Even the most ardent supporters (this writer included) of nuclear energy recognize that it has some issues. It has a safety perception issue particularly post-Fukushima. Current LWRs (great reactors by the way!) are limited to electric power production and hence limited in their ability to address some of our most fundamental energy problems. In terms of economics, large LWRs are just too expensive for many utilities.
This is the first of a series of short posts on the features and benefits of the High Temperature Gas-Cooled Reactor (HTGR). These posts will address a wide variety of topics. Examples include safety, how nuclear can power major industries; nuclear and liquid transportation fuels, the technology and market niches for the design, the potential for exports, a profile of potential users, and the respective roles of industry and government in bringing about commercial success.
Safety – A Break from Convention
Simply put, HTGR design insures that there are no circumstances, including complete abandonment by plant operators, where a harmful release of radioactivity can occur.
How is this possible? The essential features of modern HTGR safety are:
- extremely robust fuel with multiple ceramic coatings;
- a reactor core with a limited power level; and
- fundamental simple physics that shuts the reactor down in abnormal temperature conditions.
Further, HTGR control rod insertion into the core (not essential for public safety and only utilized for power output control) is achieved through automatic gravity-alone insertion.
How the HTGR handles decay heat
So, even if HTGR operators go home and don’t return after an accident, decay heat (the heat that melted the Fukushima and TMI cores), ultimately passes out of the reactor and into the ground without temperatures ever coming close to failing the fuel.
No water, other coolant or external power is required for the reactor to stay safe. It just sits there and gradually cools down.
Importantly, HTGR reactor materials (helium coolant, ceramics and graphite), including the reactor fuel, are chemically compatible and in combination with each cannot react or burn to produce explosive gases like hydrogen (to a public that remembers the images of Fukushima, this has got to be important!).
The helium coolant inside the reactor is chemically inert and cannot burn, cause corrosion, or degrade the fuel or any parts of the reactor.
Spent fuel from an HTGR is stored in casks in underground dry vaults that are cooled by natural circulation of air. No active cooling system is involved. Steel and concrete shielding prevent any release of radiation.
The next blog post in the series will describe the needs of industry for process heat and how an HTGR can meet them.
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