Transcript Electrical Cable Aging: What does IAEA Recommend?

Module 2
Electrical Cable Aging:
What does IAEA
Recommend?
Dr. John H. Bickel
Evergreen Safety & Reliability Technologies, LLC
Objective is to Understand..
Recommendations of TECDOC-1147
regarding aging management of electrical
cables.
 Aging management program process
 Types of cables previously investigated
and aging mechanisms considered
 General recommendations for tests,
inspections, and maintenance programs
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IAEA TECDOC-1147
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Title: “Management of Aging of I&C Equipment in
Nuclear Power Plants”
Prepared by experts from US, UK, France,
Germany, Finland
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”
Identify “means available to minimize or eliminate
any detrimental effects of aging”
Aging Management Program Essentials:
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Identify components whose aging may impact
safety
Determine aging mechanisms important to
safety and consequences of this 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.
General Observations:
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 accident conditions, potential for
common cause failure considered serious
enough to warrant further investigations.
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Mechanisms Which Aggravate Cable Aging:
Elevated local temperatures
 Humidity, moisture ingress
 Mechanical Stresses due to cyclic loads
 Radiation Exposure
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Cable type
Temperature
Sensitivity
Radiation
Sensitivity
Remarks
Polyvinyl chloride
(PVC)
Sensitive
Not sensitive
Embrittlement at
elevated temp.
Cross-linked
Polyethylene (XLPE)
Sensitive
Not sensitive
Embrittlement at high
temp. and under
radiation
Heat resistant PVC
Sensitive
Polypropylene/
Polyethylene (PP/PE)
Sensitive
Sensitive
Flexibility lost at
elevated temp,
radiation
Polytetraflouroethylene (PTFE)
Not sensitive
Sensitive
Cracking due to
embrittlement
Fire retardant low
smoke PVC
Not sensitive
Not sensitive
Good performance
Embrittlement at
> 105 C
Ethylene Polypropylene 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
 Mechanical testing of insulation ductility
 Electrical resistance testing of cable
conductors and insulation
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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
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Visual examinations of insulation (cracking)
Hardness testing of small cable section
Chemical analysis of sample section of cable
Measurement of resistance of insulation
Microscopy examinations of cable insulation
samples
Swept frequency tests to measure dielectric
properties (instrumentation cables)
Time domain reflectrometry (TDR) of conductor
cable and connectors
AC/DC conductor resistance measurements