ML20116L579

Forwards Current SBLOCA PCTs for Units 1 & 2.Attachment 2 Provides Addl Details on Model Error & Changes

ML20116L579
Person / Time
Site:	Farley
Issue date:	08/12/1996
From:	Dennis Morey SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9608190104
Download: ML20116L579 (6)

Text

'. South:rn Nuct:ar OperatinD Company Post Offc3 Box 1295 Birmingham. Alabama 35201 Tritphone (205) 868-5131 m

om umy SOuthem Nudear Operating Company Vice President Farley Project the southem electoc vstem August 12, 1996 Docket Nos.: 50-348 10 CFR 50.4 50-364 1

U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 l

Joseph M. Farley Nuclear Plant l Ptak Clad Temperature (PCT) Calculation Ladies and Gentlemen:

Southern Nuclear was recently informed of two new SBLOCA evaluation model errors in the calculation of PCT for Farley Nuclear Plant Units I and 2. The accumulated penalties resulting from all errors and changes, including the two above, since the last significant report are 109 F 1 for Unit 1 (up-flow configuration) and 85 F for Unit 2 (down-flow configuration).  !

Accordingly. Southern Nuclear has determined that the above accumulated penalties constitute significant errors and changes in the SBLOCA analyses for both Farley units and are reportable under 10CFR50.46 to the NRC.

l Attachment 1 provides the current SBLOCA PCTs for Farley Unit I and Unit 2. Attachment 2 provides additional details on the model errors and changes.

i Southern Nuclear will incorporate corrective model changes in the reanalysis of the SBLOCA being performed as part of the Power Uprate Program to be submitted to the NRC in the first quarter of 1997.

It has been determined that compliance with the :equirements of 10CFR50.46 continues to be maintained when the effects of plant design changes are combined with the effects of the SBLOCA Evaluation Model changes and errors apphcable to Farley Units 1 and 2.

Respectfully submitted, 9608190104 960812 /v&*

DR ADOCK0500g8 Dave Morey AA/ cit:pctcal. doc Attachments 00 cc: Mr. S. D. Ebneter, Region II Administrator (

Mr. B. L. Siegel, NRR Senior Project Manager Mr. T. M. Ross, Plant Sr. Resident inspector ik

p--- --

4 9

s ATTACHMENT 1 JOSEPH M. FARLEY NUCLEAR PLANT UNITS 1 AND 2 PEAK CLAD TEMPERATURE FOR SMALL-BREAK LOCA ANALYSES

ATTACHMENT 1 JOSEPH M. FARLEY NUCLEAR PLANT TOTAL RESULTANT SMALL-BREAK LOCA PCT (*F)

UNIT 1,*F UNIT 2,*F A. ANALYSIS-OF-RECORD (VANTAGE 5)

1. ECCS Analysis 1785* 1763*

2. T.v, Temperature Uncertainty 20* 20*

Total Analysis-of-Record PCT = 1805* 1783*

B.10 CFR 50.46 MODEL ASSESSMENTS

1. Prior Reported Assessments 171* 56*

2. NOTRUMP Specific Enthalpy Error 20* 20*

3. SBLOCTA Fuel Rod Initialization Error 10 10

4. AFW Flow Reduction to 650 gpm 25 25

5. Change in Burst and Blockage / Time in Life 54** 30**

C. 10 CFR 50.59 PLANT MODIFICATIONS None 0 0 D. TOTAL RESULTANT SMALL-BREAK LOCA PCT 2085 1924 Reponed to the NRC under the 10 CFR 50.46 Annual Repon for 1995 in Reference 1.

• For Burst and Blockage / Time in Life, penalties of 67"F for Unit I and 15"F for Unit 2 were included in B.1 above as previously reported to the NRC in Reference 1. Item B.5 is the sum of the associated changes in the Burst and Blockage / Time in Life penalty due to items B.2, B.3, and B.4 (see Notes A, B, and C in Attachment 2) since the Burst and Blockage / Time in Life penalty is a function of PCT. Thus, the total penalties for change in Burst and Blockage / Time in Life are 121*F for Unit I and 45*F for Unit 2.

Reference 1: Letter from SNC to USNRC," Joseph M. Farley Nuclear Plant 10 CFR 50.46 Annual ECCS Evaluation Model Changes Report for 1995,"

March 25,1996.

A1-1 l

l ATTACHMENT 2 W

DISCUSSION OF SMALL-BREAK LOCA MODEL ERRORS AND CHANGES

/

ATTACHMENT 2 DISCUSSION OF ShfALL. BREAK LOCA MODEL ERRORS AND CHANGES A. NOTRUMP CODE

1. NOTRUMP Specific Enthalpy Error (20 F) ,

A error was found in a line of coding in the NOTRUMP code. This line of coding was intended to model the calculation found in Equation L-127 of WCAP-10079-P-A.

Although the equation in the topical report is correct, the coding represented the last term as a partial derivative with respect to the fluid node mixture region total energy instead of the mixture region total mass. The estimated effect is 20"F for this error correction for both Unit I and Unit 2.

Note A: Associated with the above NOTRUMP error is a change in the current Burst and Blockage / Time in Life penalty since the magnitude of this penalty is a function of PCT (a 17"F penalty increase for Unit I and an 8*F penalty increase for Unit 2).

B. SBL-OCTA CODE

2. SBLOCTA Fuel Rod Initialization (10*F)

An error was discovered in the SBLOCTA code relating to adjustments which are made as part of the fuel rod initialization process which is used to obtain agreement between the SBLOCTA model and the fuel data supplied from the fuel thermal-hydraulic design calculations at full power, steady-state conditions. Specifically, an adjustment to the power which is made to compensate for adjustments to the assumed pellet diameter was incorrect. Additionally, updates were made to the fuel rod clad creep and strain model to correct logic errors that could occur in certain transient conditions. These model revisions had a small effect on the fuel rod initialization process and could produce small efTects during the transient. Due to the small magnitude of efTects and the interaction between the two items, they are being evaluated as a single, closely related effect. Representative plant calculations with the corrected model demonstrated that these revisions result in a predicted peak clad temperature increase on the order of 10*F.

Note B: As discussed in Note A above, a Burst and Blockage / Time in Life penalty change has also been appropriately assessed (a 10 F penalty increase for Unit I and a 7 F penalty increase for Unit 2) for the SBLOCTA fuel rod initialization correction.

A2-1

e C' NdTRUMP INPUT ERROR

3. AFW Flow Reduction to 650 gpm (25 F) l During the currently ongoing power uprate SBLOCA analysis, an inadvertent input crror concerning the total Auxiliary Feedwater (AFW) flow assumption was discovered. The original analysis-of-record used 1050 gpm for a total AFW flow,  !

from the combination of one motor-driven AFW pump (MDAFWP) and the turbine- {

driven AFW pump (TDAFWP) to the steam generators. The correct flow rate should  !

be 696 gpm. A conservative evaluation of the impact on the current SBLOCA PCT,  !

using 650 gpm for total AFW flow, has resulted in a 25 F penalty for both Unit I and Unit 2.

Note C: Also, as discussed in Note A above, a Burst and Blockageffime in Life penalty change has bemi assessed (a 27 F penalty increase for Unit I and a 15 F penalty increase for Unit 2) for the AFW flow reduction to 650 gpm. j l

I l

l

\

i l

l i

8 A2-2

- - .- .