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:
l should not reduce the suppression capability of the containment. 3.2 Debris Sources, Generation, and Transport 3.2.1 Licensees should assume the amount of particulates in the suppression pool before a LOCA is the maximum amount of corrosion products (i.e., sludge) expected to be generated since the last time the pool was cleaned. The size distribution and amount of particulates should be based on plant samples. The quantity and size distribution of suppression pool sludge has been analyzed for BWRs participating in the URG. 3.2.2 Licensees should not take credit for debris settling until LOCA-induced turbulence in the suppression pool has ceased. This should include the effect of the automatic depressurization system for small-break LOCAs. Sections C.1.3.4.6 and C.1.3.4.7 apply to the settlement of fine debris. 3.3 Chemical Reaction Effects 3.3.1 The post-LOCA containment conditions for BWRs may lead to different chemical interactions from those analyzed in WCAP-16530-NP-A and in other experimental and analytical studies of chemical interactions for operating PWRs. Therefore, the chemical effects for BWRs require additional evaluation. The BWROG described its evaluation of chemical effects in a letter dated November 20, 2017 (Ref. 22). The BWROG adopted a simplified approach for chemical effects related to the ECCS suction strainer, assuming negligible impact preceding the accumulation of a 1/8-inch-thick debris bed, but assuming NPSH failure if a debris bed over 1/8 inch thick forms. The NRC reviewed the BWROG letter and agreed that no further action was required, as documented in a letter dated June 29, 2018 (Ref. 23). The BWROG analysis included an evaluation of the potential for in-vessel effects. The NRC staff reviewed the BWROG work and determined that it reached acceptable conclusions. The NRC documented its findings in a staff technical evaluation issued in May 2018 (Ref. 24). DG-1385, Page 38 Figure 4 Debris blockage considerations for BWR LOCA sequences