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:
yses to refine ZOIs for some materials are documented in WCAP-17561-P, Revision 0, “Testing and Analysis to Reduce Debris Generation Zones of Influence for GSl-191,” issued May 2012 (Ref. 41), and FAI/12-058, Revision 0, “A Methodology to Calculate the Zones of Influence of Different Insulation Materials for a Flashing and Freely Expanding Two-Phase Critical Flow Jet,” issued April 2012 (Ref. 42). e. The shape of the ZOI should be consistent with the break configuration and accepted jet models. For typical evaluations, the ZOI shapes are simplified to allow reasonable estimates of debris generation at each break location. f. If the evaluation uses simplified ZOI models, such as the spherical ZOI models discussed in Section 3.2.1 of the URG and Section 3.4.2 of NEI 04-07, licensees should apply sufficient conservatism to account for simplifications and uncertainties in the model. For example, a spherical ZOI model assumes that the blowdown from a LOCA is evenly distributed in all directions radiating from the break location. Although, with sufficiently conservative inputs, a spherical model may be appropriate for estimating the loadings of debris within a ZOI, such a model does not account for nonuniform blowdown that could create damage in a particular direction at much greater distances from the break. Therefore, a spherical model may be nonconservative when specifying a ZOI for particularly problematic materials (e.g., calcium silicate insulation for a PWR with a trisodium phosphate buffer, or fibrous debris for a plant with a limited strainer area where the licensee intends to demonstrate that a fibrous debris bed cannot be formed). 1.3.3.2 Analysis can demonstrate that certain types of material used in small quantities inside the containment contribute only marginally to the debris loading for the ECCS sump. If debris generation and debris transport data have not been determined experimentally for a specific material, the material may be grouped with