ML19321A120

Forwards Addl Info Re Containment Sump Performance in Response to NRC Request

ML19321A120
Person / Time
Site:	Farley
Issue date:	07/16/1980
From:	Clayton F ALABAMA POWER CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8007220486
Download: ML19321A120 (4)

Text

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Alabama Power Company

. 600 North 18th Street Post Offica Box 2641 Birmingham. Alabam7 35291 Telephone 205 323-5341 L

S'e o ce r side'nt / lbama Power tre souttom electrc sprem July 16, 1980 Docket No. 50-364 Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. A. Schwencer Gentlemen:

JOSPEH M. FARLEY NUCLEAR PLANT - UNIT N0. 2 CONTAINMENT SUMP PERFORMANCE Per NRC request, attached is additional information on the performance of the containment sump.

Yours very truly, b

F.Q. Clayton, Jr.}>PCtw & ,i L

CLB:rt Attachment cc: fir. R. A. Thomas Mr. G. F. Trowbridge Mr. W. H. Bradford Mr. L. L. Kintner 3oo/

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lll 800 7220R(p g

ATTACHMENT NRC Requirement: Establish a housekeeping program to assure that the plant is always restored to "as-licensed" cleanliness prior to power operations.

Response: Alabama Power Company's (APCO) Technical Specification 4.5.2(c) and (d) requires an inspection of containment to

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verify cleanliness of (1) all accessible areas prior to establishing containment integrity, and (2) the areas affected within containment at the completion of each containment entry when containment integrity is established. APC0 has developed and implemented a surveillance test procedure number STP43.0 which ensures that the containment is kept free of debris which could possibly restrict flow to the containment sump prior to initial fueling and each occasion when containment is accessed.

NRC Requirement: Reevaluate the insulation used inside containment to assure that insulation debris would not be expected to block approach paths, trash racks, or screens in such a manner as to jeopardize intake performance and that debris penetrating the intake screens would not be expected to compromise safety system life or per-formance or degrade core cooling.

[~ Response: The metal reflective and anti-sweat are the or.ly types of insulation used inside the containment of Farley Nuclear Plant.

The anti-sweat insulation is a foamed, close cell plastic which is much lighter than water. Metal reflective insulation which could come off the piping systems-by the postulated primary system pipe breaks will consist of large pieces. This insulation material is much heavier than water.

Farley Nuclear Plant Unit 2 recirculation intakes from the i containment floor are comprised of two vertical 14-inch RHR and two vertical 10-inch containment spray intakes located in ,

separate intake areas all outside of the primary shield wall. j The location details of intakes are shown in Figures 6C-19 .

and 20, Appendix 6C of the FSAR. These vertical intakes- )

extend one foot above the containment floor as shown in i Figure 6C-5, Appendix 6C of the FSAR. Each intake is surrounded 1 by a protective screen-grating and grating cage structure as shown in Figures 6C-17 and 18, Appendix 6C of the FSAR.

The calculated maximum and minimum water levels in the con-tainment following a LOCA are 58.3 and 77.1 inches above the containment floor. The top of the grating cage structure is 29 and 48 inches below these water levels, respectively.

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Extensive 1:1 scale model testing of containment sump re-circulation intakes was performed to evaluate the hydraulic ,

performance of these intakes during the recirculation phase of ECCS and containment spray operation.

The results of this

- test have been documented in Appendix 6C of the FSAR and the final test report has been provided to the Staff.

One of the parameters which was investigated during these tests was the approach velocities in the bulk fluid since this is the important determining factor in formation of vortices.

Further, the flow rates approaching the intakes was increased above the nominal flow condition by 40% (augmented flow) to achieve Reynolds Numbers equal to or greater than prototype values which could occur at a calculated post-LOCA pod temperature of 2120F (0 tests were performed with water tem-peratures of up to 180 F). The results of these tests con-clusively showed that with all pumps operating and under the augmented flow conditions, the approach velocities in bulk fluid was low there was no or(maximum calculated velocity 0.49 fps) and ganized circulation or tendency for vortex formation anywhere outside the screen-grating structure.

Therefore, there is no reason to expect other than the anti-sweat insulation to float on the surface of the water at least 29 inches above the grating cage structure and the metal reflective insulation to sink to the containment floor.

Based on these test results, none of these materials or any others are expected to be carried along with the flow to the screen-grating cage structure surrounding the intakg.

In spite of the above test results, prudence was used and range of screen-grating cage blockage cases were also tested.

The blockages were selected to represent the following conditions:

Blockage Condition 1

Blockage material uniformly distributeo ..er

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the vertical screen area around periphery.

Top screen totally blocked.

2 Blockage materials are not buoyant and thus block the lower portion of the vertical screen.

Top screen totally blocked.

3 Blockage materials are buoyant and thus block the upper part of the vertical screen. Top screen totally blocked. i 4

Blockage materials are not bouyant and thus block the lower portion of the vertical screen. Top screen unblocked.

5 Blockage is postulated as occurring over screen area most exposed to approach flows. .

I The results of these blockage tests are presented in Appendix 6C of the FSAR. Blockages of up to 717, of the screen-grating surface area were perfomed. Even under these -

conservative test conditions, neither an appreciable difference in approach velocities to screen nor any organized circulation

- or tendency for vortex fomation was observed outside the screen-grating case structure. Head losses due to this extreme condition were also acceptable and is was shown that .

no degradation in pump performance will result.

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Based on these test results and the significant points presented above, it is concluded that the accident conditions inside the containment will not adversely affect the re-circulation intake performance.

The concern of debris penetrating the screens was addressed during the FSAR review, in response to NRC Question CSB-22.

As discussed in this response, the maximum particle size that could pass through the wire screens in 0.120 inches.

This size particle will have no affect on pump operation or will not clog the containment spray nozzle or'fices. Therefore, the debris, even though not considered credible based on the above discussions, passing through the wire screens is not expected to compromise safety systems life or performance or degrade core cooling.

It should be noted that the design of FNP does not include sand plugs or sand shields. _

NRC Requirement: Describe the available instruments and controls, and provide procedures penaitting the operator to detect conditions of low ECCS flow and to take corrective actions.

Response: Based on the discussion presented in the above response, it is l

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Alabama Power Company's position that the performance of re- l circulation sump intake performance under accident conditions  !

has been investigated in sufficient and adequate detail and l concluded that they will perform their intended function under  ;

these adverse conditions. Therefore, we do not expect air I entrainment, cavitation, debris blockage or entrainment to l occur to a degree which could result in inadequate core '

cooling situation.

However, if needed, existing control grade instrumentation (monitoring RHR pump motor amperage, flow and pressure) would detect and annunciate inadequate ECC3 flow. Existing plant Annunciation Response Procedures and Emergency Operation Procedures require response to these alarm signals. A procedure will be developed prior to fuel load to allow back-flushing of the containment sump utilizing water from the RWST

, in the event of low ECCS flow due to blockage of the con-l tainment sump.

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