Surveillance and Maintenance

DOE-HDBK-1129-99

from the gas stream as the bed is heated and cooled. Helium, which accumulates due to the

decay of tritium, and other non-reacting impurities remain in the overpressure gas above the bed.

To help resolve unknowns regarding consequences of air-ingress accidents in uranium beds, a

series of air-ingress experiments was conducted at Ontario Hydro Research Division, with the

participation of Princeton Plasma Physics Laboratory (PPPL) and the Idaho National

Environmental and Engineering Laboratory. The experiments indicated that the resulting reaction

was restrained with only modest temperature excursions. This leads to the conclusion that the

hazards associated with an air-ingress accident involving a uranium bed is smaller than previously

anticipated. Additionally, tests conducted by WSRC indicate that, except for catastrophic container

failure, the tritium release due to air inleakage into a uranium tritide bed is limited by diffusion.

Titanium hydride is not pyrophoric at room temperatures, is a stable material, and has been

studied for use in the long-term storage of tritium. It is reported to be less prone to spontaneous

ignition in air than the parent metal. Following the hydriding process, if the titanium hydride is

exposed to air under controlled conditions, a small quantity of hydrogen is released from the

material as the oxide layer forms on the surface of the material. Following formation of the oxide

layer, titanium hydride is stable in air. Hydrogen will not be released unless the material

temperature is significantly increased.

Palladium tritide is not pyrophoric at room temperature, is a stable material, and the overpressure

of tritium over the bed at room temperature is approximately 50 torr.

Metal tritides have the advantage of significantly decreasing the volume required to store tritium

without increasing the pressure of the gas during storage.

5.6 Surveillance and Maintenance

The level of equipment surveillance (including radiological monitoring) and maintenance required is

based on the hazard class of a facility; i.e., Hazard Category I through III or Radiological. The

specific requirements for the different classes of facility equipment are a function of the safety

issues associated with the equipment. These are specified in the facility safety analysis report or

other facility safety documentation and in the facility maintenance plan.

5.7 Seismic Considerations

This section describes 1) DOE Natural Phenomena Hazards Policy, which defines the

requirements for protection against natural phenomena such as earthquakes, and 2) Seismic

Design and Evaluation of Equipment and Distribution Systems. Seismic and Wind Design and

Evaluation of Structures and Facilities are discussed in Section 4.4.

5.7.1 DOE Natural Phenomena Hazards Policy

The DOE has developed a policy for the mitigation of natural phenomena (such as earthquakes,

extreme winds, and floods) on its facilities. This policy is in the form of an Order, an

Implementation Guide, and a series of Standards. DOE Order 420.1 and its Implementation Guide

provide the overall requirements for mitigation of the effects of natural phenomena. The Standards

lay out the basic performance requirements for structures, systems, and components (SSCs)

subjected to loads caused by earthquakes, extreme winds, and floods.