Document: NUREG-0800
Document ID: 2781386f-8b2c-401b-814a-d98c9381a202
Document Type: srp
Title: STRUCTURES, SYSTEMS, AND COMPONENTS TO BE PROTECTED FROM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070307.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.5.2
CFR Part: 
CFR Title: 

Content:
timate heat sink constitutes the source of water supply necessary to safely operate, shutdown and cool down a nuclear plant. Because the ultimate heat sink is important to safety, its SSC important to safety should be identified and their safety functions should be ensured. Protecting the ultimate heat sink SSC that are important to safety from externally generated missiles ensures that the system can perform its safety function of providing a heat sink. Identifying and protecting SSC important to safety from externally generated missiles ensures the safety function of those SSC, such as; ensuring the integrity of the spent fuel pool and thereby mitigating the potential release of fission products, and ensuring the capability of the ultimate heat sink to provide a heat sink and maintain the plant in a safe condition. 2. GDC 4 establishes requirements regarding the ability of SSC important to safety to be protected from dynamic effects, including the effects of missiles from events and conditions outside the nuclear unit. Dynamic events originating outside the nuclear unit have the potential for generating missiles, therefore, this criterion applies directly to the assessment of SSC important to safety that may be effected. Regulatory Guide 1.115 describes methods acceptable to the NRC staff for identification and protection of SSC important to safety from the effects of missiles resulting from turbine failure. Cumulative failure data for conventional plants indicate that the protection of SSC important to safety from the effects of missiles is an appropriate safety consideration. Regulatory Guide 1.117 describes a method acceptable to the NRC staff for determining which SSC should be protected from external missiles generated by tornados. The selection of SSC to be protected is based upon not allowing offsite exposures to exceed an appropriate fraction of the offsite dose guidelines of 10 CFR Part 100. Basing the limits upon an appropriate fraction ensures