t US. NUCLEAR REGULATORY COMMISSION amS.T.ANDARD REVIEW PLAN. OFFICE OF NUCLEAR REACTOR REGULATION 7.6 INTERLOCK SYSTEMS IMPORTANT TO SAFETY REVIEW RESPONSIBILITIES Primary- Instrumentation and'Control Systems Branch (ICSB) Secondary- None

The areas reviewed in this section of the applicant's safety analysis report (SAR) include those interlock systems important to safety which operate to reduce the probability of occurrence of specific events or to maintain safety systems in a state to assure their availability in an accident. These systems include interlock systems to prevent overpressurization of low pressure systems (e.g., RHR) when these systems are connected to high pressure systems (e.g., primary coolant), interlocks to prevent overpressure of the primary coolant system during low temperature operation of the reactor vessel, valve interlocks to assure the availability of ECCS accumulators, interlocks to isolate safety systems from non-safety systems (e.g., seismic and non-seismic portions of auxiliary support-ing systems), and interlocks to preclude inadvertent interties between redundant or diverse safety systems where such interties exist for the purposes of testing or maintenance. The ojectives of the review are to confirm that design considerations such as redundancy, independence, single failures, qualification, bypasses, status indi-cation, and'testing are consistent with the design bases of these systems and commensurate with the importance of the safety functions to be performed. The review performed for a construction permit application may be based on preliminary designs and the depth of information need only be sufficient to provide reasonable assurance that the final design will conform to the design bases and applicable criteria with an adequate margin for safety. The review performed for an operating license (OL) application is based upon detailed design information that confirms that the final design conforms to the design bases and applicable criteria. The depth of the review for an OL application should be sufficient to conclude that the requirements of the Commission regulations have been satisfied. The depth of the review for the balance of the criteria shoul