ANS 56.3-1977 (R1987)

This standard covers the interaction of those low pressure systems with the high pressure portions of the reactor coolant pressure boundary (RCPB) which, if assumed over pressurized by the reactor coolant, could result in failure of the low pressure system and: (1) The prevention of an orderly reactor shutdown, or (2) The inability to maintain a safe shutdown condition assuming makeup is provided by normal makeup systems only, or (3) The release of radioactive material at the site boundary exceeding 0.5 rem to the whole body or its equivalent to any part of the body. This standard covers design and testing requirements for equipment, controls and instrumentation necessary for overpressure protection of such low pressure systems. This standard does not cover high pressure systems [i.e., feedwater system on Boiling Water reactors (BWR's), charging system on Pressurized Water Reactors (PWR's), or instrument lines] nor relief valves and their associated discharge piping connected to the reactor coolant pressure boundary. This standard also does not override nor replace any other standard or code (i.e., containment isolation, residual heat removal system, safety injection, ASME Boiler and Pressure Vessel, [1] etc.), but shall be used in conjunction with these standards or codes since other system requirements must be considered in addition to the overpressure protection function.