NRC-99-0017, Responds to NRC Re Violations Noted in Insp Rept 50-341/99-02.Corrective Actions:Calculations Identified During Insp Reviewed to Assure Errors Identified Have Not Affected TS Surveillance Test Acceptance Criteria

Responds to NRC Re Violations Noted in Insp Rept 50-341/99-02.Corrective Actions:Calculations Identified During Insp Reviewed to Assure Errors Identified Have Not Affected TS Surveillance Test Acceptance Criteria

ML20206B412
Person / Time
Site:	Fermi
Issue date:	04/20/1999
From:	Gipson D DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-99-0017, CON-NRC-99-17 50-341-99-02, 50-341-99-2, NUDOCS 9904290238
Download: ML20206B412 (8)

Text

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Douglas R. Gipson Senior Ure l' resident, Nuclear Generation i,

. Fermi 2 C400 North Dixie liny, Newport, Mit higan 49 f4

, . Tel: 313ASG201 Fax: 313.5E4172 April 20,1999 Detroit Edison NRC-99-0017 US Nuclear Regulatory Commission Attention: Document Control Desk Washington DC 20555

Reference:

1) Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43

2) U S NRC Inspection Report 50-341/99002, dated March 8,1999

Subject:

Reply to a Notice of Violation,99002-01  !

Please find enclosed Detroit Edison's response to the violation for problems identified with three design calculations discussed in Reference 2. An extension of the original due date for this response was granted in an April 6,1999 telephone conversation between Mr. R. Gaston (Fermi) and Mr. J. Jacobson (Region III). The specific problems have been entered into the Corrective Action f Program. Our response describes the actions we tue taking tc address the problems discussed in the Notice of Violation. )

The following commitments are made by this letter:

1. The expectations for scope of calculation review when safety-related

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calculations are revised will b: incorporated into appropriate design j -

calculation review guidance by July 30,1999.

2. Revisions of Calculations DC-0230, DC-0367, and DC-5079 will be J

completed by July 30,1999. 1 If you should have any questions, or comments concerning this reply please  ;

contact Norman K. Peterson, Director Nuclear Licensing, at (734) 586-4258.

Sincerely

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/h Enclosure 9904290238 990420 l PDR ADOCK 05000341 1- G PDR;  ;

A DTE Energ Company I ._

NRC 99-0017

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. cc: A. J. Kugler A. Vegel M. V. Yudasz, Jr.

NRC Residents Office Regional Administrator, Region III Region III l

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NRC 99-0017 -

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- Statement of the Violation:

10 CFR 50, Appendix B, Criterion III, " Design Control," states in pan,"...The

' design control measures shall provide for verifying or checking the adequacy of design, such as by the performance of design reviews, by the use of alternate or simplified calculation methods,or by the performance of a suitable testing program. ... Design changes, including field changes, shall be subject to design control measures commensurate with those applied to the original design."

Contrary to the above; A. As of January of 1999, Calculation DC-0367," Design Caiculations for RHR System," Revision L, dated February 13,1996, incorrectly concluded that the addition of a new low pressure coolant injection (LPCI)/ residual heat removal (RHR) cross-tie header block valve would result in a LPCI/RHR pump head I requirement ofless than 86 percent of the available pump capacity at a calculated flow of 13,000 gallons per minute (gpm) per pump under post-accident conditions. The calculation failed to include all applicab'e inputs.

The calculated LPCI/RHR pump head requimment including these inputs was approximately 104 percent of the available pump capacity at the calculated ,

flow of 13,000 gpm per pump. j l

B. As of January of 1999, Calculation DC-0230, " Core Spray System," Revision ]

F, r.ddressed the test, post-accident, and mn-out flow conditions of the core spray (CS) system. This calculation sized a flow restriction orifice to prevent the specified maximum system flow from being exceeded during run-out conditions, and calculated the post-accident CS system flows based on this orifice being installed in the system. However, the orifice data included in calculation DC-0230 was not correct; this flow restriction orifice had been resized during pre-operational testing. Due to the correction of the orifice size, the margin between the calculated test pressure acceptance criterion and the Technical Specification 4.5.1.b.1 value was reduced from approximately 8.5 psi to 0.1 psi.

