ML20248G917
| ML20248G917 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/31/1989 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C311-89-2032, IEB-88-004, IEB-88-4, NUDOCS 8904130628 | |
| Download: ML20248G917 (3) | |
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GPU Nuclear Corporation
.i U Guclear m'ane B 480 s
Middletown, Pennsylvania 17057 I
717 944-7621 TELEX 84-2386 Writer"s Direct Dial Number:
C311-89-2032 March 31,1989 U.
S. Nuclear Regulatory Commission Attn:
Document Control Desk Washington, DC 20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 GPUN Response to NRC Bulletin 88-04
" Potential Safety Related Pump Loss" Decay Heat Removal (DHR) System - Supplemental Response The purpose of this letter is to follow up on our letter of January 31, 1989 regarding the adequacy of the installed minimum recirculation capacity of the Denay Heat Removal (DHR) Pumps and report that based upon the.information,we have, we do not believe that additional tests or inspections are necessary to provide further confirmation.
GPUN's. letter of August 15, 1988 provided our response to NRC Bulletin 88-04, " Potential Safety Related Pump Loss" regarding the Decay Heat Removal (DHR) Pumps (DH-P1A/B).
Our letter stated our conclusion that based upon our evaluations the DHR Pump minimum recirculation capacity is adequate to ensure that pump operability is not affected by minimum recirculation operation and that we had requested information from the pump manufacturer in accordance with the bulletin.
Also, our letter committed to the following by January, 1989:
- 1. The incorporation of additional periodic vibration readings into the existing surveillance test procedures to enhance our ability to trend the DHR Pump data,
- 2. A review of the DHR Pump vibration monitoring instrumentation setpoints and gui ince provided to the operator under alarm conditions,.atd
- 3. Informing the NRC by letter of any additional short term or long term actions that might be required if the information received from'the pump manufacturer did not confirm our own evaluations and conclusions.
Our letter of January 31, 1989 stated that we had only been able l
to partially confirm..'our evaluations and conclusions regarding 8904130628 890331 l
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the DHR Pump minimum flow with the pump manufacturer.
We stated that we had been unable to complete our review of the DHR Pump vibration setpoints and alarm responso guidance, and that we were considering plans for any additional work that might be needed to further confirm our evaluations and conclusions in lieu of the vendor's recommendations, and we would inform the NRC by letter in March, 1989.
Our initial response from the vendor, Dresser Industries Inc.,
dated December 3, 1988 approved TMI-1 DHR Pump minimum flow operation, approximately 125 gpm, up to 30 minutes quarterly for Emergency Safeguards (ES) System Testing plus 3 minutes monthly for Inservice Testing (IST).
In a letter dated January 23, 1989, Dresser proposed a long term test program to confirm the acceptability of pump operation at minimum flow for a six (6) hour continuous period.
Six (6) hours is an estimate of the time it may take to cooldown and depressurize the RCS to the LPI pressure in accordance with the Abnormal Transient Procedure (ATP) for Small Break LOCA.
We conservatively assume that the LPI pump would be left running for this period of time in recirculation while HPI is functioning.
Assuming the LOCA is as small as.007 ft2, the total DHR Pump flow in either the LPI or " Piggy-back" mode would be in excess of 300 gpm.
This is 10% of design flow which was commonly specified for pump minimum flow for safety injection pumps.
Sustained operation at this flow is judged to be acceptable.
At the time of our January, 1989 submittal, we had not completed our review to determine if the information we had on these pumps was sufficient to preclude the need for additional tests or inspections.
The purpose of this letter is to report that based upon the information we have, we believe that the existing pump recirculation configuration provides adequate assurance of continued pump operation during design basis accidents.
GPUN believes that over 15 years of successful operating experience with these pumps demonstrates that TMI-l's current modes of DHR Pump operation do not significantly degrade pump operability.
Our experience includes approximately 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> of operation at minimum flow for testing and total run times of approximately 35,000/23,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> for DH-P1A/B respectively since the last pump overhaul.
In tests performed during the outage which occurred in December, 1988, the pump which typically has higher vibration readings at minimum flow, DH-PlB, had head / flow within the 10%
tolerance limits of the manufacturer's head / flow curve at 925, 2100, at:d 3000 gpm.
These same limits were used for the initial startup of TMI-1.
Tests of both pumps on June 19, 1988 demonstrated thnt the flow rate to the RCS was greater than the t
C311-89-2032 March 31, 1989 RCS pressure vs flow rate ECCS analysis curve.
In our letter of August 15, 1988, GPUN committed to procedural changes to include additional periodic vibration readings and a review of the DHR Pump vibration monitoring alarm setpoints and guidance provided to the operator in response to an alarm.
We determined these actions to be prudent in order to enhance our ability to detect and take appropriate corrective action in the event that degradation of DHR Pump performance should occur.
Additional vibration readings have been incorporated into surveillance test procedures 1303-5.2 and 1300-3A/B.
These data have provided more information on the mechanical characteristics of the DHR Pumps in support of our determination that current operation of the DHR pumps under minimum recirculation conditions during testing has not resulted in deterioration of the pumps in excess of the normal wear that can be expected.
We have completed our review of the DHR Pump vibration alarm setpoints and alarm guidance.
The existing alarm settings for normal flow rate are satisfactory and will be maintained.
Procedures will be revised by June, 1989 to provide additional guidance that will apply when higher vibration levels are encountered at blade passing frequency while operating or testing the DHR Pumps at minimum recirculation flow rate.
GPUN does not plan additional actions to further confirm our evaluations and conclusions.
We believe that the current DHR Pump minimum recirculation capacity is adequate.
GPUN will continue to monitor the DHR Pump performance. As an additional precaution, we are taking steps to minimize the time that the DHR Pumps are operating at minimum flow during testing.
If it is later determined that additional actions may be required, GPUN will inform the NRC by letter and provide the justification for continued operation as requested by NRC Bulletin 88-04.
Sincerely,
// 8 /41LyI
. D. Hu ill Vice President and Director, TMI-l HDH/MRK cc:
J.
Stolz R. Conte R. Hernan W.
Russell i
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