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LostCosmonaut

Should the US Navy Switch to LEU for its Submarines?

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Some people think so. Apparently, Obama is one of them.

 

Personally, I think this is a highly stupid idea.

 

The reason people are proposing switching to low enriched uranium is to reduce the threat of proliferation (of nuclear weapons). True, reducing the amount of HEU in circulation definitely wouldn't hurt nonproliferation. However, I am unaware of any instances of American (or anybody else's) nuclear fuel being taken and used by a rogue nation or terrorist group to produce a nuclear device. Additionally, any reasonable country seeking to develop a nuclear program is almost certainly going to develop a domestic uranium enrichment infrastructure; having your deterrent based on how much HEU you can nick from spent fuel pools is a dubious strategy. From the other direction, one could argue that laser enrichment is going to blow the whole HEU market open, making the question moot.

 

More importantly, using low enriched uranium as reactor fuel has disadvantages. Submarines are small and cramped [citation needed], and internal space is at a premium. Using highly enriched uranium allows the reactor to run at a higher power density, meaning that the total size of your reactor is smaller for the same power output. Additionally, military reactors are designed to operate for upwards of 30 years without refueling, compared to civilian reactors which refuel every 18-24 months on average. As a result, there must be excess reactivity built into the reactor's design, to counter fuel burnup and the buildup of xenon, samarium, and other fission poisons. Again, a reactor using HEU will not have to be as large in order to accomplish this. Using LEU as submarine fuel would mean accepting a major performance penalty in exchange for the idealistic hope that if we stop using HEU, maybe all the other countries will be nice and stop too.

 

 

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I don't know, you either have to try raiding highly guarded waste pools, or take on a Submarine belonging to the largest Navy in the world to obtain said Uranium, something tells me neither is going to go so well for any budding terrorists.

 

And if it's a Boomer, who cares about the reactor fuel? they literally have access to the Tridents now, the reactor fuel should now suddenly be the least of your concerns.

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For reference:

 

Dates acquired nuclear weaponry;

 

  • US - 1945
  • USSR/Russia - 1949
  • UK - 1952
  • France - 1960
  • PRC - 1960
  • India - 1974

Dates acquired nuclear submarines;

 

  • US - 1955
  • USSR - 1958
  • UK - 1963 (with American reactor)
  • France - 1971
  • PRC -1974
  • India - 2016ish

So that point in the article about nuclear subs being a backdoor for a bomb is wrong based on data so far.

 

Although wiki says that Brazil is trying to develop an SSN. If it goes anything like the Rio Olympics it's gonna be hilarious.

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For reference:

 

Dates acquired nuclear weaponry;

 

  • US - 1945
  • USSR/Russia - 1949
  • UK - 1952
  • France - 1960
  • PRC - 1960
  • India - 1974

Dates acquired nuclear submarines;

 

  • US - 1955
  • USSR - 1958
  • UK - 1963 (with American reactor)
  • France - 1971
  • PRC -1974
  • India - 2016ish

So that point in the article about nuclear subs being a backdoor for a bomb is wrong based on data so far.

 

Although wiki says that Brazil is trying to develop an SSN. If it goes anything like the Rio Olympics it's gonna be hilarious.

 

Well we always did need a submarine version of the space shuttle challenger.

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We've already had a bunch of interesting failures.

 

To be fair, neither of the American SSNs lost were due to reactor issues (instead it was bad welding+moisture and a broken trash can). Unless you're talking about failed designs, in which case, yes we have had a couple (575 and 586 come to mind).

 

If I'm remembering correctly, nobody other than the US and USSR/Russia has actually lost a nuke boat.

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Using low-enriched uranium in any sort of performance application is un-American, given the ridiculous excess enrichment capacity the US enjoys.

 

Just re-write the damn treaty to say "We have nukes, you don't, anyone who tries to get nukes and doesn't already have them gets killed.  Because we say so.  Because we have nukes.  HAHAHAHA TRY AND STOP US YOU FUCKING PEASANTS!"

 

Also, laser enrichment will allow people to pull PU-239 out of normal reactor waste.  As soon as someone develops workable laser enrichment waste disposal and anti-proliferation strategies will have to be re-thought entirely.  I prefer fast-fissioning higher actinides in fast reactors as a solution, but there may be other possibilities.

