ML18054A358
| ML18054A358 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 07/07/1988 |
| From: | Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8807130181 | |
| Download: ML18054A358 (12) | |
Text
consumern POW~1 PllWERINli lllllCHlliAN"S l'IUlliRESS General Offices:
1945 West Pa~nall Road, Jackson, Ml 49201 * (517) 788-1636 July 7, 1988 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
RESPONSE TO NRC BULLETIN 88 POTENTIAL FOR SAFETY RELATED PUMP LOSS Kenneth W Berry Director Nuclear licensing NRC Bulletin 88-04 requested that licensees review safety-related pump and system designs with regard to the potential for loss of a pump stemming from:
- 1.
Dead heading of pump(s) with common minimum flow recirculation lines.
- 2.
Inadequate minimum flow capacity.
We have evaluated the applicable systems against the actions requested in the subject bulletin.
The systems are identified as follows:
- 1.
Auxiliary Feedwater System (AFW)
- 2.
Boric Acid Addition System (BA)
- 3.
Containment Spray System (CSS)
- 4.
Component Cooling Water System (CCW)
- 5.
High Pressure Safety Injection System (HPSI)
- 6.
Low Pressure Safety Injection System (LPSI)
- 7.
Service Water System (SWS)
Attached are the results of our investigation.
Kenneth W Berry Director, Nuclear Licensing CC Administrator, Region III, NRC NRC Resident Inspector - Palisades Attachment OC0788-0058-NL04 8807130181.880707
~DR ADOCK 05000255 PNU
CONSUMERS POWER COMPANY Palisades Plant Docket 50-255 - License DPR-20 RESPONSE TO NRC BULLETIN At the request of the Commission and pursuant to the Atomic Energy Act of 1954 and the Energy Reorganization Act of 1974, as amended, and the Commission's Rules and Regulations thereunder, Consumers Power Company submits our response to NRC Bulletin 88-04 dated May 5, 1988, entitled, "Potential Safety-Related Pump Loss."
Consumers Power Company's response is dated July 7, °1988.
CONSUMERS POWER COMPANY By~
David Sworn and subscribed to before me this 7th day of July 1988.
1~l~
Elaine E Buehrer, Notary Public Jackson County, Michigan My commission expires October 31, 1989 OC0788-0058-NL04
OC0788-0058-NL04 ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 60-DAY RESPONSE TO NRG BULLETIN 88-04 POTENTIAL FOR SAFETY-RELATED PUMP LOSS July 7, 1988 9 Pages
ITEM 1 ATTACHMENT Determine if any safety-related system has a pump and piping system which does not preclude pump-to-pump interaction during minimum flow operation*.
Response
Auxiliary Feedwater System (AFW)
Each AFW pump has an individual 2" mini-flow line containing a check valve and flow orifice.
These mini-flow lines combine into a common 6" header which returns to the condensate storage tank or hotwell reject line (see Attachment 1).
This piping configuration precludes pump to pump interaction.during mini-flow operation.
Boric Acid Pumps (BA)
Each Boric Acid Pump has a minimum flow line with a motor-operated valve which receives a closed signal on a safety injection-signal (SIS).
Normal operating practices do not align the pumps _in a configuration in which they can interact with each other.
Therefore, the pump to pump interaction during minimum flow is precluded.
Containment Spray System (CSS)
Minimum flow lines are isolated during normal plant operation; the minimum flow lines are used only during quarterly pump testing with one pump being tested at a time.
Therefore, pump-to-pump i~t~raction cannot occur.
Component Cooling Water System (CCW)
The CCW pumps do not have a minimum flow line; therefore, this item does not apply to the CCW pumps.
However, in April of 1988, we determined that during normal operation (with 2 pumps running), one combination of pumps was probably operating in a condition which allowed dead-heading of one of the pumps in low-flow conditions.
Subsequently, plant operating practices were changed to require one pump operation. This resulted in an overall reduction of pump vibration.
High Pressure Safety Injection (HPSI)/Low Pressure Safety Injection (LPSI)
The HPSI & LPSI pumps each have an individual mini-flow line containing a check valve and flow orifice.
Through a series of.
expansions these lines combine to form a 6" return line to the Safety Injection and Refueling Water (SIRW) tank (see Attachment 2).
This OC0788-0058-NL04
ITEM 2 ITEM 3 piping configuration precludes pump to pump interaction during minimum flow operation.
Special Test T-220 performed in 1986 verified this for a LPSI & HPSI pump operating simultaneously.
Service Water System SWS The service water pumps do not have a minimum flow line; therefore, this item does not apply to the SWS pumps.
However, during normal pump operation, pump-to-pump interaction may take place due to discharge piping configuration.
The vertical turbine pumps used in the SWS exhibit a characteristic curve which does not have a flat portion in the low flow range like that described in the bulletin (Attachment 3).
This minimizes the possibility of pump-to-pump interaction.
If the situation described in Item 1 exists, evaluate the system for flow division considering:
a)
Line and component losses b)
Pump characteristic curves c)
Instrument and reading error d)
Worst case parameter deviation for ASME B&PU Code Section XI.
Response
As discussed above, there are no systems in which pump-to-pump interaction during minimum flow operation is a concern.
Therefore, no response to Item 2 is required.
2 Evaluate the adequacy of minimum flow bypass lines for safety related centrifugal pumps with respect to damage resulting from operation and testing in the minimum flow mode.
Response
AFW Vibration analysis and spectral analysis were performed on the AFW pumps to determine if existing minimum flow capacity is adequate.
