Cooling Systems - Continued

DOE-STD-6003-96

without human intervention for the period specified in the safety analysis and for as

long a period as practical following shutdown of the fusion device.

h. Unavailability of the on-site electrical power supply or the off-site power supply should

be a consideration in ensuring safety-class cooling system functions, assuming a sin-

gle failure within the cooling system. Coincident failure of off-site and on-site power

systems should not be a design consideration.

Cooling system design should consider the thermal, hydraulic, and mechanical effects

of unintended operation of active components, such as valves and pump motors.

Cooling system design should consider the thermal, hydraulic, and contamination

effects of cross leaks between adjacent systems, such as the primary and secondary

sides of a heat exchanger.

k. Materials properties for cooling systems should include the effects of radiation embrit-

tlement at all levels of service temperatures.

Coolant system pumping should provide for coolant flow coastdown to prevent

exceeding design limits.

m. Discharge of coolant for pressure relief should be to a confinement tank that maintains

the confinement function of the coolant system.

n. The coolant system should include protection for overpressure to prevent degradation

of safety function.

o. The coolant system should include provisions for sampling to analyze coolant proper-

ties and to identify entrained radioactivity or other contaminants.

p. Use of a primary cooling system and a secondary cooling system is the recommended

design for containment of radioactivity where required by the safety analysis. Closed

heat exchangers are the recommended coupling between primary and secondary

cooling systems.

q. Multiple cooling loops are recommended for consideration as a design feature to

reduce the operational thermal-hydraulic transient associated with single-loop failure.

Components and headers of systems should be designed to provide individual isola-

tion capabilities to ensure system function, control system leakage, and allow system

maintenance.

s. The use of leak-before-break may be considered in the analysis of pipe break and

pipe whip events. The methodology described in Section 3.6 of the Standard Review

Plan, NUREG-0800 is recommended.

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