05000305/LER-2005-006, Re Auxiliary Feedwater Pumps Postulated to Fall Due to Air Ingestion Through Pump Packing

Re Auxiliary Feedwater Pumps Postulated to Fall Due to Air Ingestion Through Pump Packing

ML051530312
Person / Time
Site:	Kewaunee
Issue date:	05/25/2005
From:	Gaffney M Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
+sunsimjr=200611, NRC-05-067 LER 05-006-00, NRC-05-087
Download: ML051530312 (5)

LER-2005-006, Re Auxiliary Feedwater Pumps Postulated to Fall Due to Air Ingestion Through Pump Packing

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B)
3052005006R00 - NRC Website

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Kewaunee Nuclear Power Plant cOperated by Nuclear Management Company, LLC May 25, 2005 NRC-05-067 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Kewaunee Nuclear Power Plant Docket 50-305 License No. DPR-43 Reportable Occurrence 2005-006-00 In accordance with the requirements of 10 CFR 50.73, "Licensee Event Report System", the enclosed Licensee Event Report (LER) for reportable occurrence 2005-006-00 is being submitted.

This letter contains one new commitment and no revisions to existing commitments.

1. NMC will correct this design error, associated with the Auxiliary Feedwater Pump packing, before exceeding 350'F.

Michael G. Gaffney Site Vice President, Kewaunee Nuclear Power Plant Nuclear Management Company, LLC Enclosure (1) cc:

Administrator, Region 111, USNRC Project Manager, Kewaunee, USNRC Resident Inspector, Kewaunee, USNRC INPO Records Center N490 Highway 42

• Kewaunee, Wisconsin 54216-9511 Telephone: 920.388.2560

ENCLOSUREI LICENSEE EVENT REPORT (LER) 2005-006-00 3 pages follow

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 6-30-2007 (6-2004)

Estimated burden per response to comply with this mandatory collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />.

Reported lessons learned are Incorporated Into the licensing process and fed back to industry.

LICENSEE EVENT REPORT (LER)

Send comments regarding burden estimate to the Records and FOlAlPrivacyService Branch (T-5 F52), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. or byintemet e-(See reverse for required number ofmail to Infocollects@nrc.gov. and to the Desk Officer, Office of Information and Regulatory (Seerevrse or equied umbe ofAffairs, NEOB-1 0202, (3150-0066). Office of Management and Budget. Washington. D 020503.

digits/characters for each block)

If a means used to Impose an Information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person Is not required to respond to, the Information collection.

FACILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Kewaunee Nuclear Power Plant 05000305 1 of 3 TITLE (4)

Auxiliary Feedwater Pumps Postulated to Fall due to Air Ingestion Through Pump Packing EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR NUMBER NO MO DAY YEAR

._FACILtTY NAME DOCKET NUMBER 03 26 2005 2005 006-00 05 25 2005 OPERATING N

THIS REPORT IS SUBMITTED PURSUANTTO THE REQUIREMENTS OF 10 CFR 0: (Check all that apply) (11)

MODE (9) l20.2201(b) l 20.2203(a)(3)(ii) l 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)

POWER 000 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(I)(A) 50.73(a)(2)(iv)(A) 73.71 (a)(4) 20.2203(a)(2)(1)

_ 50.36(c)(1)(ii)(A) 50-73(a)(2)(v)(A) 73.71 (a)(5) 20.2203(a)(2)(ii) 50.36(c)(2) x 50.73(a)(2)(v)(B)

OTHER 20.2203(a)(2)(iii)

=

50.46(a)(3)(ii) 50.73(a)(2)(v)(C)

Specify in Abstract below or in 20.2203(a)(2)(iv) 50.73(a)(2)(')(A) 50.73(a)(2)(v)(D) 20.2203(a)(2)(v) 50.73(a)(2)(')(B) 50.73(a)(2)(vii).

20.2203(a)(2)(vi)_

50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(A) 20.2203(a)(3)(7) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Gerald Riste j

(920) 388-8424 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 13) 164ANU-REPORTABLE I:

MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX

CAUSE

SYSTEM COMPONENT FA CTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH

'DAY YEAR I_

1SUBMISSION YES (If yes, complete EXPECTED SUBMISSION DATE).

I X INO DATE (15) l_ll ABSTRACT On March 26,2005, while the Kewaunee Nuclear Power Plant (KNPP) was in the refueling shutdown mode, Nuclear Management Company, LLC, (NMC) personnel determined a potential may exist for damage to the Auxiliary Feedwater (AFW) pumps due to air ingestion through the pumps' packing glands. A conservative calculation has shown that during certain main steam line break post-accident conditions the pressure in the pump's inlet chamber can be sub-atmospheric for short periods. During those postulated short sub-atmospheric periods cooling and lubrication of the pump's packing would stop, air may flow through the packing and into the inlet chamber, potentially causing damage to the pump due to air entrainment.

Communication with the pump's vendor indicates, "...the pump can handle up to 5% gas by volume without distress. At 20% gas by volume there is a good chance that the pump will lose prime and run gas bound.

