56 Spent Nuclear Fuel: Selected Case Studies of (A) Wet Storage (B) above Ground Ventilated Storage Technologies, (C) Metal Casks and (D) Underground Storage Modules

Drs. K.P. (Kris) Singh and Tony Williams collaborate in Chapter 56 to present a comprehensive assay of the backend of the commercial nuclear power cycle. The management of the spent nuclear fuel removed from the reactor after a period of power generation in the reactor core by nuclear fission has been described as the Achilles heel of the commercial nuclear industry and the source of much of the disparate political opposition to its use, despite its evidently sterling credentials as a non-polluting and commercially viable alternative to fossil power.

The perceived undesirability of the spent nuclear fuel derives from the transmutation of uranium into an array of isotopes (known as actinides and fission products) that produce copious quantities of radiation for thousands of years after the fuel has been removed from the reactor. Although the rate of dose accretion gradually attenuates with the passage of time, a spent nuclear fuel assembly remains a highly radioactive material for millennia. The technologies developed to manage this unavoidable byproduct of commercial nuclear power generation are discussed in this chapter with a critical assessment of their strengths and weaknesses. For this purpose, spent fuel management technologies are divided into (1) reprocessing, which consists of reclaiming the fissionable portion of the spent fuel for reuse as an energy source and (2) passive storage in either deep pools or in an inert gas environment.

The essential characteristics of the reprocessing technology, namely, the PUREX process, are described in the context of its historical origins and its dependence on chemical separation techniques since the very beginning in the 1940s. The authors explain how the continuance of reprocessing in Europe and its abandonment in the U.S. because of proliferation concerns over thirty years ago led to profound differences in fuel management paths taken by the U.S. and oversea nuclear operators.

Williams and Singh provide a concise description of the wet storage technology that advanced in the U.S. in the wake of the ban on reprocessing in the U.S, but has remained a largely untapped option in those countries that rely on reprocessing and/or dry storage. The evolution of dry storage technologies in the U.S. (ventilated systems) and overseas (metal casks) is also discussed with respect to their technical attributes, safety, reliability, and maintainability. In particular, the role of the ASME Codes in providing a sound platform for the mechanical design and stress analysis of the systems, components, and structures used in wet and dry storage technologies is explained.

The special demands on the used fuel transport packages imposed by the regulations of the USNRC and the guidelines of IAEA to ensure safety in fuel transportation are explained along with the latest developments in the field. Finally, the authors also provide a succinct summary of the methodology to analyze the effect of a postulated aircraft crash on a storage or transport cask to deal with what is an unmistakably unique design consideration in the twenty-first century. (The authors wish to recognize the valuable contribution of Dr. David McGinnes in the preparation of Chapter 56.)