SAMPO Safety criteria and improved ageing management

research for polymer components exposed to thermal-

radiative environments

SAFIR2022-KYT2022 Interim Seminar

18-19.3.2021

SAMPO

WP1 - Acceptance criterion

and safety margin

assessment

T1.1 – Improved estimation

for lifetimes of critical

polymer components

T1.2 – Sensitivity of

polymer properties to

additive content and

methods to verify polymer

quality

T1.3 – Setting up safety

margins for O-rings

WP2 - Improvements in

ageing management of

polymer components

T2.1 – Online condition

monitoring techniques

T2.2 – Sensitive analysing

techniques

T2.3 – Improved

interpretation of non-

destructive testing data

WP3 - International

cooperation

T3.1 – Polymer ageing in NPP

applications – event

organization

WP1 – T1.1. Improved estimation for lifetimes of critical polymer components

• Aim: Compare artificial accelerated

ageing to real ageing of components

used in NPP in order to:

– Improve knowledge about

material status after use in

NPP i.e. in true service

environment.

– Estimate residual service life of

polymer components.

– Find relevant exchange

intervals.

• Progress and work during 2019-

2020

– Workshops at Ringhals,

Forsmark and TVO for

product/material selection and

supply for laboratory

investigations.

– Oven ageing and laboratory

tests (hardness tests and

tensile testing) of selected

materials.

• Challenges and future work: Find

materials with known service history.

MembraneReinforced seal from TVO

Tensile

strength

(MPa)

Tensile

elongation

(%)

Hardness

(IRHD)

Naturally aged 6,92 294,5 72,4

Naturally aged

+ heat ageing

7,01 283,1 78,3

The table above shows TVO (Olkiluoto) seal aged in air at 120°C for 45

days and mechanically tested (tensile and hardness test). The ageing

time simulates approximately 20 years at 45°C.

Ringhals membranes have not been tested mechanically (tensile and

hardness test). Not aged due large spread in test results and uncertainty

of service environment during use.

WP1 – T1.2. Sensitivity of polymer properties to additive content and methods to verify polymer quality (VTT)

▪ Develop methods that can be used on-site for quality

management of polymeric components

▪ Literature survey to list various analysis methods and

identify applicable analysis methods for on-site

• OIT and FTIR for antioxidants

• TGA+EDS for filler analysis

▪ Show the capability of the methods to be used as part of

quality management

• Initial proof on their resolution have been provided

→ OIT clearly changes as PE is aged

→ TGA+EDS to measure carbon black filler in EPDM

rubber

▪ Future work: show the detection limits of the techniques

and provide on-site measurement procedures

9.4.2021 VTT – beyond the obvious 4

OIT unaged PE180 min

OIT aged PE10 min

TGA of EPDM:• 40,0% filler content• Additional EDS analysis

to exclude other non-volatile additives

→ 37,8% filler content• Combining EDS to TGA

improves the accuracyof the filler analysis

Smaller sample Larger sample

Element W% A% W% A%

C 94.39 98.71 94.56 98.76

S 1.06 0.42 0.97 0.38

Zn 4.55 0.87 4.47 0.86

WP1 – T1.3 Setting up safety margins for O-rings

• O-rings are mounted in valves, pipes etc. to prevent

leakage. Upon use in under compression the rings

finally start to leak.

• Compression set properties are measured according to

standard test methods to decide end of life values for o-

rings. Leak tests are performed to better correlate end

of life values to leakage in order to improve them.

• Rig design is updated (see left picture) - Indentation

created / slot for O-ring to sit, thus more realistic to

operating conditions.

• Water leak test rigs have been tested (right picture) to

verify the test method and the re-designed test rig.

Compression set on standard samples of standard

quality EPDM was performed and compared to high

quality NPP grade EPDM.

• The old test rig showed leakage after 30 days and 60

days at 140°C, meaning that the new rig keeps the o-

rings in place resulting in sealed rigs and no leakage.

• Work during 2021: Calculate activation energies for

tested materials and simulate LOCA conditions on test

materials. RISE — Research Institutes of Sweden5

Leak test setup

Leakage was observed only for the old rig, 140

WP2 - T2.1 Online condition monitoring techniques

Fig: Main trend in change appears similar for two measurement types

performed

RISE — Research Institutes of Sweden6

Aim:

To find possible methods to monitor and detect aging of polymers in situ.

Main results:

Based on literature studies in this should be possible through detection of changes in

electromagnetic (EM) material properties (i.e. permittivity).

Borrowed equipment was used for broadband (~105 -1010 Hz) characterization of

samples.

Measurements performed on new materials and materials previously aged at different

conditions. The measurements indicate changes.

Online monitoring of samples during (slow) ageing at moderate temperature, short time

span (40 days) and low temperature (50°C). Longer time period would be preferred.

Challenges and future work include:

• High sensitivity to noise. To find equipment to use for a longer time period.

• Finding samples suitable for developing this technology including simple rubber

formulations and shape, flat surface for probe face.

WP2 - T2.2 Sensitive analysing techniques

• Accelerated ageing for life time prediction is

often performed at elevated temperature to

decrease ageing times. At high temperatures

degradation mechanisms are known to be

different to those at ambient temperature.

• Therefore the goal is to develop a sensitive

analysis methods, known as Microcalorimetry to

measure the chemical changes closer to the real

operating conditions for polymeric materials

used in NPP.

• Microcalorimetry measures evolved heat from a

sample in the test chamber.

• In the project EPDM, Nitrile, PS, FT6230 (food

grade polymer), James Walker rubber material

(standard and top quality) samples were

analysed at different temperatures.

SEM image after EPDM was aged in

IMC 45-90 °C, using 100 μm

magnification. Antioxidants have

migrated to the sample surface.

RISE — Research Institutes of Sweden7

SEM image for fresh EPDM using

100 μm magnification

Normalised heat flow (μW/g) for EPDM non-aged

and EPDM already aged at 120 °C. The IMC test

was conducted at six different temperatures 45 °C,

50 °C, 60 °C, 70 °C, 80 °C and 90 °C for two

weeks. Temperature steps are shown by a dotted

line.

WP2 - T2.3. Improved interpretation of non-destructive testing data (VTT)

▪ Modulus (E) and crystallinity degree (CD) were identified as non-

destructively measurable ageing parameters that can be predicted by MD

simulations

▪ E can be measured non-destructively by ultrasound (US) and CD by DSC

▪ Experiments indicated that:

• EaB decreases due to ageing [1]

• E and CD stays constant

• PE remains its elasticity while loses its ability to withstand plastic

deformation [2]

9.4.2021 VTT – beyond the obvious 8

▪ Goals:

1. Simulate the ageing of PE and XLPE materials by the means of experiments and molecular dynamics (MD) simulations

2. Use this knowledge to improve non-destructive condition monitoring techniques (CMTs)

▪ Material model based on MD simulations have been developed:

• Methods to create and age representative material block [3]

• Simulation of stress-strain curves

• Simulation of E as function ageing [4]

• Simulation of CD as function of ageing [5]

• The model gives currently satisfactory approximates on

sound velocity values as material is aged

▪ Future work: role of the antioxidants in ageing model and

develop ultrasound and DSC measurements as CMTs

[1]

[2]

[3]

[4] [5]

Thank you for yourattention!