It would of course be more accurate to say a bathtub of HEAVY water. Strictly speaking they are right that the fusion reaction itself does not create radioactive isotopes but the high energy neutrons released do activate the metal in the structure. The isotopes created are short lived though and the reactor could be buried on site for only 50-100 and would then be safe. tritium is not found on the moon, only helium 3.

From http://en.wikipedia.org/wiki/Nuclear_chain_reaction:

Plutonium-239 + neutron -> fission fragments + 3 neutrons (usually) + 200,000,000 electron-volts.

If your plutonium is pure enough, and it's compressed together tightly enough, and maybe it's surrounded by something that neutrons will bounce off of, then (let's say) 2 of those 3 neutrons will eventually find other plutonium atoms. And those 2 atoms will release 6 neutrons, 4 of which will find targets... which will release 12 neutrons, 8 of which will find plutonium atoms... and the numbers keep doubling and doubling until you're talking about billions and trillions and quadrillions and quintillions of atoms releasing their 200 million electron volts, at which point you're talking about truly ridiculous amounts of energy.

lolz californium is a neutron emitter. that glass bell jar would provide no protection. *continues muttering nerdishly to self.....*

For some reason I can't get the link to work in the description, but here it is:
http://www.videosift.com/video/Black-Holes-Neutron-Stars-White-Dwars-Space-and-Time

This is important. It's long, but it's important. If you have the time to listen to Dr. Robert Bussard you will be convinced about clean, cheap power. It's available and it's now. We can do this.

Here's the back-story from Google's page:

Google Tech Talks November 9, 2006

ABSTRACT This is not your father's fusion reactor! Forget everything you know about conventional ... all » thinking on nuclear fusion: high-temperature plasmas, steam turbines, neutron radiation and even nuclear waste are a thing of the past. Goodbye thermonuclear fusion; hello inertial electrostatic confinement fusion (IEC), an old idea that's been made new. While the international community debates the fate of the politically-turmoiled $12 billion ITER (an experimental thermonuclear reactor), simple IEC reactors are being built as high-school science fair projects.

Dr. Robert Bussard, former Asst. Director of the Atomic Energy Commission and founder of Energy Matter Conversion Corporation (EMC2), has spent 17 years perfecting IEC, a fusion process that converts hydrogen and boron directly into electricity producing helium as the only waste product. Most of this work was funded by the Department of Defense, the details of which have been under seal... until now.

Dr. Bussard will discuss his recent results and details of this potentially world-altering technology, whose conception dates back as far as 1924, and even includes a reactor design by Philo T. Farnsworth (inventor of the scanning television).

Can a 100 MW fusion reactor be built for less than Google's annual electricity bill? Come see what's possible when you think outside the thermonuclear box and ignore the herd.