Primary Confinement Systems

DOE-HDBK-6004-99

The safety analysis should identify the confinement safety functions and the process conditions for

which the functions are required. The confinement systems should provide the required confinement

safety functions for normal operation, anticipated off-normal events and design basis accidents with

the assumption of a single failure in the system.

Primary Confinement Systems

All tritium systems should enclose tritium within a primary confinement that provides a low leak rate,

pressure-rated static barrier. Normally, primary confinement systems are sealed systems and are

opened only for maintenance, testing and inspection of confinement subsystems.

Electrical equipment necessary to provide the required confinement safety function should be safety-

class and should have a safety-class electrical power supply including a backup electrical power

supply (DOE 3003).

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

that exhaust to the 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 safety

analysis should prescribe limits for tritium releases to the environment. The exhaust from a

confinement subsystem may be through a dedicated tritium removal system or through a secondary

confinement subsystem which has an tritium removal system. The tritium removal systems should

have capacity to recover from a design basis tritium release from primary confinement.

10CFR50(I) provides specific methods and evaluation criteria that are acceptable in implementing

ALARA with respect to exhaust systems from a confinement system. DOE 6430.1A provides

additional guidance for design of confinement systems. RG 1.140 provides guidance for design,

testing and maintenance for exhaust system cleanup systems.

Secondary and Higher Order Confinement Barriers

A secondary confinement barrier should enclose the primary confinement system. Tritium systems

should also have tertiary or higher orders of confinement in accordance with requirements of the

safety analysis. Secondary and higher order confinement barriers should comply with the criteria of

this section.

Secondary confinement barriers should have a recirculating nitrogen or inert gas atmosphere. For

the purposes of this document, when the term "inert" is used in reference to the confinement

atmosphere, any combination of reduced oxygen environments is intended. Tertiary and higher orders

of confinement should have atmospheres as directed by the safety analysis.

Secondary and higher order confinement barriers should operate at subatmospheric pressure by

exhausting some of the atmosphere to the environment. The atmospheric exhaust should be through

an tritium removal system to limit the environmental release of tritium consistent with release limits

and ALARA principles. The safety analysis should prescribe limits for tritium releases to the

environment.

10CFR50(I) provides specific methods and evaluation criteria that are acceptable in implementing

ALARA with respect to exhaust systems from a confinement barrier. DOE 6430.1A provides