While this finding means it is impossible for the water flow rate in faults or fractures to be slower than about 50 years, it could actually be much faster. For example, it is not known whether the Chlorine-36 was transported to the repository horizon in 1 year, 2 years, 5 years, or 49 years after the atomic test that generated the radioisotope. Regardless, the flow of water through the proposed repository is very rapid, something Nevada scientists have contended for years because of the highly fractured geology and the rapid pathways such conditions create.
DOE contends that it is too early to determine the significance of the Chlorine-36 and related findings and has indicated that the regulations governing site disqualification may need to be changed since they fail to permit evaluation of groundwater flow rates in light of other site characteristics. What the new finding means, however, is that licensing a Yucca Mountain repository will be even more difficult and more contentious, and may not be possible at all unless regulations are changed to be more lenient.
State of Nevada researchers have long contended that water flow rates from the ground surface through the proposed repository block into the water table are substantially faster than the 1,000 years required by the siting guidelines and NRC regulations. In comments on DOE's draft Environmental Assessment for the Yucca Mountain site as far back as 1984, Nevada Nuclear Waste Project Office staff noted that DOE's own data showed that water flow through fractures at the site was very rapid, and that the site would likely not meet DOE's own guidelines. In 1989, Governor Miller wrote to Energy Secretary Watkins recommending that the Yucca Mountain site be disqualified based, among other things, on the evidence of rapid water movement.
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State of Nevada
Nuclear Waste Project Office
Carson City, NV 89710