ML20205R742
| ML20205R742 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 10/31/1988 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 1586, NUDOCS 8811100112 | |
| Download: ML20205R742 (2) | |
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TOLEDO
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EDISON DONALD C. SHELTON (419ji49 E Y o Docket No. 50-346 License No. NPF.3 Serial No. 1586 October 31, 1988 l
l i
United States Nuclear Regulatory Commission l
Document Control Desk i
Vashington, D.C. 20555 l
Subj ec t Environmental Qualification of Hot Leg Level Monitoring System I
Componeats Gentlement r
The purpose of this letter is to provide information regarding the l
l environmental qualification of the Davis-Besse Nuclear Pover Station, Unit No.1 (DBNPS) Hot Leg Level Monitoring System (HLLMS) components with regard I
to Regulatory Guide 1.97 and 10CFR50.49 requirements. Regulatory Guide 1.97, Revision 3. "Instrumentation for Light-Vater-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and following an Accident,"
requites coolant inventory instrumentation to be provided and classifies this instrumentation as Type B, Category 1 instrumentation. This classification t
requires that this instrumentation be environmentally qualified.
i The HLLMS provides the means for satisfying the Regulatory Guide 1.97 i
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requirement by allowing the trending of reactor coolant system hot leg level.
during natural circulation or when natural circulation is lost. The l
.i locations of the HLLMS transmitters and temperature compensating thermistors l
have been reviewed for conformance to Regulatory Guide 1.97 during the current refueling outage. This review has determined that the HLLMS components are located below the maximum flood level in containment following the LOCA. The HLLMS components have been qualified for LOCA conditions but they are not qualified for submergence.
I For a large break LOCA, the HLLMS components vould becor.e submerged approximately 30 minutes following the break considering the vorst case i
assumptions oft j
1) the entire contents of the reactor coolant system, core flood i
tanks, and the pressurizer being emptied ie.nediately onto the I
containment vessel floor, with no vaporization, and i
8911100110 881031
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PDR ADOCK 05000346 P
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j THE TOLEDO ED60N COYPANY EDSON PLAZA 30] MAD $CN AVENUE TDLEDO.OH:043652 4
i Docket No. 50-346 e
3 Licdnso No. NPF-3 i
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' Serial No. 1586
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Page 2 l
2) the entire contents of the Borated Vater Storage Tank being
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pumped into the containment vessel at 9000 rpm.
However, for this type of LOCA, use of the HLLMS to trend RCS inventory would not be needed due to the rapid depressurization and blovdown of the RCS following the break.
l Submergence may also occur following a small break LOCA, which represents the most credible type of accident for which the HLLMS may provide trending information. Due to the reduced blevdown rate associated with a small break LOCA, a significantly longer period of time vould elapse prior to submergence of the HLLMS components. Toledo Edison has concluded that sufficient time is available prior to uubmergence for plant personnel to determine the approach to an (nadequate core cooling condition.
Furthermore, other redundant and diverse instrumentation is used for accident mitigation and more direct monitoring of core cooling capabilities.
This instrumentation includes the reactor coolant system saturation monitors and the core exit thermocouples vhich allow the operator to directly monitor core cooling. The availability of these indications adequately compensates for HLLMS unavailability due to component submergence.
Toledo Edison is revising the Environmental Qualification package for the HLLMS to document within the package the justification for not requiring submergence aualification consistent with the abuve discu::sfon.
Should you have any guestions concerning the above, please contact Mr. R. V. Schrauder.
Nuclear Licensing Manager, at (419) 249-2366.
Very truly yours,
/
RMC/dlm cet P. Byron, DB-1 NRC Resident Inspector A. V. DeAgazio, DB-1 NRC Senior Project Manager A. B. Davis, Regional Administrator, NRC Region III