ML17265A825

LLC Supplemental Response to NRC Request for Additional Information No. 56 (Erai No. 8793) on the NuScale Design Certification Application

ML17265A825
Person / Time
Site:	NuScale
Issue date:	09/22/2017
From:	Rad Z NuScale
To:	Document Control Desk, Office of New Reactors
References
RAIO-0917-56135
Download: ML17265A825 (4)

Text

RAIO-0917-56135 September 22, 2017 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Supplemental Response to NRC Request for Additional Information No. 56 (eRAI No. 8793) on the NuScale Design Certification Application

REFERENCES:

1. U.S. Nuclear Regulatory Commission, "Request for Additional Information No. 56 (eRAI No. 8793)," dated June 09, 2017

2. NuScale Power, LLC Response to NRC "Request for Additional Information No. 56 (eRAI No.8793)," dated July 28, 2017 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) supplemental response to the referenced NRC Request for Additional Information (RAI).

The Enclosure to this letter contains NuScale's supplemental response to the following RAI Question from NRC eRAI No. 8793:

06.02.01-2 This letter and the enclosed response make no new regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions on this response, please contact Marty Bryan at 541-452-7172 or at mbryan@nuscalepower.com.

Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8G9A Omid Tabatabai, NRC, OWFN-8G9A Samuel Lee, NRC, OWFN-8G9A (QFORVXUH1X6FDOH6XSSOHPHQWDO5HVSRQVHWR15&5HTXHVWIRU$GGLWLRQDO,QIRUPDWLRQH5$,1R



NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-0917-56135 :

NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 8793 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

Response to Request for Additional Information Docket No.52-048 eRAI No.: 8793 Date of RAI Issue: 06/09/2017 NRC Question No.: 06.02.01-2 GDC 50, Containment design basis, requires in part that the containment be designed so that the containment structure and its internal compartments can accommodate, without exceeding the design leakage rate and with sufficient margin, the calculated pressure and temperature conditions resulting from any loss-of-coolant accident. This margin shall reflect, among other considerations, the conservatism of the calculational model and input parameters.

TR-0516-49084-P, Containment Response Analysis Methodology Technical Report, which is referenced in FSAR Chapter 6 and forms the basis for the containment design pressure and temperature, states that containment initial pressure is bounding high at 2.0 psia; this is also reflected in the value in FSAR Table 15.0-6, which lists the initial condition range for safety analyses. A further spec says this is varied as an initial condition [(+~2 psia)]. However, there is no basis for these values as either an analytical limit or a technical specification limiting condition for operation. Justify the conservatism in the initial condition used, and provide a basis (such as a technical specification or that it represents a bounding value as a trip setpoint plus uncertainty) for why this value is a limiting value that could not be exceeded during operation as an initial condition, or provide a new value that represents a limiting initial condition. As part of this response, if any values are changed, provide a proposed update to the DC application and corresponding documentation as applicable.

NuScale Response:

A sensitivity calculation on the limiting containment peak pressure case was performed to calculate the impact of an increase in initial containment pressure from 2 psia to 3 psia. The sensitivity calculation modeled an inadvertent reactor recirculation valve (RRV) opening assuming minimum primary system flow, loss of normal AC and DC power, and the limiting 1000 psid IAB release pressure consistent with the limiting overall containment pressure case discussed in TR-0516-49084-P, Section 5.1.3.5. This sensitivity case resulted in a maximum calculated containment pressure of 953 psia, which is 2 psi higher than the limiting 951 psia peak pressure case presented in the technical report. The result of the sensitivity calculation confirms that changing the initial containment pressure from 2 psia to 3 psia does not NuScale Nonproprietary

substantively change the margin to the 1000 psia design pressure.

FSAR Figure 5.2-3 indicates that at the maximum pool temperature of 140F, the containment pressure must be less than 3 psia for acceptable leak rate detection. As discussed in FSAR Section 5.2.5.1, acceptable in-containment leakage detection performance, using the containment pressure instrumentation or containment evacuation system condensate monitoring, requires the containment pressure to be maintained below the vapor pressure for the lowest internal wall temperature.

FSAR Figure 5.2-3 depicts the maximum allowable containment pressure for acceptable leakage detection. This figure is based on the assumption that the minimum containment wall temperature is equal to the reactor bulk pool temperature. This is appropriate because the outside of the containment wall is in contact with the reactor pool, or the air above the reactor pool, and during normal operation the containment is evacuated to minimize heat loss from the reactor pressure vessel.

The containment conditions defined for acceptable leakage detection conservatively do not credit heat loss from the reactor pressure vessel to containment that could raise the containment inside wall temperature, or any locally higher pool temperature that could raise the containment inside wall temperature, and therefore raise the allowable pressure.

Impact on DCA:

There are no impacts to the DCA as a result of this response.

NuScale Nonproprietary