ML20085D414

Comments on Review Re Flooding of Critical Equipment.Review Indicates That Failure of Any Sys Not Meeting Class 1 Seismic Const Criteria Would Not Cause Adverse Flooding

ML20085D414
Person / Time
Site:	Robinson
Issue date:	09/22/1972
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8307250636
Download: ML20085D414 (2)

Text

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o Carolina Power & Light Company .

Raleigh, North Carolina 27602 , ,.. . . - -

September 22, 1972 j M ' @;- ", N

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Mr. Donald J. Skovholt I j "- O Assistant Director for Operating Reactors  ; y' ,,,l'h Directorate of Licensing [ ';J#N .

Atomic Energy Cor:clission A., -  !

4ff Vashington, D.C. 20545 Vl ..#

H. B. ROBINSON UNIT NO. 2 50-261 LICENSE DPR-23 FID0 DING OF CRITICAL EQUIPMENT . r

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Dear Mr. Skovholt:

As a result of the failure of an expansion belloa in a facility of another utility, your letter of August 8,1972, requested Carolina

< Power & Light Company to review our facilities to ensure that the potential for a similar incident was unlikely. This letter is submitted in respect s to our H. B. Robinson Plant.

A study of the H. B. Robinson Unit No. 2 has been made and it is concluded that failure of any Robinson system which does not meet the criteria of Class I seismic construction would not cause flooding sufficient to adversely affect the performance of engineered safety systems and that failure of any equipment woulo not cause flooding such that comon mode failure of redundant safety related equipment would result.

The outdoor type installation at the H. B. Robinson Plant, particularly in the circulating water system, is considerably different from many plants and minimizes the consequences of flooding from a circulating water system failure. The Robinson installation does not have reverse flow capabilities and, as a result, the piping installation j' is relatively simple. The eight connections at the condenser (four outlets and four inlets) each include a manually operated butterfly valve and an expansion joint. Since the butterfly valves are manually operated, the inadvertent closure of these valves as a result of valve operator failure does not exist. The rubber expansion joints, however, are of conventional design and could fail causing flooding. ,

Assuming that a condenser inlet expansion joint were to fail, the following consequences can be postulated. If, at the time of such a rupture, all three circulating water pumps were running with a normal lake level of 220 feet elevation, a flow of 8140 gallons per second could be expected. This flow rate would flood the circulating water intake and

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Nr. Skovholt O September 22, 1972 r, ,,  ! ]

discharge wells, the turbine sump, and the condensace piping trench in approximately five seconds. When these volumes filled from a pit elevation of 221.5 feet to the floor elevation of 226 feet, the water would run off to the ground floor of the turbine building. The open construction of ,

the turbine building would enable the water to flow out of the building l

onto the surrounding plant grade of approximately 225 feet elevation.

Various flood drains and storm drains and the contour of the plant grado would direct this water to the Black Creek basin adjacent to the plant.

! The wide expanse of the surrounding property precludes the possibility of accumulation of water in the turbine building to any significant depth.

All cicctrical motors on the ground floor are at least t's feet above the floor elevation. No engineered safety systems would be endangered by such flooding. All such safety features are isolated from the potential flooded area or are installed at elevations not subject to flooding.

If one of the four outlet expansion joints were to fail, the flooding of the ground floor would be no more severe than for the failure of an inlet joint. In fact, since the outlet expansion joints open l I

directly into the discharge header, it is quite likely that a major portion of the water would continue to drain off in its normal flow path.

Therefore, it is concluded that in view of the design of the Robinson circulating water system, the elevations and grade of the plant, and the open cor.struction of the turbine building, the potential for flooding of safety related equipment does not exist at H. B. Robinson Unit No. 2.

Yours very truly, ,

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E. E. Utley ')

Vice President (

Bulk Power Supply NBB/=a ec: Mr. N. B. Bessac Mr. B. J. Furr Mr. P. W. Howe Mr. R. L. Mayton, Jr.

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