Tritium Systems - std60030112

DOE-STD-6003-96

System Maintenance

Opening a confinement system such as the vacuum vessel requires prior removal of

tritium, radioactive dust, and loose toxic materials (if any) to the maximum extent feasible. If

required by the safety analysis, cleansing steps that exhaust to atmosphere should exhaust

through a tritium and particulate removal system to limit the release of tritium and other radioac-

tive and toxic materials to the environment consistent with release limits and ALARA principles.

The safety analysis should prescribe limits for tritium and other radioactive and toxic material

releases to the environment during vacuum vessel maintenance openings. The exhaust from

the vacuum vessel may be through a dedicated tritium removal system or through a secondary

confinement subsystem that has a tritium removal system. The tritium removal systems should

have capacity to recover from a design basis tritium release from the vacuum vessel.

6.2.1.2 Tritium Systems

Tritium systems include all process equipment outside the vacuum vessel with surfaces

routinely in contact with tritium and other hydrogen isotopes. Examples include tritium process-

ing and transfer systems, plasma fueling systems, blanket tritium transport and recovery sys-

tems, and the vacuum vessel pumping systems. Useful design guidance for tritium systems is

provided in IAEA 1981, IAEA 1991, and DOE 1994c.

Tritium system confinement strategies generally include primary and secondary confine-

ment. Sealed high-integrity piping and process equipment normally constitute the primary

confinement for vacuum and pressure conditions. The secondary confinement includes glove-

boxes and/or dedicated enclosures or rooms housing the primary confinement. Process piping

between gloveboxes or other secondary enclosures is generally surrounded by another pipe or

jacket sealing to the gloveboxes or secondary enclosures. Additional sealed cabinets or rooms

may extend the confinement in accordance with the facility safety analysis.

Tritium system design should include features that limit the quantities of tritium available

for release during off-normal events, limit the environmental release of tritium and exposure of

personnel during normal and off-normal conditions, and limit the unintended conversion of ele-

mental tritium to an oxide form. Consistent with facility safety analysis, design features may

include the following:

a. Segmentation

Tritium system design may provide for segmentation of the facility tritium inventory as

necessary to make acceptable the amount of tritium releasable in a single event. Design should

provide for isolation of each segment using valves or piping blanks. Where isolation valves are

employed, the failed position should be as specified in the facility safety analysis. Check valves

and other one-way valves are not acceptable as isolation devices.

Segmentation may be accomplished by utilization of processes or devices with small

inventory, separation of the tritium inventory into isolatable volumes, or storage of tritium in an

immobile condition relative to the single event (e.g., metal hydride beds).