IR 05000285/1990042

Insp Rept 50-285/90-42 on 901015-19.No Violation or Deviations Noted.Major Areas Inspected:Events Re Engineering Ongoing Design Basis Reconstitution Effort

ML20062E469
Person / Time
Site:	Fort Calhoun
Issue date:	11/07/1990
From:	Clay Johnson, Stetka T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
Shared Package
ML20062E467	List: IR 05000285/1990042 ML20062E464
References
50-285-90-42, NUDOCS 9011210025
Download: ML20062E469 (9)

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APPENDIX U.S. NUCLEAR REGULATORY COMMISSION

REGION IV

i NRC Inspection Report: 50-285/90-42 Operating License: DPR-40 i Docket: 50-?85 Licensee: OmahaPublicPowerDistrict(OPPD) l 444 South 16th Street Hall i Omaha, Nebraska 08102-2247 Facility Name: FortCalhounStat'on(FCS)

Inspection At: FCS, Blair, Nebraska inspection Conducted: October 15-19, 1990

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Inspector: .. - du oyt , # %

. E/ Johnson, Reactbr Inspector, Plant Date Syktemy Section, Division of Reactor Safety Approved: r . 1/w _ u!? 9d V. 5tf ka, lef, P~laht Systems Section Date

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DiWision of R ctor Safety inspection Summary Inspection Conducted October 15-19, 1990 (Report 50-285/90-42)

Areas inspected: Routine, announced onsite inspection of events relating to the OPPD engiiieering ongoing Design Basis Reconstitution effort, where the licensee discovered that the FCS could be outside the conteinment cooling designbasesforthecomponentcoolingwater(CCW),rawwater(RW),and containment s ray (CS) systems'following a worst-case design basis accident (DD Results: Witnin the areas inspected, no violations or deviations were identHied, it appears that as the result of the licensee's review of the containnent cooling design basis, the previous configurations of CCW, RW, and CS systems, were adequate in controlling containment peak pressure below 60 psig following a worst-case DBA. It is apparent that licensee management initiated appropriate and immediate actions to resolve the design concern '

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DETAILS l PERSONS CONTACTED

• R. Andrews, Division Manager, !!uclear Services l

• J. Biggs, Radiochemistry i

• A. Bilau, Acting Supervisor, Radwaste Operations l

• J. Chare, Manager, Nuclear Licensing i

• V. frahm, Jr., Supervisor, Radiochemistry ,

• f. Franco, Manager, Radiological Services I

, *A. Friebe, Radiochemistry Technic 4n  !

• J, Gasper, Acting Division Manger, Nuclear Operation

• J. Giantz, Chemist K. Henry, Lead Systems Engineer

• R. Jaworski, Menager, Station Engineering

• i. Krist, Environmental Scientist, Radiation Services

"L. Kusek, Manager, Nuclear Safety Review

• M. Lazar, Supervisor, Operations Training

• D. Lovett, Acting Supervisor, Radiation Program R. Mehaffey, Supervisor. Electrical / Instrumentation and Control

• T. Patterson, Manager, fort Calhoun Station

• W. Fence, System Engineer, HVAC

• R. Phelps, Manager Design Engineering l

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• R. Sexton, Supervisor, Radiation Health and Engineering

• B. Schmidt, Supervisor, Secondary Chemistry

• R. Short, Supervisor Special Services Engineerirg

• L. Sills, Operations QA Auditor

• C, Simmons. Station Licensing Engineer

• F. Smith, Supervisor, Chemistry

• D. Spires, QA Auditor

• T. Therkildsen, Supervisor, Nuclear Licensing B. VanSant, lead Mechanical Engineer

• B. Weber, Supervisor, Reactor Performance

• S. W111 rett, Manager, Nuclear Materials / Administration Stone & Webster Engineering Corporation (SWEC)

C. Morrell, Acting Mechanical Manager, Design Engineering, Nuclear NRC

• J. Jang, Senior Radiation Specialist, R1

• J. Nicholas, Senior Radiation Specialist, RIV I

• T. Reis, Resident Inspector

• Denotes attendance at the exit interview.

l The inspector also interviewed other licensee personnel during the inspection.

