Primary Confinement System

DOE-HDBK-1132-99

In general, primary confinement is the irradiated fissile material (IFM) cladding or

canning. Secondary confinement is established by the facility buildings that

enclose the dry storage area and/or the storage pool and auxiliary systems.

Primary Confinement System. The IFM cladding or cans, as appropriate,

provide primary confinement during normal and anticipated operational

occurrences. The IFM cladding or canning are used to provide a corrosion-

resistant confinement for the IFM material and to prevent an uncontrolled

release of radioactive material.

Secondary Confinement System. The facility building and ventilation system

make up the secondary confinement system.

Penetrations of the secondary confinement barrier should have positive seals to

prevent the migration of contamination. The use of positive seals should be

considered for penetration of enclosures within the facility building to provide

proper ventilation flow paths and to prevent the uncontrolled migration of

contamination.

Ventilation systems should include inlet air filtration (roughing filters) for the

main storage building to prevent dust accumulation, thus reducing the load on

other filters in the facility. Recirculated air in the main storage building should

be filtered through a HEPA filter to reduce the build-up of radioactive material in

the air. Areas with higher potential airborne radioactive contamination (e.g.,

pool water purification and waste treatment system areas) should use only

once-through airflow. Supply air to these facilities should be drawn from the

main storage building if such design is feasible. Exhaust air should be HEPA-

filtered prior to release.

Radioiodine adsorber units, such as activated charcoal or silver zeolite, should

be considered for installation in the exhaust ventilation system when radioiodine

releases are possible.

I-30