Electrical Cable Aging: What does IEEE Std Recommend? Module 5 Dr. John H. Bickel Evergreen Safety & Reliability Technologies, LLC

Objectives Describe origins of IEEE Std Describe origins of IEEE Std Describe requirements of standard regarding electrical cables Describe requirements of standard regarding electrical cables Describe results of recent application in the US Describe results of recent application in the US NOTE: Standard covers all electrical components. Emphasis will be on “difficult to replace” electrical cables for which justification to use as- is will be sought. Emphasis will be on “difficult to replace” electrical cables for which justification to use as- is will be sought.

Origin of IEEE Std Many US NPP licenses expiring in next 10 years. Many US NPP licenses expiring in next 10 years. N.R.C. issued License Renewal regulation permitting life extension subject to demonstration of acceptable safety N.R.C. issued License Renewal regulation permitting life extension subject to demonstration of acceptable safety Previous IEEE Std standard felt to be too “open ended” in considering “all possible aging mechanisms”. Previous IEEE Std standard felt to be too “open ended” in considering “all possible aging mechanisms”. Question: “How much is enough?” Question: “How much is enough?” IEEE standard developed as industry – regulator consensus on acceptable aging management program to demonstrate acceptable safety for electrical equipment. IEEE standard developed as industry – regulator consensus on acceptable aging management program to demonstrate acceptable safety for electrical equipment.

Basis of New IEEE Std Major NPP systems, components have been continually refurbished or replaced over their lifetimes. Major NPP systems, components have been continually refurbished or replaced over their lifetimes. - Steam Generators, RPV head - Turbine rotors - Pumps, motors, valves - I&C systems, plant computers Original power (and portions of I&C) cable not typically replaced for other reasons. Original power (and portions of I&C) cable not typically replaced for other reasons. Incorporation of new materials aging data Incorporation of new materials aging data It is desired to demonstrate safety basis for acceptability of existing cabling and connectors. It is desired to demonstrate safety basis for acceptability of existing cabling and connectors.

Objectives of IEEE Std Standard deals with all types of electrical equipment. Standard deals with all types of electrical equipment. EQ standards (IEEE Std ) deal with thermal, radiation pre-aging for purposes of conducting DBA qualification tests. EQ standards (IEEE Std ) deal with thermal, radiation pre-aging for purposes of conducting DBA qualification tests. IEEE Std credits that equipment typically operates for long periods at below pre-aging temperature, radiation levels. IEEE Std credits that equipment typically operates for long periods at below pre-aging temperature, radiation levels.

IEEE Std Process:

Aging Assessment Process

1. Define Evaluation Boundaries What is being evaluated? What is being evaluated? What support features are included? What support features are included? What are system interfaces? What are system interfaces? What are system boundaries with interfacing systems? What are system boundaries with interfacing systems? Why this is done: To demonstrate at end of job that all systems covered, no duplications, but also no omissions

2. Identify Intended Safety Function What safety function does system provide for DBA? What safety function does system provide for DBA? What other safety functions is system credited for? What other safety functions is system credited for? Why this is done: Frequently systems are credited for different roles in different scenarios.

3. Identify Plant Locations Identify specific rooms or zones of equipment. Identify specific rooms or zones of equipment. Why this is done: Routing of support features such as signal and power cables needed for determining most limiting rooms or zones.

4. Identify Service Conditions What are environmental conditions in each of the rooms or zones? What are environmental conditions in each of the rooms or zones? Temperature, radiation, moisture….. Temperature, radiation, moisture….. Which rooms or zones are most limiting? Which rooms or zones are most limiting? Why this is done: Identifies locations of likely greatest stressors for aging-related degradation.

5. Identify Equipment Materials What types of materials for this system are located in each room or zone? What types of materials for this system are located in each room or zone? Which materials in the system are most limiting? Which materials in the system are most limiting? Why this is done: A system may have both Power and Instrumentation cables in the same zone. Instrumentation cables may be more limiting.

6. Identify and Assess Aging Effects What aging effects are possible for given materials and environmental stresses? What aging effects are possible for given materials and environmental stresses? Which aging effect is most limiting? Which aging effect is most limiting? Why this is done: Identification of conditions to be monitored, bases for future calculations

Thermal and Radiation Aging Models

IEEE Std starts with standard aging models based Arrhenius type aging and radiation damage type aging. IEEE Std starts with standard aging models based Arrhenius type aging and radiation damage type aging. Allows credit for actual operating experience which may show significantly reduced aging rates. Allows credit for actual operating experience which may show significantly reduced aging rates.

Consideration of Operating Experience Cabling in areas of highest temperature and radiation levels is typically limiting. Cabling in areas of highest temperature and radiation levels is typically limiting. Typical EQ efforts conservatively assume, 40 years at 100% capacity factor. Typical EQ efforts conservatively assume, 40 years at 100% capacity factor. High capacity factors imply higher radiation doses and exposure to highest temperatures. High capacity factors imply higher radiation doses and exposure to highest temperatures. Actual operation may be less limiting and should be taken into consideration in projecting residual cable lifetime. Actual operation may be less limiting and should be taken into consideration in projecting residual cable lifetime.

