Kinectrics Inc.Life Cycle Management Solutions

Condition Monitoring Condition Monitoring ofof

Low Voltage CablesLow Voltage Cables

K. (Anand) ANANDAKUMARANKinectrics Inc.,

Toronto, Canada

ObjectiveObjective

Condition Monitoring of Safety Related Cables Performance under a Design Basis Accident Event (DBA)We have concentrated on three cable insulation types: PVC, XLPE, and EPRJacket types: Hypalon and PVC

Condition Monitoring (CM) of Nuclear CablesCondition Monitoring (CM) of Nuclear Cables

Cables identified as one of the major nuclear plant life assurance or extension issues

Significant replacement cost

Inside containment the polymeric cable insulation vulnerable to thermal and irradiation degradation

MATERIAL TYPESMATERIAL TYPESInsulation Materials

FRXLPE - Fire Retardant Crosslinked Polyethylene

FREPR - Fire Retardant Ethylene Propylene Rubber

FRPVC - Fire Retardant Polyvinyl Chloride

EPR - Bonded with Hypalon

Jacket MaterialsPVC Hypalon (Chloro-sulphonated polyethylene CSPE)Neoprene

Insulation Materials – Special ApplicationsTefzelKaptonPeek

Cable ConstructionCable Construction

Fire Retardant EPR FORMULATIONFire Retardant EPR FORMULATIONFORMULATION NUMBER, TRADE NAME, etc.

CHEMICAL INGREDIENTS PRESENTMANUFACTURING PROCESS

Most Popular Cable InsulationMost Popular Cable Insulation -- Used Inside Containment U.S. Nuclear Power PlantsUsed Inside Containment U.S. Nuclear Power Plants

Cable Manufacturer (Material -

Trade Name)

Number of Plants

Rockbestos Firewall III (XLPE) 61Brand – Rex (XLPE) 30Raychem Flametrol (XLPE) 23

Anaconda Y Flame-Guard FR (EPR) 35Okonite FMR (EPR) 26Samuel Moore Dekoron Dekorad (EPDM) 19BIW Bostrad 7E (EPR) 19Kerite HTK (EPR like) 25

Rockbestos (Coax, SR) 24Kerite FR (SR) 13

Ref: Electric Power Research Institute, EPRI TR-103841-R1. Low Voltage Environmentally-Qualified Cable License Renewal Industry Report, Revision 1.(1994)

CHARACTERIZATION / IDENTIFICATION CHARACTERIZATION / IDENTIFICATION -- TechniquesTechniques

FTIR SpectroscopySolubilityDensityOxidation Induction Time (OIT)Melting & Glass Transition TemperatureThermo-gravimetric Analysis (TGA)Gas Chromatography (GC)X-Ray Fluorescence (XRF)Neutron Activation Analysis (NAA)

Sample Size: XLPE/EPR ~ ½ cm long insulation specimen required

FTIR SPECTROSCOPYFTIR SPECTROSCOPYFTIR: The amount of light absorbed/ transmitted /reflected by a sampleplaced in the light path at various wavelengths of an IR light range is measured. The energy absorption spectrum is characteristic of the structure of materials absorbing the IR light.

NIR (Near Infrared) TechnologyNIR (Near Infrared) TechnologyNon-destructive – Light Colors onlyMaterials absorb IR at characteristic frequenciesCapable of discriminating between formulationsFlexible, fiber-optic probe for easy access to cablesUsed on > 10,000 cables samples in CANDU plants

NIR IDENTIFICATIONNIR IDENTIFICATION

Cable Service EnvironmentCable Service Environment

FAILURE MECHANISMS FAILURE MECHANISMS OFOF SAFETYSAFETY--RELATED CABLESRELATED CABLES

Aging stresses: temperature, radiation, vibration (for cables connected to running machines) and moisture.

For I&C cables (<1 kV) electrical stress not significantKinetics of the degradation: Controlled by the additives present in insulation and polymer structure.XLPE/EPR insulated cable – hardening, loss of flexibility, and cracking.EPR- bonded with Hypalon – hardening of Hypalon, cracking of EPRPVC insulated cable – PVC and plasticizers breakdown, forming ionic salts causing poor electrical performance during steam test.Tefzel insulated cable – Combination of radiation / steam exposure result in circumferential cracking.Kapton – Steam exposure causes unfurling of insulation and cause poor electrical performance.

