Final standards for the proposed Yucca Mountain repository for spent fuel and high-level waste published by the US Environmental Protection Agency (EPA) address possible radiation exposures to the public over a million years into the future.

EPA first issued standards for limiting radiation doses to the public from the proposed facility in 2001, with a 10,000-year compliance period for protection of people and groundwater resources from potential releases of radionuclides from the site. In 2004, the US Court of Appeals ruled that the EPA standards were not consistent with the 1 million year compliance period suggested in a 1995 study by the US National Academy of Sciences (NAS). Under the terms of the 1992 Energy Policy Act the EPA standards must be consistent with the technical recommendations and findings made by the NAS, so the Appeals Court ruled that EPA must review its standards. Only individual-protection standards, and not groundwater standards, were affected. There was no suggestion that the existing EPA standards were not sufficiently protective, rather that they did not conform to the time period identified in the NAS report.

The new standards retain the dose limit from the EPA’s original standards of 15 millirem (150 microsieverts) per year for the first 10,000 years after disposal, and set a dose limit of 100 millirem (1 millisievert) per year for the period between 10,000 years and 1 million years after disposal. Initially, EPA had proposed a level of 350 millirem per year for the latter period, close to an estimated 300 millirem per year national average background radiation exposure. The more stringent 100 millirem standard was ultimately adopted as being “well-established as protective of public health under current dose limits,” according to EPA, and representing “a robust public health protection standard in the extreme far future.”

EPA says that its final standards are now consistent with NAS recommendations. The Department of Energy (DoE), which as the operator of the repository will be regulated by the standards, must now project performance and demonstrate compliance with individual-protection and human-intrusion standards over the 1 million year compliance period, considering the effects of climate change, earthquakes, volcanoes, and the corrosion of waste packaging. The US Nuclear Regulatory Commission (NRC) must also revise its licensing requirements for Yucca Mountain to ensure consistency with the EPA standards.

The NRC formally docketed DoE’s application for Yucca Mountain on 8 September, triggering a 3-year deadline, with possible one-year extension, for the regulator to make a decision on whether to authorise construction.

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