CORRESPONDENCE

Gauging the risk from US nuclear waste

You suggest that the United States should modify its strategy for nuclear-waste disposal according to the “risk it poses” (Nature 550, 429–430; 2017). That risk would first need to be determined.

The risk calculation is a function of the type of radiation, and its intensity and radiotoxicity. It also strongly depends on the mobility of specific radionuclides in different geological environments. The potential release and transport of radionuclides that are highly mobile in the geosphere, such as long-lived iodine-129 and selenium-79, have to be part of the risk evaluation. This risk varies from site to site.

Concerning the Waste Isolation Pilot Plant (WIPP) in New Mexico, it is not the state that has “tied the DOE’s hands” by banning the disposal of tank wastes, but the Land Withdrawal Act of 1992. The act bans high-level waste and spent nuclear fuel from WIPP to ensure that the repository does not become a magnet for all manner of nuclear wastes.

You state that “by and large, WIPP has functioned as designed”. However, the construction and operation of WIPP for a few decades does not confirm its long-term performance over 10,000 years, particularly for proposals that would increase or change the type of waste. The disposal of long-lived fission products could require the extension of WIPP’s compliance period to hundreds of thousands of years, as at Yucca Mountain in Nevada.

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