Electrical Cable Aging: What does IAEA Recommend? Module 2 Dr. John H. Bickel Evergreen Safety & Reliability Technologies, LLC

Objective is to Understand.. Recommendations of TECDOC-1147 regarding aging management of electrical cables. Recommendations of TECDOC-1147 regarding aging management of electrical cables. Aging management program process Aging management program process Types of cables previously investigated and aging mechanisms considered Types of cables previously investigated and aging mechanisms considered General recommendations for tests, inspections, and maintenance programs General recommendations for tests, inspections, and maintenance programs

IAEA TECDOC-1147 Title: Management of Aging of I&C Equipment in Nuclear Power Plants Title: Management of Aging of I&C Equipment in Nuclear Power Plants Prepared by experts from US, UK, France, Germany, Finland Prepared by experts from US, UK, France, Germany, Finland Findings/recommendations reviewed by countries with large nuclear programs (Russia, Czech, Slovak Republics, India, others) Findings/recommendations reviewed by countries with large nuclear programs (Russia, Czech, Slovak Republics, India, others) Purpose: guide worldwide nuclear industry on potential effects of I&C aging on plant safety and economy Purpose: guide worldwide nuclear industry on potential effects of I&C aging on plant safety and economy Identify means available to minimize or eliminate any detrimental effects of aging Identify means available to minimize or eliminate any detrimental effects of aging

Aging Management Program Essentials: Identify components whose aging may impact safety Identify components whose aging may impact safety Determine aging mechanisms important to safety and consequences of this aging Determine aging mechanisms important to safety and consequences of this aging Identify tests, inspections and evaluation criteria for detection of safety component aging Identify tests, inspections and evaluation criteria for detection of safety component aging Establish testing and replacement strategies to assure NPP operates safely over intended lifetime. Establish testing and replacement strategies to assure NPP operates safely over intended lifetime.

General Observations: Electrical cable experience indicates cable aging problems generally less significant than for other types of I&C components. Electrical cable experience indicates cable aging problems generally less significant than for other types of I&C components. Under normal operating conditions, electrical cable lifetimes exceed most other active components. Under normal operating conditions, electrical cable lifetimes exceed most other active components. Under accident conditions, potential for common cause failure considered serious enough to warrant further investigations. Under accident conditions, potential for common cause failure considered serious enough to warrant further investigations.

Mechanisms Which Aggravate Cable Aging: Elevated local temperatures Elevated local temperatures Humidity, moisture ingress Humidity, moisture ingress Mechanical Stresses due to cyclic loads Mechanical Stresses due to cyclic loads Radiation Exposure Radiation Exposure

Cable typeTemperature Sensitivity Radiation Sensitivity Remarks Polyvinyl chloride (PVC) SensitiveNot sensitiveEmbrittlement at elevated temp. Cross-linked Polyethylene (XLPE) SensitiveNot sensitiveEmbrittlement at high temp. and under radiation Heat resistant PVCSensitiveEmbrittlement at > 105 C Polypropylene/ Polyethylene (PP/PE) Sensitive Flexibility lost at elevated temp, radiation Polytetraflouro- ethylene (PTFE) Not sensitiveSensitiveCracking due to embrittlement Fire retardant low smoke PVC Not sensitive Good performance Ethylene Poly- propylene rubber (EPR) No degradation Cellular Polyethylene (VPE) No degradation Silicon Rubber (SIR)Insulation failure possible after 25 years

Tests, Measurements for Assessing Aging Chemical testing of insulation composition Chemical testing of insulation composition Mechanical testing of insulation ductility Mechanical testing of insulation ductility Electrical resistance testing of cable conductors and insulation Electrical resistance testing of cable conductors and insulation All of these tests are based on measurements of degradation in aged cables compared to a base-line sample. All of these tests are based on measurements of degradation in aged cables compared to a base-line sample.

Recommended Methods Used to Monitor Cable Aging Visual examinations of insulation (cracking) Visual examinations of insulation (cracking) Hardness testing of small cable section Hardness testing of small cable section Chemical analysis of sample section of cable Chemical analysis of sample section of cable Measurement of resistance of insulation Measurement of resistance of insulation Microscopy examinations of cable insulation samples Microscopy examinations of cable insulation samples Swept frequency tests to measure dielectric properties (instrumentation cables) Swept frequency tests to measure dielectric properties (instrumentation cables) Time domain reflectrometry (TDR) of conductor cable and connectors Time domain reflectrometry (TDR) of conductor cable and connectors AC/DC conductor resistance measurements AC/DC conductor resistance measurements