05000498/LER-2019-001, Condition Prohibited by Technical Specifications Due to Inoperable Essential Cooling Water Pump
| ML19119A270 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/29/2019 |
| From: | Schaefer M South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-19003647, STI 34842375 LER 2019-001-00 | |
| Download: ML19119A270 (9) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 4982019001R00 - NRC Website | |
text
Nuclear Operating Company South Tew rrojixt Etvclrlc Geimatlns Sl.illon RO,ISm289 mdsworth, Tmf7/-IS3 April 29, 2019 NOC-AE-19003647 10CFR 50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Unit 1 Docket No. STN 50-498 Licensee Event Report 2019-001-00 Unit 1 Condition Prohibited by Technical Specifications Due to Inoperable Essential^ooling Water Pump Pursuant to reporting requirements 10 CFR 50.73(a)(2)(i)(B), STP Nuclear Operating Company hereby submits the attached South Texas Project Unit 1 Licensee Event Report 2019-001-00 for a condition prohibited by the plant Technical Specifications.
Causal investigation is ongoing and a supplement to this Licensee Event Report will be submitted once this evaluation is complete.
The event did not have an adverse effect on the health and safety of the public.
There are no commitments in this submittal.
If there are any questions, please contact Tim Hammons at 361-972-7347 or me at 361-972-7888.
Michael A. Schaefer Site Vice President Attachment: Unit 1 LER 2019-001-00, Unit 1 Condition Prohibited by Technical Specifications Due to Inoperable Essential Cooling Water Pump STI34842375
NOC-AE-19003647 Page 2 of 2 cc:
Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, TX 76011-4511 Glen 'Ed' Miller Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (O9E01) 11555 Rockville Pike Rockville, MD 20852 NRC Resident Inspector U. S. Nuclear Regulatory Commission P. O. Box 289, Mail Code: MN116 Wadsworth, TX 77483
NOC-AE-19003647 Attachment Attachment Unit 1 LER 2019-001-00 Unit 1 Condition Prohibited by Technical Specifications Due to Inoperable Essential Cooling Water Pump
NRC FORM 366 (04-2018)
NRC FORM 366 (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. Facility Name South Texas Unit 1
- 2. Docket Number 05000498
- 3. Page 1 OF 6
- 4. Title Unit 1 Condition Prohibited by Technical Specifications Due to Inoperable Essential Cooling Water Pump
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Number Rev No.
Month Day Year Facility Name N/A Docket Number 05000 02 27 2019 2019 - 001 - 00 04 29 2019 Facility Name N/A Docket Number 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 1 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. Power Level 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 100 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(ii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(iii) 50.73(a)(2)(i)(C)
Other (Specify in Abstract below or in summary of the event The condition of ECW Pump 1B packing was discovered during a normal pump start. Although the ECW pumps are safety-related and are required to start and run without Operator aid, normal practice is to have a plant operator check ECW pump status before and after starting. The ECW operating procedure provides information that on an ECW pump start an adequate stream of about one-half gallons per minute (gpm) seal leakage should be maintained. When the pump has run for about 20 minutes, seal leak-off should be adjusted to about one-quarter gpm. The maximum flooding rate in the Essential Cooling Water Intake Structure should be limited to 2.3 gpm, based on allowing seven days of operation before providing temporary drainage and while allowing only one-half the design basis flood accumulation. The ECW pumps are packed with four rings of John Crane C1050, Polytetrafluoroethylene (PTFE) filament, PTFE dispersion, with added lubricating oil.
When ECW Pump 1B was started on February 27, 2019, the plant operator at the pump observed no seal leakage and, eventually, vapors (smoke) exiting from the stuffing box. ECW Pump 1B was secured after running for 221 seconds. When the packing was later replaced, the top three packing rings were observed to be black (scorched) at their surface facing the pump shaft. During the 221 second pump run, the pump developed normal discharge pressure and normal flow rates with normal flow to each of the system loads.
Because the pump made it through the more demanding startup transient without receiving any indications of motor overload, the motor appears to be reasonably capable of continuing to drive the pump with the existing amount of packing friction. Previous experience with ECW pump bearing issues has demonstrated the motor sizing and breaker trip settings are such that even severe damage to shaft sleeve material does not result in a motor trip.
The contact surface of the packing was scorched and was starting to produce small flakes of black material. If the pump had not been secured after 221 seconds, heat from packing friction would have continued to have been generated and the packing surface would have continued to degrade. Because the PTFE packing rings have a higher coefficient of thermal expansion than most metal and other packing materials, continued heat up of the shaft and packing results in further compression of the packing. The most likely prospect with continued pump operation would be eventual loss of packing material from the inner diameter of the packing rings. As material is extruded from the gland, the pressure of the water in the pump stuffing box below the packing would eventually increase leakage along the shaft until the amount of water leaking up past the packing rings began removing the friction heat. As leakage continued to increase, the amount of water flow up along the shaft would eventually quench the shaft and packing, bringing the temperature back to near ECW pond temperature. With the cooling of the packing and the high coefficient of thermal expansion of PTFE, stuffing box leakage on the order of several gallons per minute could develop. Because of the tight diametric clearance of the elbow bearing of this newly refurbished pump and because the bottom packing ring had not been degraded by heat, stuffing box leakage flow can be expected to remain well below 20 gpm. Although ECW Pump 1B packing leak-off could increase well above normal rates, a spray shield covering the south opening in the motor stand protects the nearby motor control center from water spray.
Possible shaft leakage on the order of several gallons per minute would exceed the 2.3 gpm screening criterion for leakage into an ECW pump bay. The 2.3 gpm criterion relies on seven days of operation before a means of dewatering the pump bay can be implemented (credit is not taken for the non-safety sump pump).
