ULNRC-06497, 10 CFR 50.46 Annual Report ECCS Evaluation Model Revisions

10 CFR 50.46 Annual Report ECCS Evaluation Model Revisions

ML19087A040
Person / Time
Site:	Callaway
Issue date:	03/28/2019
From:	Wink R Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-06497
Download: ML19087A040 (11)

Text

~ '.t..

~ ~meren MISSOURI Callaway Plant Marc h 28, 2019 ULNRC-06497 U.S. Nuclear Regulatory Commission Attn; Document Control Desk Washington, DC 20555-0001 10 CFR 50.46 Ladies and Gentlemen:

DOC KET NUlVIBER 50-483 CALL AWAY PLAN T UNIT 1 UNIO N ELEC TRIC CO.

RENE WED FACI LITY OPERATING LICE NSE NPF-30 10 CFR 50.46 ANN UAL REPO RT ECCS EVAL UATI ON MOD EL REVI SION S Ameren Missouri hereby submits the annual report required per 10 CFR 50.46(a)(3) for Callaway Plant. Attachment 1 to this letter describes changes to the Westi nghouse ECCS Large Break and Small Break Loss of Coolant Accident (LOCA) Evaluation Mode ls which have been implemented for Callaway during the time pe1iod from March 2018 to March 2019.

Attacluuent 2 provides an ECCS Evalnation Model Margin Assessment which accounts for all peak cladding temperature (PCT) changes resulting from the resolutinn of prior issues as they apply to Callaway. No new PCT penalties are included in these attachments .

References 1 through 13 provided annual 10 CFR 50.46 report s that were issued after the LOCA analysis were revised to reflect the installation of the replacemen t steam generators in 2005. The PCT values detennined in the Large Break and Small Break LOCA analysis of record , when combined with all PCT margin allocations, remain below the 2200°F regulatory limit. Howe ver, in March 2014 Amer en Missouri was informed by Westinghouse that the absolu te magnih1de of the Large Break Loss of Coolant Accident (LBLOCA) penalty assessments that have accumulated since the cunen t analysis of record (replacement steam generator analysis approved in Callaw ay License Amen dmen t 168) e ceeded 50°F. As such, Reference 9 was submitted within the requirements of 10 CFR 50.46(a)(3)(ii), and contains a commitment to reanalyze the Large Break and Sma11 Break Loss of Coolant Accidents using the NRC-approved version ofWC AP-1 6996- P, "Realistic LOCA Evalu ation Methodology Applied to the Full Spectrum of Break Sizes (FUL L SPECTRUM LOCA Methodology)". This reanalysis will be completed on a sched ule to be detennined as part of the 10 CFR 50.46c rulemakiug process .

t * , o,t* *** ** * - *

• l

• U l , , . , , , ,.,1,000,0 0

• • • • 1,1.,,1,,,,o ** * *** * ****0o* ****** 1t " I o ooo,,.,., . ,. ,-1 ** 01,0 0 1 . . , , , 1 , * ** t '* "

• 0 0 , , . , , 0 , , , 1 , , 0 , , , ,11,.

°"""'""'*I* I** * *

........ 83 15 County Road 459 . Steedman, MO 65077 . AmerenMissouri.com

ULNRC-06497 Marc11 28, 2019 Page 2 of 4 Th.is letter does not contain new commitments. If you have any questions on this report, please contact Mr. Tom Elwood at (314) 225-1905.

Sincerely, id!- Manger, Regulatory Affairs JBL

References:

1) ULNRC-05260 dated 3-9-06

2) ULNRC-05 378 dated 3-7-07

3) ULNRC-05475 dated 3-4-08

4) ULNRC-05600 dated 3-4-09

5) ULNRC-05683 dated 3-1-10

6) ULNRC-05769 dated 3-1-1 l

7) ULNRC-05840 dated 3-1-12

8) ULNRC-05968 dated 3-6-13 9 ULNRC-06098 dated 3-25-14

10) ULNRC-06203 dated 3-31-15

11) ULNRC-06292 dated 3-30-16

12) ULNRC-06361 dated 3-30-17

13) ULNRC-06428 dated 3-29-18 Attachments;

