Nuclear Reactor With No Moving Parts

[sysreset]

There's an article in the May 12 2008 New Yorker Magazine by Malcolm Gladwell, in which he talks about brainstorming sessions by teams of inventors headed by Nathan Myhrvold. One of the ideas is a small Nuclear Reactor with no moving parts. Supposedly the core would be about 3x10 meters, enclosed in a sealed armored box. It would run for thirty years, and put out 3 gigawatts. The point was that with no moving parts there would be no possibility of human error, and nuclear accidents could be eliminated. It would also be designed to eliminate nuclear weapon fuel generation.

Are there some flaws in this idea?

[vanesch]

There's an article in the May 12 2008 New Yorker Magazine by Malcolm Gladwell, in which he talks about brainstorming sessions by teams of inventors headed by Nathan Myhrvold. One of the ideas is a small Nuclear Reactor with no moving parts. Supposedly the core would be about 3x10 meters, enclosed in a sealed armored box. It would run for thirty years, and put out 3 gigawatts. The point was that with no moving parts there would be no possibility of human error, and nuclear accidents could be eliminated. It would also be designed to eliminate nuclear weapon fuel generation.

Are there some flaws in this idea?

I guess you're talking about this kind of thing ?

http://www.science-direct.com/science?_ob=ArticleURL&_udi=B6V3X-4RWRGSF-2&_user=10&_coverDate=08%2F31%2F2008&_rdoc=7&_fmt=high&_orig=browse&_srch=doc-info(%23toc%235742%232008%23999499997%23681062%23FLA%23display%23Volume)&_cdi=5742&_sort=d&_docanchor=&_ct=113&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=27b6c4282709ce4634d1691b470c528d

[Astronuc]

One could use natural convection to drive the coolant, and that is part of the ESBWR design. I believe the no moving parts applies to the primary or recirculation system, and not the feed water system. On the balance of plant side, one would need pumps for the condensate system.

I'd like to see their idea for reactivity control.

[daveb]

I also have to wonder about the feasibility of this in regards to control systems. How would you be able to control the reactor without movable control systems?

[mgb_phys]

How would you be able to control the reactor without movable control systems?
Pebble bed reactors have decreased power output at higher temperatures so are self controlling.

[vanesch]

Pebble bed reactors have decreased power output at higher temperatures so are self controlling.

In fact, almost all modern reactors have this property - doing otherwise is considered quite unsafe (like Chernobyl's reactor). However, the excursion of temperature in certain reactors before the reactivity drops totally may be too large to be used as a practical way of controlling the reactor in normal circumstances. The pebble bed reactor, being made of graphite spheres and an inert gas, is able to withstand very large temperature excursions without being damaged (as long as no oxygen gets to the graphite...), and hence can be passively regulated entirely.

A PWR could also in principle be regulated by natural negative feedback, but the temperature variations would be too large to be practical. A BWR is regulated mostly naturally if I understand well. Some sodium-cooled fast reactors like phenix also have this property (by Doppler, and by dilatation of the set of fuel elements).