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Researching Advanced Fuel Technologies

Issue 1 and Volume 4.

 

By James P. Malone, Chief Nuclear Fuel Development Officer, Lightbridge Corp.

The global expansion of nuclear power generation predicted to occur in the upcoming decades necessitates the development of advanced technologies both in reactor and fuel designs. Increased global demand for nuclear electricity will increase the importance of fuel cycle economics, resource utilization, waste reduction, and proliferation resistance. Mobility in fuel supplier markets will only increase as new fuel technologies are demonstrated and utilities demand better performing fuels.

Without question, uranium oxide fuels have seen continued improvement in reliability and performance with fuel failures trending toward zero over the past several years. However, current oxide fuel designs may be approaching their limits with regard to power output and cycle length in light water reactors. Although the conventional fuel design has changed over the years with different cladding alloys, enhanced grid deigns, mixing vane additions, fabrication processes, and even pellet shape, the fuel material itself has gone largely untouched. This is by no means a negative as the industry has greatly benefited from a common fuel with which to grow and gain reactor operating experience. However, fuel development outside of the commercial power sector has been thriving with new materials, fuel forms, and other advances that could present significant benefits to the commercial sector.

Aside from safety and reliability, there is no single set of goals for a fuel as different markets have different needs. The goal of increased power output and cycle length in mature Western markets may be a secondary objective in certain emerging nuclear markets that may be more concerned with security of fuel supply, used fuel management options, and proliferation resistance. A variety of fuel offerings will benefit the entire supply chain.

There are many fuel technologies being developed around the world, each with a unique set of benefits and advantages. Some have evolved from past demonstration programs and some are revolutionary and will require more development effort. Because of the disparate fuel cycles that would have to be developed for some of the fuels, there are a few advanced fuel technologies for LWRs that can be seriously considered. The overall goal of these technologies is to further strengthen the role of nuclear power in global electricity generation and ensure the continued safe operation of existing and new-build power plants.

Many have probably heard about thorium fuels in the past year as they have received increased attention. Thorium has some very unique advantages and offers a wide range of flexibility as a fuel. Extension of natural uranium resources has always been a goal in countries with limited uranium reserves and the potential for enhanced proliferation resistance and reduced waste generation could be a critical factor in the success of emerging nuclear markets. Lightbridge Corp. is developing a line of thorium-based fuels for LWRs that offer enhanced proliferation resistance, used fuel reduction benefits, and improved uranium utilization.

Advances in UO2 fuels have been continually investigated over the years with varying success. We're now seeing renewed efforts to apply some of these concepts to commercial reactors, for example beryllium oxide additions to UO2 could improve the fuel thermal properties and potentially increase burnup limits. Other efforts to improve UO2 fuel lifetime include the development of advanced cladding materials such as silicon carbide. Advances in cladding alloys have likely been the most active area of research in the commercial fuel industry over the years, emphasizing the cladding’s importance for fuel reliability. Another exciting technology is the application of metallic fuels to LWRs. Lightbridge is currently developing an all-metal fuel rod and associated fuel assembly designs for power uprate and cycle length extension in LWRs. Extensive metal fuel development programs were carried out for fast reactor applications many years ago. It's not surprising that we're now seeing development of metallic fuels for commercial reactors that build on the expertise and knowledge gained from those previous programs. Lightbridge’s initial efforts are to demonstrate a fuel assembly design capable of 24 month operation at up to 17 percent uprate for existing Westinghouse-type four-loop PWRs and ultimately demonstrate up to 30 percent uprate for the same cycle length in new build PWRs.

The nuclear industry as a whole will benefit from the advanced technologies currently being developed and should work together to ensure the development of viable products. Likewise, government funding of technologies that are applicable industry-wide is paramount to their successful demonstration. Growth in nuclear power generation will lead to a growing demand for higher performance in fuels.

Author: Mr. Malone has served the nuclear industry for over 40 years as an expert in commercial nuclear fuel.

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