ABSTRACT
Extensive testing has been performed at the Lawrence Livermore National Laboratory (LLNL) to determine the corrosion characteristics of nickel (Ni)-based alloys such as Alloy 22 (N06022) and three titanium alloys. The studies focused in three major areas: (a) Immersion tests at the long-term corrosion test facility (LTCTF), (b) the determination of the corrosion potential (Ecorr), and (c) the measurement of the repassivation potential. A review summary of the previously published results from LLNL in the three mentioned areas is presented. Examination of specimens removed from the LTCTF yielded significant information regarding the general, localized and stress corrosion cracking resistance of Alloy 22, four other nickel-based and three titanium alloys. Results from the Ecorr studies were significant but not conclusive. Current Ecorr results mainly opened areas for future research. Repassivation potential studies helped understanding the role of temperature, chloride concentration and inhibitive effect of nitrate but other areas such as fabrication effects still need to be investigated in more detail. A list of suggested future studies in the three areas mentioned above is also offered.
INTRODUCTION
The Yucca Mountain Project (YMP) is currently preparing a license application for the nation's first repository for spent nuclear fuel and high-level radioactive waste. 1 For more than two decades, the Project conducted an extensive scientific effort to determine whether Yucca Mountain, Nevada is a suitable site for a deep underground facility called a repository. 1 The purpose of a repository is to safely isolate highly radioactive nuclear waste. On July 9, 2002, the U.S. Senate cast the final legislative vote approving the development of a repository at Yucca Mountain. The bill was signed into law by the current President. Existing plans call for submitting an application to obtain a license to construct the repository from the U.S. Nuclear Regulatory Commission no later than June 30, 2008. 1 Yucca Mountain is located on federal land in a remote area of Nye County in southern Nevada, about 100 miles northwest of Las Vegas, Nevada. The proposed Yucca Mountain repository withdrawal area would occupy about 230 square miles (150,000 acres) of federal land that is currently under the control of the U.S. Department of Energy, the U.S. Air Force, and the Bureau of Land Management. Yucca Mountain is a ridge comprised of layers of volcanic rock, called "tuff." This rock is made of ash that was deposited by successive eruptions from nearby volcanoes, between 11 and 14 million years ago. These volcanoes have been extinct for millions of years. Yucca Mountain receives less than 7.5 inches (191 mm) of precipitation on average per year.1 With its desert climate, deep water table, and thick layers of stable rock, Yucca Mountain provides an excellent geologic setting for a repository. Even though the geologic site is stable, it is planned to complement the many natural features with additional engineered barriers. The repository design includes a series of emplacement tunnels excavated deep underground in solid rock. The layout and attributes of these tunnels are engineered to manage the heat that would be generated by the waste.
