ML20151Y293
| ML20151Y293 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/09/1998 |
| From: | Heffley J COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| JMHLTR:#98-0241, JMHLTR:#98-241, NUDOCS 9809180186 | |
| Download: ML20151Y293 (2) | |
Text
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L' commonw eaiei r41non < onyun3 Dresden Generating Nanon 8
(>500 North Drc> den Road U HTi%, II. bl)(bO lelMl. % 42 3 20 j
September 9,1998
(
JLTR: #98-0241 I
U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555
Subject:
Dresden Nuclear Power Station Failure of the Dresden Lock & Dam NRC Docket Nos.50-010. 50-237. and 50-249
Reference:
(a).
J. M. Hefiley to USNRC letter dated March 31,1998, regarding
" Design Basis Initiative Program" (JMHLTR: #98-0085)
In the March 31,1998, letter referenced above, Comed made a commitment to evaluate the feasibility of a seismically qualified or verified path to obtain water from the ultimate heat sink (UHS) and deliver it to the shell of the isolation condenser for each unit. The purpose of this letter is to notify the NRC of the results of the feasibility study.
Section 9.2.5 of Dresden's UFSAR currently describes how the isolation condensers would be used to remove reactor decay heat following an earthquake that caused the los s of the Dresden Lock & Dam. Make-up to the shell of the isolation condensers would b:
provided by the fire protection system. The fire protection system is considered a Class 11 system (non-safety-related and non-seismic). However, using existing valves, it is possible to sectionalize the system to isolate failed parts. As discussed in the March 31,1998, letter referenced above, the vulnerability of the fire protection system to an earthquake was evaluated by the NRC during original plant licensing and during the Systematic Evaluation Program (SEP). However, the NRC imposed no additional requirements to reduce the seismic vulnerability.
Dresden Station currently meets the licensing basis requirements for safe shutdown following a dam failure. However, to satisfy Generic Letter 87-02 program requirements and enhance plant safety using the Seismic Qualification Utility Group (SQUG).
methodology, Comed searched for a method to supply make-up water to the shell of the isolation condensers through piping and components that are seismically qualified or that can be seismically verified using the Generic Implementation Procedure (GIP) of the SQUG program.
One method identified uses the Unit 2 diesel generator cooling water (DGCW) system to obtain water from the UHS. This system is capable of extracting water from the UHS l
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O USNRC September 9,1998 JMHLTR: #98-0241 Page 2 down to an elevation of approximately 488' This is 7' lower than the water level in the intake canal is projected to drop following a dam failure. A hose connection would be installed in the DGCW discharge line where it returns to the circulating water system after it has passed through the diesel engine heat exchanger. Another hose connection would be installed in the discharge line of the isolation condenser make-up pumps. Following an earthquake that disabled other means of getting water from the UHS to the shell of the isolation condensers, a portable engine-driven pump would be used to pump water from the DGCW discharge line to the isolation condenser make-up pump discharge line. The DGCW pumps and piping and the isolation condenser make-up pump discharge line to the shells of the isolation condensers are seismically qualified to withstand the effects of a safe i
shutdown earthquake (SSE).
The decision concerning whether to implement this plant modification, or a different one, will be made as part of the GL 87-02 program. The SQUG program requires that seismically verified or seismically qualified safe shutdown equipment be available to safely shutdown the units following an earthquake.
If there are any questions concerning this letter, please refer them to Mr. Frank Spangenberg, Dresden Station Regulatory Assurance Manager, at (815) 942-2920, extension 3800.
Sincerely, b
I L }L. w h N
J.M. He ey Site Vice President Dresden Station Regional Administrator, NRC Region III cc:
Senior Resident Inspector - Dresden Nuclear Power Station
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