Overall bearing vibration was found to be acceptable.
- However, analysis indicated that AFW pump P-8C exhibits significant random-broadband spectrum variability while on minimum flow.
This fact, coupled with random cavitation noise during minimum flow operation, leads us to the conclusion that P-8C may be experiencing recirculation.
Item 4 discusses both short and long term actions to be taken for this pump.
OC0788-0058-NL04
BA The minimum flow recirc lines for the boric acid pumps are pressure controlled to operate at a point near the pump's best efficiency point.
Therefore, the existing minimum flow configuration is adequate.
css The minimum flow bypass lines for the containment spray pumps are used only during quarterly pump testing (approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> per year).
The pump vendor states that the pumps should have a minimum flow rate of about 40% of design flow.
This equates to 720 gpm for the containment spray pumps.
This flowrate cannot be achieved with the existing flow lines.
To achieve adequate test flow rates, the existing pump test procedure will be revised to provide flow through an existing larger 6-inch line (see Item 4).
ccw 3
Since the CCW pumps do not have a minimum flow bypass, no response is required.
High Press~re Safety Injection The HPSI pumps have been run at minimum flow for approximately 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> to date, primarily for testing.
Since no material or mechanical deterioration was observed in the HPSI rotating elements when replaced in 1983, no damage is expected to occur for extended periods of operation at the present minimum flow rate.
Further investigation with the pump vendor to verify HPSI minimum flow requirements is being pursued.
Low Pressure Safety Injection The LPSI pumps have been run at minl.Inum flow for approximately 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> to date, primarily for testing.. One LPSI pump impeller was replaced in 1986 after three years of operation.
No damage due to cavitation or recirculation was observed.
The other LPSI pump has been in service since 1969 with no detailed inspection having been performed.
The LPSI pump vendor has recommended a 500% increase in minimum flow.for the pumps.
However, existing minimum flow lines cannot support this flow rate.
Additional long-term action will be undertaken as indicated in Item 4 below.
sws The service water pumps do not have minimum flow oypass lines; therefore, no response to Item 3 is necessary.
OC0788-0058-NL04
ITEM 4 Provide the following information:
a)
A summary of systems affected and problems.
b)
Short and long term actions to insure safe operation.
c)
Long term schedule for concerns raised by this bulletin.
d)
Justification for continued operation.
Response
AFW One area of concern arises regarding adequacy of minimum flow lines:
P-8C is exhibiting signs of recirculation during minimum flow operation.
Short-term action for P-8C has been taken to minimize the time that P-8C is operated on minimum flow.
Long-Term Actions Include:
4
- 1)
Develop a testing program to establish the exact minimum flow rate required.
This is expected to be completed during or before the 1989 maintenance outage.
- 2)
Based on the above test data, develop and schedule system modifications.
Completion will depend on the extent of the modifications required.
BA Vibration data and pump performance curves indicate that adequate pump performance will continue.
Since the pump will not operate on mini-flow during an accident, it is concluded that the pump will meet all accident requirements.
Since pump-to-pump interaction does not occur, and existing minimum flow capacity is adequate, no further action is required.
css
/
The concern regarding the containment spray pumps is that the two inch minimum flow bypass lines may not be large enough to provide proper minimum pump flow during pump testing.
Per operating procedure SOP-4,_ the containment spray pumps can be used as an alternate means of filling the safety injection bottles.
However, the containment spray pumps have not been evaluated for use in filling the safety injection bottles.
The pipe sizing (l") may prevent achieving adequate minimum flow rates.
OC0788-0058-NL04
The following actions are provided to address the concerns:
- 1.
Containment Spray Pump test procedure Q0-16 will be revised to provide greater test flow rates.
This will be done by aligning the pump discharge through the 6" recirc line.
This revision will be completed by 12/31/88.
- 2.
Use of containment spray pumps to fill the safety injection bottle will be evaluated prior to use.
If required, operating procedure SOP-4 will be revised.
Continued pump operation is justified for the following reasons:
o Pump is not run in minimum flow bypass mode subsequent to accident.
5 o
Pump will be run in minimum flow bypass mode only when testing pump.
A revised pump test procedure, providing greater flow rates, will be approved prior to end of year.
The pump has shown no sign of distress due to current testing method.
ccw There are no further concerns for these pumps pertaining to this Bulletin.
Modification of operating practices to single-pump operation (during normal operations) has resolved concerns about recirculation and pump-to-pump interaction.
No further action is planned for these pumps.
HPSI/LPSI Based qn previous pump inspections and performance testing, there are no immediate concerns for these pumps regarding the issues of this bulletin.
However, to further investigate the possibility of recirculation, the following actions will be undertaken:
The analysis will be similar to that performed on the AFW pumps ~nd will be completed by March 31, 1989.
- 2. Inspect the impeller and rotating component in LPSI pump "A" (P-67) during 1988 refueling outage.
- 3. Revise pump maintenance procedures to incorporate inspection instructions for the impeller and line components, focusing on damage due to recirculation and cavitation.
These procedure revisions will be completed by June 30, 1989.
If the vibration analysis and pump inspections do not produce evidence of recirculation or cavitation damage, no modifications to OC0788-0058-NL04
the minimum flow lines for the HPSI or LPSI pumps will be.
implemented.
sws As discussed earlier, the service water pumps do not have minimum flow bypass lines.
Therefore, no action is required.
OC0788-0058-NL04 6
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