IR 05000413/1997004

Insp Repts 50-413/97-04 & 50-414/97-04 on 970106-23.No Violations Noted.Major Areas Inspected:Operations & Engineering

ML20138J524
Person / Time
Site:	Catawba
Issue date:	01/31/1997
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20138J512	List: IR 05000413/1997004 ML20138J507
References
50-413-97-04, 50-413-97-4, 50-414-97-04, 50-414-97-4, NUDOCS 9702070324
Download: ML20138J524 (9)

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U. S. NUCLEAR REGULATORY COMMISSION

REGION II

Docket Nos: 50-413, 50-414 License Nos: NPF-35. NPF-52 Report Nos.: 50-413/97-04. 50-414/97-04 Licensee: Duke Power Company l Facility: Catawba Nuclear Station. Units 1 and 2 Location: 422 South Church Street Charlotte. NC 28242 i Dates: January 6 - January 23. 1997 i

Inspectors: R. J. Freudenberger. Senior Resident Inspector l P. A. Balmain. Resident Inspector i R. L. Franovich. Resident Inspector j Approved by: C. Casto. Chief Reactor Projects Branch 1 Division of Reactor Projects i

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Enclosure 9702070324 970131 PDR 0 ADOCK 05000413 PDR

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EXECUTIVE SUMMARY Catawba Nuclear Station. Units 1 & 2 NRC Inspection Report 50-413/97-04. 50-414/97-04 This special inspection focused on the integrated efforts of the facility staff to evaluate, determine the root cause of, and correct a licensee-identified design deficiency involving the assured suction source (nuclear service water) to the auxiliary feedwater (AFW) pumps. The report covers the resident inspection period from January 6 to January 23. 199 Doeratiqn_g

. U)on discovery of a design deficiency that impacted the operability of t7e AFW systems, control room operators made appropriate notifications in the time periods required; appropriately implemented immediate actions in compliance with Technical Specifications (TS), and promptly developed ar4d executed short-term actions to restore trains of the AFW system to operable statu Enaineerina

. Appropriate compensatory actions were developed and implemented in a timely manner to restore the AFW system to operable but degraded status until a mcdification could be implemented to permanently correct the proble . The engineering support to develop the modification plan was responsive I to resolve the design deficiency. The plan was implemented in a timely manner. 6nd no concerns with the modification were identifie . The root cause evaluation provided in an initial Licensee Event Report I (LER 50-413/96-12) was not sufficiently developed to define the scope of similar potential design issues. The licensee's rationale for

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l concluding that the root causes were different for the events documented l in LERs 50-413/96-04, 50-414/96-05, and 50-413/96-12 was not cogent and i did not drive long-term corrective actions to identify any additional l potential issues. A revised submitt61 of LER 50-413/96-12 proposed that '

the root cause investigation be continued; this corrective action was app priately scoped to ensure that similar potential design issues wou be revealed

. The design deficiency, which had existed since original construction and resulted in the AFW system being unable to perform its intended safety function under certain conditions, is characterized as Apparent Violation 50-413.414/97-04-0 ,

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E2 Engineering Support of Facilities and Equipment l E2.1 Auxiliary Feedwater System Single Failure Design Deficiency

' Insoection Scoce (37551)

l On December 11, 1996, the licensee identified a design deficiency during- l a design review of assured makeup supply to the auxiliary feedwater j (AFW) system, The design review was conducted in support of a !

modification to reduce the ice condenser ice weight limit in Technical

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Specifications (TS). The inspector discussed the issue with plant :

3ersonnel: reviewed operability evaluations modification plans the !

