

NASA’s Plutonium Problem Could End Deep-Space Exploration - hereonbusiness
http://www.wired.com/wiredscience/2013/09/plutonium-238-problem/all/

======
molecule
> NASA’s Plutonium Problem Could End Deep-Space Exploration

> By 2005, according a Department of Energy report (.pdf), the U.S. government
> owned 87 pounds, of which roughly two-thirds was designated for national
> security projects, likely to power deep-sea espionage hardware...

how about the U.S. government does less deep-sea espionage-- in the name of
deep-space science?

~~~
pintglass
Heck, there's Google
([https://www.google.com/maps/views/streetview/oceans?gl=us&hl...](https://www.google.com/maps/views/streetview/oceans?gl=us&hl=en-
us)), Virgin Oceanic
([http://www.virginoceanic.com/](http://www.virginoceanic.com/)), etc.
exploring down there. Nothing wrong with a little deep sea action- even the
military contribute.

It's much cheaper to explore the ocean than it is to explore space, and many
benefits like: OTEC
([http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion](http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion)
[http://cleantechnica.com/2013/05/05/lockheed-martin-to-
build...](http://cleantechnica.com/2013/05/05/lockheed-martin-to-build-worlds-
first-ocean-thermal-power-plant-off-china-coast/)), mining (
[http://en.wikipedia.org/wiki/Deep_sea_mining](http://en.wikipedia.org/wiki/Deep_sea_mining)),
etc.

Others agree:

[http://www.forbes.com/sites/quora/2013/01/31/why-dont-we-
spe...](http://www.forbes.com/sites/quora/2013/01/31/why-dont-we-spend-more-
on-exploring-the-oceans-rather-than-on-space-exploration/)

[http://www.cnn.com/2012/04/09/opinion/etzioni-space-
oceans/i...](http://www.cnn.com/2012/04/09/opinion/etzioni-space-
oceans/index.html)

But, I personally think we should be exploring space and our oceans. We need
to make it a top priority of all countries to fund energy and propulsion
research to help make exploration cheaper. That means allocating adequate
budget and raising taxes for something that the mass media and our government
doesn't seem to give much of a shit about, because they don't understand the
part of the world we currently are utilizing is running out of resources
quickly and that we are constantly a stone's throw from mass extinction.

~~~
masklinn
You don't need Pu238 for deep sea _exploration_.

~~~
pintglass
I wouldn't rule that out. Why wouldn't it make a great undersea battery?

Also, if we found Apollo 13 we could recover some Pu238:

[http://science.slashdot.org/story/11/11/28/1637231/will-
nasa...](http://science.slashdot.org/story/11/11/28/1637231/will-nasa-ever-
recover-apollo-13s-plutonium-from-the-ocean)

[http://unexplainedthings.tumblr.com/post/13563685365/will-
na...](http://unexplainedthings.tumblr.com/post/13563685365/will-nasa-ever-
recover-apollo-13s-plutonium-from-the)

~~~
masklinn
It would, but you don't _need_ it because you don't _need_ years or decades of
power at high depths.

------
thangalin
Directly related ("U.S. Starts Making Plutonium"):
[http://news.discovery.com/space/nasa-plutonium-production-
sp...](http://news.discovery.com/space/nasa-plutonium-production-space-
fuel-130314.htm)

~~~
ChuckMcM
I was going to supply that link as well. We have been working on a restart for
a while. Basically the Wired article is just silly.

~~~
greglindahl
It's easy to read between the lines: The NASA guys think it's likely there
will be problems, and that Congress will fail to act quickly when more money
is needed.

------
robryan
$10 million vs $20 million a year? It probably cost congress more to argue
about this than the cut has saved.

