We present a physics-informed neural network (PINN) framework for predicting the mechanical performance of elastomers exposed to concurrent thermal and gamma-radiation exposure, such as elastomers in nuclear cables or space electronics. Our demonstrated approach integrates the dual-network hypothesis with the microsphere concept to represent soft and brittle sub-networks, while embedding physical laws directly into the machine learning process. Hard constraints (e.g., incompressibility, bounded network fractions) are enforced through network architecture, and soft constraints (e.g., monotonicity, polyconvexity, and fading effects) are imposed through the loss function. This integration reduces the effective search space, guiding the optimization toward physically admissible solutions and enhancing robustness under sparse data. Validation against published datasets on silicone rubber, ethylene propylene diene monomer, and silica-reinforced silicone foam shows accurate predictions of stress-stretch behavior and elongation-at-break at exposure times not used for training. Results confirm that physics-informed constraints improve extrapolation, capture synergistic thermal-radiation effects, and provide a reliable tool for the predictive framework for property evolution of nuclear cable insulation and other radiation-exposed elastomers.

Gamma radiation used for sterilization of medical devices is challenged by cobalt-60 supply and commercial capacity. To maintain a robust radiation sterilization marketplace for the rapidly growing single-use medical device industry, investigation of potential alternatives to gamma technology, such as electron beam (e-beam) and X-ray technology, is critical. In this work, we directly compare the effects of radiation source and absorbed dose level on the polymeric materials and function of a commercial pulsed lavage device used for wound care. Product functionality, polymer mechanical, and polymer optical properties were evaluated using standard methods and input from the device manufacturer. Test results show that functionality of the product was not inhibited by radiation although the battery in the device exposed to X-ray exhibited greater voltage loss compared to batteries in products exposed to gamma or e-beam. Statistically significant differences between gamma and e-beam exposure and between gamma and X-ray exposure were also observed for product appearance in terms of yellowness index of several of the polymers considered. Overall, the results of this study support the viability of e-beam and X-ray radiation technologies as alternatives to cobalt-60 gamma technology for sterilization of the single-use pulsed lavage medical device investigated.

Sterilization of biopharmaceutical products has commonly employed gamma radiation from cobalt-60, a radioisotope with associated security and supply chain risks. Increased use of non-radioisotope alternative ionizing energy technologies, such as electron beam (e-beam) and X-rays, is promising but has been hindered by lack of thorough evaluation of the compatibility of these techniques with product materials. This study investigates radical generation in a polyethylene (PE)/ethylene-vinyl alcohol copolymer (EVOH)/PE multilayer film product (Sartorius Flexsafe (R) with the S80 film) under varying e-beam and X-ray irradiation conditions to address data gaps for these materials and technologies. Utilizing a full factorial design of experiments (DoE), we examined the effects of irradiation technology, dose level, dose rate, processing temperature, and ambient oxygen concentration on radical formation, as quantified by electron spin resonance (ESR). Our results indicate that the type of ionizing technology (e-beam vs. X-ray) does not significantly affect radical concentration generation in the materials. However, higher doses and lower temperatures were found to correlate with increased radical concentrations, while elevated oxygen levels effectively suppressed radicals through a presumed scavenging mechanism. For e-beam processing, a higher dose rate reduced radical accumulation, while the opposite trend was found for X-ray irradiation. Complementary Fourier-transform infrared spectroscopy (FTIR) and principal component analysis (PCA) revealed subtle oxidation differences of PE under specific irradiation conditions.

This study investigates thermal aging and kinetic characterization of four electrical cable insulation materials, one crosslinked polyethylene (XLPE) and three ethylene-propylene rubber (EPR) types, aged at 110 °C, 121 °C, 136 °C, and 150 °C. Five aging indicators were measured: tensile elongation at break (EAB), mass change, density, indentation modulus, and indentation relaxation time. This work introduces a novel framework that integrates time-temperature superposition with a principal component analysis (PCA)-derived composite aging metric across the five indicators to derive activation energy (Ea) from the full aging landscape, reducing endpoint bias and yielding a central measure of aging kinetics. In addition, the principal component score trajectory (PC1-PC2 plot) provides an intuitive map of aging severity across temperatures and aging times.