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-3- GENERAL 2.1 CACKGROUND During the reconciliation af design basis information and subsequent development of the fort Caboun Station (FCS) Design Basis Documents (DBDs) by OPPD, it was determined that information required to support values or statements made in the DBDs were sometimes missing or inconsistent. As the result of this determination, OP Q established a program to identify, evaluate, and resolve these discrepant and open issues within the DBDs. During this reviewandevaluation,therawwater(RW),componentcoolingwater(CCW)and containment spray (CS) systems as built flow calculations could not be retrieved from available original documents and were then identified as open items. OPPD categorized these open items in categories numbered from 1 to 6 with Category 1 having the most safety significance and Category 6 the least safety significance. These open items indicated that the potential existed that the three containment cooling systems (RW, CCW, and CS) would be unable to prevent the containment peak pressure from exceeding its maximum design pressure during a Design Basis Accident (DBA).

Based upon this preliminary information, on September 28, the licensee shutdown the plant to Hot Shutdown, pending final resolution on this issu OPPD had become aware of these concerns through preliminary calculations their contractors, Stone & Webster (SWEC) and Combustion performedby(CE).

Engineering The worst-case DBA postulated was a large break loss of coolant accident (LOCA), concurrent loss of offsite power and instrument air, and failureofEmergencyDieselGenerator(EDG)No.2. These accident conditions would have the following effects:

Upon loss of instrument air, the RU and CCW interface valves fail open thus rendering the CCW system inoperable as the result of a loss of CCW inventor These interface valves do have backup air accumalators; however, since these accumulators are nonsafety-related, no credit (from a design basis standpoint)

! can be taken for their availability. The RW system provides the backup cooling for the CCW syste *

Upon loss of EDG No. 2, the RW system would be reduced from three te two RW

' pumps. Because of the elevation difference between the RW pumps and the containment fan cooler coils, these two pumps would not provide sufficient head and flow to prevent the water in the cooling coils from flashing to steam. This would significantly degrade the heat removal performance of the containment cooler * Upon loss of EDG No. 2, only one (SI-3A) of the three CS pumps would be available to cool the containment during postulated accident conditions. The one CS pump would be aligned to both CS headers, in this configuration, the reduced system resistance and low initial containment pressure would allow the pump horsepower (HP) requirements to exceed the motor's 300 HP rated capacit r

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On September 29,1990, the licensee received additional infortnation that confirmed the preliminary information regarding equipment vulnerability in the postulated scenarios. The licensee issued a 4-hour report to the NRC pursuant to10CFR50.72(b)(2)(1).

2.2 lllSpECTION TASK .

On October 3, 1990, a conference call was held between the llRC and OPPD to discuss these events. OPPD was informed that an inspector would be dispatched to the site to review the issue. The inspector was directed to conduct:

A thorough review of the sequence of events leading to the ev(nt;

A review of the postulated design deficiencies; and,

• A review of the licensee's planned corrective action The inspector reviewed the event, inspected the affected equipinent, reviewed design calculations, and interviewed managers, operators and design engineer Documents reviewed by the inspector are listed in the Attachment to this repor . !NSPECTIONACTIVITIES 3.1 Sequence of Events The following sequence of events was developed by the inspector as the result of a conference call with engineering personnel on October 16, 1990, a memorandum from SUEC to OPPD, and interviews with manager * OPpD requested SWEC to propose a coinplete analysis of October 1989 the RW and CCW systems to document the basis of the design and licensing requireinent, and to determine the design margin availabl *

October 6, 1989 SWEC letter 00-527 provides the first proposal to perform an RW system design evaluatio '

October 26, 1989 Memorandum PED-FC-89-2360 from 0 PPD Engineering written recomending SWEC perform a FW system design evaluatio *

Novomber le 1989 Draft revision of RW DBD receive * November 1989 SWEC verbally euthorized to start RW system design analysi *

February 1990 fort Calhoun begins refueling outag *

May 1990 fort Calhoun ends refueling outage. The RW and CCW system valves were rebuilt during this outag r

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June 1990 OPPD system engineering began collection of RW system temperature and flow data for use by SWEC in the system design analysi *

September 1990 OPPD system enginetring provided RW system temperature and flow data to SWEC to be used to validate the system model * September 21, 1990 SWEC upgraded this open item (No. 59) f rom Category 2 to Category I based on the preliminary results of their RW/CCW evaluation *

September 24, 1990 OPPD received letter DB-763 from SWEC which documented the SWEC preliminary results of the PW/CCW evaluatio *

September 20, 1990 FCS plant manager informed of the preliminary results from SWE *

September 24-28, 1990 SWEC and OPPD engineering work concurrently to evaluate this issue. SWEC on site September 27-28, 199 * September 28, 1990 Plant manager mdes decision to proceed with a plant shutdown based on preliminary results of the engineering evaluatio *

