Session: OAC-04-02 Transportation of Radioactive and other Hazardous Materials II

Paper Number: 61976

Start Time: Thursday, July 15, 2021, 09:00 AM

61976 - A Numerical Approach to Correlate Compression Stress Relaxation and Compression Set of Elastomer O-Rings With Tightness 

The excellent mechanical properties of elastomer seals at a wide range of temperatures as well as their high versatility and recovery potential under several load conditions make these materials well suitable for the application in containers designed for transport and disposal of negligible heat generating radioactive waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered and prohibit an unnecessary cask handling. An extensive knowledge of the change of the elastomer’s properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the safe enclosure of the radioactive material for the required time are mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have been already made and are still planned to scientifically support this task.

Among other representative types of elastomers, specimen made from ethylene propylene diene rubber (EPDM) were tested before, after and during aging to capture the most important of their complex mechanical properties with respect to application.

Exemplary results of these investigations were used to calibrate material models implemented in the commercial finite element software ABAQUS/Standard^®. The finite element model already presented in previous works uses a sequential temperature displacement coupling. The calculated compression stress relaxation (CSR) and compression set (CS) values do satisfactorily match the experimental results.

In many investigations performed at BAM both values (CSR and CS) were identified as key indicators of elastomer’s long-term performance.

However, the possibility to correlate these equivalent indicators with performance values such as tightness and leakage rate, measurable in the mounted state, is an important goal of our future work. In the presented study the ABAQUS^® feature of “pressure penetration” is introduced in the suggested finite element model for this purpose. It provides the possibility to simulate the penetration of a gas into a possible gap between flange and O-ring causing an opening of a leakage path. Three dimensional and axis-symmetric finite element models were generated to represent flat and grooved flanges of different dimensions.

The sensitivity of the feature to several input parameters is investigated and the observed behavior of the O-ring is tried to be correlated with the results of performed leakage tests.

Presenting Author: Mike Weber Bundesanstalt fuer Materialforschung und -pruefung (BAM)

Authors:

Mike Weber Bundesanstalt fuer Materialforschung und -pruefung (BAM)
Maha Zaghdoudi Bundesanstalt fuer Materialforschung und -pruefung (BAM)
Matthias Jaunich Bundesanstalt fuer Materialforschung und -pruefung (BAM)
Anja Kömmling Bundesanstalt fuer Materialforschung und -pruefung (BAM)
Dietmar Wolff Bundesanstalt fuer Materialforschung und -pruefung (BAM)