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Nuclear Reactor With No Moving Parts

by sysreset
Tags: moving, nuclear, parts, reactor
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joelupchurch
#19
Nov25-09, 07:39 PM
P: 149
Quote Quote by mheslep View Post
Proliferation comment and question on the TWR:
The authors make the fairly inane comment (in my view) in the paper that the the TWR design eliminates proliferation concerns because the fuel, buried underground with the reactor, never gets touched. I'll grant that reducing fuel handling lowers diversion risk, but its trifling to say stop there regards weaponization, at least I didn't see it if was obvious. That is, if a TWR reactor fueled by depleted U, was handed over to a wanna be weapons state is it not possible that they could start the reactor, i.e. start the the U to Pu breeding wave, shut down the reactor, dig it up and chemically process out the Pu? Perhaps that process is not feasible due to reactivity levels, I wouldn't know.
As I recall, they would have to cut it open to get to any Plutonium and even then it would only be the front few inches of the wave that would actually contain any Plutonium-239 that wasn't contaminated with 240 and higher isotopes. Cutting it open would make restarting it problematical.

It would be easier to build a weapons reactor from scratch like the North Koreans or use centrifuges like the Iranians.

I suspect that the TWR was developed from the SSTAR reactor concept. Some of the people working on the TWR used to work at LLNL.
http://en.wikipedia.org/wiki/Sstar
mheslep
#20
Nov25-09, 08:43 PM
PF Gold
P: 3,072
Quote Quote by joelupchurch View Post
As I recall, they would have to cut it open to get to any Plutonium
Yes, but that is a small impediment.
and even then it would only be the front few inches of the wave that would actually contain any Plutonium-239
Yes, but in a ~100MW TWR , 300MW(t), that's likely to be plenty of Pu for weapon.
Edit: Or not? 300MW is about 1x10^19 fissions (200MeV) per second, a burn rate of ~4 milligrams of Pu-239 per second. That means about 6-7 milligrams per second of Pu-239 must be created by the breeder wave, the balance undergoing capture to Pu-240.
that wasn't contaminated with 240 and higher isotopes.
Pu-240 accumulation apparently is indeed the big barrier-to-entry for Pu weapons, i.e. it helps prevent proliferation. But I'm not sure of the mix here; I'm guessing a good answer requires a serious analysis. The pathways on Pu-239 are 64% fission, 36% neutron capture to 240, so 240 would certainly be in the TWR somewhere, but then at shut down all of the Np in the breed wave would be in place waiting to decay to pure Pu-239 over a few days. There might be a geometric slice of the reactor that had exceedingly pure Pu-239.
Cutting it open would make restarting it problematical.
That addresses someone trying to start an entire nuclear weapons industry, not someone trying to make 1 or 2 weapons per TWR.
It would be easier to build a weapons reactor from scratch like the North Koreans or use centrifuges like the Iranians.
It seems to me dumping the wavefront guts into a chemical PUREX bath might quickly recover high grade Pu 239. Possibly starting a new reactor from scratch is easier, I wouldn't know. The centrifuges however - there's nothing easy about them - they necessarily entail a massive, large scale facility and a lot of electricity.


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