ML19326B410

Unusual Event Rept 50-313/74-02:on 740917,reactor Bldg Cooling Units Drain Piping Found Unable to Carry 130 Gpm Flow During Design Basis Accident.Caused by Design & Installation, & Const Error

ML19326B410
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/09/1974
From:	Cavanaugh W, Phillips J, Rueter D ARKANSAS POWER & LIGHT CO.
To:
Shared Package
ML19326B405	List: ML19326B404 ML19326B410
References
NUDOCS 8004150774
Download: ML19326B410 (3)

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1. Unusual Event Report No. 50-313/74-2

2. Report Date: October 9, 1974 3. Occurrence Date: September 17, 1974

4. Facility:

Arkansas Nuclear One-Unit 1 Russellville, Arkansas

. 5. Identification of Occurrence: Inadequate drainage capability for Reactor Building Cooling Units

6. Conditions Prior to Occurrence:

Steady-State Power Reactor Power o MWth Hot Standby Net. Output 0 MWe Cold Shutdown Percent of Full Power 0  %

Refueling Shutdown __. .

Routine Startup Operation O Routine Shutdown Operation .

Load Changes During Routine Power Operation '

.c Other (Specify) In Power Escalation Testing

7. Description of Occurrence: -

• Paview of the drain piping for the Reactor Building cooling units revealed that the drains would not carry the 130 gpm flow which would occur during a Design Basis Accident. Edgh level would also occur ':

during normal operation but would be within the capacity of the drainage system.

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8004.16o'77(( . -

July S, 1974 NSP-10, Rev. O Page 1 of 3 f

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Unusual Event Report No. 50-313/74-2 Sheet 2 4

8. Designation of Apparent Cause of Occurrence:

Design X Procedure Manufacture Unusual Service Condition Including Installation / X Environmental Construction Component Failure Operator --

Other (Specify) ,

Drainage piping design and installed slope were inadequate for accident conditions. ,

f'*% 9. Analysis of Occurrence:

. The installed cooler drain piping would not drain the quantity of steam

condensate predicted during a. Design Basis Accident because of pipe size and slope. Each cooler would fill with water during a DBA to approxi-mately 50% of its volume, at which point steam condensation would equal condensate drainage. The fan and cooling coil capacities would be reduced below the values given in the FSAR, rese'. ting in inadequate s cooling of the Reactor Building. The drain system was adequate for 4

normal operation, thus the health and safety of the public was not i affected by this event. '

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10. Corrective Action: ^

The access doors on the return air end of the cooler housings were removed to prevent condensate from rising above the cooling coils by providing a means of exit. Cooling capacity was not affected by removal of the doors and emergency drainage through the door openings would not '

preclude the safe shutdown of the unit.

The permanent drainage system for these units will be modified by adding a 4 inch emergency drain pipe in the sump of.each cooler witt capacity.

• to drain 100% of the estimated steam condensed Un the unit. The exist-ing 2 inch drains will be left intact for normal drainage.

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July 5, 1974 NSP-l'O, Rev. O Page 2 of 3

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Unusual Event Report No. 50-313/74-2 Sheet 3

11. Failure Data:

NA

12. Reviews and Approvals: .

Reviewed and Approved by: Plant Safety Committee Yes ( ) No (X) b e

Plant Superintendent Yes ( ) No(20

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Reference:

Not Required Date:

Reviewed by: u8 Date: /d o */  !

, Licensing Supervisor ' '

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Date: /o Manager of NlTc' lear Servi e '

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/ 'Directo[ of Ppwer Production Approved by: ') / .

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, , / Senioi Vice Prt!Isident '

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I July 5, 1974 NSP-10,. Rei, 0 Pace 3 of 3, _ _ _ _ _ _ _ _