The USA’s Electric Power Research Institute (EPRI) has released a study that endorses the Environmental Protection Agency’s (EPA’s) existing 10,000-year radiation standard for the Yucca Mountain repository. However, the standard should be fundamentally different for periods exceeding 10,000 years, according to the study.

The study evaluates the technical issues related to establishing radiation protection standards for up to 1 million years and outlines regulatory approaches to assess compliance with the standard over such a long time.

The recommendations in the report acknowledge that detailed information about processes and events taking place many tens of thousands of years in the future will not be available and that different requirements are necessary to explicitly recognise that uncertainties increase with time.

In the study, EPRI recommends that changes to the post-10,000-year standards use a limited set of scenarios and do not introduce elements that “require arbitrary scientific assumptions to carry out the analysis.”

The report recommends that a ‘stylised’ approach be taken to regulation and compliance assessment, which is consistent with the international approaches to long-term radiation protection standards. This is because “it becomes impossible to provide accurate estimates of the details of the evolution of natural and human systems over very long time frames.”