05000301/LER-2002-001, Re Completion of Plant Shutdown Required by LCO 3.5.2 Required Action B.1

Re Completion of Plant Shutdown Required by LCO 3.5.2 Required Action B.1

ML021210438
Person / Time
Site:	Point Beach
Issue date:	04/18/2002
From:	Krause C, Thomas Taylor Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC 2002-026 LER 02-001-00
Download: ML021210438 (5)

LER-2002-001, Re Completion of Plant Shutdown Required by LCO 3.5.2 Required Action B.1

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 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)(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)(B), Prohibited by Technical Specifications 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)
3012002001R00 - NRC Website

text

Kewaunee Nuclear Power Plant N490 Highway 42 Kewaunee, WI 54216-9511 920.388.2560 Point Beach Nuclear Plant 6610 Nuclear Road Two Rivers, WI 54241 920.755.2321 CN Committed to Nuclear Ecellene Kewaunee / Point Beach Nuclear Operated by Nuclear Management Company, LLC NRC 2002-026 10 CFR 50.73 April 18, 2002 Document Control Desk U.S. NUCLEAR REGULATORY COMMISSION Mail Station P1-137 Washington, D.C. 20555 Ladies/Gentlemen:

Docket Number 50-301 Point Beach Nuclear Plant, Units 2 Licensee Event Report 301/2002-001-00 Completion Of Nuclear Plant Shutdown Required By LCO 3.5.2 Required Action B.1 Enclosed is Licensee Event Report 301/2002-001-00 for the Point Beach Nuclear Plant, Unit 2. The subject condition was determined to be reportable under 10 CFR 50.73(a)(2)(i)(A) as; "The completion of any nuclear plant shutdown required by the plant's Technical Specifications." This LER discusses the shutdown of PBNP Unit 2 as directed by Condition B.I of LCO 3.5.2. This shutdown became necessary when the repairs to a damaged Safety Injection Pump could not be completed within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion time of LCO 3.5.2 Condition A.

Corrective actions, completed and proposed, have been identified in the attached report. New commitments have been identified in italics.

If you have any questions concerning the information provided in this report, please contact Mr. C. W. Krause at (920) 755-6809.

Tom Taylor /

Plant Manager Enclosure I/4

<V (X

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004 (7-2001)

COMMISSION

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

FACIl ITY NAMF Ili nOCKFT NIJMRFR (21 PAGF 131 POINT BEACH NUCLEAR PLANT UNIT 2 05000301 1 OF 4

TITLE (4)

COMPLETION OF NUCLEAR PLANT SHUTDOWN REQUIRED BY LCO 3.5.2 REQUIRED ACTION B.1 EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR NUBER NO MO DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 02 22 2002 2002 - 001 00 04 18 2002

__05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR (Check all that apply) (1 1)

MODE (9) 1 20.2201 (b) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)

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

LEVEL (10) 100 20.2203(a)(1)

_ 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 73.71 (a)(4) 20.2203(a)(2)(i) 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) 50.73(a)(2)(v)(B)

OTHE R Specify in A bstract below or in 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 20.2203(a)(2)(iv)

X 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 20.2203(a)(2)(v)

_ 50.73(a)(2)(i)(B)

_ 50.73(a)(2)(vii)

^20.2203(a)(2)(vi)

_ 50.73(a)(2)(i)(C)

I_

50.73(a)(2)(viii)(A)

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

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Cals Wm KausSnoeuaoyC mlac nier1(2) 755-6809 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

MANU-REPORTABLE MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX

CAUSE

SYSTEM COMPONENT FA CTURER TO EPIX E

BQ P

B580 Y

_DAYEA SUPPLEMENTAL REPORT EXPECTED (14)

DAY YEAR SUBMISSION YES (If yes, complete EXPECTED SUBMISSION DATE).

I X lNO DATE (15) l l

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On 2/20/2002, at approximately 0100 (all times CST), the PBNP Unit 2 "B" train safety injection pump (2P-1 5B) was damaged while performing a monthly preventive maintenance procedure to ensure bearing lubrication. When the pump was started, motor current increased as normal, but then decayed to less than 10 amps. Based on this response, the control room operators secured the pump. In the field, an auxiliary operator monitoring the evolution heard a loud bang near the end of the pump coast down. He also observed excessive pump seal leakage following the test. The pump was declared out of service and LCO 3.5.2 was declared not met. TS Action Condition A.1 was entered which requires an inoperable ECCS train to be restored to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Subsequent inspection of the pump following disassembly of the casing revealed damage to the rotating element, the coupling and shaft keys between the pump and the motor, the pump internal wear rings, and other components. The apparent cause of the pump damage was gas binding of the pump as a result of back leakage of nitrogen-saturated fluid from the "A" SI accumulator through the pump discharge. Repair of the pump was initiated with the expectation that the pump could be returned to service within the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed. At 1400 on 2/2212002, it was determined that we were unlikely to return the pump to service in the time remaining. Accordingly, at 1448 a shutdown of Unit 2 was initiated and the unit was in Mode 3 at 1926. The 2P-15B safety injection pump was subsequently returned to service on 2/24, and Unit 2 returned to service on 2/25/2002.

