Design and Demonstration of an Additively Manufactured Integrated Pressure Limiting Structure for Insertion into a Nuclear Research Reactor

An additively manufactured 316L stainless steel pressure limiting structure (PLS) has been designed as an end cap for an irradiation capsule to be inserted into the high flux isotope reactor (HFIR) at Oak Ridge National Laboratory. The PLS was printed using a laser powder bed fusion printer and includes a thin cylindrical rupture wall, a shield, and internal supports to facilitate printing and ensure mechanical integrity. Its overall dimensions are 9 mm tall and 10 mm in diameter. The pressure at which a 160-μm thick rupture wall fails is 5270 ± 120 psi (36.34 ± 0.83 MPa) for a monolithically printed cap and 4,764 ± 36 psi (32.85 ± 0.25 MPa) for a welded cap. Because these pressures are well below that at which the capsule housing begins to plastically deform (~6250 to 6500 psi or ~43.1 to 44.8 MPa), the PLS maintains the capsule at a safe operating pressure while it is in the reactor. The printing of all capsule components was fast (<1 h/capsule), reproducible, and customizable. Applications for this type of compact PLS likely extend beyond reactor science and include aerospace/defense, automotive, petrochemical, and space.