C. As of January of 1999, Calculation DC-0885, "ECCS Suction Line Air Ingestion," Revision B, determined the submergence at which air could potentially be entrained in the emergency core cooling systems (ECCS) suction l lines from the suppression pool. Modification EDF-29024 replaced the ECCS  !

suction strainers with large strainers. Neither the calculation or the  !

modification addressed the minimum suppression pool water level allowed by j 1

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NRC 99-0017 Page 2 l

Technical Specification 3.5.3.b during operational conditions 4 and 5. The ECCS suction strainers installed by engineering design package (EDP)-29024 would be partially uncovered with the minimum suppression pool level during mode 4 and 5 operations.

Reason for the Violation:

The circumstances related to each of the calculation deficiencies identified in the violation are discussed individually. While all involved personnel error, the circumstances surrounding their occurrence was different.

Calculation DC-0367. Design Calculations for RHR System l DC-0367 was revised in 1996 to incorporate an assessment of the impact of the addition of a new low pressure coolant injection (LPCI)/ residual heat removal (RHR) cross-tie header block valve. The assessment was performed in 1994 when the engineering design package was developed to install the new 1 valve. The assessment was to determine that the LPCI/RHR system head l requirement with the new valve would be less than the available head  ;

developed by the RHR pumps. Only the dynamic head loss due to frictional effects (including the new valve) was considered. Elevation head and reactor vessel pressure erroneously were not considered in determining the new 1 system head requirements. This resulted in underprediction of the LPCI/RHR system head requirement. This deficiency in DC-0367 was the result of ,

personnel error.

DC-0367 was reviewed and updated in 1996 in support of a modification to replace ECCS suction strainers in response to NRC Bulletin 96-03, " Potential Plugging Of Emergency Core Cooling Suction Strainers By Debris In Boiling-Water Reactors." The scope of this review focused on the hydraulic impact on the RHR/LPCI system of the installation oflarger suction strainers, and did not identify the error that had been made previously.

Calculation DC-0230. Core Spray System There are three calculations associated with the deficiency related to DC-0230 identified in the violation. DC-0230 is the major design calculation for the core spray (CS) system. DC-204 sized restriction orifices in safety related applications. DC-5079 documented the bases for Technical Specifications surveillance requirements for the CS system.

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l The system hydraulic calculations were added to DC-0230 in the early 1980s.

These hydraulic pressure drop calculations include an additional 10 psi for margin. DC-204 sized the core spray system restricting orifices based on the pressure drop calculated in DC-230 required to prevent pump runout. The original orifice size determined by DC-204 was incorrect primarily because of the 10 psi margin included in DC-230, which is non-conservative for the

pump runout evaluation.

i This incorrect orifice size was discovered in 1982 during startup testing. A i smaller diameter orifice was installed based on the test results. DC-204 was revised at that time to reflect that the orifice was sized by test. However, DC-230 was not revised to reflect the effect on the overall CS system hydraulic characteristics of the new orifice pressure drop associated with the smaller l orifice size. Since DC-230 includes only the orifice pressure drop calculation i

and not the orifice sizing calculation, it would be difficult to detect this error, other than when it originally occurred in 1982. l

DC-5079 subsequently was completed in 1989 to document the basis for CS l system Technical Specifications surveillance test requirements. DC-5079 I

used the results from DC-0230 without recognizing the error that had been j made seven years before.

DC-0230 was reviewed and updated in 1996 in support of a modification to replace ECCS suction strainers in response to NRC Bulletin 96-03, " Potential Plugging Of Emergency Core Cooling Suction Strainers By Debris In Boiling-Water Reactors." The scope of this review focused on the hydraulic impact on the CS system of the installation oflarger suction strainers, and did not i identify the error that had been made previously.

Calculation DC-0885. ECCS Suction Line Air Incestion DC-0885, Revision B, determined the submergence at which air could potentially be entrained in the emergency core cooling systems (ECCS) suction lines from the suppression pool. This calculation was originally performed in 1983 and updated in 1996 in support of a modification to replace ECCS suction strainers in response to NRC Bulletin 96-03," Potential Plugging Of Emergency Core Cooling Suction Strainers By Debris In Boiling-Water Reactors." The original calculation considered only the normal suppression pool water level during operation for comparison with the calculated submergence at which air entrainment potentially could occur. At the time of the original calculation, there were no Technical Specifications.

