Study sums up questions on nuke effects on Yucca

Suzanne Struglinski

Monday, Nov. 10, 2003 | 9:08 a.m.

WASHINGTON --- Yucca Mountain's geologic makeup can help absorb some radioactive materials from nuclear waste, but more research is needed on how the overall temperature of the proposed storage site affects the absorption rate, a new study says.

In an article published today in American Mineralogist, the journal of the Mineralogical Society of America, David Bish, a former Los Alamos National Laboratory scientist, writes about the mountain's makeup of zeolites, a mineral that has high absorption properties.

The study also looked at the site's reliance on man-made barriers to contain radiation from the 77,000 tons of nuclear waste set to be stored there.

"We need to keep that a little bit better balanced, between the geologic barriers and the engineered barriers," said Bish, who is now the Haydn Murray Chair in Applied Clay Mineralogy at Indiana University in Bloomington.

Bish, along with three other Los Alamos scientists who co-authored the federally funded study, has worked on Yucca Mountain research since the 1980s, he said, but some of the information has not been distributed widely.

Bish admitted there is "nothing terribly new" in the study. It is a compilation of previous studies done for the department looking at the geologic makeup of the mountain. He wanted to put all of the mineralogy studies about Yucca into one place and have more of it in the public domain so other scientists and the public could view it.

All of the authors are no longer working on the Yucca Mountain project and Bish emphasized the Energy Department had no hand in the study. He submitted the study for publication early this year.

Bish said over the last few years there has been an "increasing reliance" on the proposed engineered barriers to keep radiation inside the repository when the original idea was to have it be a geologic storage site.

"We don't have the long-term experience with the man-made systems," Bish said, adding that the rock makeup has been studied a lot.

He does not take a position on whether the waste should be stored in Nevada.

"I'd like to know more about how introduction of a repository into the mountain will change the geology, mineralogy and hydrology, all of which will affect the ability of the mountain to contain the waste," Bish said. "We also need to know more about how water flows through the repository horizon, a zone of rock into which the waste would be placed."

The paper could be used in the licensing process with the Nuclear Regulatory Commission. The Energy Department anticipates submitting its license application in December 2004.

In the study, Bish and his coauthors studied drilled portions of rock to look at natural zeolites, or minerals in the rock with this absorbent qualities.

"Although it is a common perception that highly absorbing minerals have the ability to stop the movement of radionuclues in groundwater via cation exchange, minerals such as zeolites can only retard or slow the migration of such radionculides," Bish wrote.

Regarding potential temperatures inside the mountain, Bish wrote there is no "magic" degree "below which zeolites will be unaffected."

Although much of the information was known to those that follow the intricacies of the Yucca Mountain project, is was unclear if or how the study will affect the outcome.

"(The study) is about the effect of high temperatures due to the repository on zeolites and how these temperature effects in turn affect the overall chemistry of the rock and hence its ability to transport or retain radionuclides," according to an email from Rod McCullum, a senior project manager at the Nuclear Energy Institute, after reading the study.

"In this regard, the paper concludes that these temperature effects are important -- but doesn't conclude whether its important in a good way or a bad way."

"At this point, it is impossible to say what the impact of this study will be on Yucca Mountain," McCullum wrote.