"A key assumption of the PRA is the availability of the UHS to provide an adequate heat sink. To support passive heat removal with the DHRS or ECCS, the reactor modules are housed and partially submerged in the UHS such that most of the outer surface of the CNV directly contacts the UHS, which is a large pool of water in the reactor building (RXB). "
DHRC is decay heat. CNV is reactor containment vessel. So drain the pool and the reactor is in trouble.
https://www.nrc.gov/reactors/new-reactors/smr/nuscale.html
Here is an interesting sub-report:
https://www.nrc.gov/docs/ML2022/ML20224A525.pdf
Information withheld for security reasons. One item concerns the "ultimate heat sink". What happens when the ultimate heat sink is lost?
Well a design assumption is that it is not lost:
https://www.nrc.gov/docs/ML2020/ML20205L410.pdf
"A key assumption of the PRA is the availability of the UHS to provide an adequate heat sink. To support passive heat removal with the DHRS or ECCS, the reactor modules are housed and partially submerged in the UHS such that most of the outer surface of the CNV directly contacts the UHS, which is a large pool of water in the reactor building (RXB). "
DHRC is decay heat. CNV is reactor containment vessel. So drain the pool and the reactor is in trouble.