September 29, 1990 Plant in Hot Shutdown at approximately 3:40 * S(ptember 29, 1990 Formal letter issued to Station Engineering per Procedure PED-QP-19 notifying OPPD of a potential reportable condition relating to CCW/RW and CS system "

September 29, 1990 OPPD notifies the NP.C of this even .2 Review of the DBA Event To determine whether the licensee was outside the design basis for maximum containment pressure following a postulated accident, the inspector reviewed the following issues: The potential for loss of CCW inventory through the failed open RW/CCW interface valves upon loss of instrument ai . Availability of adequate CCW flow to provide cooling for the CS system via the shutdown heat exchangers during spray recirculation operatio . Accuracy of Technical Specification Basis 2.4 concerning the redundcncy of the CS system and containment cooling system . The potential for CS pump SI-3A to exceed its motor horsepower rating when providing flow to both spray header . .

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6-3. CCW/RW Interface Valves The inspector's review indicated that upon the onset of a DBA concurrent with a loss of instrument air, the interface valves would fail open. Since the CCW system is at a higher pressure than the RW system, CCW inventory would be lost through the RW systtm into the Missouri River. Discussions with 0FpD engineering indicated that it would take 3-5 minutes for the CCW system pressure to become icw enough to allow a reverse flow back to the CCW system from the RW system. This would restore both the CCW and RW systems. This would however, also reduce the efficiency of the containment fan coolers (CFCs)

which are required to reduce pressure in containtnen The licensee initiated a ternporary modification to hand-jack the RW/CCW interface valves closed. This inodification would prevent a potential loss of CCW inventory through these interf ace valves. Operator actions would be !

required to use RW backup cooling for the shutdown cooling Feat exchangers followingaRecirculationActuationSignal(RAS). The licensee has updated the Emergency Operating Procedures (E0ps) by incorporating instructions for completing these operator actions. Hand-jack closure of these interface valves has not been finalized as a permanent resolution. The licensee is also cent.idering upgrading the nonsafety-related air accumulators on the interface valves to safety-related accumulators. This also has not been finalize The inspector verified that this modification was cornplete by random selection of sevt:ral CCW/RW interf ace valves to determine that they were hand-jacked closed and that caution tags were applied. The inspector also verified that changes were modo to the E0ps that provide the operator actions to be take Subsequent calculations performed by CE indicate that the CS system is sufficient to naintain containment pressure below maximum design pressure without the CFC .2.2 Adequacy of CCW Flow Another concern regarding the CCW system was whether there was adequate flow distribution to provide cooling for the CS via the shutdown cooling heat exchangers following a Recirculation Actuation Signal (RAS). CE verified through calculations and assumptions usir.g the C0flTRANS computer code for containment pressure analyses that flow to the shutdown cooling heat exchangers is sufficien The inspector reviewed the preliminary hand calculations in calculation No. 002-NT90-C-012 but did not review the C0tiTRANS computer code. The inspector concluded that CCW flow would apparently be sufficient for cooling the shutdown heat exchanger .2.3 Basis of Technical Specification The original design provided SW backup cooling to the CFCs by remote manual action. This design, which formed the basis for TS 2.4, assumed that the CFCs were redundant to the CS system for controlling containment peak pressure in

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-7-the short-term. CE's analyses indicates that the function of the CFCs could be degraded or 10,t upon loss of instrument air. The system modeling analysis J showed that if RW was used to supply cooling water to the CFCs, the elevation difference between the CFCs and RW pumps would theoretically create vacuum conditions and allow water inside the coolers to flash to steam. In the inasee's latest analysis, it is assuned that the CFCs are lost and do not contr1W te in containment pressure reduction. The licensee has decided to take no credit for the CFCs as a redundant system. This is based on calculations indicating that the CS can control containment pressure without the CFC The inspector reviewed the proposed changes to the TS and USAR. These charges will be submitted to the NRC for formal revie .2.4 Containment Spray Pump SI-3A During a worst-case DBA (prior to the modification), CS pump SI-3A would be aligned to feed both CS headers. In this configuration, low system resistance and low initial containment pressure would allow the pump to operate in a runout mode, thereby causing the pump horsepower requirements to exceed the motor's 300 HP rated capacity and its 1.15 service factor (which equates to 345 HP).

