Nuclear waste in Space, disposal of...

I was thinking the same thing: put the decayed uranium back where we found it; in the mines. The other option (we think alike on this one) is to launch it towards the sun and let the sun engulf it. I think it's better to bury it back in the mines. It would take a hell of a lot of rocket fuel to send heavy metals out of Earth's orbit.

 

I vote for leaving the poisons deeply buried in the ground, where they belong.

Which I know will never happen, as long as somebody's making money digging them out.

 

"Decayed" (depleted) uranium isn't particularly dangerous or radioactive. It has a half-life of billions of years, and can be put in a warehouse. It's not even terrorist fodder since you can't get any fissionable isotope from it any more.

It's the fission byproducts - transuranics and short-lived isotopes - that pose a danger because they have much shorter half-lives and thus are dangerously radioactive. But they are just a small portion by volume of the raw nuclear waste. Once they are separated, they can be buried or shot into space or spread around areally or volumetrically (my suggestion) until they no longer pose a hazard. Perhaps after a few more days of discussion we can vote on this and let the government know our decision.

Richard

 

Correct. First postulated by Dr's Birkeland (Birkeland Current due to his work in that field of physics), Stormer (Research into the magnetosphere), and Christofilos (Credited with the Synchrotron, Project Sherwood, Operation Argus, JASON, Project Sanguine, etc).

The existence of the belt was confirmed by Explorer 1 and Explorer 3. Dr James Van Allen was project director.

Ah, if only we could get our government to work so smoothly

Much like the current "crisis" over medical isotopes, as the 50 year old reactor at Chalk River, Ontario, is down for extended maintenance.

Over 20 years ago, the Canadian government knew that an urgent replacement was needed for that ancient reactor. No matter Conservative or Liberal, governments over the past 20 years kept passing the buck, until now we face a "crisis"

So why agree to International contracts to supply medical isotopes, if you can't live up to the contract? And why piss and moan when other nations threaten monetary settlement over the isotope shortage?

But, that's politics

 

This is false. One cannot use the central body of a solar system for a gravity assist out. The assist must come from one of other bodies orbiting around it, i.e. a planet.

A direct flight out of our Solar System, from Earth, requires a delta-V of roughly 43,000 feet per second. This is very expensive, considering that chemical rocket exhaust velocities are only a fraction of that speed.

A direct flight into Sol requires a delta-V of slightly over 100,000 feet per second. A surface skimming orbit will still do the trick and save a little delta-V. But these speeds are hideously expensive, and no one has yet tried to do it.

Multiple planetary assists reduce the cost, but at the risk of more failures and collisions with things that we'd rather keep clean.

 

No, the Van Allen Radiation belts are the waste from above ground nuclear bomb explosions that was shot up and trapped in orbit. This is why above ground nuclear tests were banned in the 50's.

Edit - Apparently the "Starfish Prime" space nuclear bomb explosion test caused trapped high energy particles - source wikipedea.

 

If you are going to use Wikipedia as a reference, why ignore its section on the natural causes? See [ame="http://en.wikipedia.org/wiki/Van_Allen_radiation_belt"]Van Allen radiation belt[/ame].

 

Thank you for explaining that. Having taken physics when I was in college, I've always been thinking that once the Uranium has decayed, it's no longer dangerous - so I had been thinking that perhaps enough of it has decayed that it is no longer useful for powering a power plant but it still contains residual radiation that could harm humans (think of an battery; it can no longer power your car, but it still has some charge left). So, if I understand you correctly, you are saying that the alpha, beta, gamma particles from the remaining decay are the concern? (if I remember correctly, the alpha particles are harmless)

 

Unless I'm mistaken depleted uranium is not decayed uranium. It instead is the portion of the natural uranium remaining after the enrichment--in other words, most of it since it is primarily U-238 before and of course after. DU has a about 2/3+ of its U-235 removed and an even greater portion of the lighter U-234 removed. U-234 is in a much smaller concentration to start, but is far more radioactive than even the U-235.

I'm not even certain that DU couldn't be enriched, since it still has a substantial amount of its original U-235 content. It seems that it would make little sense to start enrichment from such depleted material as it would make the necessary enrichment at least one and probably two orders of magnitude more difficult.

 

dU is indeed uranium composed of 99.999% U-238. Whatever fissionable U-235 is left in dU is too dilute and too expensive to extract.

The U.S. Army used to use dU-tipped APFSDS (armor-piercing) rounds for the main gun in the M-1 Abrams main battle tank. When fired, the Depleted-Uranium Armor Piercing, Fin-Stabilized Sabot-Discarding round is a 40mm-diameter dart that would strike an enemy tank's armor at a velocity of 1 mile per second, penetrate, and incinerate the inside of the tank from the heat generated from the kinetic-energy strike.

dU is nasty stuff. When an APFSDS round hits, the heat generated from the KE strike turns some of the depleted Uranium into very fine dust, which contaminates the area around the killed tank. Soldiers who walk around the site and kicks up the dust will breathe it in, and come down with heavy metal poisoning from the dU. (Yes, depleted Uranium is a poisonous heavy metal, just like lead).

The danger with dU is not radiation, but heavy metal poisoning. You definitely DO NOT want to "spread it around" and "disperse it across a wide area."

That's why nowadays the U.S. Army uses Tungsten-tipped APFSDS rounds for our M-1 tanks instead of dU. Much safer for our troops.

Back to the topic of disposing nuclear waste in space.. It's not feasible due to the following reasons:

1. U.S. heavy-lift rockets to date have a 98% success rate. That means one out of every 50 launches will be a failure. So a rocket loaded with nuclear waste blowing up in the atmosphere and creating a real bad mess is not a question of IF, but a question of WHEN, if we chose that method of disposal.

