Steam generator (nuclear power)

In typical PWR designs, the primary coolant is high-purity water, kept under high pressure so it cannot boil.

It then passes through the steam generator, where it transfers its heat (via conduction through metal) to lower-pressure water which is allowed to boil.

Although no long-lived radioisotopes are produced by this reaction, the gamma radiation means that humans cannot be present in a BWR's turbine hall during reactor operation and for a short time afterwards.

The coolant (treated water), which is maintained at high pressure to prevent boiling, is pumped through the nuclear reactor core.

This primary, secondary, tertiary cooling scheme is the basis of the pressurized water reactor, which is the most common nuclear power plant design worldwide.

A steam generator's heat-exchange tubes have an important safety role, because they separate radioactive and non-radioactive fluid systems.

[2] As with many nuclear components, mechanical engineers determine the inspection frequency using the known rates of corrosion and crack propagation in the material.

Eventually, other international companies such as Babcock & Wilcox and Combustion Engineering began their own programs for research and development of the nuclear power steam generator.

Westinghouse and Combustion Engineering designs have vertical U-tubes with inverted tubes for the primary water.

Babcock & Wilcox plants (e.g., Three Mile Island) have smaller steam generators that force water through the top of the OTSGs (once-through steam generators; counter-flow to the feedwater) and out the bottom to be recirculated by the reactor coolant pumps.

[citation needed] The materials that make up the turbine and pipes of a nuclear powered steam generator are specially made and specifically designed to withstand the heat and radiation of the reactor.

The annealed, or heat treated, Alloy 600 was prone to tube denting and thinning due to water chemistry.

Due to this, pipe thinning has been taken care of, but on rare occasions, tube denting still occurs, causing leaks and ruptures.