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ORNL Restores US Capability To Produce Plutonium-238 (ornl.gov)
hypnosec writes: Oak Ridge National Laboratory has successfully produced 50 grams of plutonium-238, an isotope that produces heat without a lot of other, problematic radiation. This makes it suitable for use in radioisotope thermoelectric generators, which can power space probes. The new sample effectively revives the U.S.'s end-to-end plutonium-238 production capabilities, which have been dormant for around 30 years since work was stopped at the Savannah River Plant in South Carolina. The ORNL is optimistic this important milestone will pave the way for regular production of the material, ensuring constant supply for NASA's future missions.
All plutonium isotopes are not made equal.
Pu-238 = great source of heat, not a great source of boom.
Pu-239 = great source of boom, not a great source of heat.
Pu-240, Pu-241 = not a great source of boom or heat.
Pu-238 is not used in weapons specifically because it fissions too fast spontaneously. That's why it makes so much heat. And, because of this, your weapon would have a significant portion of it reduced to not-plutonum and neutron poisons by the time you want to use it.
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Pu-238 cannot be made into a bomb. It is not fissile. You may be thinking of another isotope.
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Terrible idea. First, flight data recorders have easy access to ample power (from the aircraft) for 99.9% of their life... It's only that 0.1% of the time that batteries would have to kick-in, and rechargeable NiMH work great and can last for decades in such an easy duty-cycle.
Secondly, an RTG costs more than your HOUSE, and is huge.
Third, PU-238 doesn't make electricity, just heat, so you need a full heat engine in there, somewhere. A simple Peltier works, but they're maybe 90% efficient, so you're talking extremely high temperatures to generate a useful amount of electricity, which need to be conducted out somewhere. That means your iPhone or flight data recorder power by PU-238 will have to run several-hundred degrees hotter than you'd find comfortable...
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Ugg... Peltiers are about 10% efficient, meaning you'll need to dump 90% of the heat coming out of the PU-238...
Stupid 4+ minute wait.
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It looks like about 4 kg of plutonium-238 is required for a Mars Rover type mission. (Inferred from wikipedia article)
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The process described starts with a solid Neptunium-237 oxide, mixes it with Aluminum, presses it into pellets, irradiates it, chemically separates the Plutonium-238, and then processes it back into a solid oxide. They don't say where the Neptunium itself comes from, other than mentioning an existing inventory. It can be recovered from spent fuel, using another convoluted process starting with solid oxides.
Creating 237Np would be a far more direct process with a LFTR, where the 2% of the fuel which does not fission mostly finds its way to be this very isotope. (The remainder become short-lived fission products.) Naturally, processing a liquid is easier than going through multiple solid oxide steps, and lends itself to a continuous process capable of producing 238Pu in volume. It would be far more interesting if ORNL were developing the processes for this instead.
A not so minor point which deserves mention: the Pu-239 must be >90% pure for weapons. Reactor grade plutonium from spent fuel is absolutely useless for weapons. The only practical method of creating it is to briefly expose U-238 to a neutron flux, separate the Pu-239 out, and repeat many times, which requires a specialized reactor. Pu-239 can't just be pulled out of spent fuel; the plutonium isotopes are too close in mass to make isotopic separation viable.
As the previous commenter notes, Pu-238 is not fissile.
Pu-238 is a great thermal heating material. A gram of Pu-238 generates about 500 mW of heat through radioactive decay and initial release of alpha particles (plain old helium nuclei). Helium nuclei are large and heavy, and are stopped by even a sheet of paper. The decay chain for Pu-238 is mostly a number of alpha particle releases and a slow and gradual walk toward Pb (lead).
In metallic or solid ceramic form, Pu-238 is safe to handle. You could arguably carry around a chunk of it, but the thermal heat generated is significant and you might get burned. Machining it is straightforward, the dust needs to be controlled.
RTGs have survived that and been retrieved. They also have survived reentry. Though there have been a couple that didn't survive.
https://en.wikipedia.org/wiki/...
There have been several known accidents involving RTG-powered spacecraft:
The first one was a launch failure on 21 April 1964 in which the U.S. Transit-5BN-3 navigation satellite failed to achieve orbit and burned up on re-entry north of Madagascar.[26] The 17,000 Ci (630 TBq) plutonium metal fuel in its SNAP-9a RTG was injected into the atmosphere over the Southern Hemisphere where it burned up, and traces of plutonium-238 were detected in the area a few months later.
The second was the Nimbus B-1 weather satellite whose launch vehicle was deliberately destroyed shortly after launch on 21 May 1968 because of erratic trajectory. Launched from the Vandenberg Air Force Base, its SNAP-19 RTG containing relatively inert plutonium dioxide was recovered intact from the seabed in the Santa Barbara Channel five months later and no environmental contamination was detected.[27]
In 1969 the launch of the first Lunokhod lunar rover mission failed, spreading polonium 210 over a large area of Russia [28]
The failure of the Apollo 13 mission in April 1970 meant that the Lunar Module reentered the atmosphere carrying an RTG and burned up over Fiji. It carried a SNAP-27 RTG containing 44,500 Ci (1,650 TBq) of plutonium dioxide which survived reentry into the Earth's atmosphere intact, as it was designed to do, the trajectory being arranged so that it would plunge into 6–9 kilometers of water in the Tonga trench in the Pacific Ocean. The absence of plutonium-238 contamination in atmospheric and seawater sampling confirmed the assumption that the cask is intact on the seabed. The cask is expected to contain the fuel for at least 10 half-lives (i.e. 870 years). The US Department of Energy has conducted seawater tests and determined that the graphite casing, which was designed to withstand reentry, is stable and no release of plutonium should occur. Subsequent investigations have found no increase in the natural background radiation in the area. The Apollo 13 accident represents an extreme scenario because of the high re-entry velocities of the craft returning from cis-lunar space (the region between Earth's atmosphere and the Moon). This accident has served to validate the design of later-generation RTGs as highly safe.
Mars 96 launched by Russia in 1996, but failed to leave Earth orbit, and re-entered the atmosphere a few hours later. The two RTGs onboard carried in total 200 g of plutonium and are assumed to have survived reentry as they were designed to do. They are thought to now lie somewhere in a northeast-southwest running oval 320 km long by 80 km wide which is centred 32 km east of Iquique, Chile.[29]
APK likes to ask for responses to the same things over and over. Maybe he just likes the responses?