Principles and practice of a bellows-loaded compact irradiation vehicle

This article describes the key design principles and application of a mini-bellows loaded irradiation creep frame technology developed for use in the high flux isotope reactor (HFIR). For this irradiation vehicle, the bellows, frame, sample, and temperature monitor are contained within a hydraulic or fixed “rabbit” capsule of a few inches in length. Of critical importance and key to this technology is the viability and stability of the metallic bellows under the elevated temperature irradiation environment. Conceptual design and supporting analysis have been performed for tension and compression specimens. Benchtop verification has substantiated the modeling regarding the ability of the bellows to produce sufficient stress to induce irradiation creep in subsize specimens. Discussion focuses on the possible stress ranges in specimens induced by the miniature gas-pressurized bellows and the limitations imposed by the size and structure of thin-walled bellows. A brief discussion of pre- and post-irradiation measurement of the integrity of load frames irradiated to 4.4 × 1025 n/m2 (E > 0.1 MeV) is presented. Following this protocol, the pre-irradiation loading to a sample is determined and post-irradiation loading inferred.