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:
tates based on simulated plant-specific post-LOCA environments. The memorandum “U.S. Nuclear Regulatory Commission Staff Review Guidance for In-Vessel Downstream Effects Supporting Review of Generic Letter 2004-02 Responses” (Ref. 9) provides updated guidance on chemical effects as they relate to fuel. DG-1385, Page 35 In its work on the in-vessel issue, the NRC staff determined that chemical effects timing was the most important factor related to effects on long-term core cooling. DG-1385, Page 36 Figure 3: PWR large-break LOCA accident progression in a large, dry containment (from NUREG/CR-6762, Figure 2-2) • Dynamic piping response • Reactor coolant system (RCS) blowdown as quasi-steady jet • Flow quality <0.05; increase with time • Impulse load on insulation • Peeled covers • Insulation destroyed • Pieces wetted • Pressurization • Recirculating vapor flows • Vapor flow velocity in excess of 100 ft/s • Water probably in suspension or on walls • Initiation on containment high pressure • Accumulator inject • Resuspension of concrete dust, etc. 10 • Two-phase jet • Flow quality >0.1 (increasing) • RCS pressure< 1,000 psia • Destruction under steady loads • Erosion of solid insulation • Concrete spallation and paint dust/chips • Cont. spray actuation. pressure > CS setpoint • Sodium hydroxide (NaOH) additive for iodine, high pH • Pressure and temp reach peak values • Fully mixed conditions • Debris break up • HPSI inject • RPV pressure > LPSI shutoff head End Blowdown • ECCS injection from refueling water storage tank (RWST) commences • Termination of debris generation by jet impingement • Washdown of insulation • Start of sedimentation • Flooded reactor (R-X) core • Design injection flow • Turbulent pool dynamics, gradually decreasing turbulent intensity • Increasing height • Depressurization and cooldown of cont. • Vapor flow velocity btwn compartments minimal • Sprays form a thin