Confinement - std60030113

DOE-STD-6003-96

b. Confinement

Tritium confinement generally includes a primary confinement subsystem and a sec-

ondary confinement subsystem. Design may also provide higher orders of confinement if the

safety analysis indicates these are necessary to reduce tritium exposure and environmental

release to acceptable levels. The confinement subsystems include the SSCs necessary to

establish the confinement barriers and the power sources necessary to maintain the barrier

operation within prescribed safety limits.

The primary confinement should provide a low leak rate, pressure-rated static barrier.

Normally, primary confinement systems are sealed and are opened only for maintenance, test-

ing, and inspection. Welded joints are preferable to compression fittings, which are preferable to

threaded fittings. Welded joints or mechanical joints are acceptable for piping enclosed in sec-

ondary confinement gloveboxes or enclosures. However, only welded joints should be used for

piping outside gloveboxes or enclosures. Pumps should comply with National Electric Code

requirements for explosion-proof installation if required by safety analysis and should generally

not use organics, hydrocarbons, or other volatiles for surfaces that will contact the tritium pro-

cess gas. Valves should meet prescribed leak requirements across the valve seat and from the

valve bonnet and body.

Secondary confinement barriers should have a recirculating nitrogen or inert gas atmo-

sphere. The term "inert" represents any reduced oxygen environment. Tertiary and higher

orders of confinement should have atmospheres as specified by the safety analysis. Secondary

and higher order confinement barriers should operate at subatmospheric pressure maintained

by a pressure control system. If required by safety analysis, the confinement exhaust should be

through a tritium removal system to limit the environmental release of tritium consistent with

release limits and ALARA principles. The safety analysis will prescribe limits for tritium releases

to the environment.

Opening a confinement subsystem requires prior removal of tritium and cleansing. If

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

a tritium removal system to limit the release of tritium to the environment consistent with release

limits and ALARA principles. The exhaust from a confinement subsystem may be through a

dedicated tritium removal system or through a secondary confinement subsystem that has a tri-

tium removal system. The tritium removal systems should have capacity to recover from a

design-basis tritium release from primary confinement.

c. Instrument and Control Systems

Design should provide for I&C to monitor parameters important to safety and to indicate a

need to isolate or otherwise control a tritium system or tritium confinement subsystem to prevent

monitored variables exceeding a safety limit. The safety analysis should identify and the design

should implement monitoring of the safety-related variables. Primary confinement typically

includes instrumentation for pressure, vacuum, and temperature monitoring, and for qualitative

gas analysis. Secondary confinement typically provides instrumentation for relative pressure

monitoring, tritium detection, and oxygen concentration analysis (if the secondary has an inert