ML24346A282
| ML24346A282 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 12/11/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24346A130 | List:
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| References | |
| LO-175762 | |
| Download: ML24346A282 (1) | |
Text
Response to SDAA Audit Question Question Number: A-15.4.1-2 Receipt Date: 04/29/2024 Question:
FSAR Sections 15.4.1, 15.4.2, and 15.4.3 do not include discussion evaluating loss of power scenarios. A description of these evaluations was provided for the DCA. Provide FSAR markup with these evaluations.
Response
In the Final Safety Analysis Report (FSAR) for the Design Certification Application (DCA) of the US600 design, discussion of loss of power scenarios was provided in the event-specific sections, including FSAR Sections 15.4.1, 15.4.2, and 15.4.3 as identified in the audit question.
However, the information was repetitive. Therefore, in the FSAR for the Standard Design Approval Application (SDAA) of the US460 design, discussion of loss of power scenarios is consolidated and provided in FSAR Section 15.0.0.6.5. Individual subsections are provided addressing normal alternating current (AC) power (FSAR Section 15.0.0.6.5.1), normal direct current (DC) power (FSAR Section 15.0.0.6.5.2), and augmented DC power (FSAR Section 15.0.0.6.5.3).
Regarding normal AC power, FSAR Section 15.0.0.6.5.1 states: Unless the event states otherwise, the limiting case is for normal AC power available. The limiting analyses in FSAR Sections 15.4.1, 15.4.2, and 15.4.3 assume normal AC power is available. The reason why is that AC power is required for the initiating event to occur (i.e., the assumed rod withdrawals that increase reactivity do not occur if AC power is lost). Therefore, consistent with the quoted statement, no specific mention or evaluation of AC power is required in FSAR Sections 15.4.1, 15.4.2, and 15.4.3.
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Regarding normal DC power (EDNS), FSAR Section 15.0.0.6.5.2 states: For the Chapter 15 analyses that do not credit immediate control rod drop or [module protection system (MPS)]
actuations based directly on loss of normal AC power, loss of EDNS is equivalent to a loss of normal AC power. Therefore, the loss of normal AC power assessment for the event addresses potential loss of EDNS and separate assessment of the loss of EDNS is not performed. The analysis in FSAR Sections 15.4.1, 15.4.2, and 15.4.3 do not credit immediate control rod drop or MPS actuations based directly on loss of normal AC power. Therefore, consistent with the quoted statement, no specific mention or evaluation of EDNS is required in FSAR Sections 15.4.1, 15.4.2, and 15.4.3.
Regarding augmented DC power (EDAS), FSAR Section 15.0.0.6.5.3 states: Based on the conclusion of this generic assessment, further evaluation of a loss of EDAS power is not provided in the Chapter 15 section of these non-LOCA DBEs. Therefore, consistent with the quoted statement, no specific mention or evaluation of EDAS is required in FSAR Sections 15.4.1, 15.4.2, and 15.4.3.
In conclusion, evaluations of loss of power scenarios are provided in FSAR Section 15.0.0.6.5 and are applicable to FSAR Sections 15.4.1, 15.4.2, and 15.4.3.
No changes to the SDAA are necessary.
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