Hazard evaluation characterizes the identified hazards in the context of the
actual facility and process. For example, simple hazard identification would be
that 2000 grams of plutonium oxide are in a steel container under a hood
waiting for entry into a glove box. One accident, which places this hazard in
the actual context of facility parameters, involves spilling the container on the
room floor. The hazard evaluation would qualitatively consider the action of
moving the container into the glove box to evaluate the likelihood of spilling
the contents. It would also consider mitigative features that would affect
potential consequences. References such as Guidelines for Hazard Evaluation
Procedures (1992) provide acceptable guidelines for selecting hazard
evaluation techniques and generic lists of initiators that need to be incorporated
in systematic evaluation with a given technique.
Public and worker safety issues are the traditional focus of hazard evaluations.
The DSA hazard evaluation also examines the potential for large -scale
environmental contamination. The information on environmental
contamination may be used in a separate cost-benefit analysis, not related to
the DSA effort, to determine if additional preventive or mitigative features are
needed in the facility.
Tables 3-1 and 3-2 provide two examples of hazard analysis output. Table 3-1
is an example of a portion of the evaluation of a hydrogen fluoride unloading
operation. It identifies accident initiators, associated preventive and mitigative
functions, and operational safety enhancements determined to be necessary.
The parenthetical numbers in the table under the headings of "Cause,"
"Consequence," and "Frequency" distinguish a numbering system that serves
to identify specific accident scenarios (i.e., cause #1 is an event that has been
judged to have consequence #1 and frequency #1, resulting in the overall
ranking aligned with frequency #1). The ranking (i.e., low, medium, a nd high)
of estimated consequences and frequencies are based on judgment of analysts,
and the overall binning rank is in accordance with the numbers assigned to the
example in Figure 3-2. Table 3-1 demonstrates how a number of basic
accidents can be ident ified and evaluated in a concise manner. The last
column of Table 3-1 presents safety enhancements in the form of two
procedural verifications and two action items for procedural alteration that
were identified in the course of the evaluation.
Table 3-1 a lso provides an example of how worker safety issues are integrated
into this presentation. However, significant worker safety evaluations
unrelated to the hazard scope defined for a DSA (i.e., standard industrial
hazards) will be occurring outside the DSA. This reinforces the importance of
the emphasis in Section 18.104.22.168, "Hazard Identification," of identifying the
dividing line between process/activity hazards covered in the DSA and those
covered by direct OSHA regulatory compliance. Specifying the location of
this dividing line is essential to developing an integrated safety posture where
the functions of DSA hazard analysis vis-à-vis health and safety plans, job task