E-Lab July - September 1998

July - September 1998

Coal-Mining Productivity:
National Aggregates Conceal Differences
[Abstract] [References]

Reducing Downtime in Nuclear Power Plants
[Abstract] [References]

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Coal-Mining Productivity: National Aggregates Conceal Large Differences

ational statistics on coal-mining productivity show that--except during the 1970s--coal mines have become steadily more efficient. More coal is removed per hour of work, causing a drop in both mining costs and coal prices. However, a new Energy Laboratory study suggests that those national statistics do not tell the whole story. When the researchers analyzed productivity data for more than nineteen thousand mines from 1972 through 1995, they found that some regions and some technologies lagged far behind others. Thus, while western longwall mines were five times more productive in 1995 than in 1972, other types of mines improved by less than half as much--a discrepancy lost in the nationally aggregated data. Detailed analyses of why productivity changed brought some unexpected results. For example, even after accounting for geology and technology, bigger mines were more productive than smaller ones. And prices affect the national aggregates. When coal prices increase relative to labor prices, companies open smaller mines with less favorable geology and overall productivity drops. Indeed, according to the analysis, price increases were more important than new regulations in causing overall productivity to plummet in the 1970s. The study shows that aggregated national productivity data do not provide an accurate picture of the efficiency with which an industry uses its resources or of the causes of changes in overall productivity.

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Reducing Downtime in Nuclear Power Plants

oday, the typical US nuclear power plant spends almost two out of every 18 months shut down for refueling. As owners of such plants face new competition for customers, they are looking for ways to reduce costs; and refueling less often is one option. Working closely with power plant operators, Energy Laboratory researchers have designed reactor cores and operating procedures that would enable power plants to run for up to about four years before needing to refuel. Because of the extra cost of the necessary enriched fuel, adopting a four-year "extended operating cycle" under today's economic conditions would be cost-effective at plants that now experience relatively long downtimes for refueling and forced shutdowns but not at plants that operate more efficiently. A three-year operating cycle requiring less highly enriched fuel would bring savings at many more plants. And if laser-based technology now being developed reduces the cost of enriched uranium, the economics of the extended cycles would improve significantly. Perhaps most important, the MIT team identified strategies that plant operators can use to reduce forced shutdowns and to perform more maintenance procedures while their plants are on-line. The researchers emphasize that any reduction in downtime will not only reduce costs but also prevent possible long-term damage to plants caused by repeated stopping and starting.

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