Document: NRC Regulatory Guide
Document ID: 6f0a99f2-d25a-44e3-b7f2-3286449a9752
Document Type: regulatory_guide
Title: Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident (Rev. 5)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2126/ML21266A185.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.82
CFR Part: 
CFR Title: 

Content:
. The debris size (e.g., fine, readily suspendable, small, large, or intact) should also be considered. The analyses should also consider the potential for further decomposition of the debris as it is transported to the ECCS strainers. 1.3.4.4 An acceptable analytical approach to predict debris transport resulting from fluid flows caused by long-term recirculation or pool fill is to use appropriately verified computational fluid dynamics (CFD) simulations in combination with experimental debris transport data. The CFD simulations can be used to predict fluid flows, while debris transport thresholds can be determined experimentally. Section 4.2.4 of NEI 04-07 and Section 4.2.4 and Appendix III in the associated SE provide guidance and an example of this approach. Alternative methods for debris transport analysis are also acceptable, provided that analytical techniques are adequately validated using experimental data to ensure that estimates are conservative with respect to the quantities and types of debris transported to the strainer. 1.3.4.5 The analysis may credit curbs for removing heavier debris that has been analytically or experimentally shown to travel by sliding or tumbling along the containment floor, and that cannot be lifted off the floor within the calculated water velocity range. Curbs around the ECCS strainers may reduce or prevent the transportation of some types of debris to floor- or pit-mounted strainers during the pool fill phase (see NUREG/CR-6772 for limitations). 1.3.4.6 If transported to the containment pool, all debris that would remain suspended because of turbulence (e.g., fine fibrous and particulates) should be considered to reach the ECCS strainers. If settlement of fine fibrous or particulate debris is credited during recirculation or pool fill, licensees should provide an adequate theoretical and experimental basis to demonstrate that such settling is prototypical of plant conditions. This settlement analysis should account for the