Analysis Procedure cont'd

DOE-HDBK-1100-2004

The questions may address any off-normal condition related to the facility, not just component

failures or process variations. The questions are formulated based on PrHA team member

experience and applied to existing drawings and process descriptions. The team generally

proceeds from the beginning of the process to its end, although the PrHA team leader can order

the analysis in any logical way he or she sees fit, such as dividing the process into functional

systems. Or the leader may direct the review to begin with the introduction of feed material and

follow the flow until the end of the process. The questions, and eventually the answers

(including hazards, consequences, engineered safety levels, and possible solutions to important

issues), are recorded by the team member designated as "scribe," so that they can be viewed by

all team members.

The questions may be divided into specific areas of investigation usually related to

consequences of interest, such as electrical safety, fire protection, or personnel safety. Each area

is subsequently addressed by a team of one or more knowledgeable individuals. The team

answers each question and addresses each concern (or indicates a need for more information)

and identifies the hazard, potential consequences, engineered safety levels, and possible

solutions. During the process, any new what-if questions that become apparent are added.

Sometimes the proposed answers are developed by individuals outside the initial meeting, and

then presented to the team for endorsement or modification.

For example, given the question:

"What if the HF cylinder fails because of corrosion?",

the team would attempt to determine how the process would respond:

"A cylinder leak would release HF to the atmosphere and eventually result in a loss

of HF feed to the vaporizer."

The team might then recommend checking with the supplier regarding cylinder inspection

practices.

The team should not be rushed, and meetings should last no longer than 4 to 6 hours per day.

What-if team meetings that last more than 5 consecutive days are not desirable. If a process is

complex or large, it should be divided into smaller segments so that the team does not spend

several consecutive days just listing questions.

DOCUMENTING THE RESULTS.

The what-if analysis produces a tabular listing of narrative-style

questions and answers that constitute potential accident scenarios; their qualitative

consequences; and possible risk-reduction methods. Table 4.7 shows the format of a what-if

analysis worksheet. Although some what-if analyses are documented in a narrative-style format,

a table makes the documentation more organized and easier to use.