Development of extra-long continuum manipulator for nuclear facility inspection

Abstract Industrial inspection often requires systems to pass through confined entrances and traverse loosely constrained paths before reaching target locations. Borescopes and long-reach continuum manipulators are susceptible to insertion-induced buckling when deployed without continuous lateral support. This work presents a modular extra-long continuum manipulator designed for such hybrid industrial environments. The system combines a self-recoverable passive body with an independently actuated dual-balloon stabilisation unit, allowing it to traverse regions without continuous lateral confinement and subsequently establish a stabilised lift-up configuration at the target location. Its modular architecture supports transport and field maintenance, while the low-cost disposable design reduces decontamination requirements in harsh or contaminated environments. A solver-free, closed-form framework combines ground, tip, wall-contact, and wrapping resistances to estimate insertion-induced buckling margins for deployment planning. Prototypes (24 mm diameter, 8.2 m length) were validated experimentally and deployed in a nuclear decommissioning hot cell at Nuclear Restoration Services (NRS) Dounreay, UK, carrying a borescope camera and a 70 g radiation sensor to support inspection for subsequent decommissioning decisions.