Identify potential contingency scenarios

DOE-STD-3007-2007

which should be considered, such as sprinkler activation, glove box rupture, rack collapse and

natural phenomena, as potential initiators of criticality accidents.

2. Identify potential contingency scenarios. Contingencies shall1 be identified. A disciplined

method should be used to identify contingencies. Examples of acceptable methods (see brief

descriptions in DOE-STD-1027-92, Change Notice 1, Section 4.1) are:

What If methods;

Qualitative Event or Fault Trees;

Quantitative Probabilistic Risk Assessment methods;

Hazard and Operability Analysis; and/or

Failure Modes and Effects Analysis.

Input should be obtained from operations personnel and process specialists thoroughly familiar

with the operations and possible abnormal conditions. Whenever practical, identified

contingencies should be eliminated by modification of the process.

3. Establish controls. Controlled parameters and their associated limits shall6 be identified in this

section. Examples of parameters subject to control include, but are not limited to, fissionable

material mass, volume, concentration, moderation, interaction, etc. Appropriate operations staff,

engineering staff, and/or process experts should review the postulated contingencies and the

proposed controls to assure practicality. The preferred hierarchy of controls shall8 be: (1) passive

engineered features, (2) active engineered features, and (3) administrative controls. Inspections,

periodic surveillances, or other quality assurance measures should be developed and implemented

to defend the reliability of the selected controls. Other factors that influence the selection of

controls and should be considered, include:

The implementation complexity of the control;

The ability of personnel to recognize the failure of the control;

The potential for common mode failure of controls; and,

The final reliability of the set of controls.

A table showing the unlikely changes in process conditions (contingencies) and the controls that

make the abnormal change unlikely may be summarized in a table. The following is an example of

a contingency control table.