The effects of electron beam (e-beam) irradiation on the dielectric relaxation behavior of polycarbonate (PC) were investigated over a broad temperature range (-90 to 185 degrees C) and frequencies (10-2 to 107 Hz) using broadband dielectric relaxation spectroscopy (BDRS). Irradiation doses influenced both the glass transition (alpha-relaxation) and local molecular motions (beta-relaxation). At 50 kGy, the alpha-relaxation process shifted to higher frequencies, indicating increased segmental mobility, while at 100 kGy, it remained unchanged, suggesting stabilization of molecular dynamics at this dose. A more pronounced effect was observed at 200 kGy, where enhanced chain mobility further altered the dielectric response. Ionic conduction was evident at low frequencies, contributing to the overall dielectric behavior. Dielectric spectra were analyzed using the Havriliak-Negami equation, which provided precise resolution of the alpha- and beta-relaxation processes. The dielectric strength (Delta e), relaxation time (z), peak broadness, and deviations in relaxation behavior exhibited strong dose dependence. The Vogel-Fulcher-Tammann (VFT) equation effectively described the alpha-relaxation kinetics across all irradiation levels. The dielectric glass transition temperature (Tg) was determined from the VFT activation curves at z =100 s, revealing a significant reduction at 50 and 200 kGy, confirming molecular rearrangements due to irradiation. E-beam irradiation doses altered the width of the alpha-relaxation spectra by creating distinct relaxation segments, leading to variations in cooperative regions and increased variability in the dynamic constraints. The beta-relaxation process, associated with localized motions of carbonyl and phenylene groups, followed Arrhenius behavior, with an activation energy of 49.5 +/- 1.5 kJ/mol regardless of the different e-beam irradiation doses. The observed dynamics are a consequence of structural molecular changes induced by e-beam irradiation, which influence the dielectric behavior and relaxation processes. These findings provide a detailed understanding of the impact of ebeam irradiation on the dielectric properties and molecular dynamics of PC, offering valuable insights into the behavior of irradiated polymeric materials.

We present a physics-informed neural network framework for predicting the mechanical performance of elastomers exposed to concurrent thermal and gamma-radiation exposure, such as elastomers in nuclear cables or space electronics. Our demonstrated approach integrates the dual-network hypothesis with the microsphere concept to represent soft and brittle sub-networks, while embedding physical laws directly into the machine learning process. Hard constraints, e.g., incompressibility, bounded network fractions are enforced through network architecture, and soft constraints e.g., monotonicity, polyconvexity, and fading effects are imposed through the loss function. This integration reduces the effective search space, guiding the optimization toward physically admissible solutions and enhancing robustness under sparse data. Validation against published datasets on silicone rubber, ethylene propylene diene monomer, and silica-reinforced silicone foam shows accurate predictions of stress-strain behavior and elongation-at-break at exposure times not used for training. Results confirm that physics-informed constraints improve extrapolation, capture synergistic thermal-radiation effects, and provide a reliable tool for lifetime assessment of nuclear cable insulation and other radiation-exposed elastomers.

The medical device industry has been investigating ways to increase the use of alternatives to cobalt-60 gamma radiation and ethylene-oxide gas sterilization, such as electron beam (E-beam) and X-ray radiation, due to regulatory and market pressures. One impediment to switching to E-beam or X-ray technology for sterilization is the lack of data on the effects of these radiation sources on medical device polymers. To provide such data this work considers irradiation and testing of a common single-use medical bone cement mixing system, the Stryker Advanced Cement Mixer (ACM (R)), that is composed of seven polymer materials. The ACM (R) devices considered here were processed to sterilization-relevant doses (15, 25, 50, and 70 kGy) using three radiation technologies: gamma, E-beam, and X-ray. The system and its polymer components were tested for product functionality, as well as mechanical and visual properties to determine how exposure effects may be influenced by radiation technology and dose level. We found that although there were instances of statistically significant differences in effects between the gamma-irradiated products and those irradiated with E-beam and X-ray, those effects were negligible in terms of retained functionality of the product and retained mechanical properties of the polymer components. Overall, results of this study demonstrate that, for of the effects studied, E-beam and X-ray are viable alternatives to cobalt-60 gamma radiation for sterilization of the polymer-based device investigated.

