05000281/LER-2006-001, Regarding Charging Pump Component Cooling Water System Inoperable Due to Inadequate Venting
| ML062760280 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 09/25/2006 |
| From: | Jernigan D Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 06-810 LER 06-001-00 | |
| Download: ML062760280 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2812006001R00 - NRC Website | |
text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 September 25, 2006 1 OCFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555-0001 Serial No.:
SPS: PAK Docket No.:
License No.:
06-810 50-281 DPR-37
Dear Sirs:
Pursuant to 10CFR50.73, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to Surry Power Station Unit 2.
Report No. 50-281/2006-001-00 This report has been reviewed by the Station Nuclear and will be forwarded to the Management Safety Revik and Operating Committee imittee for its review.
Donald E. Jernigan, Site Vice President Surry Power Station Enclosure Commitments contained in this letter:
- 1. Procedures will be revised to ensure that the charging pump intermediate seal coolers are sufficiently vented prior to returning them to service following maintenance.
cc: United States Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 Mr. N. P. Garrett NRC Senior Resident Inspector Surry Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY IMB: NO. 3150-0104 EXPIRES 06/30/2007 (6-2004)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person Is not required to respond to, the information collection.
- 3. PAGE Surry Power Station, Unit 2 05000 - 281 1 OF4
- 4. TITLE Charging Pump Component Coolin, Water System Inoperable Due to Inadequate Venting
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED E7I SEQUENTIAL R
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YER NUMBER NO MONTH DAY YEAR 05000 07 27 2006 2006 -
001 -
00 09 25 2008 6
05000
- 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
E 20.2201(b)
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E] 50.73(aX2Xvii)
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- 10. POWER LEVEL i]
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E] 50.46(aX3Xil)
E] 50.73(aX2XvXB)
E] 73.71(aX5) 20.2203(aX2Xv) 50.73(aX2XIXA) 50.73(aX2XvXC)
E] OTHER Specify In Abstract below
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50.73(aX2XvXD) or in (If more space Is required, use additional copies of NRC Form 366A) 1.0 DESCRIPTION OF THE EVENT The charging pump cooling water subsystem provides component cooling (CC) water for the charging pump seal coolers. CC water circulating in the charging pump mechanical seal cooling loops is cooled by intermediate seal coolers which reject heat to the charging pump service water system. The charging pump cooling water subsystem consists of two full-capacity charging pump cooling water pumps and two full-capacity intermediate seal coolers providing 100% redundancy. To ensure that CC water is continually available to the charging pump seal coolers, one charging pump cooling water pump is placed in operation while the other pump is maintained in standby. The standby charging pump cooling water pump is automatically actuated on low pump discharge pressure to supply CC water in the event of failure of the operating pump.
On July 27, 2006, with Unit 2 operating at 100% power, repair of a leak on the Unit 2 'A' charging pump intermediate seal cooler's CC water discharge line was completed.
After the repair, the CC water side of the intermediate seal cooler was vented in accordance with procedures by opening the intermediate seal cooler vent valve (high side) and valving in system pressure. At 1947 hours0.0225 days <br />0.541 hours <br />0.00322 weeks <br />7.408335e-4 months <br />, while restoring the intermediate seal cooler to a normal line-up, a main control room annunciator alarm was received indicating that the CC water pressure had decreased. The standby charging pump cooling water pump started automatically, as expected, but no CC water flow was observed. The operating Unit 2 charging pump continued to run throughout this event however, since the charging pump cooling water subsystem is a subsystem of the charging pumps, the Unit 2 charging pumps were declared inoperable and a 6-hour clock to hot shutdown (HSD) was entered in accordance with Technical Specifications (TSs) 3.0.1.
The charging pump cooling water subsystem was successfully vented and at 2043 hours0.0236 days <br />0.568 hours <br />0.00338 weeks <br />7.773615e-4 months <br />, CC flow was restored at 25 gallons per minute (GPM). The flow rate of the subsystem continued to increase and, at 2125 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.085625e-4 months <br />, the 6-hour TS 3.0.1 clock was exited prior to initiating actions to shutdown the unit.
