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:
ction products in the containment post-LOCA environment can contribute to blockage of the ECCS strainers and increase the associated head loss. The final SE by the Office of Nuclear Reactor Regulation on WCAP-16530-NP-A, issued December 2007 (Ref. 36), and the NRC report entitled “NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Plant-Specific Chemical Effect Evaluations,” issued March 2008 (Ref. 48), provide a general approach to conducting plant-specific evaluations of chemical effects. 1.3.10.2 During a LOCA, materials in the ZOI can become debris that may be transported to the containment pool, where spray solution, spilled reactor coolant, and water from other sources accumulate. Subsequently, the combination of spray chemicals, insulation, corroding metals, and submerged and unsubmerged materials may lead to the formation of chemical substances that could impede the flow of water through the ECCS suction strainers or downstream components in the ECCS, CSS, or reactor coolant system. 1.3.10.3 New reactors with configurations different from those of operating PWRs (e.g., different containment materials and lack of buffering agents) may require additional evaluation. 1.3.11 Debris Accumulation, Head Loss, and Vortexing a. In a letter to NEI dated March 28, 2008 (Refs. 8 and 13), the NRC provided guidance for evaluating the potential for debris accumulation and its impact on strainer head loss following a LOCA. b. Testing and analyses performed to address GL 2004-02 indicate that the maximum head losses for the ECCS strainers in some plants can occur when a layer of fiber just thick enough to fully cover the strainer accumulates on the strainer along with a bounding quantity of fine particulate matter. This may produce a thin, dense debris bed with low porosity that maximizes head loss. The thickness of the fiber layer necessary to filter fine particulate has not been generally defined, because it depends on several factors,