Document: NUREG-0800
Document ID: 9c20ec9e-fd1b-4e50-a8af-e8785949754b
Document Type: srp
Title: PHYSICAL SECURITY — REVIEW OF PHYSICAL SECURITY SYSTEM DESIGNS –
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1414/ML14140A210.pdf
Revision Date: 2023-06
Chapter: 13
Section ID: 13.6.2
CFR Part: 
CFR Title: 

Content:
d the specifications of the DBT characteristics that are protected. F. Defense-in-Depth Designs of Physical Security Systems: The designs of physical security systems should address systems diversity, independence, and separation, for defense-in-depth to achieve a high assurance of intended security functions and must meet all specific prescriptive design criteria set forth in 10 CFR 73.55. Defense-in-depth is an element of the NRC’s philosophy that is used to address uncertainty by using successive measures, including safety margin, to prevent and mitigate damage if a malfunction, accident, or natural caused event occurs at a nuclear facility. Defense-in-depth philosophy applies to measures against intentional acts as required by 10 CFR 73.55(b). The most common defense-in-depth measures apply concepts of redundancy, diversity, independences, and safety margin to enhance systems reliability. Defense-in- depth is achieved by providing multiple layers of protection, systems, and/or barriers to avoid or provide the capability to tolerate failures that would prevent the accomplishment of a function (i.e., provide reasonable or high assurance that activities involving SNM are not inimical to the common defense and security and do not constitute an unreasonable risk to the public health and safety). Redundancy is to achieve system reliability through the use of independent means of accomplishing needed function (i.e., ensuring no single failure results in loss of the intended function). Diversity and separation provide protection against dependent (common cause) failures of multiple means of accomplishing needed functions. Diversity is achieved by using different technologies, equipment, manufacturers, control logic, signals, and functions to provide a diverse way of accomplishing the intended security function. Independence is attained by physical separation and physical barriers, including electrical or motor force independence. The NRC’s philosophy applies to the