Recent developments in instrumentation have demonstrated that it is feasible to monitor the condition of energized cables online using frequency domain reflectometry (FDR) and spread spectrum time domain reflectometry (SSTDR). However, the response spectra from these measurements are complex to interpret and do not lend themselves to simple threshold alarms. To address this challenge, machine learning (ML) techniques have been used, demonstrating high accuracy in predicting normal or anomalous cable behavior when using binary normal and anomalous training and test data. A more plausible scenario for cable insulation damage, however, involves a slowly developing material change due to long-term exposure to thermal or radiation stresses, subtly altering material properties and resulting in an altered reflectometry response. The practical challenge lies in recognizing when such changes are significant enough to raise concern. The Pacific Northwest National Laboratory (PNNL) Accelerated and Real-Time Experimental Nodal Analysis (ARENA) cable motor test bed was used to measure the FDR and SSTDR responses of an energized cable as a section of it was thermally aged over 70 days. Online reflectometry spectra were collected and post -processed to simulate real-time analysis, aiming to distinguish normal from anomalous behavior. These spectra were also contrasted with off-line and direct conductor-coupled reflectometry tests. For use with ML algorithms, it was necessary to label the reflectometry results as either normal or anomalous. This was accomplished with witness samples, which were aged alongside the main cable and periodically tested for elongation at break and tensile strength two offline destructive tests indicative of cable damage. These destructive tests revealed a natural breakpoint for differentiating the two conditions at similar to 35 days. Both supervised and unsupervised ML methods were applied. The results indicated that the ML methods could effectively classify cable data as normal or anomalous and that there was a strong correlation between the reflectometry results and the elongation at break and Fourier transform infrared spectroscopy destructive off-line tests of the witness samples. In addition, the online testing was nearly as clear and effective as off-line tests. These findings suggest that the integration of ML techniques with reflectometry can provide a reliable method for monitoring and early detection of cable insulation damage.

The present study investigated the effects of gamma-ray, electron beam, and X-ray radiation on polymers in EVA/ EVOH/EVA multilayer films. Spectroscopic methods, including FTIR and UV-Vis, were employed in conjunction with chemometric treatments such as PCA, SIMPLISMA treatments, and PLS models. The feasibility of dose prediction on multilayer film, given a known dose, is attainable across various irradiation technologies. Both gamma ray and X-ray exhibit comparable effects on the multilayer film, and it is feasible to anticipate the dose released on the film by utilizing UV-Vis spectra or infrared spectra for gamma ray or X-ray of a predetermined dose.

This work aims to investigate the deployment of a reflectometry testing method for the online monitoring of photovoltaic (PV) systems. The reflectometry for frequency domain reflectometry (FDR) and spread spectrum time domain reflectometry (SSTDR) are developed at the Accelerated and Real-Time Environmental Nodal Assessment (ARENA) testbed for the Integrated Renewable Energy System (IRES) at Pacific Northwest National Laboratory. Different from traditional fault detection in commercial PV strings, reflectometry approaches can not only detect but also locate a large variety of anomalies by monitoring impedance discontinuities, such as mechanical damage, aging caused by ultraviolet light and high temperature, moisture ingress, transients, and more. Deployment of reflectometry for online monitoring of PV systems is expected to increase the efficiency of installation, operation, and maintenance (IO&M) of PV systems towards 50-year lifetimes.

Many polymer-based medical devices are sterilized by gamma irradiation. To reduce the use of cobalt-60 gamma-ray sources, transition from gamma ray to alternative irradiation technologies was proposed, namely electron beam (e-beam) and X-ray. A major impediment for such a transition is the knowledge gap in material compatibility with the different radiation sources. In this study, multi-layer films consisting of ethylene vinyl acetate (EVA) and ethylene vinyl alcohol (EVOH) components were irradiated to target doses of 30, 45, and 60 kGy by gamma-ray, e-beam, and X-ray sources. Effects of irradiation were evaluated on 12 material properties, and statistical comparisons between gamma irradiation and alternative technologies were conducted using the two one-sided t-test (or “equivalence test”) and classic t-test. Melting temperature and UV absorbance below 300 nm showed dose dependencies, while other investigated properties such as discoloration and mechanical durability did not change with dose up to 60 kGy. Based on these results, there is no material compatibility issue associated with the transition from gamma to e-beam or to X-ray as source of sterilization radiation of the studied multi-layer film.

