ML18016A794

LER 98-004-01:on 980313,identified Design Deficiency Re Potential Runout of Tdafwp.Caused by Inadequate Original AFW Sys Design.Operability Evaluation Was Completed on 980313 & Addl Engineering Analysis Was Performed by Vendor

ML18016A794
Person / Time
Site:	Harris
Issue date:	01/29/1999
From:	Ellington M CAROLINA POWER & LIGHT CO.
To:
Shared Package
ML18016A793	List: ML18016A792 ML18016A794
References
LER-98-004, LER-98-4, NUDOCS 9902020332
Download: ML18016A794 (4)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION 0

APPROVED BY OMB No. 3150%104 EXPIRES 06/30/2001 Estimated burden per response to comply with this mandatory information I6.1998) collection request: 50 hrs. Reported lessons learned are incorporated into the licensing process and fed back to industry. FonNard comments reganEng burden estimate to the Information and Records Management Branch (T4 LlCENSEE EVENT REPORT {LER) F33), U.S. Nudear Regulatory Commission. Washington, DC 20555400t, and to the Papenvork Reduction Project (3t 504104), otrce of Management (See reverse for required number of and Budget. Washington. OC 20503. If an information collection does not disptay a currently valid OMB confro( number, the NRC may not conduct or digits/characters for each block) sponsor, and a person is not required to respond to, the information collection.

FACILITYNAME Ill DOCKET NUMBER l2l PAGE I3I 1 OF 3 Harris Nuclear Plant, Unit 1 05000400 TITLE (4)

Design deficiency related to inadequate runout protection for the Turbine Driven AFW Pump.

MONTH OAY YEAR YEAR ssovENTIAL RsvISIoN MONTH OAY YEAR FACILITYNAME OOCKET NVMBER NVMBER NVMBER 03 13 1998 1998 - 004'.- 01 01 29 1999 FACILITYNAME DOCKET NVMBER 05000 OPERATING MODE {8) 20.2201(b) 20.2203(a)(2)(vl 50.73(a)(2) (il 50.73{a)(2)(viiil POWER 100 20.2203(a)(1) 20.2203(al(3) lil ~

x 50.73(a)(2)(ii) 50.73(a) {2)(xl LEVEL (10) 20.2203{a)(2) (i) 20.2203la)(3) lii) 50.73{a) l2) {iii) 73.71 20.2203(a)(2)(ii) 20.2203(aw4) 50.73(a)(2) (iv) OTHER gyp g~4wPPj~'q~g$ 20.2203(a)(2)(ui) 50.36(cl(1) 50.73(al(2)(vl pecity in Abstract below 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii) or in NRC Form 366A NAME TELEPHONE NUMBER (Inoroda Area Coda)

Mark Ellington, Senior Analyst - Licensing (919) 362-2057 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO EPIX TO EPIX EXPECTED MONTH OAY YEAR YES X No (If yes, complete EXPECTED SUBMISSION DATE).

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

On March 13, 1998, with the plant operating at 100% power in Mode 1, a design deficiency related to potential runout of the Turbine Driven AuxiliaryFeedwater Pump (TDAFWP) was identified and determined to be reportable as operation outside the design basis of the plant. Specifically, a scenario exists during a main steam line break accident or main feed line break accident where the TDAFW pump could potentially operate at runout for a design maximum of 41 seconds and result in pump failure. The Harris Nuclear Plant (HNP) Final Safety Analysis Report (FSAR) states that the TDAFW pump will be available to mitigate the consequences of these postulated accidents. This condition was reported to the NRC via the emergency notification. system per 10CFR50.72 on March 13, 1998 at 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br />.

The cause of this condition is inadequate original AFW system. design. The AFW system design did not consider the possibility of the scenario described in this LER and therefore, did not include adequate, runout protection for the TDAFW pump speed control mechanism.

Corrective actions included performing an immediate operability evaluation, which determined that the AFW system would remain capable of performing its safety function following the loss of the TDAFW pump caused by runout. Additional Engineering analysis was performed by the vendor on a duplicate pump. The test demonstrated that the pump could be operated at runout conditions for over two minutes without damage. This testing was repeated several times without damage; therefore, no further actions are required.

9'tr02020332 'P'"ri0129 PDR ADGCK 05000400 8 PDR

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6 9BI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITYNAME (1I OOCKET LER NUMBER (6) PAGE (3)

Harris Nuclear Plant, Unit 1 05000400 YEAR SEQUENTIAL NUMBER REVISION NUMBER 2 OF 3 1998 004 01 TEXT illmore space ls rerlufred. rrse addidonal copies of NRC Form 366AJ (17)

I. DESCRIPTION OF EVENT On March 13, 1998, with the plant operating at 100% power in Mode 1, a design deficiency related to potential runout of the Turbine Driven AuxiliaryFeedwater Pump (TDAFWP) (EIIS: BA - P) was identified and determined to be reportable as operation outside the design basis of the plant.

