Steam generators are an option, not a necessity

The US Nuclear Regulator Commission (NRC) recently posted a blog written by Kenneth Karwoski, Senior Advisor for Steam Generators that attempts to help people understand a little more about steam generators. The blog post was titled Where There’s Steam, There’s … a Steam Generator.

Aside: Many of my colleagues would immediately point to the title as misleading. Their professional experience includes plants that produce a large quantity of steam without using steam generators. End Aside.

Since Mr. Karwoski’s job is to be a senior advisor for steam generators at the NRC, I understand why he would make the following parochial statement:

Steam generators provide vital technical and safety functions at many U.S. nuclear power plants.

My direct experience with nuclear power plants is limited to those that include steam generators, but I am aware that my experience in the specialized application of using nuclear energy inside sealed submarines full of people breathing in the same limited air space where the reactor operates is not representative of the whole range of design options.

In the mid 1950s, a series of experimental reactors called BORAX-1, BORAX-II and BORAX-III were built at a facility in Idaho then known as the National Reactor Testing Station. Those reactors proved that the radioactivity that was introduced into the water used to cool light water reactors was low enough to allow the water to boil in direct contact with nuclear fuel rods, producing steam to turn turbines without the need for expensive heat exchangers.

Vallecitos Boiling Water Reactor

Vallecitos Boiling Water Reactor

GE followed up on those experiments with the Vallecitos Boiling Water Reactor and then developed a series of boiling water reactors that use primary coolant to directly drive steam turbines.

Boiling water reactors continue to be a safe and cost-effective design choice. They have the potential to be far more cost competitive than pressurized water reactors under regulatory regimes that impose radiation dose and dose rate rules that are based on actual, vice imaginary health effects.

It is in the full knowledge of the existence of boiling water reactors that I assert that classifying steam generator u-tubes as performing a “vital safety function” is an exaggeration. All heat exchangers should be built carefully. They are worth maintaining in order to keep the system functioning as designed. They are worth repairing if any of the heat exchange surfaces begins leaking and allowing mixing of fluids that the designers prefer to keep separate.
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