1. Changes to the Westinghouse ECCS Evaluation Model and PCT Penalty Assessments

2. ECCS Evaluation Model Margin Assessment for Callaway

: : : : . : : ; : : ; : : : : . : : : : : : : : : : . : : : . : : . : : . : : . : : : : : : ! : : : : : . : : : .. : : : : :. : : : : . :: : : : : : .. =; : : : : : : : *: : : *: : ; : : : : : : : : : ** : : : : : : : *: : : '. : : : : : : : : : : : :; : : : : : :*:: ~: : '. ; : : : : ~: : : : * : : : ** : : : : : : : *: : : *: : : : : *: : :.: ! : : : : . : : :: : . : : : : : : : : : : : ; : : : : : :

=

::::..............................

• • • • • .................................  ::::=::::::::::::::::;:::::::::::

ULNRC-06497 March 28, 2019 Page 3 of 4 cc: Mr. Scott A. M01Tis Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. L. John Klos Project Manager, Callaway Plant Office ofNudear Reactor Regulation U. S. Nuclear Regulatory Corrunission Mail Stop 09£3 Washington, DC 20555-0001

. .. .. .. . . . . ..... . .. ..-. .. ... ~*........ .. . . . *- .......... .................................

ULNRC-0649 7 March 28 2019 Page 4 of 4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 6100 Western Place, Suite 1050 Fort Worth, TX 76107 Electronic distribution fo1* the following can be made via Other Situations ULNRC Distribution:

F. M . Diya T. E . Herrmam1 B. L. Cox.

F. J. Bianco S. P. Banker R. C. Wink T . B. Elwood Corporate Communicati ons NSRB Secretary STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittinan LLP)

Missouri Public Service Conunission

:::::::::: :: :::: : :; :; ;: ::::::: :::::::::::: : : ::: ::::::~ ::::: ::: ~:::::: ::; :: :: :: : : :~: ::.; ::. : :::::::::::::::;: ::: :::: ::::::::::::::::; :~ ::.:;: ::::::: :::;: :::::: :: :: ::; ::::::::: : :

:::::: : ::: : :: : :: ;:: :~:: ::::::::: :. : :: : :~ :: *: :::::::::. ::: ::::: ::: : . : ::::: ::~. :: : : : ::* :: .:::: ::::: :: : :; ;:* ;: : : : ::;::* ::: : : : : : : :: : : ; ::~ :; : : :: . : . : :: : ::: ::: :::: :: ::  :  ::  : ::: : : :  ::

........................... ...................... ...... ...................................................... ......................... ............. .. . ...........:;:....  :: :: : ; ::: . ::: '.: ~:: . ::::~::::: ! : :: :::: :: : ;: ::: ::: :* ::: ::: . :: .

to ULNRC-06497 ATTACHMENT ONE CHANGES TO THE WESTINGHOUSE ECCS EVALUATION MODEL AND PCT PENALTY ASSESSMENTS 1

Attachment l to ULNRC-06497 TABLE OF CONTENTS

1. FUEL ROD GAP CONDUCTANCE ERROR

2. RADIATION HEAT TRANSFER MODEL ERROR

3. SBLOCTA PRE-DNB CLADDING SURFACE HEAT TRANSFER COEFFICIENT CALCULATION

4. GENERAL CODE MAINTENANCE 2

to ULNRC-0649 7

1. FUEL ROD GAP CONDUCTANCE ERROR An en-or was identified in the fuel rod gap conductance model in the NOTRUMP computer code (reactor coolant system response model) . The error is associated with the use of an incon-ect temperature in the calculation of the cladding emissivity term. This e1rnr corresponds to a Non-Discretionary Change as described in Section 4.1.2 of WCAP-13451..

Based on a combination of engineering judgment of the phenomena and physics of a small break LOCA and sensitivity calculations performed with the advanced plant version ofNOTRUMP , Westinghouse has concluded that this e1TOr has a negligible effect, leading to an estimated Peak Cladding Temperature (PCT) impact of 0°F on small break LOCA analysis results .