Corrective actions to prevent recurrence include periodic venting of the SI pumps and discharge piping.U.S. NUCLEAR REGULATORY COMMISSION (7-2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER l6l PAGE (3)

YEAR SEQUENTIAL REVISIO Point Beach Nuclear Plant, UNIT 2 05000301 NUMBER N

2 OF 4 NUMBER 2002 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Event Description

On February 20, 2002 at approximately 0100 (all times are CST), the Point Beach Nuclear Plant (PBNP) Unit 2 "B" train safety injection {BQ} pump {P} (2P-1 58) was damaged during a routine monthly preventive maintenance procedure for a "lubrication bump" of the pump. This pump start and run was being performed in accordance with Attachment 'H' of Procedure 01-163, "Si, RHR, and CS PUMP RUNS." Upon starting the pump, normal starting motor {MO} current was initially observed; however, the pump did not develop normal discharge pressure. Running amps were then observed by two licensed operators in the Control Room to decrease to below normal at which time the pump was secured. The Auxiliary Operator (AO), assigned to the pump bump evolution, and in the area of the pump at the time of the event, heard the motor/pump spin up and shortly thereafter go into coast down. He also heard a loud bang at or near end of coast down. The AO then observed excessive leakage coming from the inboard pump seal {SEAL} and reported the presence of an acrid smell. The Shift Manager (SM) overheard the radio conversation between the AO in the field and the control operator (CO) in the control room. Shortly thereafter, the SM and a second AO arrived at the pump area and concurrently observed the excessive seal leakage and perceived the acrid smell. They concluded that the acrid smell was emanating from the inboard pump seal area. The SM then directed isolation of the pump to secure the excessive seal leakage.

The safety injection (SI) pump was declared inoperable as of 0100. Technical Specification (TS) LCO 3.5.2 "ECCS-Operating" was declared not met, and TS Action Condition (TSAC) 3.5.2.A was entered. LCO 3.5.2 requires two ECCS trains to be operable in Modes 1, 2, and 3. LCO 3.5.2, Condition 'A', requires an inoperable ECCS train to be restored to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Corrective Maintenance began early on the February 20, 2002 dayshift concurrent with the start of the associated event investigation. Initial inspection of the pump/motor following the event revealed approximately 1" of the pump shaft to coupling keyway visibly distorted and angled approximately 45% down and to the right (towards the motor end) indicating that the rotating assembly shaft had been twisted. During subsequent inspection of the SI pump, the shaft coupling keys between the motor and the pump were found to be sheared. Upon disassembly of the pump several wear rings were found to be missing a piece. All pieces from the broken wear rings were recovered. A new pump rotating element with new wear rings was installed.

Replacement of the damaged parts and reassembly of the pump proceeded with the expectation that the pump repairs could be completed, and the pump tested for return to service, within the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed by the LCO action statement. Delays were experienced with the fit up of several replacement parts. At approximately 1400 on February 22, it was concluded that we were unlikely to complete the pump alignment and post maintenance testing necessary for returning the pump to service before the expiration of the 72-hour allowed outage time. Accordingly, preparations were initiated for an orderly unit shutdown. The shutdown commenced in accordance with OP-3A, "Power Operations to Hot Standby," at 1448. Unit 2 entered Mode 3, Hot Standby, at 1926 and reached Mode 4, Hot Shutdown, conditions at 0138 on February 23, 2002. The shutdown was uneventful and equipment required for the shutdown performed as expected.

As required by 10 CFR 50.72(b)(2), a four hour ENS (EN 38718) telephone call was completed at 1618 for initiation of a Technical Specification required shutdown.

The SI pump repairs and reassembly were completed on February 23 and the pump turned over to Operations for the post maintenance testing in accordance with IT 02, "High Head Safety Injection Pumps and Valves (Quarterly) Unit 2."

Following that testing and evaluation, the 2P-15B Si pump was returned to service at 2004 on February 24, 2002. A PBNP Unit 2 critical approach was initiated at 0930 on February 25 and Unit 2 returned to Mode 1 at 1435 on that date.U.S. NUCLEAR REGULATORY COMMISSION (7-2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISIO Point Beach Nuclear Plant, UNIT 2 05000301 NUMBER N

3 OF 4 NUMBER 2002 001 00 TEXT (Ifmore space is required, use additional copies of NRC Form 366A) (17)

Cause

Based on the damage observed following disassembly and inspection of the pump, we concluded that the failure of the 2P-1 5B Si pump was due to gas binding. A representative of the pump vendor who inspected the damage agreed with this assessment. During the recent operating history of the unit, we experienced decreasing fluid level from the "A" SI accumulator {ACC}at the rate of between approximately 2% to 4% indicated level per day. We had assumed that this level loss was due to leaking drain and fill valves that were scheduled to be worked during the Unit 2 Spring 2002 refueling outage. We have now determined that at least a portion of this leakage of nitrogen-saturated fluid was migrating through two or more check or closed valves to the discharge of the Si pump. At this location, the fluid pressure is approximately 55 psig due to static head of the refueling water storage tank {TK}. This is much less than the nominal 700 to 800 psig gas pressure in the accumulators. At that reduced pressure, the nitrogen gas coming out of solution ultimately resulted in the pump becoming gas bound.

