ML23352A125
| ML23352A125 | |
| Person / Time | |
|---|---|
| Site: | 99902078, 05200050 |
| Issue date: | 12/18/2023 |
| From: | Shaver M NuScale |
| To: | Document Control Desk |
| References | |
| RAIO-155148 | |
| Download: ML23352A125 (1) | |
Text
RAIO-155148 December 18, 2023 Docket: 52-050 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738
SUBJECT:
NuScale Power, LLC Response to NRC Request for Additional Information (RAI No. 10113) on the NuScale Standard Design Approval Application
REFERENCE:
NRC Letter NuScale Request for Additional Information (RAI-10113, FSAR Section 19.5) Final Letter, dated November 30, 2023, RAI# 10113 The purpose of this letter is to provide NuScale's response to NRC Requests for Additional Information (RAI), RAI# 10113, noted in the References above.
The enclosure to this letter contains NuScale's response to the following RAI Question from NRC RAI# 10113:
19.5-13 This letter makes no new regulatory commitments and no revisions to any existing regulatory commitments.
Please contact Elisa Fairbanks at 541-452-7872 or at EFairbanks@nuscalepower.com if you have any questions.
Sincerely, Mark Shaver Director, Regulatory Affairs NuScale Power, LLC Distribution: Getachew Tesfaye, NRC Alina Schiller, NRC Mahmoud Jardaneh, NRC Enclosure 1: NuScale Response to NRC Request for Additional Information RAI# 10113 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Response to NRC Request for Additional Information eRAI No. 10113, nonproprietary NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Nonproprietary Response to Request for Additional Information Docket: 052000050 RAI No.: 10113 Date of RAI Issue:11/30/2023 NRC Question No.: 19.5-13 Regulatory Basis 10 CFR 50.150(a)(1) requires a design-specific assessment of the effects on the facility of the impact of a large commercial aircraft, and using realistic analyses, the applicant shall identify and incorporate into the design those design features and functional capabilities to show that, with reduced use of operator actions: (i) The reactor core remains cooled, or the containment remains intact; and (ii) Spent fuel cooling or spent fuel pool integrity is maintained. In addition, 10 CFR 50.150(b) requires that the Final Safety Analysis Report (FSAR) contain a description of the design features and functional capabilities and how the design features and functional capabilities meet the assessment requirements.
Issue FSAR Section 19.5 identifies and describes the decay heat removal system (DHRS) and reactor coolant system (RCS) as key design features credited in the aircraft impact assessment (AIA) necessary for core cooling. FSAR 19.5 also states that all required operator actions occur before the aircraft impact, and there are no control or protective functions necessary after aircraft impact for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. However, in the NuScale US460 design, after 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following a reactor trip the emergency core cooling system (ECCS) is automatically actuated. Therefore, a realistic plant response for the NuScale US460 to an aircraft impact includes decay heat removal to satisfy core cooling functions via the RCS, DHRS, ECCS, and other support systems already identified and described in FSAR Section 19.5.
Information Requested In accordance with 10 CFR 50.150(a)(1) and (b), the applicant is requested to (1) identify in FSAR Section 19.5 that the ECCS is a key design feature for core cooling; and (2) include a description of the design feature and functional capabilities or a reference to where this information is already provided in the FSAR.
NuScale Nonproprietary
NuScale Nonproprietary NuScale Response:
Item 1: The Emergency Core Cooling System (ECCS) is a key design feature. Both the decay heat removal system and the ECCS provide core cooling. The Standard Design Approval Application (SDAA) Section 19.5 is revised accordingly as shown in the proposed markups.
Item 2: SDAA Section 6.3 provides the design and operational information for the ECCS and Chapter 15 provides the ECCS engineered safety features characteristics. The SDAA Section 19.5 is revised to provide the references to Section 6.3 and Chapter 15.
Impact on US460 SDA:
FSAR Section 19.5 has been revised as described in the response above and as shown in the markup provided in this response.
NuScale Nonproprietary
Adequacy of Design Features and Functional Capabilities Identified NuScale Final Safety Analysis Report and Described for Withstanding Aircraft Impacts Post reactor trip, two independent safety-related passive DHRSs, described in Section 5.4.3, provide redundant core cooling capability for each NPM without reliance on external power. An impact that ruptures the main steam or feedwater piping in the TGB does not affect DHRS passive cooling capability. The DHRS initiation includes closure of the associated main steam and feedwater isolation valves inside the RXB, thereby preventing a loss of secondary side water through the damaged piping. The DHRS is capable of maintaining core cooling for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Upon notification of an imminent aircraft threat, the operators in the main control room (MCR) scram the reactors, actuate the DHRS, and isolate containment.
Heat from the DHRS is transferred passively to the reactor pool that serves as the UHS (described in Section 9.2.5 and Section 3B.2), which is located below grade in the RXB.
RAI 19.5-13 The emergency core cooling system (ECCS) provides passive core cooling as described in Section 6.3 and Section 15.0.
There are no systems with open-water sources (e.g., circulating water system) in the RXB physical damage footprint for any strike. As such, internal flooding is not an issue of concern.
Containment penetrations are on the CNV, which is protected from impact by the RXB exterior walls. The location of CNV penetrations and isolation valves as described in Section 6.2.4 is a key design feature that ensures containment isolation.
There are no control or protective functions necessary after aircraft impact for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, as described in Section 9.2.5.
RAI 19.5-13 The NuScale Power Modules, reactor coolant system, containment vessel, decay heat removal system, containment isolation valves, ECCS, and ultimate heat sink are key design features for ensuring core cooling. The closure of the main steam isolation valves and feedwater isolation valves as described in Section 6.2.4, are key design features for ensuring DHRS operation. The ability to scram the reactors, isolate containment, and actuate the DHRS from the main control room, as described in Chapter 7 are key design features for ensuring the reactor is tripped, containment is isolated, and the DHRS is actuated before aircraft impact.
ECCS automatically initiates without requiring manual operator action to ensure adequate core cooling. Because there is no physical damage to the core cooling equipment in the RXB, the control rod drive system is undamaged and available to initiate a scram, either manually from the main control room or by manually tripping the reactor trip breakers. The design and location of the control rod drive system, as described in Section 4.6 is a key design feature for ensuring a scram can be initiated after impact if the reactor is not scrammed before impact.
NuScale US460 SDAA 19.5-6 Draft Revision 2