IN THIS ISSUE...
- Nevada Proposes Comprehensive, Independent Testing Program for Casks Designed to Deliver Nuclear Waste to Yucca Mountain
- Laboratory Experiments: Metal Alloy Nuclear Waste Containers Will Dissolve

Nevada Proposes Comprehensive, Independent Testing Program for Casks Designed to Deliver Nuclear Waste to Yucca Mountain

Citing serious credibility problems associated with past federal government-sponsored tests of casks being developed to deliver high-level nuclear waste to the proposed Yucca Mountain repository, the State of Nevada Nuclear Projects Agency recently asked U.S. Nuclear Regulatory Commission Chairman Richard Meserve to consider Nevada’s proposal on how to carry out a series of independent tests to oversee and verify the government’s previous findings.

In a letter to Meserve, agency Executive Director Bob Loux said the state believes that “comprehensive full-scale testing would not only demonstrate compliance with NRC performance standards, it would improve the overall safety of the cask and vehicle system and generally enhance confidence in both qualitative and probabilistic risk and analysis techniques.” 

Loux also wrote that the tests could increase public and state and local government acceptance of the shipments, and could reduce adverse social and economic impacts caused by current public perceptions of the risks of transporting the nation’s high-level nuclear waste to Yucca Mountain, 90 miles northwest of Las Vegas.

Nevada is proposing a four-pronged approach to the full-scale certification testing: meaningful stakeholder participation in development of testing protocols and selection of test facilities and personnel; full-scale physical testing, including sequential drops of casks, fire, puncture, and immersion, prior to NRC certification; additional computer simulations to determine performance in extra-regulatory accidents and to determine failure thresholds; and, reevaluation of previous risk study findings and, if appropriate, revisions of NRC cask performance standards. 

Loux said Nevada also considers destructive testing of a randomly selected production cask to be a highly desirable way of ascertaining actual failure thresholds.

Nevada in 1999 requested a comprehensive assessment of the affects of three types of terrorist attacks and sabotage on waste casks: attacks against transportation infrastructure used by nuclear waste shipments, attacks involving the capture of a nuclear waste shipment and use of high-energy explosives against the cask, and direct attacks on a cask using anti-tank missiles.  As part of that request, Nevada also recommended that the NRC consider the need for physical testing on full-scale or scale models of casks to evaluate weapons capabilities, cask vulnerability to attack with high-energy explosive and the response of spent nuclear fuel to such attacks. 

However, Loux said the NRC has yet to take any action on Nevada’s recommendation, “despite the added urgency brought about by the events of Sept. 11 and their implications for potential terrorism against spent fuel and/or high-level waste shipments.”

Loux added that during the preliminary phase of the NRC’s Package Performance Study, conducted in 1999 and 2000, the NRC repeatedly acknowledged the importance of establishing stakeholder confidence in the PPS study process and its findings.  However, the NRC has yet to release the draft PPS testing protocol for public review and comments, as it promised in summer 2002, nor has the NRC rescheduled the promised PPS public meetings in Nevada, originally planned for August and September, 2002.

“The process to date does not inspire confidence, nor does it come close to meeting NRC-stated commitments to public and stakeholder involvement in developing and review of testing protocols,” Loux said.

Laboratory Experiments: Metal Alloy Nuclear Waste Containers Will Dissolve
Scientists working for the State of Nevada recently told the National Academy of Sciences’ Board of Radioactive Waste Management that metal alloy containers designed to hold high-level nuclear waste at Yucca Mountain will in time dissolve under certain conditions.

Dr. Roger Staehle and Dr. Don Shettel conducted the experiments at Catholic University using conditions simulating those anticipated at Yucca Mountain.  They told the board that given the natural conditions found at Yucca Mountain – including moisture and heat – manmade metal alloy containers cannot safely hold high-level nuclear waste for the required regulatory period, but in time will dissolve.

“These findings reinforce our belief that the U.S. Department of Energy and the Nuclear Regulatory Commission have long used fuzzy science to prop up their plans to dump the nation’s nuclear waste in Nevada,” said Loux.  “Once again, the scientific facts are proving the fallacy of DOE’s assertion that Yucca Mountain is safe for the long-term storage of nuclear waste.”

A critical element of the proposed Yucca Mountain repository is an engineered barrier system incorporating nuclear waste canisters composed of C-22 Hastelloy and a drip shield made of titanium-7 metal. The drip shield is designed to divert any water seepage
and prevent it from reaching the waste canisters.

Dr. Staehle and Dr. Shettel have been conducting laboratory experiments to assess the stability of the two key barrier metals, C-22 and Ti-7, under anticipated repository conditions. These conditions include rock dust and precipitates covering the drip shield and hot canisters; fracture and rock-pore water dripping and flowing; microbial/fungal reactions; and man-made intrusive materials.

Using simulated Yucca Mountain pore water, Dr. Staehle’s and Dr. Shettel’s experiments strongly suggest that heating in the repository will produce a powerful acid vapor called aqua regia, which is so potent it even dissolves gold. As this caustic vapor condenses and evaporates, concentrated acid and solid precipitates form. The solid precipitates in turn attract water vapor from the air and form additional very strong acids. Under these conditions, at temperatures ranging from 70 degrees Celsius (158 degrees Fahrenheit) to 145 C (293 F), the engineered-barrier metals C-22 and Ti-7 dissolve.

The scientists’ findings just add to the list of problems with C-22 and Ti-7.  Previously, laboratory results showed that lead, mercury, fluorine, and possibly other trace elements in the water and rock of Yucca Mountain would hinder the ability of C-22 and Ti-7 to contain the nuclear wastes for the required period of time.