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:
ch 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 designed for design earthquakes if they are not intended to perform as underdrains fully during or immediately following a severe earthquake, or if the system can be expected to perform an underdrain function in a degraded condition. Certain portions of such systems, however, may be required to regularly perform other safety functions (e.g., porous concrete base mats) and should be designed for severe earthquakes. Failure of a dewatering system could cause groundwater levels to rise above design levels, resulting in overloading concrete walls and mats not designed to withstand the resulting hydrostatic pressures. In addition to causing potential structural and equipment damage, groundwater could enter safety- related buildings and flood components necessary for plant safety. The basis for staff concerns over the use of such systems is whether they can be expected to perform their function, and prevent structural failures and interior flooding of safety-related structures. The degree of concern is directly related to the corresponding degree to which the safety of the struc- tures and systems rely on the integrity of the dewatering system, particularly with a dewatering system in a degraded situation. For example, if structures can accommodate hydrostatic loads that would result with a total failure of a dewatering system, our concerns have been primarily limited to the capability of such systems to perform their functions under relatively infrequent earth- quake situations. If, however, such systems must remain functional (e.g., keep water levels down), whether in a degraded situation or not to prevent structural failures and internal flooding under potentially frequent conditions, we have been very concerned with system reliability. Many applicants have indicated that