Managing Heat in a Repository at Yucca Mountain

Abstract

When radioactive elements decay, one result is heat. Because it will contain waste packages with many tons of decaying spent nuclear fuel and high-level radioactive waste, the underground repository proposed for Yucca Mountain will generate heat for thousands of years. Engineers with the Yucca Mountain Project call the amount of heat generated by this radioactive decay within a particular area a ''thermal load''. The number, size and contents of the waste packages placed in the repository will help determine the actual concentrations of heat within the facility. How these waste packages are arranged will determine which parts of the repository will become hottest. Many packages placed closely together will concentrate considerable heat nearby. This is similar to how heaping the coals in a grill at the center focuses more intense heat there than at the edges. Placing these same packages farther apart--a low thermal load--results in lower temperatures over a greater area. Scientists consider heat management to be an essential design element for a repository This is because the way heat moves through a repository could affect its rock floors and walls, and therefore the facility's ability to do its job. Each possible arrangement comes with its own potential advantages and disadvantages. Scientists have conducted extensive underground and laboratory tests of the man-made materials and the rock at Yucca Mountain to determine which method of spacing will best contribute to the safe disposal of highly radioactive materials there.