ST-HL-AE-5774, Forwards Response to Request for Addl Info Re Doses from Potential Leakage of Sump Water Into Refueling Water Storage Tank.Calculations Encl

Forwards Response to Request for Addl Info Re Doses from Potential Leakage of Sump Water Into Refueling Water Storage Tank.Calculations Encl

ML20198J541
Person / Time
Site:	South Texas
Issue date:	10/16/1997
From:	Thomas S HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20198J547	List: ML20198J552 ML20198J558 ST-HL-AE-5774, Forwards Response to Request for Addl Info Re Doses from Potential Leakage of Sump Water Into Refueling Water Storage Tank.Calculations Encl
References
ST-HL-AE-5774, TAC-M99105, TAC-M99106, NUDOCS 9710210133
Download: ML20198J541 (5)

Text

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The Light com pa nyoch leses Propet flectric Genere 4eg beet 6ee P.o. het 269 %edewerth. Tet Mm llglity & Pow, October 16,1997 i ST llL AE 5774 i File No.: 025 10CFR50.59 U. S. Nuclear Regulatory Commission -l Attention: Document Control Desk

-Washington, DC 20555 l South Texas Project Units I and 2 Docket Nos. STN $0-498, STN 50 499 i

Response to Request for Additional Infonnation Regarding Doses from Potential Leakage of Sumn Water into the Refueline Water Storace Tank (TAC Nos. M99105 and M99106)

Reference:

1.etter from Thomas W. Alexion, NRC, to William T. Cottle, llL&P, dated

, September 18,1997 (ST AE IIL 949$0)

The referenced letter requested additional information regarding doses from potential leakage of sump water into the refueling water storage tank which was the subject of a South Texas Project Unreviewed Safety Question !! valuation being reviewed by the NRC Staff. The l response to the request is attached.

1 If you r.hould have any questions concerning this matter, please call Mr, A. W.

liarrison at (512) 972 7298 or myself at ($12) 972-7162, b

9710210133 971016 j

'27-S. II. Thomas

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y 0 j f)j s g ifngineering Oh II!!

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Attachments: 1. Response to Request for Additional Information Regarding Doses from Potential I.eakage of Sump Water into the Refueling Water Storage Tank

2. South Texas Project Calculation MC 6313, "ECCS Valve Leakage to RWST Analysis"

3. South Texas Project Calculation MC 6458, "ECCS isolation Valve Leak Analysis" mmmco*me um.,. rrow u..es , e. neww et in r.,wip.m. to in, r .h Tne. rre).o in m ..

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I ilouston Lighting & Power Company ST lil-AE 5774 South Texas Project flectric Generating Station l'ile No.: G25 Page 2 c:

Ellis W. Merschoff' Rufus S. Scott' Regional Administrator, Region IV Associate General Counsel U. S. Nuclear Regulatory Conunission llouston Lighting & Power Company 611 Ryan Plaza Drive, Suite 400 P. O. Box 61067 Arlington, TX 76011 8064 Ilouston, TX 77208 Thomas W. Alexion Institute of Nuclear Power

• Project Manager, Mail Code 13113 Operations - Records Center U. S. Neclear Regulatory Commissien 700 Galleria Parkway Wa.shington, DC 20555-0001 Atlanta, GA 30339 5957 David P.1,oveless* Dr. Ilertram Wolfe' Sr. Resident inspector 15453 Via Vaquero c/o U. S. Nuclear Regulatory Comm. Monte Sereno, CA 95030 P. O. Ilox 910 llay City, TX 77404 0910 Richard A. Ratlifl*

Ilureau of Radiation Control J. R. Newman, Esquire

• Texas Department ofllealth Morgan, Lewis & llockius 1100 West 49th Street 1800 M Street, N.W. Austin, TX 78756 3189 Washington, DC 20036 5869 J. R. Egan, Esquire' M. T. liardt/W. C. Gunst* Egan & Associates, P.C.

City Public Service 2300 N Street, N.W.

P. O. Box 1771 Washington, D.C. 20037 San Antonio, TX 78296 J. C. Lanier/M.11. l.ce' U. S. Nuclear Regulatory Commission City of Austin Attention: Document Control Desk Electric Utility Department Washington, D.C. 20555-0001 721 Ilarton Springs Road Austin, TX 78704 Central Power and Light Company' ATTN: G. E. Vaughn/C. A. Johnson P. O. Box 289, Mail Code: N5012 Wadsworth, TX 77483

'without attachments 2 and 3 s u n u. c mus.nm.,. m mm.

