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Section 4.5.14, Auxiliary systems

The application should describe the auxiliary systems, including their design basis requirements. It should also describe any other auxiliary system whose operation may influence safety, but has not been covered elsewhere in the application (for example, communication and lighting systems).

Those systems that support SSCs important to safety or safety functions should meet the expectations of the safety support system.

Water systems

As applicable to the proposed reactor facility, the applicant should provide information concerning the water systems associated with the reactor facility, including the station service water systems, the cooling system for reactor auxiliaries, the makeup system for demineralized water, the condenser cooling water system, the fire protection water supply systems, the ultimate heat sink, and the condensate storage facilities.

The application should describe the safety significance and reliability requirements of each of the water systems, taking into account any claims made in the safety case for their availability to provide cooling.

Heat transfer to an ultimate heat sink

The application should describe the systems for transferring residual heat from SSCs important to safety to an ultimate heat sink. This overall function should be subject to very high levels of reliability during operational states, DBAs and DECs.

Process auxiliaries

The application should describe the auxiliary systems associated with the reactor process system, including but not limited to the following:

·       compressed-air systems

·       process and post-accident sampling systems

·       equipment drainage and floor drainage systems

·       chemical control systems and volume control systems

·       purification system

The application should also define the guaranteed shutdown state (GSS) that will support safe maintenance activities of the reactor facility. If soluble poisons are used to provide a GSS, the application should be in accordance with section 7.11 of REGDOC‑2.5.2, Design of Reactor Facilities: Nuclear Power Plants [9].

Heating, ventilation and air conditioning systems

The application should describe the reactor facility’s heating, ventilation, and air conditioning (HVAC) systems. The description should include areas such as control facilities, the spent fuel pool area, the auxiliary and radioactive waste area, the turbine building (in boiling water reactors), and the ventilation systems for safety systems.

The safety significance of any HVAC system credited in the reactor facility safety analysis should be clearly stated, including all common safety-related functionality dependencies such as the air-conditioning system for an equipment room that may contain multiple divisions or groupings of support systems.

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