General Safety Design Criteria cont'd

DOE-HDBK-6004-99

primary barrier for tritium. Although primary confinement is sealed and leak tight, tritium is an

elusive molecule and small tritium leaks will occur inevitably. Secondary confinement, a system with

controlled outflow, collects the leaked tritium in a recirculating nitrogen (or inert) gas stream for

subsequent recovery of the tritium. Secondary confinement operates at a subatmospheric pressure,

by virtue of a small purge stream to the exhaust stack, and thus is unlikely to leak tritium to the

tertiary or higher order confinements.

Personnel may not enter primary confinement or secondary confinement zones during normal

operation. They may enter for maintenance activities, and only after tritium removal is complete for

the affected systems.

Personnel may routinely occupy the tertiary or higher order confinement zones without wearing

protective clothing and respiratory equipment. But personal protective equipment (PPE) is available

for rapid donning if the safety analysis reveals a credible event wherein tritium enters tertiary or a

higher order confinement zone.

The tritium facility' heating and ventilation system (H&V) promotes the confinement concept by

maintaining pressure differentials such that air flow is always towards zones with greater

contamination potential. In the above sketch, fresh air enters the quaternary zone then flows to the

tertiary zone from which it discharges to a stack.