ML20072S224
| ML20072S224 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 09/09/1994 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | Russell W Office of Nuclear Reactor Regulation |
| References | |
| IEB-79-14, NUDOCS 9409130480 | |
| Download: ML20072S224 (3) | |
Text
._
Comm:nwrilth Edison 1400 Opus Place s
s-Downers Grove, tilinois 60515
(
September 9,1994 Mr. William T. Russell, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington D.C.
20555 Attn. Document Control Desk j
Subject:
Quad Cities Station Units 1 and 2 l
Resolution of Piping Configuration Verification Program Discrepancies NRC Docket Nos. 50-254 and 50-265
Reference:
L.N. Olshan to T.J. Kovach letter dated September 27,1991 l
l Mr. Russell, The purpose of this letter is to transmit a status update for the Quad Cities Station Piping Configuration Verification Program (PCVP). This update includes a description of reanalysis efforts for piping discrepancies which were originally identified in 1991.
Based upon a review of NUREG 0661 in 1987, Commonwealth Edison Company (Comed) initiated the small bore PCVP at Quad Cities Station to verify the i
existence and location of pipe supports with respect to the as-designed and analyzed configurations. The program consisted of safety-related piping, greater than four inches in diameter, which was originally analyzed as part of the Mark l Torus Attached Piping /l.E. Bulletin (IEB) 79-14 Program.
The Mark l/IEB 79-14 Program was intended to re-evaluate and qualify vanous containment piping systems for design basis accident hydrodynamic load conditions.
The Mark I analysis utilized the response spectrum evaluation for the ECCS Ring Header with the attached suction piping decoupled. The suction piping was then separately evaluated utilizing response spectra. The Safety Relief Valve (SRV) loading, as adjusted by available in-plant SRV testing data, is the major load j
contributor in most cases. This was enveloped as a single load case.
These analytical methods incorporated conservatism into the piping analyses and subsequent plant modifications. During the early 1980's this was the most effective method due to the complexity and cost of main frame computer analyses, i
especially for large coupled models utilizing time history analysis, in many cases, I
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Mr. W.T. Russell September 9,1994 even main frames were not large enough to handle time history analysis of large coupled models. In addition, construction cost was relatively inexpensive, and in-plant SRV testing and analysis was not yet completed.
i in the referenced letter, the NRC formally approved the Dresden/ Quad Cities Piping Operability Criteria. Comed submitted this Operability Criteria to the NRC for the analysis of piping which exceeded the FSAR allowable values. The criteria q
allows for continued operation of systems and components when piping stresses exceed UFSAR allowable values, until appropriate modifications to the system can be implemented.
In 1992 and 1993, Comed identified modifications necessary to resolve pipe support discrepancies at Quad Cities Station Unit 1 and Unit 2 on the Residual Heat Removal (RHR) - Shut Down Cooling, HPCI, and Core Spray systems. The small bore piping associated with the above modifications was originally verified operable in February 1991, with final evaluations complete in November 1991. Comed delayed implementation of the corrective modifications pending resolution of similar large-bore piping support discrepancies. These were resolved in 1993.
Based upon potential savings in occupational exposure, and technical advances in computational and analytical methods, Comed has reinitiated analysis of the large bore and small bore piping support discrepancies described above. This reanalysis will:
i Couple the ECCS suction lines, one at a time, to the ring header and use direct integration time history method to reduce responses; Refine the SRV Enveloped load case to include all SRV actuation conditions to remove conservatism and utilize damping values for each load case, and reduce the SRV load magnitudes based on the SRV in-plant test results; Perform a code reconciliation to eliminate the requirement for weld build-up; and Re-apply the 10% cutoff criterion to eliminate applicable small bore modifications.
This reanalysis is scheduled to be completed by September 30,1995.
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o Mr. W.T. Russell September 9,1994 Comed previously verified operability of the affected systems in 1991 in accordance with the approved criteria described in the referenced letter. Comed has also reviewed that existing operability evaluation, including a verification that ongoing related modification activities do not impact the operability status of the subsystems.
Based upon this subsequent review, Comed has concluded that the affected subsystems will remain operable until all discrepancies are resolved, and any required modifications are installed.
If there are any questions, please contact John L. Schrage at 708-663-7283.
Very truly yoursg l
John USchrage Nuclear Licensing Administrator cc:
J. Martin, Regional Administrator - Region lli C. Miller, Senior Resident Inspector - Quad Cities Station R. Pulsifer, Project Manager - NRR Office of Nuclear Facility Safety - IDNS k.nla. quad letters marlu2 wpf 3