How are defects detected in reactor vessel components during manufacturing?

Comprehensive Non-Destructive Evaluation (NDE)

Defect detection in reactor vessel components relies on a multi-stage battery of non-destructive evaluation (NDE) techniques. The process begins during initial material production, where Material Testing and Analysis verifies the integrity of the raw superalloy. This foundational step ensures the material meets the stringent chemical and mechanical property specifications required for nuclear service before any manufacturing begins.

Volumetric Inspection for Internal Defects

For the detection of critical internal flaws, advanced ultrasonic testing (UT) is the primary method. Using phased-array or full matrix capture techniques, inspectors can precisely map the internal structure of thick-walled components like flanges and nozzles to identify voids, inclusions, or lack-of-fusion defects. This is often complemented by radiographic testing (RT) to provide a two-dimensional image of internal integrity, which is particularly useful for verifying complex internal geometries and welds.

Surface and Near-Surface Examination

Surface-breaking defects are identified through liquid penetrant testing (PT) and magnetic particle testing (MT). PT is highly effective on non-ferromagnetic materials, such as nickel-based superalloys, revealing fine cracks and porosity. For ferromagnetic steels used in certain vessel sections, MT provides rapid and sensitive detection of surface and slightly subsurface discontinuities. These methods are applied after major manufacturing steps, including precision forging and CNC machining.

Post-Process Validation and Corrective Actions

After critical post-processing steps, such as Hot Isostatic Pressing (HIP) and Heat Treatment, components are re-inspected to validate that the processes have successfully healed internal defects and achieved the desired microstructure without introducing new anomalies, such as distortion or surface oxidation.

Dimensional and Metallurgical Verification

Precision metrology, utilizing laser scanners and coordinate measuring machines (CMMs), ensures that all critical dimensions and tolerances are consistently maintained. Furthermore, metallographic analysis on witness coupons processed alongside the component provides direct evidence of the achieved grain size, phase distribution, and absence of detrimental microstructural features, closing the loop on the quality assurance cycle for the nuclear industry.