ML18081A921
| ML18081A921 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 01/15/1980 |
| From: | Mittl R Public Service Enterprise Group |
| To: | Parr O Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18081A922 | List: |
| References | |
| NUDOCS 8001180371 | |
| Download: ML18081A921 (4) | |
Text
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- Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/430-7000 January 15, 1980 Director of Nuclear Reactor Regulation
- u. S. Nuclear Regulatory Commission Washington, D. c.
20555 Attn~
Mr. Olan D. Parr, Chief Light Water Reactors Branch 3 Division of Project Management Gentlemen:
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION CONTAINMENT SUMP DESIGN NO. 2 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO.
50-311 PSE&G hereby submits its response to your request for additional information concerning containment sump design, dated October 12, 1979.
We have reevaluated the containment sump design and have modified the design as described in the attachment to this letter to decrease velocities to an acceptable level, and to eliminate vortex formation within the sump.
With regard to model testing of the containment sump, an outside research laboratory will be contracted to perform model testing of the containment sump as modified herein, with the objective of investigating free surface vortex formation and other undesirable flow conditions that could adversely effect the performance of the RHR pumps during the recirculation mode.
Operating conditions involving a wide range of approach flow distributions, water depth, screen blockage effects, and pump operating conditions will be tested with the model.
An acceptable model testing program will be developed by March 1, 1980 and submitted to you for approval.
It is anticipated that the model testing program can be completed prior to start up following the first refueling outage.
Should the model testing indicate the need for further modi-fication, such modifications would be incorporated in the sump design prior to start up following the first refueling.
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Mr. Olan 1/15/80 It is requested that the sump modifications attached to this letter be reviewed in an expeditious manner, such that approval may be obtained to enable us to perform the additional NPSH analysis requested in your letter of October 19, 1979.
Should you have any questions in this regard, please do not hesitate to contact us.
Attachment
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~~ r 4fl41!l R. L. Mittl General Manager -
Licensing and Environment Engineering and Construction
CONTAINMENT SUMP MODIFICATIONS NO. 2 UNIT SALEM NUCLEAR GENERATING STATION
- The containment sump has been redesigned to eliminate vortex formation.
The conceptual arrangement is shown on the attached figure.
The modifications are described below.
- 1.
Screens:
The sump screen design consists of two inverted boxes providing two screens, an outer trash rack, and an inner fine screen.
- a.
Outer Box:
The outer box grid has a dimension of 11'6" x 8'6" x 3'3", with vertical sides made of 1-1/4" x 3/16 grid bars located at 1-3/16" centers and a solid 3/16" top cover plate located at eleva-tion 81'11".
The vertical grid sides form the outer screen to prevent large debris from reaching the fine inner screen.
The outer box is sized to enve-lope the normal sump pumps and to prevent inter-ference with the existing steel structures (See attached drawing).
Also, a clearance of at least l ft. is provided between the inner and outer box screens to reduce the resistance to the annular space flows.
- b.
Inner Fine Screen:
The inner fine screen box has a dimension of 9'6" x 5'0" x 3'1" with top of the box located at an elevation of 81'9".
The vertical sides and the top of the box are made of 1/8" x 1/8" mesh of 0.12" diameter wire suitably supported on a welded angle frame. The vertical sides of the fine screen box are set back l foot from the four walls of the sump pit and extended to the top cover plate of the outer grid box.
The 1/8" x 1/8" fine mesh size is based on the mini-mum restrictions found in the system served by the sump, i.e., supply recirculation water to the reac-tor vessel.
The most restrictive clearance in the 17 x 17 fuel assembly matrix core for free flow into or through the core region either in a radial or axial direction is approximately 1/8".
With regard to ECCS pumps, the running clearances for these pumps are obviously smaller than the critical flow passages in the core.
However, since only a small percentage of the total pump flow passes through the pump bearings, these clearances are not considered to be limiting physical restrictions for the major flow path.
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- 2.
Vertical Separation of Sumps:
A vertical grid (l-1/4" x 3/16" on 1-3/16" centers) is provided midway between the two outlet pipes extending from the floor to the top of the sump.
- 3.
A 1/8" x 1/8" fine screen is provided at the weir between the normal leakage and safety sumps.
- 4.
Vortex Breakers:
Two removable horizontal grids are located one 6" below the weir and another at 18" above the sump floor.
Also, vertical fins "4" x 1/4" on 4" centers) starting 6" from the sump corner, are located below the lower horizontal grid.
- 5.
The containment sump screen assembly is made of ASTM Grade A240 Type 304 stainless steel.
The screen assembly is designed to withstand vibratory motion of seismic events without loss of structural integrity.
- 6.
The sump screen components (outer box, inner box and horizontal grids) are of removable design to permit in-service inspection.
- 7.
Pressure Drop:
The head loss for the modified contain-ment sump screen is estimated to be less than 0.5 feet for a two pump flow of 7000 GPM.
The head loss is esti-mated with 50% blockage of the outer and inner screns with credit taken for flow through the vertical sides only.
M P79 58 31 1/2