ML24346A336

LLC - Response to SDAA Audit Question Number A-19.2-33

ML24346A336
Person / Time
Site:	05200050
Issue date:	12/11/2024
From:	NuScale
To:	Office of Nuclear Reactor Regulation
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Download: ML24346A336 (1)

Text

Response to SDAA Audit Question Question Number: A-19.2-33 Receipt Date: 06/10/2024 Question:

SDAA FSAR Section 19.2.3.3.6, Containment Bypass, states that the probability of a steam generator tube failure (SGTF) is calculated using the tube failure/creep rupture model presented in NUREG-1570. This section further states that the nominal temperature and stress conditions that the tubes are exposed to are derived from a representative MELCOR severe accident simulation, but it does not describe the simulation nor justify why it is representative for calculating the probability of a SGTF.

NuScale is requested to:

1.

Summarize the MELCOR severe accident simulation referenced in SDAA FSAR Section 19.2.3.3.6 and justify why this simulation is representative for calculating the probability of a SGTF.

2.

Describe if the MELCOR severe accident simulation referenced in SDAA FSAR Section 19.2.3.3.6 is one of the six severe accident scenarios described in SDAA FSAR Section 19.2.3.2, Severe Accident Progression, and, if so, identify the designation of the scenario.

Response

1. The MELCOR severe accident simulation referenced in the US460 Standard Design Approval Application (SDAA) Final Safety Analysis Report Section 19.2.3.3.6, Containment Bypass, is

((2(a),(c) The US600 Design Certification Application assessment uses the same simulation for thermally induced steam generator tube failure (SGTF). As shown in ER-116288, Thermally Induced Steam Generator Tube Failure Probabilistic Risk Assessment, Revision 1, NuScale simulated a variety of chemical and volume control system loss-of-coolant accidents with core damage, NuScale Nonproprietary NuScale Nonproprietary

considering different emergency core cooling system failure modes, decay heat removal system availabilities, and MSIV failures, using the US460 MELCOR model. (( }}2(a),(c)

2. The representative MELCOR severe accident simulation referenced in SDAA Section 19.2.3.3.6 is not one of the six severe accident simulations described in SDAA Section 19.2.3.2, Severe Accident Progression, but is similar to ((

}}2(a),(c) No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}