TY - JOUR
T1 - A new analytical model for predicting the radio-thermal oxidation kinetics and the lifetime of electric cable insulation in nuclear power plants
T2 - Application to silane cross-linked polyethylene
AU - Hettal, Sarah
AU - Roland, Sébastien
AU - Sipilä, Konsta
AU - Joki, Harri
AU - Colin, Xavier
N1 - Publisher Copyright:
© 2021
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/3
Y1 - 2021/3
N2 - The radio-thermal oxidation of silane cross-linked polyethylene (Si-XLPE) was studied in air under different γ dose rates (6.0, 8.5, 77.8, and 400 Gy.h−1) at different temperatures (21, 47, and 86°C). The changes in the physico-chemical and mechanical properties of Si-XLPE throughout its exposure were determined by FTIR spectroscopy, differential scanning calorimetry (DSC), swelling measurements, rheometry in rubbery (DMTA) and in molten states, and uniaxial tensile testing. It was found that oxidation leads to the build-up of a wide variety of carbonyl and hydroxyl products (mostly carboxylic acids and hydroperoxides) and an efficient chain scission process that catastrophically reduces the concentration in elastically active chains and the elongation at break from the early periods of exposure. A new analytical model was derived from the current radio-thermal mechanistic scheme without making the usual assumption of thermal stability of hydroperoxides. After an initial period where the oxidation kinetics occurs with a constant rate, this model allows also predicting the auto-acceleration of the oxidation kinetics when the hydroperoxide concentration reaches a critical value of about 1.6 × 10−1 mol.L−1. Choosing this critical value as a structural end-of-life criterion allows a more direct assessment of the lifetime of Si-XLPE in the various radio-thermal environments under study, except at the highest temperature (i.e. 86°C) where the kinetic model can still be noticeably improved.
AB - The radio-thermal oxidation of silane cross-linked polyethylene (Si-XLPE) was studied in air under different γ dose rates (6.0, 8.5, 77.8, and 400 Gy.h−1) at different temperatures (21, 47, and 86°C). The changes in the physico-chemical and mechanical properties of Si-XLPE throughout its exposure were determined by FTIR spectroscopy, differential scanning calorimetry (DSC), swelling measurements, rheometry in rubbery (DMTA) and in molten states, and uniaxial tensile testing. It was found that oxidation leads to the build-up of a wide variety of carbonyl and hydroxyl products (mostly carboxylic acids and hydroperoxides) and an efficient chain scission process that catastrophically reduces the concentration in elastically active chains and the elongation at break from the early periods of exposure. A new analytical model was derived from the current radio-thermal mechanistic scheme without making the usual assumption of thermal stability of hydroperoxides. After an initial period where the oxidation kinetics occurs with a constant rate, this model allows also predicting the auto-acceleration of the oxidation kinetics when the hydroperoxide concentration reaches a critical value of about 1.6 × 10−1 mol.L−1. Choosing this critical value as a structural end-of-life criterion allows a more direct assessment of the lifetime of Si-XLPE in the various radio-thermal environments under study, except at the highest temperature (i.e. 86°C) where the kinetic model can still be noticeably improved.
KW - Analytical kinetic model
KW - Carbonyl build-up
KW - Chain scissions
KW - Hydroperoxide decomposition
KW - Lifetime prediction
KW - Radio-thermal oxidation
KW - Silane cross-linked polyethylene
KW - Structural end-of-life criterion
UR - http://www.scopus.com/inward/record.url?scp=85099687287&partnerID=8YFLogxK
U2 - 10.1016/j.polymdegradstab.2021.109492
DO - 10.1016/j.polymdegradstab.2021.109492
M3 - Article
AN - SCOPUS:85099687287
VL - 185
JO - Polymer Degradation and Stability
JF - Polymer Degradation and Stability
SN - 0141-3910
M1 - 109492
ER -