Electrical cables are essential within nuclear power plants (NPPs) to support power, control, and instrumentation systems. Given the importance of these systems in servicing NPPs, prevention and detection of electrical cable failure is a vital part of aging management programs. As such, nondestructive examination (NDE) techniques are commonly used to evaluate the degradation of electrical cables. Common offline electrical NDE techniques for condition monitoring (CM) may include lowfrequency dielectric spectroscopy (LFDS), time domain reflectometry (TDR), frequency domain reflectometry (FDR), and time domain dielectric spectroscopy (TDDS). However, there is no single NDE method to comprehensively evaluate cable condition and, in many cases, a combination of local and global tests is required. In this work, we evaluate the sequentially applied thermal and gamma radiation aging of electrical cable insulation using electrical diagnostic test methods to better understand damage detection in cables using a combination approach. Gamma radiation aging was performed on cross-linked polyethylene (XLPE) polymer cable insulation material commonly used in NPPs. Long “30-foot” cable mandrels of XLPE were irradiated at room temperature, using Co-60 gamma-rays, to intervals of 100 kGy each, for a combined total dose of 500 kGy. Post irradiation electrical testing was performed on these cables. Preliminary results of the electrical diagnostics indicate trends with increasing aging conditions in the XLPE cable insulation samples. The results of this study advance electrical-based diagnostic techniques for condition monitoring of electrical cables in NPPs, providing plant operators with more complete information to support repair, mitigation, or replacement decisions.

Nuclear power plant (NPP) electrical cables are essential components of power, control, and instrumentation systems. Environmental stressors, such as heat and radiation, can reduce electrical cable service life. Electrical reflectometry methods are commonly employed to identify and locate cable degradation. However, most reflectometry methods require cables to be de-energized and de-terminated prior to testing. Spread spectrum time domain reflectometry (SSTDR) has been identified as a potential solution to these issues but additional work is needed to understand the influence of a wide variety of fault types on SSTDR response. In this work, we explore development a fully 3D SSTDR digital twin to predict cable degradation. A typical 3-conductor low-voltage electrical cable was selected for evaluation and 20-m of cable was simulated within COMSOL Multiphysics((R)). Insulation damage was induced over 1-m through scaling of empirically-derived permittivity. The results demonstrate the feasibility of the approach to accurately detecting cable damage but additional work is needed to reduce noise due to the connection.

Over the last few decades, several marine renewable energy (MRE) technologies, such as wave energy converters (WECs) and current energy converters (CECs), have been developed. As opposed to traditional materials such as metal alloys, the structure of these technologies is made up of polymer and polymer composite materials. Most structures have been made using thermoset polymer composites; however, since thermoset polymer composites are not recyclable and lack sustainability, and with recent innovations in recyclable resins, bio-based resins, and the development of additive manufacturing technologies, thermoplastic polymers are increasingly being used. Nevertheless, the methodologies for identifying end-of-life options and recovering these polymer composites, as well as the recycling and reuse processes for MRE structures, are not well-studied. Specifically, since these MRE structures are subjected to salinity, moisture, varying temperature, biofouling, and corrosion effects depending on their usage, the recyclability after seawater aging and degradation needs to be explored. Hence, this review provides an in-depth review of polymer composites used in marine applications, the hygrothermal aging studies conducted so far to understand the degradation of these materials, and the reuse and recycling methodologies for end-of-life MRE structures, with a particular emphasis on sustainability.

Stemming from security threats and shortages in supply, a recent push has emerged to expand alternatives to radioisotope Cobalt-60 gamma radiation for sterilization of polymeric medical products, including electron beam (E-beam) and X-ray machine-based sources. However, before large-scale implementation, the effects of these non-isotope-based methods must be thoroughly investigated from several perspectives, involving their potential detrimental effects on the structural, thermal, and mechanical properties of polymers in medical devices. This paper investigates such effects in commonly used medical device polymers, including polypropylene homopolymer (PPH), polyolefin elastomer (POE), low-density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and chlorobutyl rubber (CIIR). To connect radiation-driven changes in polymer structural and thermal properties and corresponding changes in mechanical properties, several characterization techniques were utilized, including gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). We found that the tensile strength of X-ray irradiated PPH, as well as X-ray, E-beam, and gamma irradiated CIIR decreases due to chain scission, which is corroborated by GPC and DMA. The GPC results of LDPE suggest chain scission, but interestingly without a corresponding decline in tensile strength. By comparison, POE and ABS appear to undergo further crosslinking with increasing irradiation dose, which generally strengthens them. Importantly, in the vast majority of the cases, there were small to no changes in properties upon changing radiation technologies (at a given dose), i.e., no radiation source dependence. However, in a few specific cases, radiation method dependencies did arise, for instance, in terms of the molecular weight of PPH being significantly increased upon X-ray irradiation, while the melting temperature, glass transition temperature, and elongation at break reduced compared to gamma. Overall, this study provides valuable insight into radiation-driven chemical and structural changes in polymers that produce changes in physical and functional properties.