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:
year per reactor. The construction costs of alternatives to underdrains for structural purposes alone (exclusive of inleakage treatment) is estimated to range upward from $300K per unit and is highly dependent on site conditions. Structural alternatives to permanent underdrains include additional concrete and steel in the lower portions of buildings, and the use of anchor systems to resist floatation. Dewatering systems are generally composed of three components; the collector system, the drain system, and the discharge system. Water is first collected in collector drains adjacent to buildings or excavations. Interceptor drains or piping are then used to convey this water to a final discharge, system. The discharge system can be either gravity flow or a pumping system. Most underdrain structures, systems and components are buried alongside and under structures, although some systems employ pumping systems within larger structures (such as reactor or auxiliary buildings) to discharge collected water. Finally, permanent dewatering systems are not a required feature at any plant, but may be proposed as a cost-effective feature. 2.4.12-11 Rev. 2 - July 1981 Many permanent dewatering systems at nonnuclear facilities, such as dams and large buildings, have functioned over the years. However, the likelihood of a portion of such a system becoming ineffective and, therefore, not performing its intended function may well be considerably greater than the probability of occurrence of a nuclear power plant design basis event such as a probable maximum hurricane, probable maximum flood, or safe shutdown earthquake. Losses of function in the past have generally been attributable to piping of fines, inadequate capacity, or clogging. We have concluded that safety analyses of such systems should consider reliability and failures of features of the system itself, as well as potentially adverse effects of failures of nearby nonsafety- related features. Such systems need not be