Projecting Residual Cable Lifetime Based on Operating Experience Based on actual operating history conservative “envelope” on temperature or radiation can be constructed. Based on actual operating history conservative “envelope” on temperature or radiation can be constructed. “Envelope” is conservative but also more realistic. “Envelope” is conservative but also more realistic.

Construction of Effective Time at Temperature Desire is to construct effective temperature T eff for residual life calculations. Desire is to construct effective temperature T eff for residual life calculations. Assume total time t tot Assume total time t tot

Condition Monitoring

Observation, measurement, trending of condition indicators with respect to critical parameter known to cause degradation. Observation, measurement, trending of condition indicators with respect to critical parameter known to cause degradation. Example parameters: Example parameters: cumulative radiation dose cumulative time at effective temperature Monitor: degradation vs. radiation dose Monitor: degradation vs. radiation dose Monitor: degradation vs. time at T eff Monitor: degradation vs. time at T eff

Acceptable Condition Monitoring

Some Results from Applying IEEE Std

What is Max T eff for 60 Years ?

Calvert Cliffs SER Findings: Effects of Aging “The cable insulation material types include silicone rubber, ethylene propylene rubber (EPR), crosslinked polyethylene (XLPE), crosslinked polyolefin (XLPO), mineral, Kapton, polyvinyl chloride, Teflon, and other miscellaneous insulation types. The external environment is air. The applicant identified the applicable ARDMs as thermal aging, synergistic thermal and radiative aging, and insulation resistence reduction. Although the license renewal rule requires management of aging effects and does not require specific identification of ARDMs, the applicant elected to evaluate specific ARDMs. The applicant considered a comprehensive list of potential ARDMs in its evaluation. The staff finds this acceptable because the potential ARDMs of thermal/radiative aging, and insulation resistence reduction are considered to be plausible for cables. Accordingly, the staff finds the applicant's approach of identifying ARDMs acceptable because aging effects are results of ARDMs.”

Calvert Cliffs SER Findings: The operating experience information in the application indicates that the number of cable failures during normal operating conditions (all voltage classes) that have occurred throughout the industry have been extremely low. However, thermal aging resulting in embrittlement of insulation is one of the most significant aging mechanisms for low-voltage cable during normal operating conditions. The operating experience information in the application indicates that the number of cable failures during normal operating conditions (all voltage classes) that have occurred throughout the industry have been extremely low. However, thermal aging resulting in embrittlement of insulation is one of the most significant aging mechanisms for low-voltage cable during normal operating conditions.

Calvert Cliffs SER Findings: Effects of Synergistic Thermal and Radiative Aging “Group 3 cables may be subjected to synergistic radiative and thermal aging when both aging mechanisms are active and at least one may be significant. Radiation-induced and thermal-induced degradation in organic materials (cable jacket and insulation) produces changes in the organic material properties, including reduced elongation and changes in tensile strength. Visible indications of radiative/thermal aging may include embrittlement, cracking, discoloration, and swelling of the jacket and insulation. To manage the aging effects on Group 3 cables, they will be replaced before the extended period of operation if they are found to have plausible aging.”

IEEE Std Process Aging Management Process has proven to be: Aging Management Process has proven to be: Orderly Orderly Repeatable Repeatable for both NPP operators making license extension applications and for NRC in reviewing and approving. for both NPP operators making license extension applications and for NRC in reviewing and approving.

License Renewal Status in US: License Extensions Approved: Calvert Cliffs, Units 1 and 2 Oconee Nuclear Station, Units 1, 2 and 3 Arkansas Nuclear One, Unit 1 Edwin I. Hatch Nuclear Plant, Units 1 and 2 Turkey Point Nuclear Plant, Units 3 and 4 North Anna, Units 1 and 2, and Surry, Units 1 and 2 Peach Bottom, Units 2 and 3 St. Lucie, Units 1 and 2 Fort Calhoun Station, Unit 1 License Extensions Pending: McGuire, Units 1 and 2, and Catawba, Units 1 and 2 - Joint application received June 14, 2001 H.B. Robinson Nuclear Plant, Unit 2 - Application received June 17, 2002 R.E. Ginna Nuclear Power Plant, Unit 1 - Application received August 1, 2002 V.C. Summer Nuclear Station, Unit 1 - Application received August 6, 2002 Dresden, Units 2 and 3, and Quad Cities, Units 1 and 2 - Application received January 3, Farley, Units 1 and 2 - Application received September 15, Arkansas Nuclear One, Unit 2 - Application received October 15, D.C. Cook, Units 1 and 2 - Application received November 3, 2003