ML20056H023
| ML20056H023 | |
| Person / Time | |
|---|---|
| Issue date: | 07/15/1993 |
| From: | Thadani A Office of Nuclear Reactor Regulation |
| To: | Lewis M LEWIS, M. |
| References | |
| IEB-93-002, NUDOCS 9309080087 | |
| Download: ML20056H023 (1) | |
Text
Mr. Marvin 1. Lewis July 15, 1993 Suite 62 7801 Roosevelt Blvd Philadelphia, PA 19152
Dear Mr. Lewis:
In your letter dated June 5,1993, to Dr. Murley, you expressed concern, in the context of NRC Bulletin 93-02, about thermo-lag and its impact on reactor systems in the event that it fails. As you know, licensees use Thermo-Lag fire barriers to satisfy HRC fire protection requirements. These licensees separate one train of cables and equipment needed to shutdown the plant in the event of a fire from its redundant train with Thermo-Lag fire barriers.
L Thermo-Lag is mainly used to separate redundant raceways located outside of primary containments by surrounding one of the raceways within a Thermo-Lag enclosure.
Some licensees have also used Thermo-Lag to construct radiant energy shields inside containment. This is a limited application.
The bulletin was narrowly focused on temporary sources of fibrous material in the primary containments of boiling and pressurized water reactors (BWRs and PWRs). The purpose of the bulletin was to have such material removed promptly if it is not designed to withstand a loss-of-coolant accident (LOCA). Our concern, as expressed in the bulletin, is that debris generated from such sources during a LOCA might be transported to the suppression pool for a BWR or to the containment sump for a PWR.
If this material is deposited on the surface of strainers for the emergency core cooling system and the containment spray system, then the pumps in those systems might not have adequate net positive suction head and may fail to perform as designed.
We are also pursuing a broader concern that relates to fibrous material that is permanently installed in drywells of some BWRs.
That concern was previously addressed in our review of Unresolved Safety Issue A-43,
" Containment Emergency Sump Performance." As a result of recent operating experiences, we are reviewing how this material and other materials would perform during a LOCA and the impact of these materials on the performance of safety-related systems. The scope of this review would include thermo-lag if it were present in significant quantities within the drywell. However, very little thermo-lag is located there.
I would like to thank you for your interest in the safety and performance of licensed nuclear power plants.
Sincerely, g g D109 @N AshoK C. lhaoan s, Director yy/j "
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