CNL-15-034, Submittal of 30-Day Report of Changes and Errors to the Calculated Peak Cladding Temperature

Submittal of 30-Day Report of Changes and Errors to the Calculated Peak Cladding Temperature

ML15037A725
Person / Time
Site:	Watts Bar
Issue date:	02/06/2015
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-15-034
Download: ML15037A725 (5)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga , Tennessee 37402 CNL-15-034 February 6, 2015 10 CFR 50.46 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington , D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Construction Permit No. CPPR-92 NRC Docket Nos. 50-391

Subject:

10 CFR 50.46 Day Report for Watts Bar, Unit 2

Reference:

TVA Letter to NRC , "10 CFR 50.46 - Annual Report for Watts Bar, Units 1 and 2,"

dated April 25, 2014 [ML14119A332]

The purpose of this letter is to provide a 30-day report of changes and errors to the calculated peak cladding temperature (PCT) for the Watts Bar Nuclear Plant (WBN), Unit 2, Emergency Core Cooling System (ECCS) evaluation model. This report is required in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors,"

paragraph (a)(3)(ii).

The last 10 CFR 50.46 annual report for WBN Unit 2 was subm itted to the United States Nuclear Regulatory Commission (NRC) on April 25, 2014 (Reference) . The last annual report (Reference) indicated that in accordance with 10 CFR 50.46(a)(3)(ii) , subsequent changes or errors affecting the WBN Unit 2 large break loss of coolant accident (LBLOCA) analysis are considered significant for reporting purposes because the absolute magnitude of the accumulated changes in PCT since the last LBLOCA analysis exceeds 50 degrees Fahrenheit.

On January 7, 2015, Westinghouse Electric Company (WEC) notified Tennessee Valley Authority (TVA) of the estimated effect of a change in accumulator injection line resistances for the WBN Unit 2 small break loss-of-coolant accident (SBLOCA) analysis and the LBLOCA analysis. The identified change to the LBLOCA analysis is reportable to the NRC in a 30-day report for WBN Unit 2, in accordance with 10 CFR 50.46(a)(3)(ii) .

As indicated in the Enclosure, the current updated (net) licensing basis PCT for the WBN Unit 2, LBLOCA analysis of record remains unchanged at 1711 degrees Fahrenheit. The updated (net) licensing basis PCT for the SBLOCA evaluation model is unchanged from the SBLOCA analysis of record baseline PCT, and remains at 1184 degrees Fahrenheit.

U.S . Nuclear Regulatory Commission CNL-15-034 Page 2 February 6, 2015 There are no regulatory commitments in this letter. Please direct questions concerning this report to Gordon Arent at (423) 365-2004.

President, Nuclear Licensing

Enclosure:

Watts Bar Nuclear Plant, Unit 2, 10 CFR 50.46 30-Day Report cc (Enclosures):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant Unit 2

ENCLOSURE WATTS BAR NUCLEAR PLANT, UNIT 2 10 CFR 50.46 30-DAY REPORT In accordance with the reporting requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.46(a)(3)(ii), the following is a summary of the limiting design basis loss of coolant accident (LOCA) analysis results established using the current Watts Bar Nuclear Plant (WBN)

Emergency Core Cooling System evaluation models for Unit 2. This report describes the changes and errors affecting the calculated peak cladding temperatures (PCTs) since the last analysis of record was submitted to the Nuclear Regulatory Commission (NRC) .

The last 10 CFR 50.46 annual report for WBN Unit 2 was submitted to the NRC on April 25, 2014 (Reference 1). The last annual report (Reference 1) indicated that in accordance with 10 CFR 50.46(a)(3)(ii), subsequent changes or errors affecting the WBN Unit 2 large break loss of coolant accident (LBLOCA) analysis are considered significant for reporting purposes because the absolute magnitude of the accumulated changes in PCT since the last LBLOCA analysis exceeds 50 degrees Fahrenheit (°F) .

Table 1 lists the changes and errors in the LBLOCA and small break loss of coolant accident (SBLOCA) analyses since each of the respective analysis of record (AOR) and the associated effect on PCT. The change that was not previously identified in reference 1 is described in a note to Table 1.

The updated (net) licensing basis PCT for the LBLOCA and SBLOCA remain unchanged from the last annual report (Reference 1).

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ENCLOSURE WATTS BAR NUCLEAR PLANT, UNIT 2 10 CFR 50.46 30-DAY REPORT Table 1 Year Description LBLOCA LBLOCA SBLOCA SBLOCA Note Reference

~PCT l~PCTI ~PCT l~PCTI

(°F)* (°F)* (°F)* (°F)*

2013 LBLOCA AOR PCT 1766 --- --- --- --- 2 2010 SBLOCA AOR PCT --- --- 1184 --- --- 3 2013 Elevations for Heat Slab 4 Temperature Initialization 0 0 --- --- ---

2013 Heat Transfer Model Error 4 0 0 --- --- ---

Corrections 2013 Correction to Heat Transfer 4 0 0 --- --- - --

Node Initialization 2013 Mass Conservation Error Fix 0 0 --- -- - --- 4 2013 Correction to Split Channel 4 Momentum Equation 0 0 - -- --- - --

2013 Heat Transfer Logic 4 Correction for Rod Burst 0 0 --- -- - ---

Calculation 2013 Changes to Vessel 4 Superheated Steam 0 0 --- --- ---

Properties 2013 Update to Metal Density 4

0 0 ---

Reference Temperatures 2013 Decay Heat Model Error --- 4 0 0 --- ---

Corrections 2013 Correction to the Pipe Exit --- 4 0 0 --- ---

Pressure Drop Error 2013 WCOBRA/TRAC File --- 4 0 0 --- ---

Dimension Error Correction 2013 Revised Heat Transfer

--- --- --- 4

-55 55 Multiplier Distributions 2013 Initial Fuel Pellet Average 0 0 4 Temperature Uncertainty Calculation --- --- ---

2014 HOTSPOT Burst Strain Error 0 0 --- --- --- 5 Cold Leg Accumulator 2014 Injection Lines Hydraulic 0 0 0 0 1 ---

Resistance Chanqes Updated (net) licensing

--- basis PCT --- --- --- ---

1711 1184 (AOR PCT + 2: i'.iPCT)

Cumulative sum of PCT

--- changes --- 55 0 0 --- ---

LI ~PCT!

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ENCLOSURE WATTS BAR NUCLEAR PLANT, UNIT 2 10 CFR 50.46 30-DAY REPORT Note 1:

Pre-operational testing conducted at WBN Unit 2 determined the accumulator injection line hydraulic resistances used in the SBLOCA and LBLOCA analyses should be changed . The change in the

. accumulator injection line resistances was estimated to have a negligible impact on the SBLOCA analysis and LBLOCA analysis results , leading to an estimated PCT impact of 0°F.

References:

1. Letter from TVA to NRC , "10 CFR 50.46 Day and Annual Report for 2013," dated April 25, 2014 [ML14119A332]

2. WCAP-17093-P , Revision 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Unit 2 Nuclear Plant Using the ASTRUM Methodology," June 2013

3. WBT-D-1460, "Final Small Break LOCA Summary Report for WBN Unit 2," January 2010

4. Letter from TVA to NRC , "Watts Bar Nuclear Plant, Unit 2 - Emergency Core Cooling system Evaluation Model Changes - 30 Day Report - 10 CFR 50.46 Notification," dated August 28, 2013.[ML13246A076]

5. Letter from TVA to NRC, "10 CFR 50.46 Day Report for Watts Bar, Units 1 and 2," dated February 28, 2014.[ML14064A431]

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