Attachment i ST ill, AI! 5774 Page1 of 2 Response to Request for Additional Infonnation Regarding Doses from Potential I cakace of Sump Water into the Refueline Water Stornt'Dmk

1. Please provide supporting calculations, including assumptions relating to: (a) buoyancy and natural circulation within the pipes that are postulated to leak sump water into the refueling water storage tank (RWST) and (b) leak rates for each valve.

Provide the above for Imth the previous analysis which resulted in a transport time of 13.4 days, and the current analyses. Please justify the assumptions discussed above.

South Texas Project Response:

The previous analysis is calculation hic-6313 "l!CCS Valve 1.cakage to RWST Analysis."

Calculation MC-6313 was superseded by calculation h1C 6458, "liCCS isolation Valve 1.cak Analysis," copics of which are attached.

The analyses calculate the amount of time required for sustained leakage to traverse the shortest distance back to a common header through one of three possible leakage paths:

RWST suction line isolation valves, l.ow llead/Iligh llead Safety injection Pumps' recirculation line isolation valves, and Containment Spray Pumps' test line isolation valve.

In MC 6313, leakage through the Train C Containment Spray Pumps' test line isolation valve was determined to be most limiting and would reach the common header in 13.4 days.

htC 6458 recognized that the Containment Spray Pumps will operate no longer than 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the loss of coolant accident at which time the leakage through the Containment Spray Pumps' test line isolation valve would cease, htC-6458 determined that leakage through the Train C 1.uw Ilead/lligh IIcad Safety injection Pumps' recirculation line isolation valves is the most limiting leakage path and would reach the common header in 42.3 days.

(a) Calculations htC-6313 and htC 6458 do not assume buoyancy or natural circulation within the pipes that are postulated to leak sump wate, into the RWST. These assumptions are not considered necessary because of other conservatisms in the calculation, For example, to reach the common henaer line, leakage from the 1.ow licad/lligh licad Safety injection Pumps' recirculation line isolation valves must traverse an equivalent of approximately 72 feet of 6" pipe. This common header line is at an elevation below the valves postulated to leak and the leakage from the valves is required to further traverse approximately 92 feet of 6" pipe to reach the RWST.

hic 6458 conservatively assumes that the additional 92 feet is traversed immediately to account for diiTusion of the contaminated leakage water. This conservative assumption similarly could be used to account for buoyancy and natural circulation.

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Attachment 1 ST ill..Ali 5774 l Page 2 of 2 (b) The leak rate for each valve is provided in Table 1 of calculation hic-6458. The leak rates used in hic-6458 are unchanged from the previous analysis (hic.6313). The leak rates used in the analysis were conservatively set at 10 times the purchase specification allowable leakage rate.

2. Provide the isometric drawings of the piping from the leaking valves to the RWST.

South Texas Project Response:

Isometric drawings are part of attached calculation hic 6458.

3. Provide a discussion on the safety classification and seismic qualification of the piping in the leak path from the sump water source to the RWST.

South Texas Response:

There are three postulated leakage paths for each train (A, B, and C). The safety classification and seismic qualification of piping for each leak path are:

a. RWST suction line isolation valves (SI 0001, SI 0002) - valves and piping are Safety Class 2/ Seismic Category 1.

b. Low Ilead/Iligh llead Safety injection Pumps' recirculation line isolation valves (SI 0011, St.0012, SI 0013, SI 0014) - valves are Safety Class 2/ Seismic I; safety classification changes just downstream of valves; piping is Non Nuclear Safety ,

Seismic 11/I; safety classification of piping changes just before RWST back to Safety Class 2/ Seismic 1.

c. Containment Spray Pumps' test line isolation valve (CS 0008) - Valves are Safety Class 2/ Seismic 1; safety classification changes just downstream of valves; piping is Non Nuclear Safety , Seismic 11/1; safety classification of piping changes just before RWST back to Safety Class 2/ Seismic 1.

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1 Attachment 2 ST llL All 5774 South Texas Project Calculation MC-6313, "l!CCS Valve Leakage to itWST Analysis"

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