Interim Dry Storage – Delayed Hydride Cracking

ZIRAT30 Special Topic Report on Delayed Hydride Cracking (DHC) provides a comprehensive state-of-the-art review of hydrogen-related degradation mechanisms in zirconium alloys, with particular focus on delayed hydride cracking during interim dry storage of spent nuclear fuel. The report consolidates decades of international operating experience, experimental studies, fracture mechanics evaluations, and recent advances in mechanistic understanding related to DHC and hydride behaviour in zirconium alloy fuel claddings and pressure tubes.

The report covers the fundamental behaviour of hydrogen in zirconium alloys, including hydrogen solubility, diffusion, hydride precipitation, hydride fracture properties, and the influence of stress, temperature, irradiation, alloy composition, and texture on DHC susceptibility. Extensive operating experience from BWR, PWR, VVER, CANDU, and RBMK reactors is reviewed together with detailed discussions on crack initiation, crack growth mechanisms, threshold stress intensity factors (KIH), and dry storage performance assessments.

Special attention is given to recent international research on DHC mechanisms, including advanced experimental techniques, neutron radiography, finite-element modelling, hydride phase characterization, and the evolving understanding of diffusion-controlled crack growth models. The report also evaluates the impact of irradiation hardening, liner concepts, hydride reorientation, temperature history, and material microstructure on DHC behaviour under storage-relevant conditions.

The report provides utilities, regulators, fuel vendors, and technical specialists with an up-to-date technical reference on delayed hydride cracking, supporting informed decision-making related to spent fuel dry storage, fuel integrity assessments, long-term storage safety, and zirconium alloy performance under extended storage conditions.

DOWNLOAD SAMPLE

Interim Dry Storage – Creep (ZIRAT29/IZNA24)

Dry storage of commercial spent nuclear fuel (CSNF) is a well-established technology. As of 2024, spent nuclear fuel elements from commercial power plants and from research reactors have been stored in a dry state for nearly 40 years and 50 years, respectively. The overarching goal is preventing CSNF degradation that would result in multiple fuel rod failures during dry storage, at least through post-storage retrieval for reprocessing or placement and sealing in a container at a final disposal repository. Since performance with dry storage has already been shown acceptable for tens of years, the emphasis is presently on any changes that may occur during extensions of the dry-storage time periods to a hundred years. This Special Topic Report addresses Thermal Creep. It is shown that thermal creep under normal conditions of storage is unlikely to result in cladding rupture for present, as well as later.

DOWNLOAD SAMPLE

STR on Interim Dry Storage of Commercial Spent Nuclear Fuel – An Update (ZIRAT28/IZNA 23)

Except for a few countries (Finland, Sweden, France, and possibly Canada), the timing for establishing a geologic repository has been shown to be unpredictable. Therefore, spent fuel storage will remain the last backend operation for the foreseeable future in many countries. With proper attention, the radiological impact of storage is very low, but regulatory agencies have placed a heavy burden on licensees because of concerns related to the highly negative public perception related to the presence of spent fuel storage facilities in our biological environment. Therefore, locations where spent nuclear fuel (SNF) is or will be stored and their chosen storage technologies are the subjects of much scrutiny.

The focus of this review is on the spent nuclear fuel rods, and not on the storage system components such as the casks or the canisters  and their internal hardware elements. More specifically, the following topics are treated in the report: 

• Update of “Back-end” issues
• Thermal creep behaviour in relation to hydride reorientation
• PWR fuel rod cladding failure due to the hydrogen migration in spent fuel
• Update on any work on storage, transportation, long term issues
• Correlation between cooling rate and hydride reorientation. In particular, the case of fast cooling when the cask containing SNF is flooded with water, from a cladding temperature of ~350°C to ~30°C, is examined.

DOWNLOAD SAMPLE