Specifically, a scenario exists during a main steam line break (MSLB) or main feed line break (MFLB) accident where the TDAFWP could potentially operate at runout for a design maximum of 41 seconds and result in pump failure.

The TDAFWP is designed to be protected from runout by its variable speed - differential pressure controller. This differential pressure controller will control turbine speed between 2300 and 4100 rpm to maintain a 28 psig differential between the TDAFWP discharge pressure and the turbine steam inlet pressure. When Steam Generator (S/G) pressures are low, the main steam pressure at the turbine inlet drops and the pressure differential controller will demand a drop in turbine speed to decrease discharge head and maintain the set differential pressure. Therefore, TDAFWP discharge pressure will increase and decrease as S/G pressure increases and decreases respectively. The maximum design speed that the TDAFW speed controller will allow the turbine to operate is 4125 rpm. If a failure occurs in the speed controller system, a mechanical overspeed trip set at 125% of rated speed will trip the turbine by unlatching the trip and throttle valve and shutting off the steam supply.

During a MSLB or MFLB accident scenario, it appears that the speed controller will not prevent the TDAFWP from going into a runout condition. Both a MSLB and MFLB will initially depressurize all three S/Gs. As the S/Gs depressurize, the turbine speed controller will lower pump speed to maintain the required setpoint. However, once the Main Steam Isolation Valves (MSIVs) close, steam will be isolated from the faulted S/G and the two intact S/Gs re-pressurize causing turbine steam inlet pressure to follow the intact S/G pressures. AFW flow isolation will not automatically occur for a design maximum of 41 seconds after the MSIVs are closed and during this period the majority of AFW flow will follow the path of least resistance to the faulted S/G . Therefore, the TDAFWP discharge pressure will remain at essentially zero (that of the faulted S/G) and the pump discharge pressure will fall below the steam inlet pressure. This will cause the turbine speed control system to go to maximum speed and place the pump in a runout condition. For a maximum of 41 seconds the pump will be turning at 4125 rpm and pumping unlimited flow at zero discharge pressure with no protection.

The HNP Final Safety Analysis Report (FSAR) does not specifically address this condition and states that the TDAFW pump will be available to mitigate the consequences of these postulated accidents.

This condition was reported to the NRC via the emergency notification system per 10CFR50.72 on March 13, 1998 at 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br />.

NRC FORM 366 (6.9BI

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I6 BBI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITYNAME I1I DOCKET LER NUMBER I6) PAGE IBI Harris Nuclear Plant, Unit 1 05000400 YEAR SEQUENTIAL NUMBER REVISION NUMBER 3 OF 3 1998 004 01 TEXT (lfmore space ls required, use sddlt(ops( copies of NRC Form 368AJ 117I II. CAUSE OF EVENT The cause of this condition is inadequate original AFW system design. The AFW system design did not consider the possibility of the scenario described in this LER and therefore, did not include adequate runout protection for the TDAFW pump speed control mechanism.

III. SAFETY SIGNIFICANCE There were no actual safety consequences. This LER documents a potential failure scenario associated with the loss of the TDAFWP during a MSLB or MFLB accident.

The AFW system is designed and operated to include design ma'rgins and engineering margins of safety. The AFW system design is such that no initiating failure and assumed single failure will render all three AFW pumps and associated train unavailable in providing the necessary coolant flow to the S/Gs. With no specific runout protection, it is conservative to assume a consequential TDAFWP failure for a MSLB or MFLB accident as described in this LER. However, the consequential loss of the TDAFWP will not prevent the AFW system from performing it's design basis safety function of providing a flowrate of 400 gpm flow to the S/Gs. This is based on the continued availability of the remaining motor driven AFW pump.

This report was originally submitted pursuant to the criteria of 10CFR50.73(a)(2)(ii ) for a possible unanalyzed condition. This revision is being submitted, due to supplemental information becoming available, pursuant to 10CFR50.73(c).

IV. CORRECTIVE ACTIONS

1. An operability evaluation (ESR 98-00100) was completed on March 13, 1998, which determined that the AFW system would remain capable of performing its safety function following the loss of the TDAFW pump caused by runout.

2. Additional Engineering analysis was performed by the vendor on a duplicate pump. The test demonstrated that the pump could be operated at runout conditions for over two minutes without damage. This testing was repeated several times without damage; therefore, no further actions are required.

V. SIMILAR EVENTS There have been no previous conditions identified or reported related to a potential TDAFWP runout and consequential failure du'ring a MSLB or MFLB accident scenario.

NRC FORM 366A I6 BBI