With leakage exceeding 2.3 gpm, ECW Pump 1B could not be ensured to meet its design requirements for continued operation.
On February 18, 2019, when ECW Pump 1B was started for system fill and vent, a similar packing condition was observed and the pump was secured after running for 138 seconds. On February 19, 2019, the pump was restarted a few hours later with maintenance adding water to the top of the gland and shaft to keep the stuffing box from heating. The system was successfully filled and vented and after about an hour of monitoring the pump and keeping the gland cool with external water, stuffing box leakage reached the point that gland temperature remained satisfactory. After running for about 14.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, ECW Pump 1B was secured following successful surveillance testing and returned to service. ECW Pump 1B remained idle until February 27, 2019.
Because ECW Pump 1B did not complete a long run-in period after the run on February 19, 2019, the packing condition of excessive tightness that leads to continued heating could have existed shortly after the pump was secured on February 19, 2019. Because continued pump operation, such as for an automatic start in response
to a design basis accident, could progress to a condition where the 2.3 gpm leakage into an ECWIS pump bay criterion would be exceeded, reasonable assurance that ECW Pump 1B could have met its design basis requirements after February 19, 2019, cannot be assured.
Timeline (Note: All times are Central Standard Time):
February 13, 2019 [1819]: ECW Train 1B declared inoperable with ECW Pump 1B pressure dropping.
February 18, 2019 [2241]: Started ECW Pump 1B for Train 1B fill and vent following completion of ECW Pump 1B pump and motor replacement.
February 18, 2019 [2243]: Secured ECW Pump 1B due to insufficient packing leak-off.
February 19, 2019 [0047]: Started ECW Pump 1B for Train 1B fill and vent.
February 19, 2019 [0109]: ECW Pump 1B packing and stuffing box heat up due to lack of packing leak-off documented in corrective action program (Condition Report 19-1954). The Condition Report documents a plan to loosen the packing and pour water onto the stuffing box and packing until leak-off is sufficient to keep packing cool.
February 19, 2019 [1536]: Secured ECW Pump 1B following surveillance testing.
February 19, 2019 [1712]: ECW Train 1B declared operable following completion of maintenance, post maintenance testing, and package closure.
February 27, 2019 [1353]: Started ECW Pump 1B to support work week activities.
February 27, 2019 [1357]: Secured ECW Pump 1B due to loss of seal leak-off. Train 1B ECW declared inoperable.
February 28, 2019 [1303]: Started ECW Pump 1B for post maintenance testing following packing replacement.
March 1, 2019 [1305]: Secured ECW Pump 1B after a 24-hour run.
March 1, 2019 [1434]: Started ECW Pump 1B for post maintenance testing.
March 1, 2019 [1445]: Declared ECW Pump 1B operable.
F. Method of discovery
This event was discovered after starting ECW Pump 1B to support work week activities.
II. Component failures
A. Failure Mode, mechanism, and effects of failed component The failed component in this event is ECW Pump 1B. The pump failed as a result of a lack of packing leak-off. There was smoke and evidence that the packing was heating up.
B. Cause of component failure
Causal evaluation is ongoing. A supplement to this Licensee Event Report will be submitted upon completion of the evaluation.
C. Systems or secondary functions that were affected by failure of components with multiple functions Train B ECW was declared inoperable. The following Train B safety systems were also declared inoperable because the ECW System supplies cooling for these systems: Engineered Safety Features Standby Diesel Generator, Emergency Core Cooling System, Residual Heat Removal System, Component Cooling Water System, Essential Chilled Water System, Containment Spray System, Reactor Containment Fan Cooler System, and Control Room Makeup and Cleanup Filtration System.
D. Failed component information
Essential Cooling Water System {BI}
Pump {P}
Manufacturer: Hayward - Tyler Pump Company {R165}
Model: 24VSN
III. Analysis of the event
A. Safety system responses that occurred No safety systems were required to respond as a result of this event.
B. Duration of safety system inoperability
ECW Pump 1B is considered inoperable from the conclusion of the successful post maintenance run following pump replacement on 02/19/2019 at 1536, until the pump was declared operable on 03/01/2019 at 1445 for a period of 9 days and 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />.
C. Safety consequences and implications
The expected leak rate (less than 20 gpm) caused by the eventual failed packing had the pump not been secured is minimal in comparison to the total flow obtained by the ECW pump and would not affect the ability of the pump to provide sufficient cooling to the credited loads. Because ECW Train B produced design flow rates to all serviced components, ECW Pump 1B was considered capable of performing its safety functions in support of reactor safe shutdown, residual heat removal, and in support of equipment for accident mitigation (except when it was taken out of service to replace the packing). Therefore, this event is not considered to be a Safety System Functional Failure.
A review of flooding calculations for the ECW Intake Structure determined that the net volume of space available before submerging an ECW pump motor is 6296 cubic feet (includes 15% conservatism). Based on the maximum consequential leak rate of 20 gpm, ECW Pump 1B would have been unaffected for approximately 39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br /> The event did not result in any offsite release of radioactivity or increase of offsite dose rates, and there were no personnel injuries or damage to any other safety-related equipment associated with this event.
Therefore, there was no adverse effect on the health and safety of the public.
IV. Cause of the event
The causal evaluation is ongoing. A supplement to this Licensee Event Report with additional information will be submitted upon completion of this evaluation.
V. Corrective actions
ECW Pump 1B packing was replaced to return the system to an operable status. The causal evaluation is ongoing. A supplement to this Licensee Event Report with additional information regarding corrective actions will be submitted upon completion of the evaluation.
VI. Previous similar events
An operating experience review identified previous events at South Texas involving pump packing issues with large pumps and a limited few specific to a lack of packing leak-off. None of the events met the threshold for a Licensee Event Report and corrective action was limited to repacking the pump.