ML20087L603
| ML20087L603 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/17/1974 |
| From: | Burstein S WISCONSIN ELECTRIC POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8403270293 | |
| Download: ML20087L603 (3) | |
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b April 17, 1974 Mr. John F. O' Leary, Director Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C.
20545
Dear Mr. O' Leary:
DOCKET NOS. 50-26& AND 50-301 POINT BEACI-NUCLEAR PLANT AUXILIARY FEED PUMP SUCTION STRAINERS This letter is to report the details of an abnormal occurrence at Point Beach Nuclear Plant, Facility Operating License Nos. DPR-24 and DPR-27, as defined by Sections 15.1.a.B and 15.1.a.D of the Technical Specifications.
This written re-port is submitted in accordance with Section 15.6.6.A.2 of the Technical Specifications and follows a telephone report on the incident to Mr. Ed. Jordan of Region III, Directorate of Regu-10tcry Operations, cn 7.pril 0, 1074, as rcquired by Occtica 15.6.6.A.1 of the Technical Specifications.
At approximately 11:30 P.M. on-April 7, 1974, Unit 1 at Point Beach was in the final stages of cooldown in prepara-tion for its second refueling.
While running the "A" motor-driven auxiliarf feed pump to maintain steam generator water levels following shrinkage, the operator noted that the pump was not delivering feedwater at an adequate flow rate.
An immediate investigation of the pump led to the dis-covery of an in-line conical strainer fitted at a flanged portion in the pump suction piping.
The strainer was removed and the pump placed back in service at approximately 12:00 P.M. the same date.
An investigation of the suction piping of the "B"-
motor-driven auxiliary feed pump and the Unit 1 and Unit 2 steam-driven auxiliary feed pumps disclosed similar in-line strainers.
All were removed.
A visual inspection of.the four' strainers showed that the two removed from the motor-' driven pumps were approximately 95% plugged.
The two removed from the steam-driven pumps, whil y
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Mr. John F. O' Leary April 17, 1974 dirty, exhibited a full mesh pattern throughout the whole of the strainer area.
We believe these latter strainers would not have reduced the flow rate to the suction side of the steam-driven pumps significantly.
Three separate means of injecting feedwater into the steam generators are available at Point Beach Nuclear Plant:
1.
Each unit is equipped with two main feed pumps, each rated at 7800 gpm at 935 psig and driven by 4160~k? motors normally sup-plied off the main generator unit trans-former.
Power to these motors is also supplied from either the 345 kv switchyard or the on-site gas turbine generator.
Each pump is capable of supplying approximately 60% of that unit's total requirements of i
2.
Two motor-driven auxiliary feed pumps capa-ble of delivering a total of 400 gpm of feedwater can feed to either unit.
These pumps, while normally supplied from the l
plant's 480 y huses cre capable of receiv-ing their electrical supply from the plant's emergency diesel generators.
3.
Two steam-driven auxiliary feed pumps, one per unit, each have a capacity of 400 gpm.
Steam supply to the turbine drives of these pumps may be taken from both or either of that unit's steam generators.
t The prime purpose of the auxiliary feedwater system des-cribed in (2) and (3) is to maintain a satisfactory. water inven-tory for removal of heat energy from the reactor coolant-system by secondary side steam release should a reactor trip coincide 4
with a total loss of both main feed pumps.
In reviewing the~ safety analysis'for loss ofl normal feedwater supply (See Volume 4, Section 14.1.11 of the' Point Beach. Nuclear Plant Final Facility Description and Safety Analysis Report),.the worst case is-presumed to be that only one motor-driven pump (200 gpm) is-available and capable of pumping feed water into~one steam ~ generator only.
In the period Februaryf3, s
4
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O Mr. John F. O' Leary. April 17, 1974 1974 (Unit 1 reactor tripped on that date and the motor-operated auxiliary feed pumps performed satisfactorily) until April 7, 1974, both main feed pumps have operated satisfactorily and the steam-driven auxiliary feed pumps have been fully available to perform their intended feedwater makeup function.
Examination of the conical strainers has shown them to be of a type commonly installed in piping systems at the con-clusion of construction and normally removed after a system has experienced a measure of initial operation.
No record apparently
. exists with respect to the installation of such filters on the suction lines to the auxiliary feed pumps.
None of these strainers was provided with an external "tell-tale" or flag.
Such devices are included as part of our usual construction and startup prac-tice to provide visual evidence of temporary strainer installa-tion.
The four auxiliary feed pumps are each tested on a monthly basis; however, the test is run essentially at " shutoff head", the only flow being through a one inch diameter minimum flow bypass line.
Sufficient flow was passed by the nearly-plugged suction strainers of the motor-driven auxiliary feed pumps during Liiese tests to suash the strainers existence end their condition.
~
To prevent a recurrence of this problem in the auxili-ary feed system or other safeguards systems in the plant, a careful visual survey is being conducted of these systems pri-marily by those persons responsible for and familiar with sur-veillance of such systems during plant construction and initial startup.
No additional strainers have been found to cate.
While it is not expected that the surveillance effort will disclose any further strainers, we will consider any such findings to merit an additional report.
Very truly yours, n
,/
r Sol Burstein Exec tive Vice Presidenti cc:
Mr. James G. Keppler, Regional Director Directorate of Regulatory _ Operations, Region III
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