ANSI/ANS-56.2-2026

Containment Isolation Provisions for Fluid Systems After a LOCA

This standard specifies minimum design, actuation, testing, and maintenance requirements for the containment isolation of fluid systems after a loss-of-coolant accident (LOCA). These fluid systems penetrate the primary containment of light water reactors (LWRs) and include piping systems (including instrumentation and control) for all fluids entering or leaving the containment. The provisions for containment isolation impose additional requirements which are not required for the fluid system function. This standard does not consider any isolation requirements that could exist for controlled leakage areas either enclosing the primary containment or contiguous to the primary containment. Also, this standard does not address containment isolation requirements for events other than LOCAs. This standard presents requirements and conditions that are needed for the isolation of the containment and covers requirements for isolation barriers, their actuation, their operators, and connecting piping between isolation barriers. This standard does not cover penetration assemblies, protection systems, power supplies, and equipment qualification. The design requirements in this standard consider (1) the system isolation and actuation function, (2) isolation function testing, (3) leakage rate monitoring and testing, and (4) maintenance. This standard gives general requirements or refers to other standards, codes, and regulations for the following requirements: fire protection; protection against natural phenomena such as earthquake, tornado, or flood; environmental conditions such as normal operation, maintenance, testing, and postulated accidents (including the dynamic effects from missiles, pipe whip, and discharging fluids); and separation criteria.