------
slacka
Thorium reactors produce PU-238 as a “free” byproduct. One more reason we
should be pursuing LFTR reactor research.

~~~
InclinedPlane
Erm, sort of. It doesn't actually help that much.

As a short, but helpful, side discussion consider the breeding of Pu-239 in a
reactor for use in nuclear weapons. Pu-239 works great in a nuclear bomb but
other isotopes of Plutonium cause problems, specifically the high spontaneous
fission rate of Pu-240 can create so many background neutrons that having a
significant amount of it in a bomb can vastly increase the "pre-detonation"
(fizzle) risk, which causes the bomb to have very low yield (on the same scale
as the chemical explosives in the bomb). As Plutonium remains in a reactor
subject to neutron flux it will naturally breed other isotopes, which is why
there is a difference between weapons grade and reactor grade Plutonium.
Reactor grade Plutonium can contain any variation of isotopes, essentially all
of them are suitable for use in a reactor, but weapons grade Plutonium can
only have a very small amount of Pu-240. And for this reason the way that
weapons grade Plutonium is made is by removing fuel rods from a reactor on
very short time scales and reprocessing it to remove the Plutonium then
forming it back into new fuel rods and so forth. This is a very costly and
complex endeavor which is why you can't just use ordinary power reactors for
generating weapons grade Plutonium.

Interestingly, Pu-238 also exists in reactor grade Plutonium in substantial
amounts (1% or more of the Plutonium, so nearly an entire tonne per year
worldwide). However, because it's mixed up with all of the other Plutonium it
would require extremely costly isotopic separation.

So, how is this relevant to Thorium reactors? Well, let's go back and look at
what actually happens when Pu-238 is produced in a Thorium reactor. You start
with Th-232, and under neutron flux you'll breed U-233, which is the reactor's
main fission fuel. If U-233 is hit by a neutron and absorbs it instead of
fissioning then you can end up with U-234, U-235, U-236, Np-237 (through a
decay), and Pu-238 (through another decay). However, it's not as though things
don't stop there. Pu-238 will breed into Pu-239, Pu-240, and so on, just as in
a conventional Uranium power reactor.

So here you have the same problem as producing weapons grade Plutonium, you
have a process that you need to stop before it goes too far, and in order to
do that you need to pull the Plutonium out of the reactor at regular, short
intervals. Otherwise you'll just get a buildup of ordinary reactor grade
Plutonium. However, the problem is worse here because instead of being the
product of just one neutron reaction (natural U-238 becoming Pu-239) the
breeding of RTG grade Plutonium is the product of a long chain of reactions
(taking 6 steps between the isotopes in the reactor fuel at the start and the
production of Pu-238). This means the amount of production and the time scales
of production are very much not helpful from the perspective of pure Pu-238
production, especially if you want to also operate a power reactor cost-
effectively at the same time.

(Edit: also, there's an additional problem, because Thorium reactor fuel
contains U-232, which has a short half-life and has decay products that are
prodigious gamma ray sources, making reprocessing and handling even more
difficult than ordinary reactor fuel. You can handle Plutonium in a glove box,
but with used Thorium fuel containing U-232 you'd need to handle it via
robotic manipulators in a heavily shielded area distant from humans, except
that gamma radiation kills electronics like nobody's business, which is a bit
of a catch-22. This is one of the key technical hurdles of Thorium reactor
designs in general.)

In short, the fact that Thorium reactors produce Pu-238 isn't helpful, because
existing reactors do too, but in either case it's hard to get at.

~~~
tanzam75
Contamination with plutonium-240 was a big problem during the Manhattan
Project. They'd done the preliminary calculations based on cyclotron-produced
plutonium-239, which was pure enough that a gun design with a long tube was
feasible. ("Thin Man")

The plutonium-239 that came out of the Hanford reactor had a much higher
contamination rate. This required a much faster assembly of the critical mass
in order to avoid a fizzle. The gun design would have to be so long that it
couldn't fit on a plane. Whereas implosion could provide the required rapid
assembly in a limited space. Thus, "Thin Man" was out, and "Fat Man" was in.
Implosion was no longer a secondary option -- it was the only option.

------
runarb
According to Wikipedia [0] it isn't all sorrows. There are other fuels
available in large quantities at a low price, like Strontium-90 used in many
Russian radioisotope thermoelectric generators. Other fuels like Americium-241
are also showing big promise, and are available commercially in large
quantities. Americium-241 also has a much longer half-life, and can
hypothetically power a device for centuries.

0:
[https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Fuels)

------
hereonbusiness
It's actually really interesting what a relatively tiny amount of Pu-238 is
needed to power deep space missions for decades, 36lb (16.3kg) of Pu-238
amounts to a sphere with a radius of 5.82cm according to wolfram alpha.

------
jevinskie
> Every so often an atom of neptunium-237 absorbs a neutron emitted by the
> core’s decaying uranium, later shedding an electron to become plutonium-238.

Doesn't it shed a proton to become plutonium 238 and, as a consequence, loses
an electron?

~~~
pjscott
Proper description of what's going on:

[http://en.wikipedia.org/wiki/Beta_decay](http://en.wikipedia.org/wiki/Beta_decay)

~~~
jevinskie
Thank you very much, I was under the impression that the electron was lost
from the orbital cloud, not the nucleus!

Edit: Looking back at my math it was an off-by-one error in the wrong
direction. :)

------
jlgreco
France has the resources to make Pu-238, though I am not sure if they
currently have the facilities/equipment. If the situation really is
politically impossible in the US and Russia keeps on flaking out, we could
always try buying more from the French again and let them deal with the
politics.