2. RADIATION HEAT TRANSFER MODEL ERROR Two enors were discovered in the calculation of the radiation heat transfer coefficient within the fuel rod model of the NOTRUMP computer code (reactor coolant system response model) . First, existing logic did not preclude non-physical negative or large (negative or positive) radiation heat transfer coefficients from being calculated. These en-oneous calculations occuned when the vapor temperature exceeded the cladding surface temperature or when the predicted temperature difference was less than 1 °F. Second, a temperature tenn incorrectly used degrees Fahrenheit instead of Rankine. These errors represent a closely related group of Non-Discretio nary problems in accordance wfth Section 4.1.2 of WCAP-13451 .

Based on a combination of engineering judgment of the phenomena and physics of a small break LOCA, and sensitivity calculations perfonned with the advanced plant version ofNOTRUMP , Westinghouse has concluded that this error has a negligible effect, leading to an estimated Peak Cladding Temperature (PCT) impact of 0°F on small break LOCA analysis resl.llts.

3. SBLOCTA PRE-DNB CLADDING SURFACE HEAT TRANSFER COEFFICIENT CALCULATION Two e1rnrs were discovered in the pre-departure from nucleate boiling {pre-DNB) cladding surface heat transfer coefficient calculation in the SBLOCTA code ( cladding heat-up ca1culatfons) . The first enor is a result of inconsistent time units (hours vs . seconds) in the parameters used for the calculation of the Reynolds and Prandtl numbers, and the second en-or relates to an inconect diameter used to develop the area tenn in the cladding smface heat flux calculation. Both of these issues impact the calculation of the pre-DNB convective heat transfer coefficient, representing a closely related group of Non-Discretio nary Changes to the Evaluation Model as described in Section 4.1 .2 of WCAP-13451 .

These enors have been con-ected in the SBLOCTA code. Because this condition occurred prior to DNB , it was judged that these e1Tors l1ad nci direct impact on the cladding heat-up related to the core uncover period. A series of validation tests were perfonned by Westinghouse and confirmed that tbese errors have a negligible effect on SBLOCA analysis results, leading to an estimated Peak Cladding Temperature (PCT) impact of 0°F.

3 to ULNRC-06497

4. GENERAL CODE MAINTENANCE Various changes have been made to enhance the usability of the codes and to help preclude errors in analyses. This includes items *such as modifying input variable definitions, ututs, and defaults; improving the input diagnostic checks* enhancing the code output; optimizing active coding; and eliminating inactive coding. These changes have been evaluated for impact on existing Small Break LOCA analysis results and they represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-1345.

Westinghouse has judged tlus issue to have an estimated PCT impact of 0°F on existing Small Break LOCA analysis results.

4

Attaclu11ent 2 to ULNRC-06497 ATTACHME NT TWO ECCS EVALUATION MODEL MARGIN ASSESSMENT FOR CALLAWAY to ULNRC-0649 7 LARGE BREAK LOC A A. ANALYSIS OF RECORD (AOR) PCT = 1939°F B. PRIOR ECCS MODEL ASSESSMEN TS + 58°F C. CURRENT LOCA MODEL ASSESSMEN TS - + oop March 2018 LICENSING BASIS PCT + MARGIN ALLOCATIO NS 1997°F ABSOLUTE MAGNITUD E OF MARGIN ALLOCATIO NS 5gop SINCE LAST ANALYSIS OF RECORD OR LBLOCA 30-DA Y REPORT 2

to ULNRC-06497 SMALL BREAK LOCA A. ANALYS1S OF RECORD (AOR) PCT= 1043°F B. PRIOR ECCS MODEL ASSESSMEN TS + oop C. CURRENT ECCS MODEL ASSESSMENTS - + 0°F March2018 LICENSING BASIS PCT+ MARGIN ALLOCATIONS 1043°F ABSOLUTE MAGNITUD E OF MARGIN ALLOCATIONS 0°F SINCE LAST ANALYSIS OF RECORD OR SBLOCA 30-DAY REPORT 3