ML20086D447
| ML20086D447 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 01/13/1976 |
| From: | Utley E CAROLINA POWER & LIGHT CO. |
| To: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| AO-50-261-76-1, NG-76-040, NG-76-40, NUDOCS 8312010486 | |
| Download: ML20086D447 (3) | |
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gpag Carral'.ta Power & Light C.ompany January 13, 1976 FILE NO: NG-3513 (R)
SERIAL NO: NG-76-040 f#J..e ~\\
Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commissioner Region II, Suite 818 di 0(hgb 230 Peachtree Street, N.W.
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Dear Mr. Moseley:
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- 11. B. ROBINSON UNIT NO. 2
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DOCKET 50-261 FAILURE OF "B" BORIC ACID TRANSFER PUMP In accordance with 6.6.2.a of the Technical Specifications for
- 11. B. Robinson Unit No. 2, the attached Abnormal Occurrence Keport is submitted for your information. This report fulfills the requirement for a written report within ten days of an Abnormal Occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16, Re-vhion 1.
Yours very truly,
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E, tle BulkPowerSupply\\
Vice-President CSB:ka cc:
Mr. D. C. Knuth Mr. W. G. Mcdonald 5312010486 760113 PDR ADOCK 05000261 34 S
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4 ABNORMAL OCCURRENCE 1.
Report No:
50-261/76-1 2a. Report Date:
January 5,1976 2b. Occurrence Date:
January 2,1976 3.
Facility:
H. B. Robinson Hartsville, South Carolina 29550 4.
Identification of occurrence Failure of "B" Boric Acid Transfer Pump constituted an abnormal occurrence in that it resulted in the failure of one component of an engineered safety feature that caused or threatened to cause the system to be incapable of performing its intended function. This is defined as an abnormal occurrence per paragraph 1.8.d of facility Technical Specifications.
5.
Conditions Prior to Occurrence The plant was operating at 100% power with 701 MWe net.
"B" Boric Acid Storage Tank was being recirculated using "B" pump. All other systems were normal.
"A" pump was operating at the time of the occurrence.
6.
Description of Occurrence At 0636 hours0.00736 days <br />0.177 hours <br />0.00105 weeks <br />2.41998e-4 months <br /> on January 2, 1976 recirculation of "B" Boric Acid Storage Tank was commenced using "E" Boric Acid Transfer Pump. At 0701 hours0.00811 days <br />0.195 hours <br />0.00116 weeks <br />2.667305e-4 months <br /> the operator noticed that the RTCB 0FF light was illuminated for "B" pump. Attempts to restart the pump f ailed, and it was declared out of service.
"A" Boric Acid Transfer Pump was operabic and running at the time of the occurrence.
7.
Designation of Apparent Cause of Occurrence An inspection of the pump internals revealed a damaged rotor can which was caused by failure of the rear graphite bearing. Fragments of this bearing apparently entered the area between the rotor and stator, cut-ting the thin stainless can allowing boric acid solution to enter and short out the rotor.
8.
Analysis of Occurrence At the time
- the failure and during the period when "B" Transfer Pump was inopetable, "A" Boric Acid Transfer Pump was operable and capable of providing the necessary supply of boric acid for any normal or emergency condition. At no time was there any threat to the public health and safety. The failed pump was returned to service within the twenty-four hour inoperative period al?. owed by facility Technical Specifications.
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Corrective Action "B" Boric Acid Transfer Pump was replaced with a spare pump and returned to service at 2031 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.727955e-4 months <br /> on January 2,_1976.
The pump failure was attributed to the rear bearing failure. There was no indication of excessive bearing wear nor was the failure anticipated based upon past experience of bearing lifetime. The pump that failed had been rebuilt at the plant, and the replacement components, including bearings were inspected prior to assembling the pump. No bearing discrepancies were noted at that, time. There-fore, it is concluded that this failure was of an isolated nature and may have resulted from an internal bearing flaw.
In view of this, there has been no corrective action formulated for prevention of the reoccurrence.
The subject pump was a GE-20K Chempump with the modified stub shaft.
The " stub shafting" of this pump was an' effort to reduce the stress t
riser in the area near the keyway.
It had been in service since July of 1975 and no problems have been experienced with shaft breakage on this pump. 'This failure was not related in any manner to the modified shaft.
An inspection of the stub shaft showed it to be in good condition.
- 10. Failure Data Manufacturer: Crane Chempump Series : G Model: GE-20K The following is a list cf previous failures involving bearings:
1 September 26, 1974 "B" Pump failed due to broken shaft, front bearing exhibited excessive wear.
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i' December 4, 1974 "B" Pump failed due to broken shaft, front bearing exhibited excessive wear.
May 21, 1975 "B" Pump failed due to broken shaft, front bearing exhibited wear.
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