA should be undertaken, especially as it pertains to maintenance planning. CECO has previously considered the value of using the 1980 PRA for Zion in current planning or evaluation activities. When Generic Letter 88 20 was issued requesting plant specific PRAs, CECO evaluated the merits of using and/or upgrading the 1980 Zion PRA. It was concluded that PRA technology had substantially evolved and improved, and that certain Zion models in the 198n PRA had changed and did not match current plant configuration or use as described by procedures. A decision was made to provide a new PRA for Zion based on the latest plant data and PRA technology. For the same reasons, CECO did not actively pursue using the 1980 PRA for real-time decision making so as to preclude basing decisions on out-of-date information.
CECO has attempted to apply some basic risk analysis philosophy in managing maintenance activities. As an example, Zion Station in conjunction with the Engineering organization, reviewed the backlog of work requests which were not completed prior to Unit 1's return to servico. CECO did not directly employ the existing Zion PRA in the activity, however the team performing the review ascessed if any of the deferred work could pose a significant transient initiator or could decrease accident mitigation capability. As the work request screenings progressed the team felt that work which could impact extended power generation should also be evaluated. The review was performed by experienced personnel knowledgeable of plant operation. In some cases, the review generated an adjustment in work request priorities. A similar review was performed for Unit 2.
As part of CECO's ongoing effort in the PRA area, we are evaluating ways to effectively employ the results of the PRAs in future planning and prioritization activities. As we finalize plant specific IPEs and our plans for their application, we would be pleased to meet with you to discuss these initiatives.
ZNLD/1020/2
Attachment A(Continueo) lR 50 304/91006 The second AIT recommendation was that Zion review the criteria in use for classification of events for root cause analysis. In November,1990 a similar inadvertent deluge of the Unit 2 System Auxiliary Transformer (SAT) was investigated under the Root Cause Program. A review of Zion Station's procedures for classifying root cause analyses has beeri conducted (this was done from both a generic viewpoint and as they were applied to the November event). From this review it has been determined that the previous event was in fact correctly classified as a level Ill investigation to be performed per Zion's Devi-n reporting procedures.
Howe cer, as indicated b reference (1), t! >
ot cause analysis methodology used for the November 1990 event was suspect. A6 failing to reach a firm conclusion in that analysis, no effort was made to look at other possible, though less obvious postulations for root cause analyses. The Root Cause Committee has since altered its methodology. Once the investigation of an event is complete, the Root Cause Committee will review the results and evaluate the corrective actions to ensure that they fully address the root cause of the event. If the root cause was not identified, the committee will attempt to determine whether all possible root causes have been properly evaluated. This approach precludes acceptance of inconclusive results v'ithout thorough consideration of other plausible root causes and is consistent v<ith the
" questioning attitude" philosophy that Zion is aggressively promoting.
ZNLD/1020/3
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