2. The cost of sending payload into space is $10,000 per pound using current heavy-lift rocket technology. Considering the weight of the nuclear waste (remember Uranium and Plutonium are heavy metals similar to lead) and the weight of the shielding necessary to protect the payload to withstand a launch failure, and that even the Saturn-V had a payload of only 50 tons, the cost quickly becomes prohibitive.

3. Reprocessed waste with fission byproducts are not merely short-lived isotopes or transuranics. There are plenty of nasty stuff in there you don't want to have dispersed, like Strontium-90 (which can be taken up by living things as a Calcium analogue) as well as other poisonous substances like Radium or Arsenic. You don't want that stuff dispersed in a booster failure explosion just as much as you don't want uranium or plutonium dispersed in an explosion.

 

Yep, I was wrong, and ignorant. It happens, hi!

 

That's not right either. It isn't 99.999% for starters. The spec is 0.3% U-235 max, DoD states that their DU is 0.2% U-235 so 99.8% is close vs. 99.2-99.3% as natural uranium. U-238 is also radioactive, it just has a very long half life.

I'm aware of the density properties, shear effects, and incindiary nature that make it an excellent kinetic penetrator.

DU is mildly toxic as heavy metals go, less than arsenic or mercury for example. There has been a lot of effort to link it to various illnesses and cancers, but those efforts have largely failed. Lead is actually much more toxic than DU.

A short review of depleted uranium toxicity - Defence News - Jane's Defence News

There is plenty of heavy metal floating about after a penetrator hit on modern armor, you don't need ANY DU to make the area dangerously toxic from a metals standpoint. In fact, several of the tungsten alloys studied (cobalt, nickel) have been shown to be 100% effective in producing cancers in lab animals.

DU is heavy and insoluble so the toxicity just isn't there as you propose.

There is a difference between this and reactor byproducts produced in a fissile environment. That's why I was making the distinction between depleted uranium and depleted reactor fuel (which is enriched anyway.)

While the DU is not particularly dangerous from a radiological standpoint, it is important to remember that it still contains enough U-235 that it could be used to produce enriched uranium. It's just not economically feasible to do so since natural uranium is available. (There are some studies out there about the commercial feasibility of enriching the large DU inventory.)

 

I just want to point out that solar sails is for going out of the solar system, not going towards the sun.

How a solar sail works:

1) the spacecraft you want to send out of the solar system is launched towards the sun, with the solar sail stowed.

2) once the spacecraft passes as close to the sun as possible, it unfurls the solar sail. That's where the solar sail gives the spacecraft the biggest amount of push and sends it on its trajectory out of the solar system.

3) the solar sail will continue to push the spacecraft with ever-decreasing force out past Jupiter, where sunlight become so weak it no longer generates any significant push on the solar sail. But by then the cumulative force on the sail from the time it was unfurled near the sun to Jupiter has accelerated the spacecraft to tremendous speeds.

 

To clarify (or, of course, obscure) a couple of points:

1: My suggestion of areal or volumetric disposal may or may not be viable, but is worth considering. On the one hand, reactor waste is very, very radioactive and dangerous. OTOH, there is a LOT more planet and ocean than there is waste. There's an old saying, "The dose makes the poison." Drink a small vial of cyanide and it will kill you. Pour that vial into the ocean, wait for a few minutes, and it will be undetectable. There is already plenty of natural uranium in seawater, believe it or not. And, obviously, plenty in the earth, since that's where you find "mines." Concentrating the waste and then forgetting about it is clearly dangerous for millenia if it's stumbled on. Dispersing it properly will render it less harmful since there will be nothing to stumble on and no practical way to concentrate it again. Will that be enough?

2: Disposal in space is problematic from a technological point of view for the reasons many have discussed. Even with gravity assist for final removal, you still have to get it off earh, which requires a good fraction of escape velocity and the danger and inefficiency of chemical rockets. One possibility I didn't see mentioned here is the "space elevator" concept, which is a technical challenge, but at least not theoretically impossible. Combine that with the Libby drive, which is theoretically impossible, and that nasty stuff is gone.

Richard

 

This is very low thrust, therefore it does take a long time, many orbits. A constant burn forming a slow spiral into the sun is horribly energy inefficient. An increasingly eccentric ellipse, dropping perihelion with each orbit but keeping aphelion in our neighborhood, is much more efficient. This means burning the engine only in the outer portion of the orbit, shutting it off the rest of the time. But as perihelion drops closer to Sol, the heat is very likely to kill the vehicle's controls and propulsion system before the job is done, leaving the waste stranded in orbit.

Solar sails are also weak thrust. If tacking against the solar wind is possible (I haven't checked), then a slow spiral into the sun is more tenable -- at least until the heat fries the sails, leaving the waste stranded still in orbit, but probably inside Mercury's domain.

I'd like to know more about how the sun is used. The [ame="http://en.wikipedia.org/wiki/Gravity_assist"]wikipedia [/ame]article is succinct: "Interplanetary slingshots using the sun itself are impossible because the Sun is at rest relative to the solar system as a whole." This slingshot action is based on slinging around moving objects. (Using this action to drop something into a very low orbit, then doing a traditional rocket burn at perihelion, is really just an extension of ordinary orbital mechanics.)

Gravity assists of extra-Solar objects are not relevant to this discussion, as all the materials we are talking about moving are starting deep inside Sol's gravity well.

 

This is why I don't dismiss ocean dilution out of hand, despite it being politically untenable now.

Various sources I see show natural seawater uranium concentration in the range of 0.15 to 3 ppt. This should translate to about 0.6 to 13 tons per cubic mile of seawater.

 

In the planets early geologic history, there were even *natural* nuclear reactors

Oklo: Natural Nuclear Reactors - Fact Sheet

Fascinating!