NASA Restarts Plutonium Production 139
Celarent Darii writes "In what looks like good news for the American Space program, NASA has restarted production of plutonium. According to the article, after the closure of Savannah Rivers reactor NASA purchased plutonium from Russia, but since 2010 this was no longer possible. The native production of plutonium is a step forward for the space program to achieve the energy density for long term space exploration."
If not at the Savannah River Site, then where? (Score:5, Informative)
My first thought upon reading the summary was that if the Savannah River Site is closed, where are they making the new plutonium?
The answer, according to TFA, is the Oak Ridge National Laboratory.
UK Plutonium (Score:5, Informative)
Am I wrong in thinking the UK has a plutonium stockpile it really doesn't know what to do with? Simply not juicy enough?
http://www.bbc.co.uk/news/uk-21505271 [bbc.co.uk]
Re:Dehabitation (Score:4, Informative)
RTGs are designed to survive both the explosion and an uncontrolled impact with the ground.
Even if ruptured by the impact, plutonium is an immensely dense material - it's not easily scattered.
Re:Dehabitation (Score:5, Informative)
it scatters in smoke just fine. look up "windscale fire"
Re:Dehabitation (Score:5, Informative)
Re:UK Plutonium (Score:3, Informative)
Different isotope of plutonium.
http://en.wikipedia.org/wiki/Plutonium-238 - Fun stuff for space travel.
UK has a supply of a few different isotopes mixed together. Much less useful.
Re:Why do this when... (Score:5, Informative)
The Pu in the fuel rods is not the right isotope, it is almost all Pu239 (U238 + neutron = Pu239, [after a stage as Np239]). NASA needs Pu238. What Pu239 is in there would be a real bear to separate from the Pu239 (more difficult than the separation of U235 from U238 because the mass difference is less).
Re:Dehabitation (Score:4, Informative)
Re:Dehabitation (Score:5, Informative)
The wiki article on that fire notes that it released large amounts of iodine-131. The fire was caused by attempting to produce plutonium, not by burning plutonium and the reports on its cause seem to be either uranium and magnesium/lithium cartridges.
Plutonium dioxide is already oxidized. It's chemically impossible for it to catch fire, and again, dense and heavy with a high melting point.
Re:UK Plutonium (Score:5, Informative)
It's the wrong isotope - bombs and reactors use Pu-239, while RTGs use Pu-238. The key difference is half-life and thus the heat generated, as the heat drives the thermocouples in the RTG to produce power. Pu-239 has a half life of 24 kyears, which means it decays slowly and thus doesn't produce much heat (relatively speaking). Pu-238 has a half life of 87 years, which means it emits considerable heat.
That short half life is also why NASA has been trying to figure out how to re-start production for some years now, since production was halted in 1988 a considerable quantity of the stockpiled fuel has essentially 'evaporated'. (And the stockpile wasn't that large to begin with.) Since the 'evaporated' fuel doesn't actually physically go anywhere, this means that you either have to use a bigger and heavier RTG or redesign the mission to use less power. (The first is obviously bad, and the second can paint you into a bit of a corner if the launch is delayed.) Processing the fuel to remove the decay products and restore energy density is... Very Expensive, so it's not an option (especially since it doesn't solve the problem of 'evaporation').
Re:Why do this when... (Score:3, Informative)
We can just start reprocessing existing spent fuel and recover the material we need from that?
We can't. The path to Pu-238 (the isotope used in RTGs) is Np-237 -(n)-> Np-238 -(beta-decay)-> Pu-238. Np-237 is a byproduct of neutron irradiation of U-238, but it must be separated and fabricated into target pins before further irradiation, otherwise your Pu-238 will be drowned in a mass of Pu-239 and higher isotopes, and there is no practical way to separate it. (Separating U-235 from U-238, three atomic units of difference, is difficult enough; Pu-238 and Pu-239 are a single atomic unit apart.)
Plutonium 238 (Score:5, Informative)
Re:Dehabitation (Score:5, Informative)
you need more information. the pu-238 used in RTGs is in oxide form, bound with Oxygen 16 to absorb the occasional neutron (it is mostly an alpha emitter) that can be formed. So, the pu-238 is "already burned", in a sense, and in a form to be safer to humans.
Re:Why do this when... (Score:5, Informative)
Commercial reactor waste has very little weapons-grade material in it, because in order to maximize production of weapons-grade Plutonium, you have to use a commercially inefficient fuel cycle to minimize the amount of spontaneously fissioning Plutonium isotopes being created through continued neutrox flux.
More succinctly: the more time U238 spends being bombarded in a reactor (thus, the more energy you create from the same fuel assembly), the more likely it is going to pass the "sweet spot" of Pu-239 into the undesireable Pu-240 or Pu-241 which poisons a prompt supercriticality which is created during a nuclear detonation. The reactors at Hanford that made the vast majority of weapons-bound Plutonium for the US weapons stockpile used somewhere around 6-month fuel cycles, where the average commercial reactor uses the fuel assembly for several years.
No Plutonium is pretty useful. (Score:5, Informative)
1g of Pu-238 produces .5 watts, which is really useful for long-lasting portable devices. There are some early pacemakers running from Pu-238 that are still operational.
For example, a few grams of Pu-238 could power an iPhone for a century without ever recharging...
(but would cost tens of thousands of dollars..)