Overview of Occurence Investigation

Condition. Any as-found state, whether or not resulting from an event, that may have adverse

safety, health, quality assurance, security, operational, or environmental implications. A rendition is

usually programmatic in nature; for example, an (existing) error in analysis or calculation, an anomaly

associated with (resulting from) design or performance, or an item indicating a weakness in the

management process are all conditions.

Cause (Causal Factor). A condition or an event that results in an effect (anything that shapes or

influences the outcome). This may be anything from noise in an instrument channel, a pipe break, an

operator error, or a weakness or deficiency in management or administration. In the context of DOE

Order 5000.3A there are seven major cause (causal factor) categories. These major categories are

subdivided into a total of 32 subcategories (see Appendix A).

Causal Factor Chain (Sequence of Events and Causal Factors). A cause and effect sequence in

which a specific action creates a condition that contributes to or results in an event. This creates new

conditions that, in turn, result in another event. Earlier events or conditions in a sequence are called

upstream factors.

Direct Cause. The cause that directly resulted in the occurrence. For example, in the case of a

leak, the direct cause could have been the problem in the component or equipment that leaked. In the

case of a system misalignment, the direct cause could have been operator error in the alignment.

Contributing Cause. A cause that contributed to an occurrence but, by itself, would not have

caused the occurrence. For example, in the case of a leak, a contributing cause could be lack of adequate

operator training in leak detection and response, resulting in a more severe event than would have

otherwise occurred. In the case of a system misalignment, a contributing cause could be excessive

distractions to the operators during shift change, resulting in less-than-adequate attention to important

details during system alignment.

Root Cause. The cause that, if corrected, would prevent recurrence of this and similar

occurrences. The root cause does not apply to this occurrence only, but has generic implications to a

broad group of possible occurrences, and it is the most fundamental aspect of the cause that can logically

be identified and corrected. There may be a series of causes that can be identified, one leading to another.

This series should be pursued until the fundamental, correctable cause has been identified.

For example, in the case of a leak, the root cause could be management not ensuring that

maintenance is effectively managed and controlled. This cause could have led to the use of improper seal

material or missed preventive maintenance on a component, which ultimately led to the leak. In the case

of a system misalignment, the root cause could be a problem in the training program, leading to a

situation in which operators are not fully familiar with control room procedures and are willing to accept

The objective of investigating and reporting the cause of occurrences is to enable the identification

of corrective actions adequate to prevent recurrence and thereby protect the health and safety of the

public, the workers, and the environment. Programs can then be improved and managed more efficiently

and safely.

The investigation process is used to gain an understanding of the occurrence, its causes, and what

corrective actions are necessary to prevent recurrence. The line of reasoning in the investigation process

is: Outline what happened step by step. Begin with the occurrence and identify the problem (condition,

situation, or action that was not wanted and not planned). Determine what program element was