heatexchanger: Nuclear Power-Plant Heat Exchanger Tube Cracks
In Auburngrads/SMRD.data: Statistical Methods For Reliability Data - Datasets

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Inspection data for heat exchanger tubes across three different nuclear power plants. The data were recorded in 1983, at this point in time, Plant 1 had been in operation for 3 years, Plant 2 for 2 years, and Plant 3 for only 1 year. Because all of the heat exchangers were manufactured according to the same design specifications and because the heat exchangers were operated in generating plants run under similar tightly controlled conditions, the data from the different plants was combined for the sake of making inferences and predictions about the time-to-crack distribution of the heat exchanger tubes.

A data.frame with 9 rows and 5 variables:

[, 1]	lower	Start of an inspection interval (in years)	Numeric
[, 2]	upper	End of an inspection interval (in years)	Numeric
[, 3]	event	Event observed in the interval (left-censored/right-censored/interval-censored)	Categoric
[, 4]	count	Number of events observed in the interval	Numeric
[, 5]	plant	Plant where the tube was installed	Categoric

Nuclear power plants use heat exchangers to transfer energy from the reactor to steam turbines. A typical heat exchanger contains thousands of tubes through which steam flows continuously when the heat exchanger is in service. With age, heat exchanger tubes develop cracks, usually due to some combination of stress-corrosion and fatigue. A heat exchanger can continue to operate safely when the cracks are small. If cracks get large enough, however, leaks can develop, and these could lead to serious safety problems and expensive, unplanned plant shut-down time. To protect against having leaks, heat exchangers are taken out of service periodically so that its tubes (and other components) can be inspected with nondestructive evaluation techniques. At the end of each inspection period, tubes with detected cracks are plugged so that water will no longer pass through them. This reduces plant efficiency, but extends the life of the expensive heat exchangers. With this in mind, heat exchangers are built with extra capacity and can remain in operation up until the point where a certain percentage (e.g., 5%) of the tubes have been plugged.

Meeker, W. Q. and Escobar, L. A. (1998), Statistical Methods for Reliability Data, New York, NY; John Wiley & Sons.

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