 

There are some idiots, particularly elected ones, who want to stop funding laser enrichment to avoid these problems.  Because, according to the model of reality that runs in their tiny skulls, nobody outside the United States can do science.  Yes, it will be a disruptive technology, but everyone knows that it's possible so there are years of warning to get ready for its arrival.  Physics tells us that laser enrichment can be made to work, so it eventually will be made to work.  Wishful thinking will not change reality.

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I'm slowly doing research on an idea I had for proliferation prevention in the era of laser enrichment.  Basically it involves forcing everyone who doesn't already have nukes at gunpoint, or nukepoint, to use a thermal reactor design that runs on PU-240.  Per the nuclear weapons archive, PU-240 is fissile.

 

The basic problem is that current proliferation control rests on the fact that enrichment is required for making bombs, and enrichment is a very energy intensive process that requires huge facilities.  This is the Oak Ridge facility that the USA made all of its weapons material in at the end of WWII:

 

300px-K-25_aerial_view_cropped.jpg

 

The damn thing is three stories tall and half a mile long.  And it guzzled electricity.  There's simply no way you could hide this sort of activity.

 

But laser enrichment, which works on the principles of laser magic and laser voodoo, is at least two orders of magnitude more efficient than any currently existing method.  So once it gets perfected, it can no longer be assumed that enrichment activities will be so conspicuous.

 

So instead, all client states of nuclear patrons will have to use reactors that run on PU-240 that is produced in the patron states.  Obviously, the patron states can run whatever the hell kind of reactors they want to; they have nukes, so nobody can tell them what to do.  PU-240 is fissile, but can't be used to make nukes because its spontaneous fission rate is too high.  Even a modest amount of PU-240 contamination (~6%) makes other plutonium useless as a bomb material.  This, combined with scrupulous monitoring and control of actinides and the laser technology needed to make the enrichment plants, should provide a workable security framework for the future.  Basically all fissile material gets produced in preexisting nuclear powers, all fissile material supplied to patrons is unsuitable for the production of bombs (and not even laser enrichment could make it suitable), and you watch like hell for anyone trying to get around this.  I like to call it "nuclear mercantilism."

 

I would need to see eta curves for PU-240 to make sure that there's not some other mischief you could get up to with the stuff in a thermal reactor.  There are two possible hitches; that PU-241 can be collected from the spent fuel, and that PU-240 has really high eta with thermal neutrons (like U-233 does).  With some enforced uniformity of reactor design these problems could be sidestepped, which fits in well with the mercantilism theme.

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On second thought, I think we should actually switch to LEU, it's far more effective and efficient as it's been demonstrated it can use energy from a "Triggered Colli state", the energy of which generated when the reaction starts is 235 orders of magnitude higher then Matter-Antimatter annihilation.

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There was a talk about this at work the other day, and while I'm not going to go into details here one interesting thing that came to mind was the challenges associated with handling spent LEU fuel. Normal sub fuel is 93-97% enriched, meaning that the proportion of U238 is fairly small. However, LEU fuel would only be about 20% enriched, meaning that it will be mostly U238. The result of this is that the spent fuel is going to contain far more transuranic wastes than comparable HEU fuel.

 

SQKP447.png

As you can see, U238 can get transmuted into all sorts of transuranium elements through various neutron capture and beta decay reactions. Some of it will them will be lost through fissioning (such as Pu239, which also gives you a bit of bonus U235 through alpha decay), but you'll still have a pretty decent amount of heavy, long lived radioactive isotopes. Transuranics are why waste ends up in places like Yucca Mountain or WIPP; fission products tend to decay much more quickly (on human timespans), but Pu239 for instance has a half life  of ~24,000 years.

 

One point in favor of the nonproliferation argument to LEU is that claiming your HEU is to be used for naval propulsion seems to let you circumvent some IAEA safeguards. I don't think that's a big point in its favor (nobody has ever used an SSN program as a backdoor for a bomb, and any competent state can probably think of other ways to be sneaky), but for completeness it should be mentioned.

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