Jpdated Final Safety Analysis Report (UFSAR) facility TS, LER 50-413.414/96-12 (Revisions 0 and 1), and station Problem Identification a Process (PIP) reports 0-C96-3241 and 0-C96-3266: evaluated the root :

cause investigation and proposed corrective actions: and observed ;

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portions of modifications implemented to correct the design oversigh Observations and Findinas

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Because they provide condensate quality water, the normal suction sources for auxiliary feedwater (AFW) are the AFW condensate storage ,

tank, upper surge tank, and condenser hotwell. However, these sources are not seismically qualified. Therefore, the' assured suction source for the AFW system (as described in FSAR Section 9.2.1) is nuclear ,

service water (NSW), which is seismically qualified but not of condensate quality. To ensure that a reliable source of water would be i available during a security event that would require operation of the '

standby shutdown system (SSS), the licensee incorporated a design that i would provide an additional suction source for the AFW pumps. Check '

valves were located in the suction piping to enable the additional suction source to feed all three AFW pumas, though only the turbine- 1 driven AFW pump was assumed to be availa]le during such a security even During a design review, the licensee determined that the flow of NSW !

(the assured supply) to the.AFW pumps was inadequate under certain -

accident scenarios. Specifically, with all three AFW pumps running with I high flow demand and loss of the normal suction sources, a single i

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failure of one of the two assured (NSW) makeup source valves (1(2)RN-250A or 1(2)RN-310B) would cause the remaining train of the assured source to attempt to supply all three AFW pumas. This would result in inadequate net positive suction head to all t1ree pumps, rendering them :

inoperabl The design deficiency involved the absence of check valves in locations j that would provide separation between the 'A' and 'B' trains of the ,

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assured source suction to the AFW system. As indicated above, check '

valves were located upstream of a common header to the AFW pumps where train separation could not be achieve ;

The licensee promatly informed the NRC resident inspector of the design :

deficiency and su)mitted a 10 CFR 50.72 notification within the required i time period. At 11:15 a.m., on December 11. the licensee declared all ;

three AFW pumps on both units inoperable and entered TS action .

3.7.1.2.c. which required them to immediately initiate corrective action !

to restore at least one AFW pump to o)erable status as soon as possibl l To restore two trains of AFW to operaale status, the licensee closed and i

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removed power from the Train B NSW supply valve (s) (1(2)CA-85B) to the turbine-driven AFW pump (s). This provided separation between the A and >

B Trains of AFW suction for both units, but also rendered the turbine- !

driven AFW pump (s) inoperable by elimir'ig one of the two assured !

suction sources. Consequently, this plE #1 both units in TS action i 3.7.1.2.a. which required restoration of the turbine-driven AFW pump (s) 1 to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The inspector concluded that i appropriate notifications were made in the time periods require ,

immediate actions to comply with TS were appropriately implemented, and

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short-term actions to provide train separation and restore the motor- >

driven AFW pumps were promptly developed and execute '

To restore the turbine-driven auxiliary feedwater pump (s) to operable !

status and maintain operability of the motor-driven AFW pumps, the !

licensee o)ened the assured source suction valves (1(2)RN-250A and 1(2)RN-3103) and then removed power to ensure that their open position was maintained. In addition. the NSW system was aligned to its assured :

source (i.e.. the standby nuclear service water pond). This ensured l that all other related credible single failures on the NSW system would i not prevent the AFW system from performing its intended safety functio t

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The licensee performed an operability evaluation to demonstrate that the Unit 1 and Unit 2 AFW systems were operable but degraded in this  ;

configuration. The inspector concluded that this action was appropriate to ensure system operability until a modification could be implemented to permanently correct the problem. The operability evaluation supported the action and adequately demonstrated the operability of the system in a degraded conditio A modification plan was developed by the engineering organization to install check valves in appropriate locations of the AFW system. The modification for Unit 2 was completed during a forced shutdown (to correct a nitrogen entrainment condition in the 2B residual heat removal pump and discharge piping) from December 16. to December 20. 1996: the modification for Unit 1 was completed on January 9.1997. The inspector concluded that the engineering support to develop the modification plan was responsive in resolving the design deficiency and implemented in a timely manner. No concerns with the modification were identifie ~he design deficiency was documented in Licensee Event Report (LER)

00-413/96-12. which was superseded by a subsequent revision. The original LER. submitted on January 9.1997, stated that the root cause Enclosure

