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IEC TR 61244-4
Edition 1.0 2019-09
TECHNICAL
REPORT
Determination of long-term radiation ageing in polymers –
Part 4: Effects of different temperatures and dose rates under radiation
conditions
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IEC TR 61244-4
Edition 1.0 2019-09
TECHNICAL
REPORT
Determination of long-term radiation ageing in polymers –
Part 4: Effects of different temperatures and dose rates under radiation
conditions
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.240; 29.035.01 ISBN 978-2-8322-7429-3
– 2 – IEC TR 61244-4:2019 © IEC 2019
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
4 Radiation induced degradation mechanisms at standard ambient conditions . 8
4.1 General conventions . 8
4.2 Effect of presence of oxygen . 9
4.3 Effect of dose-rate effect-1: Physical aspects . 9
4.4 Effect of dose-rate-2: Chemical aspects . 10
4.5 Research on degradation mechanism . 10
4.6 Experiences and acceleration factors . 11
4.7 Low dose-rate tests and LOCA survivability . 11
4.8 Effect of LOCA test environment . 11
4.9 Order effects, synergistic effects, and antagonistic effects . 12
4.10 Sequential test conditions equivalent to simultaneous methods. 12
4.11 Studies after TMI and later . 13
4.12 Arrhenius law and limitations . 13
4.13 Slow degradation behaviour observed in service-aged cables . 16
4.14 Inverse temperature effects . 17
4.15 Role of antioxidants . 17
4.16 Other thermal and radiation environment degradation characteristics . 18
5 Accelerated ageing test methods . 18
5.1 Sequential ageing test . 18
5.1.1 General . 18
5.1.2 Sequence of testing and synergistic effects . 19
5.1.3 Guidance on test sequences . 20
5.1.4 Assessment of accelerated ageing. 20
5.2 Simultaneous ageing test . 21
6 Conclusion . 22
Bibliography . 23
Table 1 – Dose rate conditions which do not cause inhomogeneous degradation . 10
Table 2 – E value according to materials, manufacturers, and grades . 14
a
Table 3 – Changes in various properties due to inverse temperature and annealing
recovery effects, investigated by several instrumental analyses [111]. . 17
Table 4 – Typical standard acceleration ageing sequence for qualification . 19
Table 5 – More recent standard acceleration ageing sequence for qualification . 19
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF LONG-TERM RADIATION AGEING IN POLYMERS –
Part 4: Effects of different temperatures
and dose rates under radiation conditions
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a Technical Report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 61244-4, which is a Technical Report, has been prepared by IEC technical committee
112: Evaluation and qualification of electrical insulating materials and systems.
The text of this Technical Report is based on the following documents:
Draft TR Report on voting
112/442/DTR 112/446/RVDTR
Full information on the voting for the approval of this Technical Report can be found in the
report on voting indicated in the above table.
– 4 – IEC TR 61244-4:2019 © IEC 2019
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61244 series, published under the general title Determination of
long-term radiation ageing in polymers, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
INTRODUCTION
IEC 60216 (all parts) and IEC 60544 (all parts) give reference and guidance for managing
accelerated thermal and radiological ageing steps for type testing procedures applicable to
electrical insulating materials. The actual application of electrical equipment usually requires
the consideration of effects which are a consequence of simultaneous occurrence of
temperature and radiation at varying intensities.
The CIGRE WG D1.42 study presents degradation data in particular with respect to cable and
wire insulation materials gathered from tests where thermal and radiation loads were applied
simultaneously. Even if there is a broad range of materials available from the industry, only
insulation materials commonly used were selected for this study. These materials are
crosslinked polyethylene (XLPE), ethylene-propylene-rubber (EPR), silicon-rubber (SIR) and
polyvinylchloride (PVC). Using these test data, power plant operators were in the position to
meet requirements defined by regulatory bodies in the frame of ‘long term operation
application’, showing that most insulation materials which have been in operation for 30 to 40
years were in good condition. Furthermore, material samples were collected from real
positions and test results were compared with reference samples, unaged as well as
artificially aged.
The main objective of the industry is to yield reliable values of the residual lifetime of the
insulation materials and linked pieces of equipment made up of these materials. However
more research is necessary as the in-service degradation of insulating materials appears to
be deviating from estimation based on accelerated ageing tests. For a better determination of
the degradation processes of insulation materials it is important to gain a wider knowledge on
material degradation and linked synergistic e
...