Section I Vacuum Vessel

DOE-HDBK-6004-99

SECTION I

VACUUM VESSEL

Many of the components within and part of the vacuum vessel vacuum are unique to fusion systems.

Thus, there is little precedence in the established codes and standards and little experience in the

design of those components. Much of the design experience is taken from the design of plasma

experiments where the power levels and radiation fluxes are much lower.

The vacuum vessel is assumed to be a torus-shaped container usually made of a metal or metallic

alloy, and its volume can be several times the plasma volume. It can be thin-walled or thick-walled.

It may be double-walled with coolant passages between the walls. The perimeter of the vacuum

vessel is outfitted with a number of ports for mounting hardware for plasma fueling and heating,

plasma conditioning and for vacuum pumping. These ports can vary in size and shape and are usually

located above, below, and on the horizontal plane as well as on top and bottom of the vacuum vessel.

It may be of all-welded, continuous construction or use bolts between toroidal segments with vacuum

seal welds at the joint.

GENERAL SAFETY DESIGN CRITERION

If required by the facility safety analysis, the vacuum vessel will be a confinement or containment

barrier for tritium and tritiated compounds, radioactive impurities and activated dust. The

requirement for robustness of the barrier will be defined in the safety analysis and implemented in the

design. In performing this function, the vacuum vessel will be classified as a safety-class system. If

the vacuum vessel is not considered a confinement or containment barrier in the safety analysis, those

vacuum vessel components whose single failure results in loss of capability of another safety-class

system to perform its safety function should be designated as safety-class components. The vacuum

vessel may also be a physical barrier between different fluid streams (such as liquid metal and water)

whose interconnection could potentially produce large energy release events which could compromise

nearby safety-class systems.

POTENTIAL SYSTEM SAFETY FUNCTIONS

If the safety analysis requires that the vacuum vessel be a confinement or containment barrier, the

following safety functions are specified:

1. Normal operation including anticipated operational likely and unlikely events - to act as the first

barrier for tritium and tritiated compounds, radioactive impurities and activated dust.

2. Maintenance

a) To act as the first barrier for tritium and tritiated compounds, radioactive impurities and

activated dust during maintenance external to vacuum vessel.

b) To act as a partial confinement barrier as defined in the safety analysis for tritium and

tritiated compounds, radioactive impurities and activated dust during maintenance inside the

vacuum vessel.