05000483/LER-2003-005, Failure of Both Containment Spray Pumps Due to Air Binding

Failure of Both Containment Spray Pumps Due to Air Binding

ML032120541
Person / Time
Site:	Callaway
Issue date:	07/21/2003
From:	Witt W AmerenUE
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-04876 LER 03-005-00
Download: ML032120541 (8)

LER-2003-005, Failure of Both Containment Spray Pumps Due to Air Binding

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4832003005R00 - NRC Website

text

AmerenUE Callaway Plant PO Box 620 Fulton, MO 65251 July 21, 2003 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 ULNRC-04876 wiAmereg UE Ladies and Gentlemen:

DOCKET NUMBER 50483 Callaway PLANT UNIT 1 UNION ELECTRIC CO.

FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2003-005-00 Gas binding of containment spray pumps due to valve testing.

The enclosed licensee event report is submitted in accordance with IOCFR50.73(a)(2)(i)(B) to report gas binding of both containment spray pumps due inadequate filling and venting of system piping after conducting surveillance valve testing.

Very truly yours, Warren A. Witt Manager, Callaway Plant WAW/ewh Enclosure I--,'

a subsidiary ofAmeren Corporation

ULNRC-04876 July 21, 2003 Page 2 cc:

Mr. Thomas P. Gwynn Acting Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 760114005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)

Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 7E1 Washington, DC 20555-2738 Manager, Electric Department Missouri Public Service Commission PO Box 360 Jefferson City, MO 65102 Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339

Abstract

On 5/22/03, with Callaway Plant in Mode 1 at 100 percent power, surveillance testing was being performed involving "B" Containment Spray pump, PENO lB. Upon starting, the pump failed to develop normal discharge pressure and flow for approximately 5 minutes. The pump then developed pressure and the test was completed satisfactorily. Subsequent review determined the pump had been gas bound. Ultrasonic exams and dynamic venting demonstrated that PENO lB was water solid and operable. An extent of condition review revealed that Containment Spray pump, PENOlA had experienced a 2 minute gas binding event on 4/29/03. Ultrasonic exams and venting were conducted and verified that PENOlA was operable. It was determined that both pumps were gas bound due to an inadequate system venting configuration after Mode 5 valve testing on 3/30/03 resulting in both trains of Containment Spray being inoperable upon entering Mode 4 on 3/31/03 until PENOIA was run on 4/29/03, and "A" train was declared operable. This resulted in noncompliance with Technical Specification 3.6.6 for a period of time greater than allowed. Potential corrective actions being evaluated include installing additional vent valves, and procedure improvements to address dynamic venting.

NRC FORM 366 (7-2001)

(If more space is required, use additional copies of SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES At 0210, 5/22/03, with Callaway Plant in Mode 1 at 100 percent power, surveillance testing was being performed on "B" Containment Spray Pump, PENOIB [IEEE component designator P]. Upon starting, initial pressure and flow indications were below normal. Locally, discharge pressure indication and noise levels also were below normal.

After approximately 5 minutes, local pump noise levels increased and it was suspected that pump cavitation was occurring. PENOIB was secured and the local test gauge installation was checked for proper operation. At 0242, PENOIB was started for a second time and all indications were normal. Surveillance testing was completed satisfactorily and PENOIB was declared operable.

Subsequent review determined that PENOIB had experienced gas binding during the initial pump run at 0210 and PENOIB was declared inoperable starting at 0209, 5/22/03. Plant personnel vented the containment (ctmt) spray piping (Callaway system designator EN) [IEEE system designator BE] associated with PENOIB and I to 2 seconds of gas was vented from the suction supply line. Ultrasonic testing (UT) data was collected which revealed a void present in an associated eductor line. No other voids were found in the "B" train of the EN system. The pump and eductor line were dynamically vented for approximately 30 minutes. A post-run UT found that the void was no longer present. PENOIB was declared operable at 2134.

