Vacuum Pumps

DOE-STD-6003-96

B.4.8.4 Vacuum Pumps

Fusion devices employ large vacuum pumps. Turbomolecular pumps generally have

high-speed rotors that pose mechanical safety concerns. Vacuum reservoirs can be dangerous

unless guarded to prevent personnel from being drawn against a leak location. Cryopumps have

the additional concern of large gas inventories that may expand when the pumps are allowed to

come to ambient temperature, causing pressurization and possible tritium contamination

problems.

B.4.8.5 Wall Conditioning and Bakeout Systems

Wall conditioning of in-vessel components is performed by a variety of techniques (e.g.,

glow discharge cleaning, bakeout, and diborane deposition) to remove impurities from surfaces.

In addition, external systems containing tritium may undergo bakeout and/or cleaning to reduce

tritium inventories in the material. Accidents under these conditions need to be considered in

addition to accidents during operation.

B.4.8.6 Energy Storage

Because of their pulsed operation, some fusion systems may use energy storage devices

(e.g., alternating rotor and flywheel) in the power plant; the failure of these devices could pose a

hazard not usually found in other power-conversion systems.

B.4.9 Maintenance Events

Activation of structures by fusion neutrons will require much of the maintenance of facili-

ties such as ITER to be done remotely. While this may reduce direct exposure of personnel to

radiation, the probability of accidentally breaking something is significantly increased. There will

be hazards of fluid conduit rupture, activated dust dispersion, and similar kinds of events asso-

ciated with remote maintenance. Also, for items removed to hot cells for maintenance or other

activities, normal hazards associated with hot-cell facilities should be considered.

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