A root cause evaluation team was initiated on February 23, 2002, to identify why this event occurred and to determine corrective actions to prevent recurrence. This evaluation identified that the organization had not properly responded to adverse SI accumulator leakage trends that increased the potential for gas binding of the SI pumps. We also determined that the stations industry operating experience program was not effective to ensure timely implementation of corrective actions from previous lessons learned.

Corrective Actions

• Prior to returning the 2P-15B SI pump to service an Operability Determination (OD) that addressed requirements to ensure the future operability of both trains of Si for both units was approved. In addition to the direct issue of gas binding of the SI pumps, this evaluation also addressed the following considerations:

1) Potential for unacceptable water hammers due to rapid refilling of the voided pipe upon pump start

2) Possible instrumentation effects due to gas voids in sensing lines,

3) Potential effects of various leaking (or failed open) valves in the system,

4) Potential for gas migrating to portions of the ECCS piping that may render other adjacent pumps sharing common piping inoperable, and

5) Potential impact on Accident Analysis of having voided volumes in the Si pump discharge line(s).

• The OD evaluation determined that the Si pumps would remain operable provided periodic venting of the SI discharge lines is conducted

• Procedure 01-1 00, "Adjusting SI Accumulator Level and Pressure," has been revised to accomplish the periodic SI line and pump venting required by the OD.

• A review and backlog "scrub" of open industry operating experience issues was conducted to provide assurance that other similar issues or events have been properly addressed.

1. The Root Cause Evaluation identified a series of additional corrective actions to avoid recurrence and improve organizational performance. These action items will be entered and tracked within the PBNP corrective action program.

1. During the PBNP Unit 2 refueling outage that commenced this April, inspections and maintenance are being performed as appropriate on several valves, which contributed to the accumulator fluid back-leakage.U.S. NUCLEAR REGULATORY COMMISSION (7T2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISIO Point Beach Nuclear Plant, UNIT 2 05000301 NUMBER N

4 OF 4 2002 001 00 TEXT (if more space is required, use additional copies of NRC Form 366A) (17)

Component and System Description:

The SI system is described in Section 6.2 of the PBNP FSAR. The primary purpose of the safety injection (SI) system is to automatically deliver cooling water to the reactor core in the event of a loss-of-coolant accident. This limits the fuel clad temperature and thereby ensures that the core will remain intact and in place with its heat transfer geometry preserved. The principal components of the high head safety injection system consist of two accumulators (one for each loop) and two high head pumps.

The accumulators are pressure vessels maintained filled at their designated levels with borated water and pressurized with nitrogen gas. During normal plant operation, each accumulator is isolated from the reactor coolant system by two check valves in series. Should the reactor coolant system pressure fall below the accumulator pressure, the check valves open and borated water is forced into the reactor coolant system. Mechanical operation of the swing-disc check valves is the only action required to open the injection path from the accumulators to the core via the cold leg. The normal accumulator pressure is 750 psig with a minimum water volume at operating conditions of 1100 cubic feet.

Additional design parameters are presented in Table 6.2-4 of the FSAR.

The two high head safety injection pumps for supplying borated water to the reactor coolant system are horizontal centrifugal pumps driven by electric motors. Parts of the pump in contact with borated water are stainless steel or equivalent corrosion resistant material. A minimum flow bypass line is provided on each pump discharge to recirculate flow to the refueling water storage tank in the event the pumps are started under low flow or shutoff head conditions.

The pumps have a design pressure of 1,750 psig and a design flow rate of 700 gpm. The pumps are driven by 700 HP, 4160-volt motors. Additional design parameters are presented in Table 6.2-6 and Figure 6.2-4 of the FSAR.

Safety Assessment

As discussed in the Event Description, the Technical Specification required unit shutdown that prompted this LER was achieved in accordance with the Technical Specification and approved plant procedures. Equipment required to function during the shutdown to Mode 4 conditions performed as expected and in accordance with design. The subsequent reactor heat-up and return to power was accomplished without any unusual equipment malfunctions. The TS LCO Action statement for the "B" ECCS train out of service permitted 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for restoring the train to operable status. When it became apparent that pump repairs and testing would exceed that completion time, the plant staff conservatively took immediate actions to shutdown the plant although approximately eleven hours remained on the allowed outage time for the "B" SI train. During the time that the "B" ECCS train was inoperable, the "A" ECCS train remained in standby service and capable of providing adequate core cooling and the negative reactivity addition required for accident mitigation. Accordingly, the safety and welfare of the public and the plant staff were not impacted by this event. At no time during this event, was there a complete loss of system, structure, or component related safety functions. Accordingly, we have also concluded that this event did not involve a safety system functional failure.

Similar Occurrences:

A review of LERs for the past three years identified no other unit shutdown that were the result of a Technical Specifications required action or condition.