IEEE Std 1205-2000 pdf download
IEEE Std 1205-2000 pdf download.IEEE Guide for Assessing,Monitoring, and Mitigating Aging Effects on Class 1E Equipment Usedin Nuclear Power Generating Stations.
Contacts, linkages, and bearings are inorganic parts of electrical equipment that may also be susceptible to aging.
6.6 Identify and assess aging effects
Aging effects are identified and assessed to determine whether any additional aging management efforts are needed to prevent the effects from becoming significant over time. Significant aging effects are those that can detrimentally affect the equipment safety function or functions identified in 6.2.
The following suhclauses describe aging effect identification, other supportive information needed, and use of aging models and condition monitoring to perform aging assessments.
6.6.1 Identification of aging effects
Aging effects are identified from either plant-specific or industry failure or degradation experience with the specific equipment or its materials of construction (from 6.5) in a similar application. Alternatively, plant- specific service conditions (stressor values) and materials information may be used to determine applicable and potentially significant aging effects from the tables of Annex A.
6.6.2 Other supportive information needed
Next the following information should be researched or established as feasible or available:
a) Evaluation period: Most materials degrade somewhat over time, even in fairly benign environments; it is useful to set a specific goal for the equipment’s life to be evaluated. The evaluation period is normally selected on the basis of the plant’s 40-year operating license, but can he selected for any other specific time period (e.g., outage to outage for specific equipment, time periods between tests as dictated by safety analysis, or 60 years for license renewal).
NOTE—For EQ Program equipment. ills necessary to include the mission (or postaccident required operating) time in the evaluation period to assure sufficient margin for posaccident operability beyond the normal life goal.
h) Past and future service conditions (from 6.4) as a function of time or as enveloping values for the evaluation period.
c) Degree of flexibility in controlling or limiting future service conditions.
d) Aging mechanisms likely to cause the identified aging effects in the identified materials of construction (determined from Annex A or similar sources of information, such as EPRI NP- 1558 [B 121 and NUREG-1377 [B65j, NUREG/CR-3629 [B66], NUREG/CR-4156 1B671, NUREG/CR4731 jB68j, NUREG/CR-4715 [B691, NUREG/CR-4740 1B70], NUREG/CR-5051 [B71], NUREG/CR-5057 [B72]).
e) Dependence of the aging mechanism and resulting aging effects on the identified service conditions.
Aging information, such as activation energy, accelerated aging test data (temperature and time), temperature rating or maximum continuous-use temperature, radiation dose threshold, and related information, for the equipment or its materials of construction.
To perform the aging assessment, the material’s withstand capability is compared to the intensity of a service condition stressor. Results from tests of material properties, after being subjected to accelerated aging, are the best and most readily available sources of material aging information.
The aging assessment can be performed to achieve either one or both of the following objectives, depending on information availability, expected or estimated remaining life margin, and whether specific equipment life goals have been established or are needed. The objectives of the aging assessment are to determine
— How long (years) a material will remain functional while exposed to its stressors, or
— A maximum stressor (heat, radiation) value that a material would be able to withstand for a specified period (years) and still remain functional.
Knowing the equipment materials and stressors, it is possible to assess the effects of aging on the material to date and to determine how in the future aging will affect the equipment safety function. For a given material, aging effects (some type of material degradation) can be directly related to a specific environmental or operational stressor. The intensity of the stressor normally determines the rate that the material degrades.
Next, one or a combination of methods is used to assess aging effects for the equipment’s future service conditions. Two models, which extrapolate test results and condition monitoring, are discussed in the following subclause.
6.6.3 Use of a thermal aging model
Thermal aging is commonly assessed by using the Arrhenius model, which is described in EPRI NP-1558 [B 12] and Nelson [B58]. The model establishes aging degradation as a function of temperature and allows an estimation of thermal life at a given temperature. It is also used to relate remaining life at one temperature to remaining life at another temperature. Alternatively, it can be used to determine a maximum continuous temperature for a specific length of time.