Seizure of the rotor would then occur almost immediately." Therefore, the potential existed that during certain post-accident conditions the inlet chamber pressure may become sub-atmospheric, which may cause sufficient damage to the pump's packing to allow air ingestion in to the pump, which may reach 20% where there is a good chance for the pump to lose prime and be damaged.

This event report does not constitute a safety system functional failure as this failure was found during the evaluation of the failure documented in KNPP LER 2005-002-00.U.S. NUCLEAR REGULATORY COMMISSION (1.2001)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER 2 LER NUMBER (6)

PAGE (3)

Kewaunee Nuclear Power Plant 05000305 lMYEAR EUNTBEIL NUMBER 2 of 3 1 2005 006 00 TEXT (I! mote space is quiredz use adctional cies of NRC Form 366A) (17)

Event Description

On March 26, 2005, while the Kewaunee Nuclear Power Plant (KNPP) was in the refueling shutdown mode, Nuclear Management Company, LLC, (NMC) personnel determined a potential existed for damage to the Auxiliary Feedwater (AFW) [AB] pumps [P] due to air ingestion through the pump's packing gland. A conservative calculation has shown that during certain main steam line break (MSLB) post-accident conditions the pressure in the pump's inlet chamber can be sub-atmospheric for short periods. During those short sub-atmospheric periods cooling and lubrication of the pump's packing would stop, air could flow through the packing and into the inlet chamber, causing damage to the pump due to air entrainment.

Communication with the pump's vendor indicates, "...the pump can handle up to 5% gas by volume without distress. At 20% gas by volume there is a good chance that the pump will lose prime and run gas bound.

Seizure of the rotor would then occur almost immediately."

The AFW pump shafts are sealed with mechanical packing and require a small amount of leak-off water to cool the packing and seal the pump. When the leak-off cooling water is lost, the packing can become damaged due to overheating. Damaged packing can cause an increase in the clearance between the packing and the shaft. If the inlet chamber conditions are sub-atmospheric, air could be drawn into the pump. In the case of KNPP's AFW pumps, air ingestion will potentially air bind then damage the pump.

During operation of the AFW pumps under certain accident conditions, the pressure at the pump suction could go below atmospheric pressure. Consequently, the KNPP system design is potentially vulnerable to the AFW pumps ingesting air. As stated above, the AFW pump can handle up to 5% gas by volume without distress and at 20% gas by volume there is a good chance that the pump will lose prime and run gas bound.

It is not currently known or easily calculated if the gap formed when the packing erodes will restrict air ingestion enough to keep the pump below 20% gas by volume during the period this condition is postulated to exist.

Event Analysis

This event is being reported under § 50.73(a)(2)(v)(B) "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (B) Remove residual heat." The plant had already been placed in a shutdown condition where AFW system was not required to be operable at the time of discovery. Therefore, no 10 CFR 50.72 event notification was made.

This condition was postulated to occur during conditions of high flow rates through the AFW pumps. A conservative calculation was performed to determine if the AFW pump suction pressure could drop below atmospheric pressure during postulated accidents. The limiting accident assumed was a main steam line break (MSLB) where the faulted steam generator (SG) immediately depressurized. The analysis assumed the AFW pumps could be operated as directed by the Integrated Plant Emergency Operating Procedures (IPEOP's) and during multiple single failure events. This analysis determined that the worst-case scenario assumed a MSLB in either SG with all pumps operating. The result of the worst-case scenario shows that the AFW pump suction pressure is sub-atmospheric for 7 minutes. The limiting AFW pumps suction pressure starts at 0.26 psig and decreases to 0.0 psig in 2.2 minutes. Subsequently the suction pressure decreases to a minimum pressure of -0.81 psig where the turbine driven (TD) AFW pump is stopped, as directed by the IPEOP's, and suction pressure increases to greater than atmospheric.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE 3 YEAR ISEQUE NUMBERVIS3IofN Kewaunee Nuclear Power Plant 05000305 UER M

REVISION of 3 2005 006 00 TEXT (it more space Is required, use additional copies of NRC Fonm 366A) (17)

There is a very low safety significance associated with this event. The risk significance is very low (less than 1 E-7/year core damage frequency), because it only applies to a steam line break with initial condensate storage tank level of 68% or less. Historical data has shown that Kewaunee operates with CST levels below 68% less than 0.2% of the time.

Cause

The cause of the event was a previously undetected original system design error. Had the sub-atmospheric inlet chamber pressure condition been postulated during original construction the design of the AFW system components could have been modified to account for the sub-atmospheric condition.

Corrective Actions

NMC will correct this design error, associated with the Auxiliary Feedwater pump packing, before exceeding 350 degree F.

Similar Events

LER 2005-002, Auxiliary Feedwater Pumps Assumed to Fail from Postulated Loss of Primary Water Source

- Safe Shutdown and Accident Analysis Assumptions Not Assured - Inadequate Design of Pump Protective Equipment