ST-HL-AE-1962, Forwards Response to Question 480.28 (Part C) Re Effect of Debris Particles on Recirculation Flow Path.Response Will Be Incorporated in Upcoming FSAR Amend.Conclusions in SER (NUREG-0781) & Suppls 1 & 2 Remain Valid & Unaffected

Forwards Response to Question 480.28 (Part C) Re Effect of Debris Particles on Recirculation Flow Path.Response Will Be Incorporated in Upcoming FSAR Amend.Conclusions in SER (NUREG-0781) & Suppls 1 & 2 Remain Valid & Unaffected

ML20212P931
Person / Time
Site:	South Texas
Issue date:	03/09/1987
From:	Wisenburg M HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-0781, RTR-NUREG-781 ST-HL-AE-1962, NUDOCS 8703160359
Download: ML20212P931 (5)

Text

0 0 The Light NE Mf Ilouston Lighting & Power P.O. Box 1700 llouston. 'Icxas n001 (713) 228-9211 March 9, 1987 ST-HL-AE-1962 File No.: G9.17 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Question 480.28 (part c);

Effect of Debris Particles During Recirculation Attached is the response to Question 480.28 (part c). This response addresses the effect of debris particles, which may pass through the containment sump screens, on the recirculation flow path (spray nozzles, fuel assemblies, pumps, etc.).

The response given in the attachment is provided for your immediate use and review and will be incorporated in an upcoming FSAR Amendment. Houston Lighting & Power is of the position that conclusions given by the South Texas Project Safety Evaluation Report (NUREG-0781), including Supplements 1 and 2, remain valid and are not affected by this submittal.

If you should have any questions on this matter, please contact Mr.

J. S. Phelps at (713) 993-1367.

k a '

M. R. Wi enburg Deputy P oject Manage JSP/yd

Attachment:

Response to NRC Q480.28(c) pg32tBBBAE8Bjhe i

'A Ll/NRC/bi

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ST-HL-AE-1962 File No.: G9.17 Houston Lighting & Power Company Page 2 cc:

Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Drive, Suite 1000 P.O. Box 1088 Arlington, TX 76011 Austin, TX 78767-8814 N. Prasad Kadambi, Project Manager M.T. Hardt/A von Rosenberg U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771' Bethesda, MD 20814 San Antonio, TX 78296 Robert L. Perch, Project Manager Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue 1717 H Street Bethesda, MD 20814 Washington, DC 20555 Dan R. Carpenter Senior-Resident Inspector / Operations e/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414

.Claude E. Johnson Senior Resident Inspector /STP c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 M.D. Schwarz, Jr., Esquire Baker & Botts One Shell Plaza Houston, TX 77002 J.R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.W.

Washington, DC 20036 T.V. Shockley/R.L. Range Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 L1/NRC/bi Revised 2/3/87

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h,TAH ET STP FSAR j PAGE l OFb i

Question 480.28N j To provide additional assurance that long term cooling of the reactor core can i be achieved and maintained following a postulated LOCA: .y A. Establish a procedure to perform an inspection of ths containment, and the containment sump area in particular, to identify any materials which have the potential for becoming debris capable of blocking the containment sump when required for recirculation of coolant water. Typically, these materials consist of: plastic bags, step-off pads, health physics instrumentation, welding equipment, s'caffolding, metal chips and screws, portable inspection lights, unsecured wood, construction materials and tools as well as other miscellaneous loose equipment. Containment cleanliness should be periodically assured; at a minimum this inspection should be performed at the end of each refueling outage.

. B. Describe any changes deemed necessary to reduce vertical flow in the neighborhood of the sump. Ideally, flow should approach uniformly from all directions. Pipe breaks, drain flow and channeling of spray flow released below or impinging on the containment water surface in the area of the sump can cause a variety of problems; for example, air entrainment cavitation and vortex formation.