Visual InspectionVisual Inspection

Cable ConditionsDiscolorationDull SurfaceGreen OozeOily SurfaceCrackingCrystals (plasticizer hydrolysis by-products)

White DustStiff

Visual Inspection Visual Inspection –– PVC AgingPVC Aging (As Rec(As Rec’’d and Thermal Aged)d and Thermal Aged)

Visual Inspection Visual Inspection –– PVC Jacket AgingPVC Jacket Aging

Degraded PVC Shrink SleevesDegraded PVC Shrink Sleeves

Hypalon Jacket CrackingHypalon Jacket Cracking –– White Powdery DepositWhite Powdery Deposit

Photograph of XLPE insulated coax cable showing cracking of Hypalon jacket after LOCA

Hypalon Jacket CrackingHypalon Jacket Cracking

Tefzel InsulationTefzel Insulation –– Cracking after Steam ExposureCracking after Steam Exposure

Before Steam Exposure (+10 to 15Mrad) After Steam Exposure

VisualVisual Inspection Inspection -- KaptonKapton

Condition MonitoringCondition Monitoring –– Destructive CM TechniquesDestructive CM Techniques

Elongation-at-BreakUseful to assess aging for all cable materialsFailure is due to insulation Hardening, Loss of Flexibility and insulation cracking (XLPE & EPR insulated cables)Dumbbell or tubular (without conductor) specimen pulled at 50 mm/min until breakage. % Elongation = {(L2- L1) / L1} X 100

L1 = initial gauge spacingL2 = gauge spacing at rupture

Acceptance CriterionAcceptance Criterion--XLPE/EPR InsulationXLPE/EPR Insulation

Elongation Values of XLPE 2 Insulation After Radiation,

Thermal, and Sequential Radiation + Thermal Exposures.

Elongation Values of EPR 2 Insulation After Radiation, Thermal, and Sequential Radiation + Thermal Exposures.

Acceptance criteria: 50% Absolute Elongation

Sample Dimension for Sample Dimension for Destructive TechniquesDestructive Techniques

DSC Oxidation Induction Time (OIT)DSC Oxidation Induction Time (OIT)

10 Mg Sample RequiredIndicator of Stabilizer EffectivenessLength of Induction Time which precedes active oxidationStabilizer Concentration Depletes with Aging - OIT ↓ with aging

Correlation of OIT with ElongationCorrelation of OIT with Elongation

OIT & ELONGATION DATA OF OIT & ELONGATION DATA OF FIELD AGED EPR 1 INSULATIONFIELD AGED EPR 1 INSULATION

NonNon--Destructive Technique Destructive Technique –– Cable IndenterCable Indenter

Developed by EPRISuitable for Installed Cables in US plantsPrimary Aging Environment –ThermalHypalon and Neoprene Jackets Jackets Hardens with Thermal Aging

NonNon--Destructive Technique Destructive Technique –– Cable IndenterCable Indenter

NonNon--Destructive Technique Destructive Technique –– Cable IndenterCable Indenter

Test Results Test Results -- Cable IndenterCable Indenter

0

10

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0 1000 2000 3000 4000 5000 6000 7000

Shifted Aging Time, Hours at 110˚C

Inde

nter

Mod

ulus

(N/m

m)

Jkt 110˚C (1X)

Jkt 120˚C (2.4X)

Ins 110˚C Jacketd Aging (1X)

Ins 120˚C Jacketd Aging (2.4X)

Ins 120˚C (2.4X)

Indenter results for CSPE outer jacket and EPR/CSPE composite insulation

Test Results Test Results -- Cable IndenterCable Indenter

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0 1000 2000 3000 4000 5000 6000 7000

Shifted Aging Time, Hours at 110˚C

% E

long

atio

n

Jkt 110˚C (1X)

Jkt 120˚C (2.4X)

Ins 110˚C (1X)

Ins 120˚C (2.4X)

Elongation results for CSPE outer jacket and EPR/CSPE composite insulation

CONCLUSIONS

Nuclear power plant operators may be required by licensing authorities to present evidence that installed their I & C cables which were environmentally qualified for a 30 to 40 years life are able to perform their safety related function for the additional 20 to 30 year plant life extension.This provision would mean that the nuclear power plant operators will be required to know:The installed cable types at their nuclear power stations,The environmental conditions to which each of the installed I&C cables at their nuclear stations will be exposed,The results of comparison of the extended cable life conditions with the previous EQ test data which was derived using accelerated aging conditions in order that cable life can be extended through analysis.OrWe have shown:The ability to identify different insulation formulation types and to link them to known formulation types,Condition monitoring techniques to assess the condition of installed cables by destructive and non-destructive means,The ability to estimate the remaining life of the cable by comparing its aging data with the already known experimentally determined aging trends for various insulation formulationsThis will allow for replacement decisions to be made for only in the worst cases of cable insulation aging.

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