ML18153B499
| ML18153B499 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/08/1988 |
| From: | Cruden D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 88-275A, IEB-88-004, IEB-88-4, NUDOCS 8808120288 | |
| Download: ML18153B499 (7) | |
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 August 8, 1988 D. S.CBUDBN VICB PBEBIDENT-NUCLEAB U. S. Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C.
20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS I AND 2 NRC BULLETIN 88-04:
POTENTIAL SAFETY-RELATED PUMP LOSS Serial No.
NL/RCB:jmj Docket Nos.
License Nos.
88-275A 50-280 50-281 DPR-32 DPR-37 NRC Bulletin 88-04: "Potential Safety-Related Pump Loss" identified concerns with minimum flow designs and requested licensees to investigate these concerns and correct them where applicable.
By our letter dated July 11, 1988, Virginia Electric and Power Company. notified the Nuclear Regulatory Commission that potentially susceptible configurations did exist at both Surry and North Anna, that evaluations were in progress, and that our response would be provided by August 8, 1988.
Our response for Surry Power Station is included in Attachment 1.
The information contained herein is true and accurate to the best of my knowledge.
If you have any questions, please contact me.
Very truly yours, Attachment Surry Evaluation 8E:oa 12028a 880808
~DR ADOCK 05000280 PDC
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U. S. Nuclear Regulatory Commission 101 Marietta Street, N.W.
Suite 2900 Atlanta, GA 30323 Mr. W. E. Holland NRC Senior Resident Inspector Surry Power Station
e COMMONWEALTH OF VIRGINIA)
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CITY OF RICHMOND
)
e The foregoing document was acknowledged before me, in and for the City and Commonwealth aforesaid, today by D. S. Cruden who is Vice President - Nuclear, of Virginia Electric and Power Company.
H~ is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.
Acknowledged before me My Commission expires:
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Notary Public
ATIACHMENT 1 SURRY POWER STATION UNITS 1 AND 2 RESPONSE TO NRC BULLETIN 88-04:
POTENTIAL SAFETY-RELATED PUMP LOSS I.
SCOPE OF EVALUATION As directed by NRC Bulletin No. 88-04, Virginia Electric and Power Company has investigated minimum flow recirculation design concerns in safety~related systems.
These concerns are the potential for dead-heading of one or more pumps that have a minimum flow recirculation line common _to two or more pumps or other piping configurations that do not preclude pump-to-pump interaction, and the adequacy of the minimum flow recirculation l*ine for even a single pump in operation.
Our investigation determined that the following systems were of possible concern:
A.
B.
Low Head Safety Injection (LHSI)
C.
High Head Safety Injection (HHSI)
D.
Auxiliary Feed. Water (AFW)
II.
Su11111ary of Conclusions and Problems A.
- 1.
T~e pump-to-pump interaction issue is not a concern since these pumps are normally run one at a time except during pump changeover.
- 2.
A pump may, however, be run*on recirculation for a significant period of time during system cool down which results in accelerated wear rates and increased maintenance.
The minimum flow recirculation line is not adequately sized for extended operation on recirculation.
B.
Low Head Safety Injection (LHSI)
- 1.
The LHSI pumps operate in parallel upon receipt of a Safety Injection signal.
If the Reactor Coolant System pressure remains above the shutoff head for the LHSI pumps, they will operate on recirculation through a
common minimum flow recirculation line to the Refueling Water Storage Tank, and this line is not adequately sized for extended operation on recirculation.
The recirculation line was sized based on thermal considerations rather than possible *hydraulic instability phenomena which may exist.
- 2.
Flow tests have been completed for the Unit 1 LHSI pumps operating in the recirculation mode and found that neither pump significantly affected the other.
- 3.
The LHSI pumps are tested individually on miniflow recirculation during the monthly performance testing.
C.
High Head Safety Injection CHHSI}
L The HHS I pumps al so serve as charging pumps and *were des*i gned for this dual service.
Because of their design, the configuration of their individual recirculation lines, and the verification from the vendor that existing recirculation flow rates are adequate, these pumps are not of concern.
