Document: NUREG-0800
Document ID: 48fb37ec-8e3e-4c2c-96c3-daa5e7da62f9
Document Type: srp
Title: of the applicant's SAR is reviewed to identify any missing data,
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340557.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.12
CFR Part: 
CFR Title: 

Content:
drains. 2.4.12-4 Rev. 2 - July 1981 The underdrains will consist of a series of interconnected flow channels spaced on 20-foot centers located under the foundation slabs. The exterior wall drains will consist of zoned filter materials around the walls, which will drain to a horizontal perforated pipe. located at mat level. Both the underdrains and the perforated pipe will discharge to a sump located inside the auxiliary building from which the water will be pumped to the plant storm drains system for gravity flow to an auxiliary holding pond onsite. The underdrain system of connected flow channels will be located at the top of rock or at the top of first level of fill concrete below each foundation slab. Each channel will run the full length of the building excavation but will be closed at each end so that no sediment can be transported into it from backfill, outside the walls. All channels in the grid system will drain by gravity through eight pipes to a 15-foot square sump located inside the auxiliary building. The exterior wall drains will be located around the exterior walls of the auxiliary and reactor building and will drain to the same sump as the underdrain system. No connection between the wall drains and the underdrain system will exist such that each drains to the sump through independent and separate conduits. The exterior wall drain system will consist of a zoned filter system which extends from 5 feet below yard grade to the bottom of the excavation. The continuous perforated pipe will extend around the perimeter of the building exterior walls at the bottom of the zoned wall filter. Twol120-gallon-per-minute seismic Category I pumps will maintain the water level automatically in the sump with each pump capable of handling the total computed flow of up to 35 gallons per minute per unit. We conclude that the system meets the requirements of General Design Criterion 5 in that those portions which are shared between reactor units have sufficient