General Recommendations

DOE-HDBK-6004-99

General Recommendations

For large DT fusion facilities the cryostat volume may be of order 10,000-30,000 m3. This volume

is a significant fraction of the internal volume of a fission reactor containment vessel and it may be

appropriate to design the fusion cryostat under the rules for metal containment structures rather than

designing it as a pressure vessel. Double bellows with a vacuum tight interspace are recommended.

CONFINEMENT

General

Confinement/HVAC systems include structures, systems, and components designed to serve as

barriers against the spread or uncontrolled release of radioactive or other hazardous materials

throughout the facility or to the environs.

The facility confinement strategy may consist of successive confinement barriers based on the hazards

present. The successive barriers are generally referred to as primary, secondary, tertiary, etc. and are

defined by the facility safety analysis. Primary confinement is often the function of the vacuum vessel,

cryostat, or system piping, but may be the function of ex-vessel structural barriers and process

enclosures such as gloveboxes, piping, tanks, and ductwork.

Secondary confinement consists of building structural elements and associated ventilation systems that

confine any potential release of hazardous materials from the primary confinement system. This

system includes the operating area boundary and the ventilation system and associated air cleaning

systems serving the operating area. Penetrations of the secondary confinement barrier are generally

provided with positive seals to prevent migration of contamination out of the secondary confinement

area.

Tertiary confinement consists of building elements and associated exhaust system of the process

facility. This is often the final barrier to release of hazardous material to the environment. Tertiary

confinement surrounds the secondary confinement with space which is controlled but not expected

to become contaminated.

Ventilation/HVAC

Ventilation systems should be designed to operate in conjunction with their associated physical

barriers to limit the release of radioactive or other hazardous material to the environment. The

ventilation system capabilities should be sufficient to allow for any intentional breaches of the

confinement system that are required during maintenance on any portion of the facility.

Leak-tightness of the confinement pressure boundary should be considered in the design. Air locks

to achieve the required leak-tightness between confinement/containment zone boundary interfaces

should be considered.

Appropriate filtration may be accomplished by multistage HEPA filtration of the exhaust or by an

equivalent filtering capability. The exhaust ventilation system must be sized to ensure adequate

inflow of air in the event of the largest credible breach of confinement.