ML19128A236

NON- PROPRIETARY- Request for Additional Information- Amendment Request Regarding Utilization of Tvel TVS-K Lead Test Assemblies Braidwood Station, Units 1 and 2

ML19128A236
Person / Time
Site:	Braidwood
Issue date:	05/02/2019
From:	Joel Wiebe Plant Licensing Branch III
To:	Bryan Hanson Exelon Generation Co
Wiebe J
References
EPID L-2018- LLA-0208
Download: ML19128A236 (3)

Text

ENCLOSURE 1 (NON-PROPRIETARY)

REQUEST FOR ADDITIONAL INFORMATION AMENDMENT REQUEST REGARDING UTILIZATION OF TVEL TVS-K LEAD TEST ASSEMBLIES EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. 50-456 AND 50-457 Proprietary information pursuant to Title 10 of the Code of Federal Regulations Section 2.390 has been redacted from this document.

Redacted information is identified by blank space enclosed within double brackets as shown here (( )).

REQUEST FOR ADDITIONAL INFORMATION AMENDMENT REQUEST REGARDING UTILIZATION OF TVEL TVS-K LEAD TEST ASSEMBLIES EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. 50-456 AND 50-457

1. In its letter dated July 19, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18204A169), Exelon discussed power margin calculations that were performed to determine the cutback in the enthalpy rise hot channel factor (FH) needed to ensure the requested TVS-K lead test assemblies (LTAs) will not be limiting with respect to critical heat flux (CHF) during anticipated operational occurrences (AOOs) and normal operation. The letter stated that the power margin calculations used the CRK CHF correlation, which was developed by TVEL specifically for TVS-K fuel. By letter dated October 19, 2018 (ADAMS Accession No. ML18296A288), Exelon provided additional information on the CRK correlation and its development.

In its letter dated July 19, 2018, Exelon also stated that the prior LTA experience at the Ringhals 3 nuclear power plant in Sweden prompted changes to the TVS-K LTA design for Braidwood. One of the listed changes includes a new mixing vane next to the guide thimble to improve flow mixing. During its audit, the NRC staff learned that the CRK correlation was developed based on CHF testing performed prior to the spacer grid changes made for the Braidwood LTAs. Since changes to the spacer grid configuration can substantially affect the thermal-hydraulic performance of a fuel assembly, the NRC staff requests the following information to ensure the adequacy of the assembly power cutback calculations.

Provide a more detailed description of the spacer grid updates that were made for the TVS-K lead LTAs proposed for use at Braidwood relative to the spacer grids irradiated in TVS-K LTAs at Ringhals and tested to support development of the CRK CHF correlation. Discuss any additional testing that may have been done to validate that the CRK correlation provided adequate or conservative predictions of CHF for the updated spacer grid. If new CHF testing using the updated spacer grids was performed at a facility other than those already discussed in letters dated July 19 and October 19, 2018, provide a description of the test facility consistent with the level of detail provided for the two facilities already described.

2. The NRC staffs initial look at the qualification and validation of PRIME models for the TVEL LTAs and the Braidwood fuel rod thermal mechanical evaluation reveals sufficient information to demonstrate acceptable results for the first cycle. However, information is currently not available that demonstrates acceptability for additional cycles as allowed by the requested license condition. Provide information regarding the controls that are in place to require obtaining this additional information and verification that acceptable performance is demonstrated prior to continuing use of the TVEL LTAs in additional

cycles. In particular, explain how the PRIME models and application methodology will be updated to accommodate

((

)) and address DNB propagation during accident conditions. Discuss how the updates will be validated against relevant measurements from experiments or post-irradiation examination.