ML20081C966
| ML20081C966 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/12/1984 |
| From: | Herborn D ILLINOIS POWER CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| U-0700, U-700, NUDOCS 8403150089 | |
| Download: ML20081C966 (5) | |
Text
7 U- 0700 0210 B50-84 (03-12 )-L ILLINOIS POWER OOMPANY CLINTON POWER 0? ATION. P.o. BCx 678. CLINTON. ILLINOIS 61727 March 12, 1984
(
Docket No. 50-461 i
Director of Nuclear Reactor Regulation l
Attention:
Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 5UBJECT: Clinton Power Station Unit 1 HVAC DUCTWORK Illinois Power Company responses to the NRC Mechanical Engineering Branch Qur.tions #210.05 r.nd #210.06 are attached for review. The questions were geacrated as a result of Mr. D. Terao's visits on December 8 & 9, 1983, to the Sargent & Lundy offices in Chicago and the l
Clinton Power Station site. The design and installation of the HVAC ductwork and supporting members were examined during those visits.
I Illinoir Power Company plans to incorporate its responses into the FSAR at the next available 'pportunity.
t Sincerely yours, J.k'!:
Daniel I. Herborn Director - Nuclear Licensing and Configuration Nuclear Station Engineering Attachments RW/ lam G. A. Harrison, NRC Clintoa Licensing Project Manager cc:
D. Terto, NRC MEB NRC Resident Office Illinois Department of Nuclear Safety
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P U- 0700 I
0210 B50-84 (03 -12 )-L l
QUESTION 210.05 In our review of your HVAC design criteria, " Design Criteria for Design Verification of Structures and Components in Category I Buildings," (DC-ME-16-CP)
Revision 0 dated 10/24/80, the staff noted that the HVAC ductwork allowable stress for the faulted condition was given as 1.5 Sy (membrane + bending).
The staff's position is that the HVAC ductwork stress shall not exceed 0.9 Sy for the faulted condition.- Furthermore, your FSAR does not provide the design limits used for seismic Category I HVAC components.
Provide in your FSAR the design stress limits used for the HVAC components. In addition, provide the basis for allowing HVAC ductwork stresses to reach a 1.5 Sy limit (unless it can be demonstrated that the staff acceptence criteria has been met).
RESPONSE 210.05 We plan to meet the intent of yov.: position on the HVAC ductwork stress for the faulted condition in accordance with the agreement on an Sy factor of 0.95 reached duro.g the NRC audit meeting held at Sargent &
Lundy offices on 12/8/83.
These stress limits for ductwork and duct supports will be included in a new FSAR paragraph 3.9.3.5 and Table 3.9-14.. The ductwork and duct support stresti limits for the faulted condition to be provided in Table l
3.9-14 is 0.95 Sy.
S&L's " Design Criteria for Design Verification of Structures and Components in Category I Buildings" will be revised to specify 0.95 Sy instead of 1.5 Sy as the allowable stress limit for the faulted condition.
l The requested stress limits for HVAC components are in FSAR Table A3.9-5, titled " Load Combinations and Allowable Stress Limits for BOP Equipment." The existing Table A3.9-5 served as a design reference, but the new Table 3.9-14 shows the actual design basis for HVAC ductwork and supports.
(See new subsection 3.9.3.5 and new Table 3.9-14) i l
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Table 3.9-t4
. Stress Limits for Ductwork and Duct Supports s.
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I stress z.u::its Duct Supports P.Lant Icad t*M4natien (Hancers)
Drt *t:rk Cerdition b.. Normal CI) (Weight + Pressure ATSC A1%ble G=0.6S Normal y
+ Tbarmal) values 2.
Icad Cases 2 & 3 Q:sa 33% Increase in ci = 0.6 LWt Table A3.9 ATSC A11-3La OC =0.95 3
.. values
- 3.,I$ad Cases 4 throtr) 15'fri:xa
- D.95 S q = 0.95 Sy F=1'M y
4able A3.9-6
-.v.a:Org3y g
q - sentirane se=es.
U"g - '(Mamh-ar m + :Berdig) Stress Sy - Yield St:ess at Ocrremfondig Tet:yenture T m values for CBE and pool dynamic loads i
24 N
4%.mT 5. values.for SSE and pool dynamic Ioads 4
4 1
9 e
e l
l 6
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3.9.3.5 avAC Ductwork and Duct sdecort structures BVAC ductwork and duct supports are designed using a frequency controlled design approach.
By using a frequency I
controlled design, the ductwork and duct supports are ef-factively decoupled and each ' component is designed in the rigid ' frequency range of the appropriato floor response spectra.
The qualification is done independently for tha ductwork and the duct supports.
For the. ductwork.supp' ort evaluation.it.is... assumed-that -all EVAC ductwork and. act.ersary 'tributory weights are trans.-
'forred to the supporting structure The stresses in the ductwork support structures are limited to the AISC Specifications, Part I, for the loading combinations specified in Tables A3.9-6 and A3.9-7 and the stress Limits shown in Table 3.9-t 4 The evaluation of the EVAC ductwork stresses is done for both local and gross effects.
biedesig'nrulesof' AISI (Cold-Formed Steel Design Manual - Part 1) are used with the stres'ses limited to those shown in Table 3.9-t+
for the loading combinations specified in Tables A3.9-6 and A3.9-7.
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U- 0700 0210 B50-84 (03-12 )-L QUESTION 210.06 In reviewing your HVAC ductwork design, the staff noted that, in several cases, a single support at the top of long vertical duct risers was provided for weight and seismic loadings.
In reviewing your HVAC ductwork design calculation, it was not evident that the localized buckling of the duct sheet metal near the HVAC support members was considered in the design. Provide the basis for assuring that the HVAC duct sheet metal is capable of withstanding the localized buckling stresses induced in the ductwork by the HVAC supports for weight and seismic loadings.
RESPONSE 210.06 During the NRC site inspection, two vertical duct risers were discovered to contain buckled portions near the top-most supports.
A subsequent investigation revealed that an inadequate duct gauge thickness ccabined with a non-optimum installation sequence caused the buckled conditions.
The two long vertical duct risers were constructed of 22 gauge material instead of 18 gauge as designed. They were constructed from the top cnd downward.
Sargent & Lundy evaluated the stress in the two ducts and found that buckling of the 22 gauge material was expected. However, the analysis disclosed that the buckled 22 gauge ductwork would not have failed under design dynamic loads. The calculations also showed that buckling of the specified 18 gauge material under similar construction methods would not occur.
In its review of the design calculations for the two HVAC risers, Sargent & Lundy verified that the ductwork can withstand all normal and seismic forces, including the normal weight loads experienced during the construction of long vertical duct risers.
A program has been initiated to replace the buckled 22 gauge portions of the two ducts with 18 gauge material.
Also, all vertical risers cre being reviewed for proper material gauge.
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