ML19326B329
| ML19326B329 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/10/1974 |
| From: | Phillips J ARKANSAS POWER & LIGHT CO. |
| To: | |
| References | |
| 4230, NUDOCS 8004150711 | |
| Download: ML19326B329 (4) | |
Text
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s H EL PIN G UUILO A H r< A N S A S k
ARK ANS AS POWER & LIGHT COMPANY STH & LOUISI AN A ST..ETS. LITTLE CCK. A AK ANS AS 72203.(5011372-4311 May 10, 1974 Mr. D. F. Knuth Director of Regulatory Operaticns
(
Office of Regulation United States Atomic Energy Commission 4
Washington, D. C.
20545
Subject:
Arkansas Power 6 Light Company Arkansas Nuclear One-Unit Docket No. 50-313 Service Water Pumps
Dear Mr. Knuth:
On April 24, 1974, we reported to Mr. M. S. Kidd, Reactor Inspector, Region II, a possible significant deficiency regarding cracks found in a structural member of the service water pump motor PM4A lower motor
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base (end bell).
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Attached is our report providing the details of our investigation and corrective action for this item.
Very truly yours,
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D. Phillips*
Senior Vice President JDP:cc Attachments
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Mr. Norman C. Moseley Directorate of Regulatory Operations Region II United States Atomic Energy Commission 230 Peachtree Street, N.W. - Suite 818 Atlanta, Georgia 30303 d h-[,,N jp(
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J. D. Phillips, being duly sworn, states that he is & Senior Vice President of Arkansas Power G Light Company; that he is authorized on the part of said Company to sign and file with the Atomic 1:nergy Commission this Supplementary Information; that he has read all of the statements contained in such Information, and that all such statements made and matters set forth therein are true and correct to the best of his knowledge, information and belief.
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J. D. Phillips
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SUBSCRIBED AND SWORN TO before me, a Notary Public in and for the County and State above named, this /p day of @y
, 1974
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Notary Public My Commission Expires:
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Attachment to L er l
Phillips to Knuth May 8, 1974 (vl J
SERVICE NATER PUMP MOTOR BASE CRACKS i
Description of Incident During pump and motor alignment operations to eliminate high vibration in the service water pumps it was discovered that cracks had formed in a structural member of the service water pump motor PM4A lower motor base (end bell), which is made of grey cast iron.
Of the four webs supporting the motor, one contained two cracks. He0 degree web was cracked at a corner intersection with the 315 degree access port as well as within the web itself. He latte was a three-inch long through crack. The mounting base was damaged at intermittent locations all around the base except at the 225 degree access port.. In addition to exhibiting deformed metal, the damaged areas exhibiter. sharp indentations on flat web surfaces which were attributable to possiMe hammer impact.
The upper portions of this motor were visually inspected and the weld connecting the motor case to the upper bearing support structure (not a casting) was examined at 10X. No evidence of damage was noted.
Minor indentations were also noted on service water pump motor PM4B in the webs at 0 degrees and 270 degrees and the mounting base was damaged at 225 degrees. Dye penetrant inspection failed to reveal cracks at these, or any other locations.
G No evidence of any damage was noted on service water pump motor PM4C.
Cause of Incident Upon reviewing the installation history of PM4A, it became evident that it had been assembled to the pump and again removed on numerous occasions for inspection and alignment checks due to persistent high vibration.
It was thus concluded that the damage resulted from rough handling during the numerous realignment operations; that the damage is not due to a generic design defect; and that the damage was not caused by the high vibration observed during initial operation of the pump.
Safety Implications The three service water pumps provide cooling water to plant systems during nomal and emergency operations. Two redundant trains are provided, with one required for safe shutdown of the unit.
Ilad the cracks gone undetected, the motor would have continued to operate in a normal manner because:
(a) the motor load is shared by three sound webs in addition to the cracked web; (b) the lower bearing casting is predominantly loaded in compression; and (c) motor vibrations were found to be essentially dampened out at the web location.
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However, had PM4A failed, the remaining pumps would have continued to v
function. Missiles generated by the failure of PM4A would not jeopardize i '
the remaining pumps as they are separated by concrete walls. One of the l
remainj.ng pumps would provide adequate cooling water for the plant.
Thus, the health and safety of the public would not be affected by the failure of the service water pump motor.
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Corrective Action A replacement lower bearing housing casting will be installed on PM4A.
PM4B and PM4C will be left in normal service with the minor damage noted on PH4B removed by grinding to reduce stress concentrations. High vibration problems on PM4A have been corrected.
Personnel involved in alignment operations will be instructed to follow proper alignment procedures and avoid rough handling of motors and pumps during alignment.
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