Desired and Remaining Lifetime

DOESTD107393

might be more prudent to terminate operations rather than to repair or replace the equipment. In other

cases, the replacement of an item is not technically feasible. If the failure of an SSC might result in a

decision to terminate facility operations, that equipment is potentially life-limiting for the facility.

Avoidance of a facility life-limiting failure is highly desirable, and therefore, understanding the cause of

such failures and estimating the remaining lifetime are important. Predicting the end of facility life can

avoid catastrophic failure and can allow an orderly shutdown.

Desired and Remaining Lifetime. The design of any facility SSC carries with it a finite lifetime. In other

words, the equipment, either active or passive, specified by the design can be expected to operate

under a particular set of conditions for some period of time before failure. Figure I-B-3 depicts the

general concept of lifetimes for a facility across its various life-cycle phases. After the design phase

and the construction phase, the facility enters the operational phase of its life-cycle, which has a finite

length. At any point during the operational phase, only a certain amount of the operating lifetime

remains available.

Remaining lifetime is the time still available for operation without applying life extension techniques.

Several components within a facility could be potentially life-limiting for the facility. The first life-limiting

component to actually fall would signal the end of the operational lifetime for the facility. The facility

remaining lifetime is determined by the current material condition of life-limiting equipment and by the

stresses of the subsequent operation of that equipment. If the current material condition can be

determined accurately, it might not be necessary to determine the stresses or operating cycles that

previously occurred.

While the facility remaining lifetime is indicated by the current material condition, the desired lifetime is

the period specified by DOE as necessary to fulfill the programmatic mission of that facility. Figure I-B-

3 depicts two situations regarding remaining lifetime relative to the desired lifetime. In the first situation,

the desired lifetime of the facility is shorter than its remaining lifetime. In the latter situation, the desired

lifetime is greater than the remaining lifetime. In this situation, if that desired lifetime is to be achieved,

life extension techniques need to be developed and applied.

In some cases, DOE has directed the contractor to continue operating the facility for a specified period

or only until a specified date. In those cases, the facility desired lifetime is known. In other cases, DOE

has not specified a desired lifetime. DOE may determine the facility desired lifetime based, in part, on

the remaining lifetime estimated by the contractor and on the estimated costs of life extension

techniques for additional years.

Life Extension Techniques. Life extension techniques are those actions that would extend the lifetime

of potentially life-limiting components for a facility to achieve the desired facility lifetime. The life of a

particular component might be extended by actions such as reducing the number of operating cycles,

reducing the speed of each operating cycle, reducing vibrations, and lowering the ambient temperature

for the equipment. To develop life extension techniques, the potentially life-limiting components are

identified, aging degradation mechanisms are evaluated, and actions are identified that would reduce

the stresses on the equipment to prolong its lifetime.

While life extension techniques focus on extending the lifetime of a component, aging management

focuses on controlling aging degradation to the extent of ensuring reliable operation and avoiding

failure before the expected lifetime expires.

I-B-17