ML18121A405

SMR DC RAI - Request for Additional Information No. 451 Erai No. 9517 (15.06.05)

ML18121A405
Person / Time
Site:	NuScale
Issue date:	05/01/2018
From:	NRC
To:	NRC/NRO/DNRL/LB1
References
Download: ML18121A405 (3)

Text

NuScaleDCRaisPEm Resource From: Chowdhury, Prosanta Sent: Tuesday, May 1, 2018 2:58 PM To: Request for Additional Information Cc: Lee, Samuel; Cranston, Gregory; Franovich, Rani; Karas, Rebecca; Thurston, Carl; NuScaleDCRaisPEm Resource

Subject:

Request for Additional Information No. 451 eRAI No. 9517 (15.06.05)

Attachments: Request for Additional Information No. 451 (eRAI No. 9517).pdf Attached please find NRC staffs request for additional information (RAI) concerning review of the NuScale Design Certification Application.

Please submit your technically correct and complete response within 60 days of the date of this RAI to the NRC Document Control Desk.

If you have any questions, please contact me.

Thank you.

Prosanta Chowdhury, Project Manager Licensing Branch 1 (NuScale)

Division of New Reactor Licensing Office of New Reactors U.S. Nuclear Regulatory Commission 301-415-1647 1

Hearing Identifier: NuScale_SMR_DC_RAI_Public Email Number: 482 Mail Envelope Properties (BN7PR09MB260908790BFD6AF625F854C39E810)

Subject:

Request for Additional Information No. 451 eRAI No. 9517 (15.06.05)

Sent Date: 5/1/2018 2:58:19 PM Received Date: 5/1/2018 2:58:23 PM From: Chowdhury, Prosanta Created By: Prosanta.Chowdhury@nrc.gov Recipients:

"Lee, Samuel" <Samuel.Lee@nrc.gov>

Tracking Status: None "Cranston, Gregory" <Gregory.Cranston@nrc.gov>

Tracking Status: None "Franovich, Rani" <Rani.Franovich@nrc.gov>

Tracking Status: None "Karas, Rebecca" <Rebecca.Karas@nrc.gov>

Tracking Status: None "Thurston, Carl" <Carl.Thurston@nrc.gov>

Tracking Status: None "NuScaleDCRaisPEm Resource" <NuScaleDCRaisPEm.Resource@nrc.gov>

Tracking Status: None "Request for Additional Information" <RAI@nuscalepower.com>

Tracking Status: None Post Office: BN7PR09MB2609.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 556 5/1/2018 2:58:23 PM Request for Additional Information No. 451 (eRAI No. 9517).pdf 74320 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Request for Additional Information No. 451 (eRAI No. 9517)

Issue Date: 05/01/2018 Application

Title:

NuScale Standard Design Certification 048 Operating Company: NuScale Power, LLC Docket No.52-048 Review Section: 15.06.05 - Loss of Coolant Accidents Resulting From Spectrum of Postulated Piping Breaks Within the Reactor Coolant Pressure Boundary Application Section:

QUESTIONS 15.06.05-6 Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix A, General Design Criterion (GDC) 35, Emergency Core Cooling, requires that a system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts. DSRS Section 15.6.5 provides guidance for complying with GDC 35. It requires that evaluation models meet the requirements of 10 CFR 50.46, which states that the evaluation model must include sufficient supporting justification to show that the analytical technique realistically describes the behavior of the reactor system during a loss-of-coolant accident.

In FSAR Chapter 15.6.5 and Section 9 of the Loss-of-Coolant Accident Evaluation Model, TR-0516-49422-P, Rev. 0, which is incorporated by reference into the FSAR, indicates that a stable natural recirculation flow pattern with the reactor recirculation valves and steam venting through the reactor vent valves (RVVs) is relied upon to remove decay heat passively via boiling in the core. The staff noted that its sensitivity calculations, using the applicants NRELAP5 LOCA input models, show that flows in core hot and average channels appear to be artificially exaggerated by high reverse flow in the bypass channel during the recirculation phase of the LOCA, a condition not noted in the LOCA TR. This appears to be an artifact of the 1-D core and riser modeling that causes excessive recirculation cooling via the bypass.

Please provide an analysis that quantifies NRELAP5 bypass flow rates during the ECCS recirculation phase and provide any updates to the LOCA methodology needed to resolve this issue to support the staff's GDC 35 finding.