Controlling Uranium Inventories

DOE-HDBK-1113-98

Radiological Safety Traning for Uranium Facilities

Module 105 - Criticality Safety

analyzing work environments to assess the risk of criticality and eliminate likely

criticality concerns;

using carefully planned and approved procedures;

providing specific training for those personnel working in areas where fissile materials

are present; and

implementing system design features that are favorable to criticality safety. These

features include:

- using contain ers with a size and geometry that will not allo w criticali ty,

- designing pipi ng systems to preven t buildup of ur anium and preven t critical ity,

- using materials known as poisons to absorb neutrons and prevent them from being

absorbed by the uranium atoms,

- controlling material that surrounds containers or systems containing uranium, and

- controlling uranium inventories.

Controlling Uranium Inventories

One method to prevent a criticality is controlling uranium inventories. Inventory control

involves knowing where the uranium is at the facility and the level of enrichment of the

uranium. Uranium enriched in 235U or the presence of 233U is of concern for critica lity;

therefore, these are materials of concern for inventory control. Criticality is a concern

for 238U if fast neutrons are present.

Loss of control of fissile material presents a threat to criticality safety at the facility and,

in a worst case scenario, to national security. It is no secret that groups throughout the

world are striving to become nuclear powers. Even the appearance of a loss of inventory

control must be avoided to keep the public trust and assure continued operations of DOE

programs. For these reasons, inventories of fissile material are closely monitored.

Facility-Specific Criticality Safety Controls

Provide facility-specific information.