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:
selecting break locations, because limiting conditions for ECCS strainer performance are not related to the pipe vulnerability issues addressed in BTP 3-4. 1.3.2.6 Licensees should consider locations that result in unique debris source terms (i.e., not multiple, identical locations). Particular consideration should be given to breaks that result in the destruction of materials known to cause high head loss, such as microporous insulation (e.g., calcium silicate, Min-K, and Microtherm). 1.3.2.7 If the LOCA blowdown does not generate a significant amount of fibrous debris, the contribution of latent debris sources may become the limiting factor in ECCS strainer and downstream evaluations. 1.3.2.8 If long-term cooling requires recirculation flow through the ECCS strainer for non-LOCA HELBs (e.g., main steam and feedwater line breaks), then licensees should use the same selection criteria for break locations on that piping as those specified for a LOCA. 1.3.3 Debris Generation/Zone of Influence The energy associated with jet impingement can generate debris from the blowdown of a ruptured pipe. The jet can damage insulation, coatings, fire barriers, shielding blankets, and other materials located close to the break. The distance from the break within which a material may be damaged depends on the robustness of the material. The material-specific volume of space affected by the jet, or ZOI, is modeled to define and characterize the debris generated. 1.3.3.1 Zone of Influence Model a. The size of the ZOI should be consistent with experiments performed for specific debris sources (e.g., insulation, coatings, and fire barrier materials). The ZOI should extend until the jet pressures decrease below the experimentally determined damage pressures appropriate for the debris sources. b. Licensees should use the volume of material contained within the ZOI to estimate the amount of debris generated by a postulated break. The size distribution of debris created in the ZOI should be