Electrical Power - STD-1128-98master0331

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

C.5.2 Electrical Power

Both normal and emergency power supplies should be available to a plutonium facility to

ensure that critical systems can continue to operate under both normal and accident

conditions.

C.5.2.1 Normal Power

A plutonium facility's normal electrical power needs should be met by two primary

feeders. The preferred primary feeder should provide basic service to the facility

and consist of a radial feeder connected directly to the main substation serving the

area. To minimize power outages, this feeder should be an express feeder and

should not have any other loads connected to it.

The alternate primary feeder should be in ready standby to provide backup power

to the preferred primary feeder power supply. In the event of a forced outage or

planned maintenance of the preferred primary feeder, the power load should

automatically transfer to the alternate feeder. The alternate primary feeder should

also be a radial feeder connected directly to a substation and should have no other

loads connected to it. To minimize simultaneous outages of the preferred and

alternate primary feeders due to lightning or other physical damage, the two feeders

should have maximum physical separation.

C.5.2.2 Emergency Power

The facility should be provided with a reliable, local source of emergency power if

both primary sources fail. The emergency power source should be completely

independent of the preferred and alternate primary feeders. The emergency power

should be generated onsite by turbines or diesel generators with automatic starting

and switch-over equipment. The emergency system should be physically separated

from the normal power systems, except at the automatic transfer switch, so that any

electrical or mechanical breakdown of the normal power system will not render the

emergency system inoperative.

The time lag between electrical power failure and the resumption of emergency

power should not exceed 20 seconds, and the emergency system should remain

energized for at least 5 minutes after the restoration of primary power to allow for

an orderly transition. The emergency power sources should have sufficient

capacity and sufficient fuel supplies stored onsite to maintain the integrity of all

critical building systems for approximately 48 hours. The amount of time that

emergency power is necessary should be determined by the requirements for

bringing the processes to safe shutdown condition. Chemical and thermal inertia

also should be considered. The emergency power system should be able to carry

identified critical loads such as air exhaust and supply systems, fire-detection and

fire-suppression systems, related instrumentation and control functions, necessary

criticality and radiation-monitoring instrumentation, certain processing equipment,

and any other essential building systems identified during safety analysis.

Sensitive safety equipment should be tested to verify that it will remain operable

during the switch-over and after enduring the electrical transient.

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