Some of the Reasons I Oppose the Deep Fission nuclear reactor project in Kansas

The Deep Fission idea sounds very foolhardy to me. Here's some thoughts:

Before they're ever turned on, SMNRs are environmental trouble: They all use a much higher enrichment of U-235 and/or Pu-239 than a PWR or BWR reactor: Perhaps 19.999% (instead of the 5.5ish percentage which is about the most a current U.S. reactor uses). Making the highly-enriched fuel is more difficult and more polluting, and proliferation risks are increased. (That's why it's below 20% — above that gets too close to "bomb grade" than anybody is comfortable with in a commercial environment. But having the first 20% already made, makes further refinement just that much easier.)

The Deep Fission reactor will be converting U and/or Pu to fission products which will all exist for varying time-spans. Some will have extremely long half-lives (I call them the Ignoble Seven).

All this just to boil water, send hot steam to the surface, spin a turbine, cool the steam back to water, drop it back down again, and repeat until...??? It will never be cheaper than solar or wind power! Not in a million years — but the waste from trying it today will still be around then!

And when does it end? When something suddenly goes seriously wrong and superheated radioactive steam comes shooting out instead? Who's going to approach that in order to pour cement down the hole? How long will they have to wait to do it? A mile-long funnel of water fed by a large cooling pond can keep spewing radioactive steam for quite some time! And then what?

But assuming they keep it cool during a very, very slow and proper shutdown, and somehow manage to "plug the hole" with cement. then what? Build another Deep Fission reactor on top? How many feet above it? If they build one next to it, how close will the next one be? If one melts down or causes abandonment of the area, what happens to the rest of them (this question is valid for all multi-reactor sites, large or small)?

Leaving a hot used reactor encased in rock and cement a mile down after use has all the difficulties of a spent fuel canister (i.e., it cannot be inspected) plus it has more highly enriched fuel: And a Deep Fission reactor, a mile underground, is surrounded by really good insulation (rock) that can crush it — perhaps into a critical configuration? Just guessing that it's NOT impossible. But inspection and recovery are both impossible.

For eons, water intrusion could be a very serious problem (perhaps from a leak from reactor above it?). If the water turns to steam that's definitely not good, but even if not, water slows neutrons down and thus, can increase reactivity. (Side thought: Could wet cement hold enough water to make cementing up the hole not so easy to do?) When Yucca Mountain was started, the public was assured there couldn't possibly be any significant water intrusion. Water intrusion turned out to be one of the decisive factors ending the project!

I don't know if criticality events would be "very unlikely" or "extremely unlikely" (or whose definition of those terms to use) but I don't think there's any chance criticality events would be "impossible" if there is water intrusion in any way, even many thousands of years from now.

So I'm opposed to Deep Fission. It's not practical, useful, necessary, or safe.

Ace Hoffman, Carlsbad, California USA

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Contact information for the author of this newsletter:

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Ace Hoffman
Carlsbad, California USA
Author, The Code Killers:
An Expose of the Nuclear Industry
Free download: acehoffman.org
Blog: acehoffman.blogspot.com
YouTube: youtube.com/user/AceHoffman
Email: ace [at] acehoffman.org
Founder & Owner, The Animated Software Company

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