ML18066A277

Part 21 Rept Re Deficiency in CE Current Screening Methodology for Determining Limiting Fuel Assembly for Detailed PWR thermal-hydraulic Sa.Evaluations Were Performed for Affected Plants to Determine Effect of Deficiency

ML18066A277
Person / Time
Site:	Millstone, Calvert Cliffs, Palisades, Palo Verde, Saint Lucie, Arkansas Nuclear, Waterford, San Onofre, Maine Yankee, Fort Calhoun
Issue date:	08/13/1998
From:	Rickard I ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY, ASEA BROWN BOVERI, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-98 LD-98-024, LD-98-24, NUDOCS 9808190183
Download: ML18066A277 (5)

Text

'. Jl11 1111 1 \1111 August 13, 1998 LD-98-024 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Report Pursuant to 10 CFR 21 Regarding Methodology to Select the Limiting Assembly for PWR Thermal-Hydraulic Safety Analysis Gentlemen:

The purpose of this letter is to notify the Nuclear Regulatory Commission of a defect pursuant to 10 CFR 21, "Reporting of Defects and Noncompliance."

Combustion Engineering, Inc. has evaluated a deficiency in its current screening methodology for determining the limiting fuel assembly for detailed PWR thermal-hydraulic safety analysis. The deficiency is that the screening methodology based on low inlet flow may not consistently identify the most limiting assembly in the presence of very flat core and assembly power distributions. The conclusion of the evaluation was that the deficiency could, under some circumstances, constitute a defect as defined by 10 CFR 21. The thermal-hydraulic analysis methods themselves, when applied to the limiting assembly, yield valid results and are not at issue.

The Attachment contains information specifically required by 10 CFR 21.

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cc: - M. -F. Barno_ski-(f-XBB CE)

S. Magruder (NRC)

ABB Combustion Engineering Nuclear Operations Combustion Engineering. Inc. P.O. Box 500 Telephone (860) 285-1911 2000 Day Hill Road Fax (860) 285-9512 Windsor, CT 06095-0500

Attachment to LD-98-024 Combustion Engineering, Inc.

10 CFR 21 Report of a Defect or Failure to Comply The following information is provided pursuant to 10 CFR 21.21 (c)(4):

(i) Name and address of the individual informing the Commission:

Ian C. Rickard, Director Nuclear Licensing Combustion Engineering, Inc.

2000 Day Hill Road Windsor, CT 06095-0500 (ii) Identification of the facility, the activity, or the basic component supplied/or such facility or such activity within 'the United States which fails to comply or contains a defect:

The basic component is the assembly inlet flow basis of the screening*

methodology used in selecting .the limiting fuel assembly for PWR thermal-hydraulic safety analysis.

(iii) Identification of the firm constructing the facility or supplying the basic component which fails to comply or contains a defect:

Combustion Engineering, Inc.

2000 Day Hill Road Windsor, CT Q6095-0500 (iv) Nature of defect or failure to comply and the safety hazard which is created or could be created by such defect or failure to comply:

7 A screening procedure based on fuel assembly inlet flow has traditionally been used in identifying the limiting assembly for PWR thermal-hydraulic safety analysis. This screening procedure may not consistently result in identifying the most limiting assembly location when core and assembly power distributions are very flat. This circumstance could lead to non-conservative thermal-hydraulic safety analysis re~_ults.

2 Attachment to LD-98-024 (v) The date on which the information of such defect or failure to comply was obtained:

The discovery phase of the 10 CFR 21 evaluation process was initiated on July 1, 1998 by ABB CE.

(vi) In the case of a basic component which contains a defect or fails to comply, the number and location of all such components in use at, supplied/or, or being supplied/or one or more facilities or activities subject to the regulations of this part:

The current analyses ofrecord for the following U.S. nuclear power plants are affected by the defective screening method:

AN0-2, Calvert Cliffs-112, Palo Verde-1/2/3, SONGS-2/3, St. Lucie-2, Waterford-3, And, possibly, Ft. Calhoun,.

ABB CE does not know the applicability for other ABB CE designed nuclear power plants in the US, as it has not recently been involved with nuclear safety analyses of nuclear fuel at those plants. For these plants, ABB CE will issue a letter informing them of this condition and advising them to evaluate the applicabilitx of the situation. These plants are:

Millstone-2, Maine Yankee (shutdown),

Palisades, and

- St. Lucie -1.-

(vii) The corrective action which has been, is being, or will be taken; the name of the individual responsible for the action; and the length of time that has been or will be taken to complete the action:

"for all ABB CE analyzed plants, evaluations were performed by ABB CE to determine whether the defective screening methodology had any effect and if so, what effect, and what measures were necessary to compensate for it. For all ABB CE analyzed plants, except Calvert Cliffs-112, SONGS-2/3, and St. Lucie-2, these evaluations concluded that the analyses of record remained valid. Similar evaluations are being recommended to those utilities which conduct thermal-

3 Attachment to LD-98-024 hydraulic safety analysis themselves using ABB CE methods.

Thermal-hydraulic analyses of Calvert Cliffs Unit 1 Cycle 14 and Calvert Cliffs

. Unit 2 Cycle 12 indicate increases in the CETOP/TORC benchmarking overpower penalties of approximately 4% and a slight degradation in the 3-:pump TORC model results provided for transient analysis compared to the analysis of recoro. Baltimore Gas & Electric was notified in writing of adequate existing margin to compensate for the more adverse CETOP/TORC benchmarking overpower penalties.

• Thorough thermal-hydraulic safety analysis of SONGS Unit 2 Cycle 9 and SONGS Unit 3 Cycle 9 indicated less than 11Kand 1.5% increases, respectively, in the CETOP/TORC benchmarking overpower penalties. The analysis ofrecord DNBR probability distribution function (pdf) and Specified Acceptable Fuel Design Limits (SAFDL) and TORC models used in transient analyses remain conservative. Although conservatisms may already exist in the overall setpoirit and transient. analysis process to compensate for the poss(ble non-conservatisms, ABB CE identified adjustments to on-line COLSS and CPC addressable constants to conservatively set !lSide margin for the m~re adverse overpower penalties, and Southern California Edison was notified in writing of these recommended adjustments.

Thorough thermal-hydraulic analysis of St. Lucie Unit 2 Cycle 10 indicates an increase in t~e CETOP/TORC benchmarking overpower penalties of

• approximately 2%. The analysis of record DNBR pdf and SAFDL and TORC models used in transient analyses remain conservative. Florida P~wer & Light was notified in writing of adequate existing margin to compensate for the more adverse CETOP/TORC overpower penalties.

The inlet flow basis of the screening methodology will be revised by ABB CE to eliminate the reportable defect in the screening methodology. The revised screening methodology will supersede

. the current screening methodology, and the revised screening methodology will be used in all cases where screening for the continued applicability of the analysis of record is appropriate. The revised

• screening methodology will be completed by September 30, 1998, with customers notified in writing by October 15, 1998.

(viii) Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees:

The prior section describes information provided to utilities for which ABB CE performed screening analyses in preparation for fuel thermal-hydraulic safety analyses.

-' I * '..t 4 Attachment to LD-98-024 Interim advice has been provided to companies who perform their own thermal-hydraulic safety analyses using ABB CE methods. This advice consists of directions for performing a very extensive review of fuel assembly locations based on assembly flow and core and assembly power distributions in the process of selecting the limiting fuel assembly for thermal hydraulic safety analysis. The same interim screening methods are being applied in ongoing ABB CE thermal-hydraulic safety analyses to conse.rvatively identify the most limiting assembly(s).