- 0.
Auxiliary Feed Water CAFW)
- 1.
The pump-to-pump interaction issue is not a concern since each pump has a minimum flow recirculation line with a flow restricting orifice that discharge to a common recirculation header.
The pressure drop across the orifice is large enough to preclude any "strong-weak" pump operational problems.
- 2.
After the steam generator water 1 evel s are returned to the specified range, however, the pumps can be operated at low flow/minimum flow recirculation for signi-ficant periods of time and the minimum flow recirculation lines are not adequately sized for extended operation on recirculation.
- 3.
The motor driven AFW pumps are a 1 so used to pressurize and leak-test the steam generators following maintenance.
- 4.
Technical Specificatfons currently require monthly testing on minimum flow recirculation.
III. Corrective Actions A.
Residual Heat Removal CRHR)
No corrective actions necessary.
Engineering will initiate a study to evaluate enhancements.of cooldown and possible heatup operation which may reduce pump maintenance requirements.
B.
Low Head Safety InJection CLHSil
- 1.
Short tenn - Sma 11 break LOCA scenarios wi 11 be conducted by November 1, 1988 on the simulator to verify the EOPs adequately address and therefore minimize operation of the LHSI pumps on the recirculation mode.
C.
High Head Safety InJection CHHSil
- 1.
No corrective actions are deemed necessary.
e D.
- 1.
Short term
- a.
Appropriate procedures wi 11 be reviewed and revised, as necessary, by November 1, 1988 to minimize operation at low flow/minimum flow recirculation.
- b.
Operation/Engineering personnel will be directed to limit use of these pumps in leak testing.
- 2.
Long term
- a.
One auxiliary feedwater pump will be disassembled and inspected for degradation during the 1989 and 1990 refueling outage for each unit.
The remaining pumps will be inspected during subsequent outages.
Inspection results wi 11 determine the required inspection frequency and number of pumps inspected.
- b.
Larger minimum flow recirculation lines are scheduled to be installed in the 1989 and 1990 refueling outages for Units 1 and 2, respectively.
IV. Justification for Continued Operation A.
Residual Heat Removal {RHR)
I.
Only one of the two pumps for each unit is required for safe shutdown, and alternate means (e.g. auxiliary feedwater) exist for removing co_re decay heat.
- 2.
These pumps are frequent 1 y run during operations.
As a result, a substantial is available indicating that these maintained and operated.
norma 1 shutdown p 1 ant amount of information pumps are properly
- 3.
Pump vibration analysis will continue to be performed in order to ensure that the pumps are fully operable and not experiencing significant deterioration.
- 4.
Operation of the RHR system in minimum flow recirculation will be avoided whenever possible.
- 8.
Low Head Safety Injection CLHSI)
I.
Any one of the two pumps is cap ab 1 e of providing the mini mum required flow in a recovery scenario, and therefore the operator may secure one of the pumps.
.1 e
- e.
- 2.
Flow tests have been completed for the Unit 1 LHSI pumps operating in the recirculation mode and found that neither pump significantly affected the other.
- 3.
Quarterly performance testing is for short durations at flows of 340 gpm.
The vendor has stated that this recirculation flow rate is adequate for the modes and duration of operation expected.
- 4.
Pump vibration analysis will continue to be performed in order to ensure that the pumps are fully operable and not experiencing significant deterioration.
- 5.
Operation of the LHSI system on minimum flow recirculation will be avoided whenever possible.
C.
High Head Safety Injection (HHSI)
- 1.
No justification for continued operation is deemed necessary.
D.
- 1.
Any one of the three pumps is capable of providing the m1n1mum required flow in a recovery scenario, and therefore the operator may secure two of the pumps at his option.
2:
Pump vibration analysis will continue to be performed to monitor bearing and major rotating element performance and to ensure that the pumps are fully operable and not experiencing significant deterioration.
- 3.
During the recent Units 1 and 2 outages, the auxiliary feedwater pumps were inspected and refurbished as necessary.
- 4.
Operation of the AFW system in minimum flow recirculation will be avoided whenever possible.