C. Compare the size of opening in the fine screens with the minimum dimensions in the pumps which take suction from the sump, the

! minimum dimension in any spray nozzle and the fuel assemblies in the

reactor core or any other line in the recirculation flow patch whose size is comparable to or smaller than the sump screen mesh size, in

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order to show that no flow blockage will occur at any point past the screen. Estimate what effect debris particles, capable of passing through the fine screen, would have on the operability and performance of all pumps used for recirculation cooling. Address effects on pump seals and bearin;s.

Response

A. Procedures will be established to implement the requirements of Technical i

Specification 4.5.2 which address these concerns.

I i B. As identified in the response to Q480.25N, an analysis to evaluate the I overall containment emergency aump performance was performed and I determined that vortex formation is a potential. Following the guidelines in proposed Rev. 1 to RG 1.82, the containment sumps did not l 53 meet all of the criteria for zero air ingestion thus avoiding pump cavitation. Additionally, the sumps did not meet all the criteria for a 53 less than 2 percent air ingestion, thus avoiding degradation of pumping capability. Accordingly, a vortex breaker per the guidelines in RC 1.82 i has been included in the design of the sumps to reduce air ingestion and 53

. vertical flow. ,

t Vol. 2 Q&R 6.2-29N hmendment56

ATTACHMENT ST-HL AE 1%1 STP FSAR PAGE 2.0F ;9 Response (Continued)

Following this modification, the sump design is adequate to ensure uniform flow thus avoiding the subject problems. In the vicinity of the emergency sumps there are no high energy piping, drains or spray flov .

paths which would adversely impact the effectiveness of the sumps.

C. fThesmallestoftheabovecomponentsisthespraynozzle(3/8" diameter).

The sump screen opening is 1/4", therefore blockage is not considered a 53 problem. Effects of debris on the pump and core will be provided later.

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e Lui X Vol. 2 Q&R 6.2-30N Amendment 53

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_PRGE 30F A Insert X The containment spray, High head and Low head pumps all take suction from the containment sump. The RHR pump is used for recirculation cooliag following a small break LOCA.

RHR Pumps 1 The RHR pumps were specified for satisfactory operation following a LOCA with water in the containment sump containing solid particles of concrete, insulation and paint flakes which could pass through the sump screens and into the suction of the RHR pump (via the safety injection system). Particular attention was given to the design of these pumps to handle this debris.

Containment Spray Nozzles The containment spray nozzles will not be subject to clogging following a design basis large LOCA. The containment spray nozzles are SPRACO type 1713A.

These nozzles have a swirl chamber design (referred to as ramp bottom by SPRACO) and thus have no internal parts, such as swirl vanes which would be subject to clogging. In addition, the nozzle discharge orifice diameter is 3/8" which is sufficiently large to preclude clogging by any particles which

.buld pass through the 1/4" mesh of the fine sump screens.

High Head Safety Injection. Low Head Safety Injection. and Containment Spray Pumps These pumps were specified for a satisfactory operation following a LOCA with water in the containment sump containing particles of_ concrete, insulation and paint flakes which could pass through the sump screens into the suction of the high head, low head and containment spray pumps. Particular attention was given to the design of these pumps to handle this debris.

Long Term Core Cooling For certain hypothetical LOCA's, the ECCS will be aligned to draw suction from the containment sump following depletion of the RWST. Upon this alignment, it is possible to ingest debris carried into the sump by primary coolant that has flowed through the break. The fine screens in the sump limit the size of this debris to a dimension of no more'than 1/4". This debris could then pass through a recirculating pump and into the RCS, For the first 18 to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the ECCS is aligned to deliver flow to the RCS cold legs. The recirculating flow proceeds downward into reactor vessel

! lower plenum, turns, and flows upward into the reactor core. It is expected that the low recirculating flow rate and large flow area in the lower plenum region will result in small local fluid velocities. These local fluid velocities are sufficiently small such that larger debris will settle out of solution in the reactor vessel lower plenum. Smaller debris is expected to be

carried upward by the recirculating flow into the core. Thus the formation of j flow blockages in the core by debris following a hypothetical LOCA is not a j concern for long term core cooling.

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