[ RadSafe ] RE: Modular nuclear reactor

[Brennan, Mike (DOH)]

Interesting material; I think Hyperion should have some of this
information at their site.  

I like the self-regulating aspect of hydrogen moving in and out of the
fuel with temperature, increasing and decreasing the level of moderation
depending on how much heat is being removed from the system.  

I am sure that there are some pretty bright people working on this, and
I doubt that I can spot any problems that they haven't considered, but I
do wish they would address them.  For example, on one of the blogs
someone questions whether the hydrogen transfer would remain constant
through many cycles, of if the characteristics of the surface of the
fuel would change in a way that interferes.  A good question, worthy of
addressing on their page.  

Personally, I think they are a too dismissive of some of the end of life
issues for their reactor.  Five years of producing power through fission
will leave create a non-trivial inventory of fission fragments, and the
entire sealed unit will be not only thermally hot, but radiologicly hot.
I see issues being raised at the idea of trucking such a spent reactor
back to the factory.

If hydrogen can move in and out of the fuel, then one assumes that other
gasses can, too.  I would expect Kr-85 and the various iodine isotopes
(gaseous at the temperature the reactor operates at) to move out of the
fuel.  Should the vessel be breached the release of the hydrogen would
shut down the reaction and prevent the reactor from being damaged, but
the release of large amounts of radioactive gas could have a negative PR
impact.

While designing the reactor to not need an operator certainly decreases
ongoing costs, I wonder about the feasibility of it.  The reactor may
not have moving parts, but it does have systems that need to be
monitored and probably adjusted.  As one of my professors used to say,
"Hydrogen's a slippery bugger."  I suspect that there will be loss and a
need for occasional make-up over the life of the reactor.  The heat
removal system uses a liquid metal as its fluid.  I didn't see which
metal they were talking about, but whichever one they use there will be
some interesting possible failure modes.

Again, I have no doubt that the people at Hyperion have given these
issues some thought, and may well have interesting answers.  I do think
they would do well to share their answers with anyone interested enough
to look up their web site. 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Joel Cehn
Sent: Wednesday, November 26, 2008 9:11 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] RE: Modular nuclear reactor 

More info on the Hyperion reactor can be found at:
http://physicsworld.com/cws/article/news/36758

Found this at?a good nuclear energy blog:
http://www.atomicinsights.blogspot.com/


Joel I. Cehn, CHP
Oakland, California
joelc at alum.wpi.edu 

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