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:
rios. In some cases, more than one scenario will need to be modeled during a plant test program. This may be necessary if a plant has various debris types that are not uniformly distributed throughout containment and if the inclusion of all potential debris types results in unacceptable head loss. 1.3.12.4 Posttest evaluations are required to validate the head loss results, apply the results to the proposed strainer, and ensure that the debris penetrating the strainer cannot cause adverse effects to downstream equipment. Licensees wishing to scale the results of head loss tests conducted using colder water to the plant water temperatures should ensure that boreholes, bed degradation, open strainer area, and other phenomena that could affect the head loss response of the debris bed do not have a nonconservative effect when the head loss is scaled. The NRC does not recommend scaling of head loss results to alternate approach velocities or debris loadings, because the theoretical debris bed head loss behavior is not well understood and the results of experiments examining these parameters have varied. 1.3.12.5 Licensees may need to extrapolate the results of head loss testing for a time period matching the mission time of the ECCS. The method of extrapolation should conservatively fit the data (e.g., linear, log, quadratic) over the time period of interest. 1.3.12.6 Because it is difficult to model and scale multiple complex physical phenomena in a single test, licensees should conduct head loss tests in a manner that ensures complete transport of debris (as determined by transport analysis) to the test strainer. Agitation of the test fluid may be necessary to achieve conservative debris transport. The agitation should not disturb the debris bed. Licensees may conduct separate tests to credit reductions in debris transport to the strainer (i.e., settling) under conditions that are conservatively or prototypically scaled to the plant conditions. Head loss or debris