Performance Category 4 - STD-102020020077

DOE-STD-1020-2002

of operations may be acceptable for Performance Categories 1 and 2, however, for Performance

Category 3 the DBFL must be mitigated such that the flood does not impact operations.

The design of Performance Category 3 SSCs that may be impacted by the DBFL should

be based on the loads (i.e., hydrostatic forces) and other hazards (i.e., ice forces, debris) that

occur. The design requirements in applicable regulations should be used to incorporate flood

loads in the design. If mitigation systems such as watertight doors, sealants, etc. are used,

manufacturer specifications should be applied. Section 4.3 describes design requirements for

flood-mitigation systems such as levees, dikes, etc.

For SSCs that may be impacted by the DBFL, emergency operation plans must be

developed to evacuate personnel not involved in the emergency operation of the facility, secure

hazardous materials, prepare the facility for possible extreme flooding and loss of power, and

provide supplies for personnel who may have an extended stay on-site. Emergency procedures

should be coordinated with the results of the flood hazard analysis, which provides input on the

time variation of flooding, type of hazards to be expected and their duration. The use of

emergency operation plans is not an alternative to hardening a facility to provide adequate

confinement unless all hazardous materials can be completely removed from the site.

4.2.4 Performance Category 4

The performance goals for Performance Category 4 are basically the same as for

Performance Category 3. However, a higher confidence is required that the performance goals

are met. SSCs in this category should be located above flood levels whose mean-annual

probability of exceedance is 10-5, including the combinations of events listed in Table 4-2.

4.3

Flood Design Practice for SSCs Below the DBFL Elevation

For SSCs located below the DBFL level, mitigation measures can be designed that

provide an acceptable margin of safety. In practice, a combination of structural and non-

structural measures (i.e., flood warning and emergency operation plans) are used. The design

criteria for facilities that must consider flood loads are described for SSCs located below the

DBFL level, in this section.

4.3.1 Flood Loads

To evaluate the effects of flood hazards, corresponding forces on structures must be

evaluated. Force evaluations must consider hydrostatic and hydrodynamic effects, including the

impact associated with wave action. In addition, the potential for erosion and scour and debris

loads must be considered. The flood hazards that must be considered are determined in the flood

hazard analysis. Good engineering practice should be used to evaluate flood loads (Refs. 4-8 to

4-12) including the forces due to ice formation on bodies of water.

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