If we are shitcanning missions because we don't have Pu-238, then why doesn't
NASA just take the money they _would_ have spent on those programs and spend
it on more Pu-238 instead? Surely that should buy us enough Pu-238 for at
least remaining uncancelled missions.

~~~
maaku
> If we are shitcanning missions because we don't have Pu-238, then why
> doesn't NASA just take the money they would have spent on those programs and
> spend it on more Pu-238 instead? Surely that should buy us enough Pu-238 for
> at least remaining uncancelled missions.

Requires an act of congress. Need I say more?

~~~
dalke
To elaborate on maaku's answer, as the article points out, "the Atomic Energy
Act forbids NASA to manufacture plutonium-238."

~~~
jlgreco
The idea is for NASA to _buy_ Pu-238, not make it. I am not sure how much
Congress micromanages their budget though, it may very well be the case that
money meant for probes cannot be redirected to buy Pu-238.

~~~
dalke
Buy it from ... whom? As the article points out, Russia "reneged on a deal to
sell 22 pounds to the U.S." and might not have any left for sale.

There are no other producers of 238Pu. (And for that matter, Russia stopped
producing it years ago.)

Edit: Here's a link for you.
[http://www.nasa.gov/pdf/636900main_Howe_Presentation.pdf](http://www.nasa.gov/pdf/636900main_Howe_Presentation.pdf)
.

> In the past, the United States had an adequate supply of 238Pu, which was
> produced in facilities that existed to support the U.S. nuclear weapons
> program. The problem is that no 238Pu has been produced in the United States
> since the Department of Energy (DOE) shut down those facilities in the late
> 1980s. Since then, the U.S. space program has had to rely on the inventory
> of 238Pu that existed at that time, supplemented by the purchase of 238Pu
> from Russia. However, Russian facilities to produce 238Pu were also shut
> down many years ago, and the DOE will soon take delivery of its last
> shipment of 238Pu from Russia. The committee does not believe that there is
> any additional 238Pu (or any operational 238Pu production facilities)
> available anywhere in the world.

Full details are in "Radioisotope Power Systems: An Imperative for Maintaining
U.S. Leadership in Space Exploration", National Research Council committee
report. ISBN: 0-309-13858-2, 74 pages, (2009)

~~~
tanzam75
> _Buy it from ... whom? As the article points out, Russia "reneged on a deal
> to sell 22 pounds to the U.S." and might not have any left for sale._

Now, that's interesting.

The Chinese are planning to land an RTG-powered spacecraft on the moon in
December 2013. That's just 3 months away. Evidently they managed to get hold
of some Pu-238 to power their spacecraft with.

Either they manufactured the isotope themselves, or they outbid us for the 22
pounds that Russia was planning to sell.

~~~
dalke
Interesting indeed!

There's talk about it at
[http://forum.nasaspaceflight.com/index.php?PHPSESSID=a4sdshu...](http://forum.nasaspaceflight.com/index.php?PHPSESSID=a4sdshu2jb19cmbhm4qj3uggq7&topic=26848.0;all)
. The best they found is this quote:

> "The nuclear power system will make China the third country apart from the
> United States and Russia to be able to apply nuclear technology to space
> exploration," Ouyang said.

Various newspaper article use that quote to say it was domestic production.

Parsed carefully, that doesn't say that they created the RTG, only that they
applied it.

------
strictfp
> Political ignorance and shortsighted squabbling, along with false promises
> from Russia, and penny-wise management of NASA’s ever-thinning budget still
> stand in the way of a robust plutonium-238 production system.

Biased much?

------
zyb09
Probably a non-issue, because more Plutonium-238 can be easily created using
existing infrastructure. As demand of this stuff goes up and supplies dwindle,
someone is gonna make more of it sooner or later.

~~~
maaku
There are legal constraints on Pu-238. Market forces do not apply,
unfortunately...

~~~
spiritplumber
Maybe they can use a box full of old pinball parts.

~~~
tanzam75
> _Maybe they can use a box full of old pinball parts._

That would be Pu-239, not Pu-238. Remember, the Libyans wanted him to build a
bomb -- not a spaceship.

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guelo
Actually DOE has started a production program using $10mil appropriated
through NASA,
[http://spaceflightnow.com/news/n1303/20pu238/#.UjuOO6x3O4B](http://spaceflightnow.com/news/n1303/20pu238/#.UjuOO6x3O4B)

The original plan was to fund $10mil through NASA and $10mil through DOE for a
total of $20mil per year, but DOE lost their half of the funding due to
Solyndra-related politics.

~~~
dalke
You sound like you didn't read the linked-to article, which details all of
that except for the Solyndra politics.

~~~
sliverstorm
There's no ambiguity here. He didn't.

