Fusion Test Facilities

DOE-HDBK-1132-99

Other gases like argon and nitrogen may be used, but in most cases air is

more effective at decontaminating the surfaces. Ambient air entering the

purged volume contains several thousand parts per million of normal water

along with the nitrogen and oxygen. Some of the tritium and HTO on the

internal surfaces of the purged volume exchanges with the hydrogen and H 20

contained in the ambient air and is pumped out during the next purge cycle.

This evacuate/backfill cycle is repeated from 3 to 6 times to remove as much of

the tritium in the gases and from the surface of the volume as possible before

disconnecting the component. Three ambient air purge backfill cycles are

typical and in practice more than six purge backfill cycles have not proven to be

beneficial.

Designers should evaluate all maintenance operations in tritium facilities that

offer a potential for significant exposure; such facilities should, where practical,

be designed for remote repair or service. In those instances in which remote or

enclosed maintenance cannot be achieved, a compressed-air breathing air

system should be provided to support the use of supplied-air suits by

maintenance personnel. However, every effort should be made to allow

routine maintenance activities to be conducted without the need for supplied

breathing air. Systems should be designed, to the extent practical, to minimize

the conversion of elemental tritium to releasable tritium oxide, which poses a

greater radiological hazard than elemental tritium. Although shielding may not

be required to maintain occupational radiation exposures ALARA, shielding

may be required for other radionuclides that present a direct radiation hazard.

Shielding may be required in facilities that handle irradiated tritium production

assemblies. Area radiation monitoring should be provided as appropriate.

2.11

FUSION TEST FACILITIES.

Introduction . Fusion facilities include magnetic confinement and inertial

2.11.1

confinement fusion devices. Fusion devices range from experimental

machines intended to operate below the break-even point to experimental or

demonstration facilities intended to operate at or beyond the break-even point.

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