ML18121A235

SMR DC RAI - Request for Additional Information No. 447 Erai No. 9508 (15)

ML18121A235
Person / Time
Site:	NuScale
Issue date:	05/01/2018
From:	NRC
To:	NRC/NRO/DNRL/LB1
References
Download: ML18121A235 (3)

Text

NuScaleDCRaisPEm Resource From: Chowdhury, Prosanta Sent: Tuesday, May 1, 2018 11:14 AM To: Request for Additional Information Cc: Lee, Samuel; Cranston, Gregory; Franovich, Rani; Karas, Rebecca; Schmidt, Jeffrey; NuScaleDCRaisPEm Resource

Subject:

Request for Additional Information No. 447 eRAI No. 9508 (15)

Attachments: Request for Additional Information No. 447 (eRAI No. 9508).pdf Attached please find NRC staffs request for additional information (RAI) concerning review of the NuScale Design Certification Application.

The NRC Staff recognizes that NuScale has preliminarily identified that the response to one or more questions in this RAI is likely to require greater than 60 days. NuScale is expected to provide a schedule for the RAI response by email within 14 days.

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: 478 Mail Envelope Properties (BN7PR09MB2609BA633C4A3E20450BF0EF9E810)

Subject:

Request for Additional Information No. 447 eRAI No. 9508 (15)

Sent Date: 5/1/2018 11:14:04 AM Received Date: 5/1/2018 11:14:11 AM 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 "Schmidt, Jeffrey" <Jeffrey.Schmidt2@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 675 5/1/2018 11:14:11 AM Request for Additional Information No. 447 (eRAI No. 9508).pdf 71814 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Request for Additional Information No. 447 (eRAI No. 9508)

Issue Date: 05/01/2018 Application

Title:

NuScale Standard Design Certification 048 Operating Company: NuScale Power, LLC Docket No.52-048 Review Section: 15 - Introduction - Transient and Accident Analyses Application Section:

QUESTIONS 15-7 10 CFR 50 Appendix A, GDC 34, Residual heat removal, and NuScale's PDC 34, in FSAR Section 3.1.4.5, state, "A system to remove residual heat shall be provided. The system safety function shall be to transfer fission product decay heat and other residual heat from the reactor core at a rate such that specified acceptable fuel design limits and the design conditions of the reactor coolant pressure boundary are not exceeded."

As discussed in FSAR Section 15.0.5, there are two systems to remove decay heat: the DHRS and the ECCS. The Long Term Cooling technical report, TR-0916-51299, which addresses long term decay heat removal after ECCS actuation, and supports the FSAR Chapter 15 analyses, states, "during long-term cooling, maintaining a collapsed liquid level in the riser above the core and demonstrating cladding temperatures remain acceptably low indicate that MCHFR is not challenged."

The RCS water mass is a function of the reactor power and there may be an initial power in which the water level drops below the riser after a reactor trip. If the RCS level drops below the riser, but not low enough to actuate the ECCS, it is unclear to the staff if fuel cladding temperatures would remain low enough to preserve the SAFDLs consistent with PDC 34. The staff is requesting the applicant address this potential scenario involving the interruption of continuous RCS natural circulation and, if necessary, demonstrate that cladding temperature remains acceptable low indicating that MCHFR is not challenged in a similar manner to that evaluated in the LTC report. If credit is taken for degraded DHRS heat removal capability (i.e.,

intermittent RCS natural circulation) the applicant should provide experimental data which validates the degraded DHRS heat removal capability.