Table 2 Issues highlighted in this paper and potential NA support for required laboratory and modelling studies

Distribution of failure times for thick steel OP

Long-term (multi-decade) data under relevant conditions

Extension of release models to incorporate distribution of OP failures in space and time

Assess potential increased performance for thinner wall OP variants

Re-analysis of archaeological analogue data to derive failure distributions

Focused sampling of artefacts to determine potential role of environment and composition on corrosion rate

Internal IRF radionuclide transport within a failed OP

Scale model multi-decade simulations (maybe in URL)

Development of a 3D model for scoping calculations

Analysis of fractures in old steel containers or well castings (if any can be found)?

Uptake of key radionuclides by corrosion products

Accelerated, small-scale experiments on scavenging, Ostwald ripening

Development of a 3D model for scoping calculations

Re-analysis of analogue data on trace elements at redox fronts, possible sequential extraction of existing/new samples

Data mining on trace element analysis on Fe oxides of different age

Possible sampling of new sites where Fe oxides may contact relevant elements

Modify design to improve internal OP transport resistance

Lab studies of potential infilling materials (e.g. zeolites)

Extend scoping 3D model to allow the impact of such materials on performance to be assessed

Focused literature search of possible natural analogues of relevant materials

Extent of radiolysis at SNF surface

Re-assessment of existing experimental data: check for relevance to real systems

Extension of existing bulk surface models to consider partially saturated environments

Assessment of surface redox conditions in deep, rich ore bodies?

Mechanisms of redox buffering in relevant systems

Re-assessment of experimental data to rigorously determine extent of inorganic/microbially catalysed reactions

Extension of thermodynamic models to better represent kinetic constraints (including mass balances and supply of nutrients to microbes)

Focused analysis/new analogue studies of relevant redox fronts (especially within clay/in deep geological settings)

Modify design to improve internal OP redox buffering

Lab studies of potential redox buffers (e.g. Fe(II) minerals)

Extend scoping 3D model to allow the impact of such materials on performance to be assessed

Literature search of possible natural analogues of relevant materials

Development of uplift/erosion assessments for SNF

Accelerated/small scale simulation of SNF package nearing the surface

Development of new models to realistically represent system evolution in 3D

Synthesis of NA information to communicate timescales until exposure

Focused NA to assess impact of erosion of a rich ore body