ML20077L441
| ML20077L441 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 08/07/1991 |
| From: | Kovach T COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9108120237 | |
| Download: ML20077L441 (3) | |
Text
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Commonw3alth Edison O
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v' Downers Grove. Illinois 60515 August 7,1991 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
i.aSalle County Station Units 1 and 2 Response to Unresolved item Inspection Report Nos. 50-373/91010; 50-374/91009 NBC_DocketNosm50-3Z3.and 50-314
Reference:
G.C. Wright letter to Cordell Reed dated July 8,1991 transmitting NRC Inspection Report 50 373/91010; 50 374/91009
Dear Sirs:
Enclosed is Commonwealth Edison Company's (CECO) response to the subject Unresolved item. The item addressed the adequacy of the 10 CFR 50.59 safet) evaluation performed for a temporary system change in the off gas system. The response to this item is provided in Attachment A.
If your staff has any questions or comments concerning this letter, please refer them to Annette Denenberg, Compliance Engineer at (708) 515-7352.
Very truly yours, ach Nuclear Licensing Manager Enclosure cc:
A.Bert Davis, Regional Administrator - Rill B. Siegel, Project Manager - NRR T. Tongue, Senior Resident inspector - LSCS
- 1. Yin, inspector - Rill
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ATTACHMENT A RESPONSE TO UNRESOLVED ITEM INSPECTION REPORT 373/91010; 374/91009 UNBESQLVfD ITEM (373/91010-01; 374/91009-01)
The inspection Report identified an unresolved item related to the ade uacy of the 10 CFR 50.59 safety evaluation performed for LaSalle Temporary ystem Change (TSC) 1-1719-88, Removal of Off Gas (OG) High Flow Contr Room Annunciation. The concern expressed was that the 50.59 ovaluation did not adequately address the system and Safety Analysis effects related to operailon of j
the off gas cystem in an increased flow condition.
Subsequent to the NRC Inspection, CECO requested technical assistance from General Electric regarding 11e effects of the increased flow and has reperformed a 50.59 evaluation under CECO's current program to determine if any Unreviewed Safety Questions exist. This evaluation has verified that the present system operation is within the bounds of the system design and the Safety Analysis. A copy of the 50.59 safety evaluation of the current Off Gas System operating status is available at the site for review, CECO has reviewed the circumstances that led to the approval of the TSC and concluded the following:
The preparer of the TSC properly recognized in screening the TSC that it involved a change to the facility as described in the UFSAR and performed the required 50.59 evaluation.
The preparer correctly identified that the alarm being modified did not perform an active protective function and identified the relevant source of safety protection (the Off Gas Post Treatment Rad Monitor) as being unaffected. However, not specifically documented was the effect that administrative control (of system flow rate) plays in the initial conditions of accident secuences.
The preparer of the TSC referenced the evaluation of the effects of higher than normal Off Gas flow, to a procedure which was written specifically for that purpose. CECO considers it acceptable to reference existing evaluations when applicable. In this case, it was logical for the areparer to rely upon the existing evaluation performed per procedure
_TP 900-1 (Rev. 0 - May 1986), "Off Gas System High Flow Alarm Setpoint Change Evaluation."
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i ATTACHMENT A(CONTINUED)
RESPONSE TO UNRESOLVED ITEM INSPECTION REPORT 373/91010; 374/91009 However, when used as the technical basis for operation with abnormal
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off gas flows, LTP 900-1 did not establish specific operational limits or require evaluation of the UFSAR effects of the condition being evaluated. During the development of this procedure, CECO obtained an evaluatlot from the architect engineer which did evaluate operation with abnormally high flows, Review of this evaluation showed that system operation and plant shielding were the focus of the review and that the potential for deviation from UFSAR analysis inputs was not addressed. To correct this deficiency in the procedure, LT P 900-1 will be revised to include specific limits on routine operation. Completion of this revision is expected by October 1,1991.
Tne UFSAR has shown that for the off gas line break event, the bounding release occurs at the lowest off gas flow, in summary, the LTP 900-1 procedure's 50.59 evaluation was deficient for the reasons stated above; however, this deficiency did not affect off gas system operation. Operation of the system has been shown to be acceptable, with no adverse effects on the system or the results of analyzed accidents.
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