A reactor containment structure relies on reinforced concrete to maintain a barrier against radiological release, so active monitoring of aging concrete is essential to safety and regulatory compliance. Causes of degradation include alkali-silica reaction, chloride-driven reinforcement corrosion, carbonation, freeze–thaw cycling, thermal stresses from operational transients, and radiation-induced changes in near-surface materials. Consequences range from reduced structural capacity and leakage paths to costly repairs, extended outages, or loss of public confidence in nuclear safety. Guidance from the U.S. Nuclear Regulatory Commission and the International Atomic Energy Agency recommends integrated surveillance combining periodic inspection, nondestructive evaluation, and embedded sensing to detect both incipient and progressive damage.
Nondestructive evaluation techniques
Common nondestructive methods include visual inspection with high-resolution imaging and drone-assisted access for external surfaces, ultrasonic testing to evaluate thickness and detect delamination, ground-penetrating radar to map internal voids and reinforcement location, and infrared thermography to reveal subsurface moisture or debonding. Acoustic emission monitoring can detect active crack growth in real time, while impact echo and guided wave techniques assess layer integrity. The Electric Power Research Institute describes best practices for combining several NDE methods to improve detection probability and reduce false positives. Laboratory confirmation through core sampling and petrographic examination remains necessary for definitive diagnosis of mechanisms such as alkali-silica reaction.
Embedded sensing and electrochemical monitoring
Long-term surveillance increasingly relies on embedded sensors: fiber-optic distributed strain and temperature sensors, vibrating wire gauges, and corrosion potential and resistivity probes to track reinforcement corrosion kinetics. Electrochemical sensors and half-cell potential surveys quantify active corrosion risk and are widely used by utilities and research institutions. Oak Ridge National Laboratory and EPRI publications document deployments that correlate sensor trends with laboratory corrosion rates, enabling predictive maintenance rather than reactive repair. Environmental monitoring for humidity, chloride deposition, and radiation levels complements structural data to contextualize observed deterioration.
Effective monitoring programs integrate inspection data, NDE results, embedded sensor trends, and periodic material testing into a risk-informed framework. This approach aligns with regulatory expectations, supports transparent communication with affected communities, and helps minimize environmental and territorial impacts by enabling timely intervention before containment function is compromised.