Valve Container Operations

DOE-HDBK-1129-99

01, "Guidelines for Valves in Tritium Service," and users should be prepared for potential leaks

across the valve seat in addition to bellows leaks.

Modifications to existing designs could be incorporated into future revisions. In addition to valve

overtorque protection and/or hardware upgrades, the HTV use of thin-walled SS 348 may lead to

more than desired outgassing as the number of cycles accumulates. The upgrading of material or

jacketed design are potential options. Other design improvements could include internal baffling

and different (types, sizes, and locations) filters. An operational practice of tracking and

segregating containers that are used for high-purity shipments and those used for other shipments

(e.g., scrap shipments) would be beneficial in ensuring the capability to ship War Reserve gas by

not contaminating the U bed with mixed isotopes.

6.3 Valve Container Operations

The use of two valves in series on containers filled with tritium that are to be disconnected from the

tritium apparatus on a routine basis has been in common use for several years. When the failure

of a single valve seat can result in the release of significant quantities of tritium, two valves in

series should be used. If the seat of a single valve develops a leak during storage and the

container port is uncapped, the tritium will be released into the containment system through the

failed valve seat.

Valve seat failure is often associated with damage to the seat caused by long exposure to tritium

or by misalignment resulting from improper operation or maintenance practices. Double valves are

recommended in all cases where the container valve seat is exposed to tritium for long periods of

time or is susceptible to misalignments. Additional guidance for tritium valve selection, operation

and maintenance is contained in the Office of Nuclear and Facility Safety's Technical Notice 94-01.

This document describes desirable features and material for various tritium applications and lists

recommended practices.

It is assumed by experienced tritium handlers that valve seats can fail, and, therefore, the basic

strategy in double-valve use is depicted in Figure 6-1 and described as follows:

The container is connected, leak tested, and filled with the required quantity of tritium, and the

second container valve is closed.

The tritium between the second valve and the tritium supply is pumped away, and the section

is isolated and monitored for pressure rise.

If a pressure rise indicates that the second valve seat is leaking, then the container is emptied

while connected to the manifold, and the valve seat is repaired.

If no leak is detected, then the first valve is closed and the second valve is opened, and the

tritium trapped between the first valve and the second valve is pumped away. This section is

isolated and monitored for a pressure rise.

If this test indicates that the first valve seat is leaking, the container is emptied, and the valve

seat is repaired.

If no leak is detected, then the second valve is closed, the container is disconnected, and the

container port is capped and sealed.

The container is transported to a new location or placed in storage as appropriate to the task.