As part of an extent of condition review, the "A" train Ctmt Spray pump, PENOIA and associated piping, the Refueling Water Storage Tank (RWST) emergency core cooling system (ECCS) pump suction header and the Residual Heat Removal (RHR) pump return to the RWST header were also inspected via UT to determine if any of these lines contained voids. A void (smaller than that found in the "B" train) was found in the associated eductor recirculation line of the "A" train containment spray pump. Approximately I second of gas was vented from the suction supply line. The "A" pump and associated eductor line were dynamically vented and the void was removed.

The RWST suction header and the RHR pump return line were also inspected and found to be water solid.

The extent of condition review revealed that on 4/29/03, a similar gas binding occurrence had occurred to PENOlA [IEEE component designator P] and went unrecognized. PENOIA was tested with approximately 2 minutes run time without discharge pressure and low motor current. Review of computer data shows the motor current was approximately 1/2 of the expected level for 132 seconds. The pumps discharge pressure did not reach the expected 250 psig for 166 seconds.

Flowserve, the pump vendor, was contacted regarding the gas binding issue. They determined that if no leakage from the pump seals existed and there were no significant changes in vibration or performance levels, no damage likely occurred and returning the pump(s) to service would be acceptable. As previously noted, additional testing (ff more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Farm 366A) (17)

III.

CAUSE OF THE EVENT

The cause of the event was gas intrusion due to inadequate filling and venting after performing surveillance valve testing. Failure to recognize abnormal indications during pump operation and delayed documentation of those abnormal indications contributed to the event.

A formal Root Cause Analysis (RCA) team was assembled to investigate and determine the root cause(s) of the gas binding event and subsequent failure to identify this problem. The RCA concluded that there were 3 causal factors:

1. No vent valve was installed on the pump casing. This lack of vent valve prevents proper venting using only static fill and vent techniques.

2.

No dynamic venting was performed.

3.

A 1996 evaluation failed to recognize pump PENOlA casing voids.

IV.

CORRECTIVE ACTIONS

Initial corrective actions taken by plant personnel involved static venting the containment (ctmt) spray piping (system designator EN) associated with PENOIB with I to 2 seconds of gas being vented from the suction supply line.

Ultrasonic testing (UT) data was collected which revealed a void present in an eductor line. No other voids were found in the "B" train of the EN system. The pump and eductor line were dynamically vented for approximately 30 minutes. A post-run UT found that the void was no longer present. PENOIB was then declared operable at 2134, 5/22/03.

As part of an extent of condition review, the "A" train pump (PENOIA) and associated piping, the Refueling Water Storage Tank (RWST) emergency core cooling system (ECCS) pump suction header and the Residual Heat Removal (RHR) pump return to the RWST header were also inspected via UT to determine if any of these lines contained voids. A void (smaller than that found in the "B" train) was found in the eductor recirculation line of the "A" train containment spray pump. Approximately 1 second of gas was statically vented from the suction supply line. The "A" pump and associated eductor line were dynamically vented and the void was removed. The RWST suction header and the RHR pump return line were also inspected and found to be water solid.

Recommended corrective actions to prevent recurrence that are being evaluated include:

Modification of the current seal piping of PENOIA and PENOIB plus install a vent valve for each pump to provide for proper static fill and vent capabilities.

Revise plant procedures to provide instructions for optional dynamic venting of the system.

Enhance plant procedures to include monitoring computer indication of motor currents in addition to pump parameters.

V.

PREVIOUS SIMILAR EVENTS

NUREG 1022 requires a review of historical events within the last 3 years, however, none were identified.

A review of LERs within the last three years documents one other gas binding event. This was documented in LER 2002-001-00, in which foreign material caused the "A" Motor Driven Auxiliary Feedwater pump to become gas bound approximately 14 seconds after starting. Although this is a gas binding event, the gas binding is due to a different mechanism and not directly relevant to the containment spray pump event described in this LER.

(if more space is required, use additional copies of NRC Form 366A) (17)

VI.

ADDITIONAL INFORMATION

The system and component codes listed below are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 respectively.

System:

BE Component:

P