fnord wrote:
I keep seeing concerns that separated Pa forms a serious proliferation hazard as it seems like it can be easily processed to pure Pa-233, and thus to U-233 (iirc, the IAEA-determined LEU boundary for U-233 is 12% as opposed to 20% for U-235). Can you maintain the breeding ratio attainable with Pa separation while not actually separating it?
I would just hire more guards. "proliferation hazard" is an anti-nuclear buzzword which ignores the fact that any new nation into the nuclear pile will be using uranium-based devices because they're much simpler (the Pakis tried to make a plutonium gun-type device and it FIZZLED, they made a gun-type device
fizzle, an event previously thought impossible--part of the reason, as I understand it, was using plutonium instead of uranium).
As for the more serious issue of Protactinium, it has a half-life of 27 days before it decays into U-233, and then it can be reinjected back into the reactor cycle. That means that it can be stored on site (for a full cycle reactor installation, as is proposed for Thorium Cycle MSR) while it decays and then simply fed back in, which is exactly what is proposed. Now, apparently there are dumbfucks out there who think that terrorists are going to assault a heavily guarded nuclear powerplant, steal Protactinium, let it decay into U-233, and then use it to make a bomb. Because you can make a nuclear bomb with U-233 in a farmhouse while the largest federal manhunt in recorded history is looking for you. Yeah, sure.
The issue of proliferation--someone is going to steal nuclear material and smuggle it out of the United States? Again, we have had nuclear bombs for more than sixty years now, and no foreign country has ever stolen one and walked away with it. I again submit that rather than trying to design a workaround for the production of Protactinium, we just adopt 1960s-vintage SAC nuclear security protocols for the waste and, if we're that worried about it, outright detail a platoon of soldiers to guard the plants--of significant value when it allows us to have a 99.6% efficient reprocessing cycle which can be colocated with the powerplant.
How usable would a GW(e) sized liquid flouride reactor be in burning up spent nuclear fuel during the course of its operations (even if you just remove the transuranics from the SNF, chuck them in, while sending the now-clean U back for re-enrichment)? Could you start one up on SNF (that way, you're not only cleaning up SNF but breaking chicken-and-egg problem of where the hell do you get the fissile to start the critter up while not paying exorbitant amounts)?
That, I'm afraid, exceeds the limits of my technical knowledge at the moment--I'm only a student!, so I'll cede the question hopefully to someone else on the board who may know.