Consequently, there were no reduced suppression pool water level operating modes originally considered. The Technical Specifications now permit a t.

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NRC 99-0017 Page 4

. , l reduced suppression pool water level when the plant is in cold shutdown or refueling where ECCS requirements are minimal. Reduced suppression pool water level operating modes were not recognized or considered when the l

calculation was revised in support of the ECCS suction strainer modification l since they were not included in the original calculation The design calculation deficiencies identified above resulted from different circumstances in each case. There is no underlying cause common to each of the three examples. What is cornmon is that all three of the calculations had been reviewed or revised recently in support of plant modifications. As the resulting changes to the calculations were considered to be minor in nature at the time of the calculation, the opportunity was not used to question the underlying assumptions or methodology. This resulted in two of these discrepancies not being identified and corrected. The third problem was an error made when the calculation was revised.

The depth of review a design calculation receives when it is revised to reflect a design modification depends on the degree ofimpact that the modification is anticipated to have on the calculation. Where plant modifications had a major impact on a design calculation, the assigned engineers reviewed the calculation in detail to ensure that the modification was properly addressed in the calculation. In some cases, the calculation was completely redone. However, most. design calculation changes associated with a design modification are simple changes to quantify and document the minor effect that the modification has on the calculation. In these cases, only the portion of a design calculation directly affected by a design change was reviewed. This narrow focus in the above cited examples contributed to pre-existing errors in these calculations not being detected by engineering personnel when the calculations were revised.

Corrective Steps that Have Been Taken and the Results Achieved:

The calculations identified during the inspection have been reviewed to assure the errors identified have not affected Technical Specification surveillance test acceptance criteria. Reviews were completed during the inspection to quantify the effects of these errors. The errors did not affect component or system operability.

Calculation DC-0885, ECCS Suction Line Air Ingestion, has been revised. The revision reflects reduced suppression pool water level permitted in the cold shutdown and refueling modes of operation. Ample margin above the minimum required submergence to prevent air entrainment exists.

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NRC 99-0017 Page 5 A revision to Calculation DC-0230 to correct the identified problems has been prepared and is under review in accordance with the Fermi design calculation procedure. A revision to Calculation DC-0367 is currently in preparation.

Design calculations for other restricting orifices in safety related systems were reviewed for similar problems. No similar problems were identified.

A review of trend data from the corrective action program, quality assurance audits and surveillances, and Independent Safety Engineering Group reviews over the past two years has not indicated an adverse trend or underlying programmatic weakness in the area of design calculations. Although, these activities have identified discrepancies, none of the discrepancies have resulted in safety equipment not being able to perform specified functions.

Examples of the types of calculation deficiencies identified in this violation have been reviewed with engineering personnel who perform and revise design calculations to heighten awareness for tb~e types of problems. Expectations regarding the extent of review when calculations are revised were also communicated including:

• Review assumptions for correctness and applicability; e Review calculation method for correctness of approach and consistency with current philosophy; e Review input from other calculations or sources for correctness; and,

• Documentation of this review in the calculation revision.

This enhanced awareness is expected to improve identification of potential calculation deficiencies when calculations are revised.

Corrective Steps that Will Be Taken to Avoid Further Violations:

The expectations for scope of calculation review when safety-related calculations are revised will be incorporated into appropriate design calculation review guidance by July 30,1999.

Revisions of Calculations DC-0230, DC-0367, and DC-5079 will be completed by July 30,1999.

As a matter of course, Fermi's corrective actiou program documents, Condition Assessment and Resolution Documents (CARD), are trended. In addition, QA Design Control audits and surveillances routinely examine design calculations.

These programs will assess the effectiveness of corrective actions taken in response to this violation and identify any need for additional improvements.

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Date when full compliance will be achieved:

Full compliance will be achieved when the calculation revisions noted above are completed by July 30,1999.

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