Evaluation of Existing Facilities

DOE-STD-1020-2002

followed such that the performance goal associated with the Performance Category of the SSC

under consideration is achieved. For each category, the criteria include the following steps:

NPH loads are determined at specified NPH probabilities as per DOE-

STD-1023 (Ref. 1-11).

Design and evaluation procedures are used to evaluate SSC response to

NPH loads.

Criteria are used to assess whether or not computed response in

combination with other design loads is permissible.

Design detailing provisions are implemented so that the expected

performance during a potential NPH occurrence will be achieved.

Quality assurance and peer review are applied using a graded approach.

For each Performance Category, target performance goals are provided in the Appendices

B and C in terms of mean annual probability of exceedance of acceptable behavior limits. In

Item 1, the annual probability of exceedance of an NPH parameter such as ground acceleration,

wind speed, or water elevation is specified. The level of conservatism in Items 2, 3, 4, and 5

above is controlled such that sufficient risk reduction from the specified NPH probability is

achieved so that the target performance goal probability is met. DOE-STD-1020 provides an

integrated approach combining definition of loading due to natural phenomena hazards, response

evaluation methods, acceptance criteria, and design detailing requirements.

Performance goals and NPH levels are expressed in probabilistic terms; design and

evaluation procedures are presented deterministically. Design/evaluation procedures specified in

this document conform closely to common standard practices so that most engineers will readily

understand them. The intended audience for these criteria is the civil/structural or mechanical

engineer conducting the design or evaluation of facilities. These NPH design and evaluation

criteria do not preclude the use of probabilistic or alternative design or evaluation approaches if

these approaches meet the specified performance goals.

1.3

Evaluation of Existing Facilities

Evaluations of existing SSCs must follow or, at least, be measured against the NPH

criteria provided in this document. For SSCs not meeting these criteria and which cannot be

easily remedied, budgets and schedule for required strengthening must be established on a

prioritized basis. A back-fit analysis should be conducted. Priorities should be established on

the basis of Performance Category, cost of strengthening, and margin between as-is SSC

capacity and the capacity required by the criteria. For SSCs which are close to meeting criteria,

it is probably not cost effective to strengthen the SSC in order to obtain a small reduction in risk.

As a result, some relief in the criteria is allowed for evaluation of existing SSCs. It is

permissible to perform such evaluations using natural phenomena hazard exceedance probability

of twice the value specified for new design. For example, if the natural phenomena hazard

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