Nuclear glass corrosion by groundwater involves coupled processes at various scales that need to be well understood to develop predictive kinetic models. Here we highlight and discuss key scientific questions arising from the current state of knowledge and presentations given at the SumGLASS 2013 summer school - (2nd International Summer School on Nuclear Glass Wasteform: Structure, Properties and Long-Term Behavior, SumGLASS 2013). These issues concern fundamental processes as well as how chemical, hydraulic, thermal, and mechanical constraints related to the design of the multi-barrier system in the geological disposal facility affect the rate-limiting mechanisms. Those that are deemed of high importance have to be addressed to improve the robustness and reliability of predictions of radionuclide release from the glass on a geological timescale.