Discussions with OPPD engineering indicated that even with only pump SI-3A providing flow through both CS headers, there would be sufficient cooling to redu a pressure inside containment. Review of the LOCA long-term cooling containment response curve indicated that when containment pressure is about 45 psig, the SI-3A pump motor will be operating in the 300 to 345 HP range delivering minimum required flow. The curve also indicated that containment pressure would peak at 59.816 psig with the pump motor running at approximately its rated 300 HP capacity. When containment pressure is reduced to about 30 psig, pump SI-3A would be operating at 345 HP. The response curve indicates 1 that it takes approximately 48 minutes for pressure to decay from a peak pressure of 59.815 psig to 30 psig. At 30 psig, pump SI-3A would continue to run at approximately 345 H t OPPD engineering informed the inspector that CE and the pump motor vendor (General Electric) held a conference call on September 28, 1990. During that conf erence call General Electric stated that the pump motor can run continuously '

for 60 days at 345 H To assure a conservative approach to this issue, the licensee expanded their evaluation to assume that pump SI-3A has failed. The licensee's calculation /

assumptions indicate that with no operator actions taken to realign the CFCs or to realign the power supply for the other CS pump (SI-3C), the peak containment pressure of 59.816 psig would not be reached until 3.84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br /> into the acciden The licensee considers this to be ample time to compensate for the event with operator actio To assure that these design rcviews and assumptions were consistent with operator activities, the inspector interviewed two shift supervisors to determine if the operators would have any control room indication that pump SI-3A was failin Discussions with the operators and review of the Emergency Operating

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-8 Procedures (EOPs),indicatethatinanaccidentscenario,theE0Psrequirethe operators to perform safety function status checks which include the monitoring of containment integrity and CS operation. The operation of CS pump SI-3A motor would be monitored using CS flow indications and CS pump motor curren Based upon this review, it was apparent to the inspector that the design of the CS system and operator guidance would have been sufficient to mitiCate the potential for a breach of containment integrity during a DB To prevent a runout of CS aurop SI-3A from occurring, the licensee initiated a modification which would clange the control circuit logic of CS header isolation valve HCV-344 A Containment Spray Actuation Signal (CSAS) would normally open both CS header isolation valves HCV-344 and HCV-345. 1his n.odification provides on interlock that will Leep HCV-344 closed if the two pumps powered from DG-2 (51-3B and SI-3C) are not operating. This modif1 cation was completed prior to plant restar .2.5 Conclusion As the result of the inspector's review, it was conneluded that the CS, RW, and CCW systems would have been adequate to maintain containment peak pressure below 59.816 psig during this accident scenario. Even though operator actions would be required to restore the CCW system function, it appears that there was artple time for operators to initiate manual actions to mitigate an increasing coi;tainment pressure. The modification installed on valve FCV-344 will assure that the CS system will be available, in addition, the licensee will be pursuing changes to the TS and USA The inspector concluded that the licensee's design basis reconstitution program is functioning to identify and resolve issues as they are identifie . EXIT MEET 1HG An exit meeting was held October 19, 1990, with the personnel indicated in paragraph 1 of this report. At this meeting, the scope of the inspection and the findings were sunnarized._ The licensee did identify the calculations developed by SWEC as proprietary informatio I s

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ATTACHMENT

E0Ps Reviewed E0P-00, " Standard Post Trip Action," Revision 2, June 30, 1990

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E0P-02, " Loss of Off-Site Power / Loss of Forced Circulation," Revision 4,

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llay 19,1990 E0P-03, " Loss of Coolant Accident," Revision 10, fiay 19,1990

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E0P-05, " Uncontrolled Heat Extraction," Revision 7, May 19,1990

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_ E0P-20. " Functional Recovory Procedure," Revision 9 June 30,1990

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Technical Specifications Section2.4(Basis)

Section 4.2.3

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calculation 002-HT90-C-012, Revision 0

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Modifications

{ MR-FC-90-053, " Containment Spray Header Valve Interlock," September 29, 1990

- TM-90-022, "Handjack Closure of the CCW/RU Interf ace Valves," October 1,1990 (Temporary Modification)

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Hemorandum PED-FC-90-2925, dated September 29, 1990 Letters LIC-90'-0776, dated October 12, 1990-LIC-90-0738, dated October 1,1990 UB-763, dated September 21, 1990

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0-MPS-90-078, dated September 29, 1990 Procedures PED-QP-19.1, " Evaluation of Potentially Reportable Coriditions," Revision 0, November 17, 1989

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