ML24215A009
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Response to SDAA Audit Question Question Number: A-3.4.1-1 Receipt Date: 12/18/2023 Question:
SDAA Section 3.4.1.1 indicates, The pipe size, schedule, location, and maximum operating conditions for each potential source are documented. but its not clear where parameters are documented. SRP 3.4.1 evaluation criteria are to ensure applicant has provided sufficient information to identify all possible sources of internal flooding. Previous certified NuScale FSAR contained a table defining flooding sources, however the staff is unable to locate the similar documented parameters and operating conditions within the SDAA.
a.
Provide location of documented parameters used to define potential sources of flooding.
b.
Provide documented parameters for limiting sources included in Table 3.4-1 c.
Provide list to identify all possible sources evaluated for internal flooding.
Response
A. Piping that could potentially rupture and be a flooding source in the Reactor Building (RXB) and Control Building (CRB) is identified by review of Plant Design Information System (PDIS), P&IDs, and the piping overlay drawings. The pipe size, schedule, location, and maximum operating conditions for each potential source are considered. Additional information is provided in Part C of this response.
B. While drains are not credited with lowering flood levels, each flood zone is analyzed for the potential for backflow through drains. If the potential backflow does not result in a maximum flood height for the zone, a disposition with the reasoning below is given. These are the limiting sources included in Table 3.4-1 when they result in the highest steady state flood level of possible sources within the flood zone.
Limiting Source - If the flood zone already contains the limiting source (8 fire protection line break), then the flood height from potential backflow through the drains does not exceed the calculated flood height from the circumferential break.
NuScale Nonproprietary NuScale Nonproprietary
Limiting Source by Elevation - If the flood zone contains the largest source at the given elevation or any higher elevations, then the potential drain backflow volume does not exceed the flood volume already analyzed for a pipe rupture.
Limiting Source via Stairwell or Floor Openings - Flow propagation from stairwells and other floor openings is considered by determining if any flood sources from higher elevations could exceed the limiting flood source at lower elevations.This flood height bounds any flood height calculated for potential backflow through drains.
Drains not Connected to Other Flood Zone - These flood zones have drains, but the drains are not connected to the drains of another flood zone.
C.
Identification of piping that could potentially rupture and be a flooding source in the RXB and CRB were established by reviewing the P&ID drawings and considering the pipe size, schedule, location, and maximum operating conditions for each potential source. During the determination of flooding sources within the RXB and CRB, all applicable systems within the buildings are considered and evaluated.
Fire protection system, fire suppression, site cooling water, demineralized water system, utility water system, main steam system, condensate and feedwater system, pool cooling and cleanup systems, chemical and volume control system, module heatup system, boron addition system, chilled water, reactor component cooling water system, and liquid radioactive waste management system were determined to be internal flooding sources within specific source flood zones.
Containment evacuation, containment flooding and drain system, gaseous radioactive waste management system, instrument and control air system, nitrogen distribution system, pool leakage detection systems, process sampling system, radioactive waste drain system, reactor building HVAC, service air system, solid radioactive waste management system, and ultimate heat sink makeup line were evaluated and determined to not be a viable flood source due to:
Infrequent use - these systems are used infrequently and would contain little to no fluid during normal plant operation
Not liquid - systems containing gasses or solids that do not contribute to flooding
Pipe size - systems with no piping over 1 inch in diameter are not considered flooding sources
Small tank size - tanks less than 100 gallons in volume are not considered viable flooding sources due to a total volume having negligible flood effects NuScale Nonproprietary NuScale Nonproprietary
No changes to the SDAA are necessary.
NuScale Nonproprietary NuScale Nonproprietary