Containment Systems

DOE-HDBK-6004-99

Containment Systems

For containment systems, RG 1.140 presents guidance for design testing and maintenance for exhaust

systems air filtration that is acceptable to the DOE. As with the confinement systems the basic

criteria are based on the As Low As Reasonably Achievable (ALARA)As Low As Reasonably

Achievable (ALARA) concept given the present state of technology. 10CFR50(I) presents specific

methods and evaluation criteria that are acceptable to DOE in implementing ALARA with respect

to exhaust systems from a containment system.

Inspection

Components should be designed to permit periodic inspection and testing of important areas related

to the intended safety function to assess their structural and leak tight integrity. There should be an

appropriate material surveillance program.

RECOMMENDED DESIGN PRACTICE

Windows

In the analysis of the windows, the condition of the edge restraint is important. It is recommended

that it be assumed that the window is simply supported at the edges, since this is a more conservative

approach (Robinson). However, the weak point in the window may be the edge glass-to-metal braze.

The braze must be analyzed for stress with the fixed-edge assumption. All calculations should be

based on the modulus of rupture which is equal to the ultimate tensile strength/1.75. Factors of safety

lose meaning for glass, because subsurface imperfections can cause failure below the expected tensile

strength. Therefore, a factor of safety of 10 on the modulus of rupture is recommended. Windows

should be designed to minimize the risk of cracking due to a water leak onto the hot disc. This can

be accomplished by providing an inner sacrificial disc with the main sealed disc on the outside. The

connecting inner space is vented to the vacuum by a small hole. This hole would allow vacuum pump

down but would prevent a water leak from reaching the outer window. (Caldwell 89)

Bellows

Double bellows with a vacuum-tight inner space are recommended. See the Standards of the

Expansion Joint Manufacturers Association, 6th Edition, 1885.

Ceramic Breaks

Ceramic breaks are used to insulate electrical lines that penetrate the vacuum boundary or to insulate

attached piping that is connected to external equipment at a different potential or ground. Where

possible, ceramic breaks should be designed to be shielded from direct line-of-sight with the plasma

or potential spray from rupture of coolant lines.

Ceramic breaks are used on radio frequency (RF) antennas to isolate inner and outer coaxial

conductors at the vacuum boundary. The volume outside of the vacuum boundary contains a

pressurized gas. These RF ceramic breaks are subject to voltage breakdown which could cause local