This report is being issued pursuant to 10 CFR 50.73(a)(2)(i)(B), any operation or condition prohibited by TSs. Since the event caused two independent trains to become inoperable, this report is also being issued pursuant to 10 CFR 50.73(a)(2)(vii).
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
During normal operation, the charging pumps are used as part of the chemical and volume control system and take suction from the volume control tank. Normal operating temperature of the source water is within the operating range of the mechanical seals.
Durin ccdn codtos th hring pumps are used as high head safety injectionU. S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION 50R I
NUMBER NUMBER Surry Power Station 05000-281 3 of 4 2006 001 00 (SI) pumps and take suction from the cool refueling water storage tank (RWST).
However, after recirculation mode transfer (RMT), the high head SI pumps take suction from the discharge of the low head SI pumps, which take suction from the containment sump. Water pumped from the containment sump is expected to be warmer than the maximum SI pump seal operating temperature, therefore the charging pump cooling water subsystem is required to maintain the SI pump mechanical seals temperature within operating range during accident conditions.
The PRA model reflects the high head SI pump's dependency on the charging pump cooling water subsystem after RMT. An analysis of this event indicated that the Allowed Configuration Time (the time required to accumulate a Core Damage Probability (CDP) of 1.OE-6) for this configuration was 955 hours0.0111 days <br />0.265 hours <br />0.00158 weeks <br />3.633775e-4 months <br />. Since the charging pump cooling water pumps were unavailable for one hour and 38 minutes, the CDP associated with this event was 1.7E-9. In addition, during the limited time the Unit 2 charging pump cooling water subsystem was unavailable, the charging pump crosstie from Unit 1 was available to provide charging to Unit 2. Therefore, with the low risk and availability of the crosstie, the health and safety of the public was not affected by this event.
3.0 CAUSE
The procedure used to return the charging pump intermediate seal cooler to service was determined to be inadequate to ensure proper venting of the entire intermediate seal cooler. Procedure guidance did not account for the intermediate seal cooler piping configuration that required the cooler to be slowly filled during return to service to ensure sufficient venting of the cooler. As a result, air remaining in the cooler was introduced into the charging pump cooling water subsystem and caused air binding of both charging pump cooling water pumps.
4.0 IMMEDIATE CORRECTIVE ACTION(S)
Both charging pump cooling water pumps were stopped and the outlet of the 'A' intermediate seal cooler was isolated. The standby charging pump cooling water pump discharge valve was also isolated. The standby charging pump cooling water pump was then started and its discharge valve slowly opened while monitoring discharge pressure. The cooling water subsystem was vented and the standby charging pump cooling water pump was restored to partial flow at 2043 hours0.0236 days <br />0.568 hours <br />0.00338 weeks <br />7.773615e-4 months <br />. The standby charging pump cooling water pump discharge valve was fully opened and CC water flow was restored to normal flow on the standby pump at 2125 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.085625e-4 months <br />.
5.0 ADDITIONAL CORRECTIVE ACTIONS
The Unit 2 'A' charging pump intermediate seal cooler was placed in service following completion of all Post Maintenance Testing (PMT).U. S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE TEAR SEQUENTIAL REVISION Surry Power Station 05000-281 NUMBER NUMBER 4 of 4 2006 001 00 6.0 ACTIONS TO PREVENT RECURRENCE Procedures will be revised to ensure that the charging pump intermediate seal coolers are sufficiently vented prior to returning them to service following maintenance.
7.0 SIMILAR EVENTS
Surry Unit 1 LER 87-033-00, Charging Pump Cooling Water System Inoperable Due to Inadequate Test Procedure, documented a similar air binding event; however, at the time the system was vented at the charging pump cooling water pump casing.
Corrective actions moved the venting to the high point of the intermediate seal cooler and the cooler has since been successfully vented several times.
8.0 MANUFACTURERIMODEL NUMBER Goulds/3996ST