U-600248, Responds to Questions Re Use of Silicone Sealant in Main Control Room HVAC Ductwork.Ductwork Has in-leakage Acceptance Criteria Less than Allowed by ANSI N509
| ML20133F133 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 10/08/1985 |
| From: | Spangenberg F ILLINOIS POWER CO. |
| To: | Butler W Office of Nuclear Reactor Regulation |
| References | |
| U-600248, NUDOCS 8510100132 | |
| Download: ML20133F133 (3) | |
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L30- 85(10-08)-L 1A.120 ILLIN0/8 POWER COMPANY CLINTON POWER STATION. P.o. BOX 678. CLINToN. ILLINOIS 61727 October 8, 1985 Docket No. 50-461 Director of Nuclear Reactor Regulation
. Attention:
Mr. W. R. Butler, Chief Licensing Branch No.2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Clinton Power Station Responses to NRC Questions on Silicone Sealant in HVAC Ductwork
Dear Mr.,
Butler:
Attached is Illinois Power Company's responses to the Staff's questions identified by Mr. J. Lee (NRC) regarding the use of silicone sealant in the Main Control Room (MCR) air-conditioning ductwork at the Clinton Power Station. As explained in the attachment, the ductwork of concern, located outside the MCR habitable boundary, has an in-leakage acceptance criteria (230 cfm) considerably less than that allowed by ANSI N509 (646 cfm). The thyroid dose to the MCR operators, assuming an
[
in-leakage of 230 cfm and a Recirculation Air Filter I-131 removal efficiency of 70 percent, was calculated to be approximately 12 Rem.
This is significantly less than the 10CFR100 limit of 30 Rem.
Based on these calculations, Illinois Power concludes that the use of silicone sealant is satisfactory and adequate radiological dose protection is provided. Please contact us following the Staff's review of this material if you have any questions.
Sincer
- yours,
)
,AW s f%N F. A. ypang therg Manager - Licensing and Safety TLR/kaf Attachment cc:
B. L. Siegel, NRC Clinton Licensing Project Manager NRC Resident Office Regional Administrator, Region III USNRC f
Illincis Department of Nuclenr Safety I
8510100132 851006 -
I I PDR ADOCM O 1
F.
- e Attachment to U-600248 dated 10/08/85 Following is the additional information requested by the NRC:
NRC Question #1 What is the~ calculated acceptable in-leakage for the Control Room HVAC duct work per ANSI N509 criteria?
IP Response #1 The allowable in-leakage for the Control Room negative pressure ductwork calculated in accordance with ANSI N509-1980 Health Physics criteria is 646 cfm. The negative pressure Control Room ductwork outside the Control Room boundary is air conditioning duct work whereas the ANSI N509-1980 criteria applies to air cleaning duct work. ~The air cleaning effectiveness and duct quality criteria for calculation of in-leakage are, therefore, not applicable to the Clinton Power Station Control Room HVAC ductwork.
NRC Question #2 What is the maximum allowable in-leakage for the Control Room HVAC system to meet the NRC's Control Room dose requirements for 40%,
.50%, 60%, and 70% recirculation charcoal absorber filter
. efficiency?
IP Response #2 The calculated maximum allowable in-leakage to meet the Control Room dose requirements as a function of recirculation charcoal filter efficiency is:
Recirc.. Filter-Allowable Efficiency, %
In-leakage, cfm 90 2278 80 1090 70 646 60 411 50
~269 40 173
.The model for.these calculations is based on the following:
- Recirculating Filter Bypass Damper Leakage = 1200 cfm
' Unfiltered In-leakage Downstream of Filter Cabinet = 10 cfm
' Thyroid Dose = 27 rem.(90% of the~10CFR100 dose limit)
It should be noted that charcoal filter efficiency w'ill be 90% when
. initially installed. Because the filter construction is not strictly in accordance with Regulatory. Guide 1.52, the NRC has accepted an efficiency of 70%. 'Present Technical Specifications
. require charcoal filter efficiency be tested ~every 18 months, or every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of filter operation.
1 Attachzint to l
U-600248 dated 10/08/85 NRC Question #3 What is the expected actual leakage for the Control Room negative presaure duct work?
IP Response #3 The negative pressure duct work will be leak tested as a part of system start-up, therefore, actual leak rates are not currently available. The present acceptance criteria at operating duct pressures for sections of negative pressure air conditioning duct work outside the Control Room boundary is 230 cfm. The Control Room dose at 230 cfm in-leakage and a 70% efficient recirculating filter will be 12 Rem. This provides a factor of safety of 2.5 before the Control Room dose limit is approached.
Based on these factors, we believe there is adequate margin in the design to withstand either an increase in in-leakage or decrease in filter efficiency from initial acceptance conditions.
NRC Question #4 How much effort does IPC have to put forth to perform testing of
=the Control Room negative pressure ductwork?
IP Response #4 Total time frame to perform the test will be approximately two weeks. Some design modifications would be required because a test of negative pressure ductwork outside the Unit 1 Control Room pressure boundaries, with the present design, will disable return air ductwork (located at elevation 800' on Unit 2 side) common to both Train A and Train B.
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