ML20134F268
| ML20134F268 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 10/30/1996 |
| From: | Schnell D UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-22, ULNRC-3482, NUDOCS 9611050115 | |
| Download: ML20134F268 (3) | |
Text
_.
o 1901 Chouteau Avenue Post Office Box 149 St Louis. Missouri 63166 314 554-2650 Uuron Octoher 30, Etscraic fe;f!;eT;j;,
1996 uvse.
M U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station P1-137 Washington, DC 20555-0001 l
Gentlemen:
ULNRC-3482 DOCKET NUMBER 50-483 CALLAWAY PLANT RESPONSES TO NRC RAI LETTER ON CALLAWAY IPEEE
Reference:
ULNRC-3319, dated February 2, 1996 The referenced letter submitted Union Electric's responses to the NRC Request for Additional Information (RAI) Letter concerning the Callaway Plant Individual Plant Examination of External Events (IPEEE)
Report.
A telecon between the NRC Staff and Union Electric was held on October 15, 1996 to discuss our response to the RAI to close out Generic Issue 103,
" Design for Probable Maximum Precipitation," with respect to roof ponding of water on safety-related structures.
Callaway Plant was designed to conform with the requirements of the Standard Review Plan and the requirements contained in Regulatory Guides 1.59 and 1.102.
As part of the IPEEE evaluation of external l
flooding, Union Electric evaluated the effects of the l
revised National Weather Service methodology for estimating local intense rainfall.
The new methodology changed the Probable Maximum Precipitation (PMP) estimates for higher rainfall intensities over shorter l
time intervals and smaller areas.
Through Generic Letter 89-22,, licensees were requested to assess the effects of these new estimates on their plants.
The Union Electric evaluation that was performed for the revised PMP, for increase in roof loadin~g, demonstrates that the revised PMP estimates l
would not resulc in roof ponding depths which would adversely affect the safe operation of the plant.
The roofs of the safety-related structures have no parapets or any other similar features that would induce loading in excess of the design basis in the event the roof drains could not discharge the maximum precipitation
/ C)ll Yo C
9611050115 961030 PDR ADOCK 05000403 G
PDRu
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U.S. Nuclear Regulatory Commission October 30, 1996 Page 2 intensities of the revised PMP estimates.
The roofs of the safety-related structures are designed to minimize l
ponding.
Water could pond to a maximum of 2" at the edge of the roofs (slightly-higher at the drains) if the roof drain system could not accommodate the revised PMP.
Any additional accumulation of water would overflow the roof edges onto the ground.
The load from
)
this accumulation of water however is still less than the design snow load of 125 lb/ft8 In conclusion the use of the latest PMP criteria to assess the affects on roof ponding has 1
shown that there will not be any additional roof loading due to the increased local intensity of rainfall because the current roof design configurations of the safety-related structures precludes this from occurring.
Very truly yours,
("]
Donald F.
Schnell JMC/jdg e
\\
cc:
M. H.
Fletcher Professional Nuclear Consulting, Inc.
19041 Raines Drive Derwood, MD 20855-2432 l
l L.
Joe Callan Regional Administrator l
U.S. Nuclear Regulatory Commission l
Region IV 611 Ryan Plaza Drive l
Suite 400 Arlington, TX 76011-8064 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 i
Kristine M. Thomas (2)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 1 White Flint, North, Mail Stop 13E16 11555 Rockville Pike Rockville, MD 20852-2738 i
Manager, Electric Department Missouri Public Service Commission i
P.O. Box 360 Jefferson City, MO 65102
,