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was suspected to be an initial design oversight. The LER also referred l to two previous events involving design issues associated with the Standby Shutdown System (SSS): these events are documented in LERs 50-413/96-04 and 504414/96-05. The licensee asserted in LER 50-413/96-12  ;

that the root causes associated with the referenced LERs and LER 50- l 413/96-12 were different to support a conclusion that the event documented in LER 50-413/96-12 was nonrecurrin No long-term l corrective actions'were defined. The inspector determined that the root  :

cause evaluation was not sufficiently developed to define the scope of  :

similar potential design issues. In addition. the licensee's rationale i for concluding that the root causes of the events documented in LERs 50-413/96-04, 50-414/96-05, and 50-413/96-12 were different was not cogent  ;

and did not drive long-term corrective actions to identify any  ;

additional potential issues. The inspector discussed these observations i with the license i Revision 1 to LER 50-413/96-12. submitted on January 17. elaborated on l the root cause. The revised LER established that common contributing

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factors existed between itself and the two events documented in LERs 50- '

l 413/96-04 and 50-414/96-05. The difficulty was encountered in the l verification of information from original design sources immediately .

available. The licensee concluded that a broader investigation and ,

l corrective actions.to ensure that no further problems exist was warranted. The inspector determined that the proposed continuation of

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the root cause investigation was appro)riately scoped to ensure that similar potential design issues would ]e reveale ,

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The revised LER also delineated long-term corrective actions to:

(1) conduct an investigation into the sequence of changes since the original design of the AFW system to ensure that the root cause investigation is appropriately scoped for corrective actions to be ,

effectively determined: (2) conduct a reconstitution of the electrical l and mechanical system design basis for the SSS interfacing systems; and .

(3) conduct a review of the Operating Experience Database for SSS interfacing systems to identify any other adverse trends. The inspector ;

concluded that the planned corrective actions delineated in the revised ;

LER were sufficiently thorough to identify potential weaknesses in i previous design reviews associated with the addition of SSS interface '

c. Conclusions .

l The failure to correctly translate the design described in FSAR Section 9.2.1 resulted in a violation of 10 CFR 50. Appendix B. Criterion III i (Design Control) and TS 3.7.1.2. However, the licensee identified the i

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design deficiency, took effective immediate and short-term corrective actions and has planned comprehensive long-term corrective action This licensee identified and corrected violation is characterized as >

l Apparent Violation (EEI) 50-413.414/97-04-01: AFW System Single Failure i Design Deficiency. Unresolved Item (URI) 50-413.414/96-20-02: .

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Auxiliary Feedwater Assured Source Single Failure Design Deficiency, is closed.

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II. Manaaement Meetinas X1 Exit Meeting Summary The inspectors ) resented the inspection results to members of licensee management at t1e conclusion of the inspection on January 23. 1997. The licensee acknowledged the findings presented. No proprietary information was identi fie l

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Partial List of Persons Contacted Licensee Bhatnager A., Operations Superintendent Coy, S., Radiation Protection Manager Forbes, J., Engineering Manager Harrall. T., IAE Maintenance Superintendent Kelly C., Maintenance Manager Kimball. D., Safety Review Group Manager Kitlan M., Regulatory Compliance Manager McCollum, W., Catawba Site Vice-President Peterson, G., Station Manager Tower. D.. Compliance Engineer

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Inspection Procedure Used IP 37551: Onsite Engineering Items Oh.ned Doened 50-413.414/97-04-01 EEI Auxiliary Feedwater System Single Failure Design Deficiency Closed 50-413.414,96-20-02 URI Auxiliary Feedwater Assured Source Single Failure Design Deficiency Discussed 50-413/96-12 (Rev.1) LER Auxiliary Feedwater System Found Outside Design Basis l

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LIST OF ACRONYMS USED

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Auxiliary Feedwater System Code of Federal Regulations

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CFR -

DPC -

Duke Pwer Company EEI -

Escalated Enforcement Item (Apparent Violation)

FSAR - Final Safety Analysis Report IR -

Inspection Report

LER -

Licensee Event Report NSW -

Nuclear Service Water PIP -

Problem Investigation Process SSS -

Standby Shutdown System TS -

Technical Specifications UFSAR - Updated Final Safety Analysis Report URI -

Unresolved Item VIO -

Violation

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Enclosure