Speaking of Thorium and Navy Nuclear Power verses Polywell

[Axil]

While our nuclear Navy has thrived with a continuing record of zero reactor accidents. . .

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Em, sorry but your definition of what constitutes a "reactor accident" is up for appraisal. I like the vast bulk of your post but it glosses over the fact we've lost not one but two nuclear vessels and the environmental hazards of this are formidable.

USS Scorpion was lost in 1968 and USS Thresher in 1963. There's all that atomic junk sitting on the bottom of the sea poisoning whatever is around it. Lets not pretend nukes are safe. They're not. We mitigate the risk through careful and hard work, but fission reactors with all their products are NOT safe. They have never been. Fusion will be much safer.

It is important to understand that the size of the radiation threat becomes smaller with the passage of time. Locations where radiation fields once posed immediate mortal threats, such as much of the Chernobyl power plant on day one of the accident and the ground zero sites of Japanese atomic bombings (6 hours after detonation), are now safe as the radioactivity has decayed to a very low level.



See for instance the graph above of the gamma dose rate due to Chernobyl fallout as a function of time after the accident. Many of the fission products decay through very short-lived isotopes to form stable isotopes, but a considerable number of the radioisotopes have half lives longer than a day.

The radioactivity in the fission product mixture is mostly due to short lived isotopes such as I-131 and Ba140, after about four months Ce141, Zr95/Nb95 and Sr89 take the largest share, while after about two or three years the largest share is taken by Ce144/Pr144, Ru106/Rh106 and Pm147. Later Sr90 and Cs137 are the main radioisotopes, being succeeded by 99Tc. In the case of a release of radioactivity from a power reactor or used fuel, only some elements are released; as a result, the isotopic signature of the radioactivity is very different from an open air nuclear detonation, where all the fission products are dispersed.



Futhermore, time as cleansed the Bikini island US nuclear test site



The special International Atomic Energy Agency (IAEA) Bikini Advisory Group determined in 1997 that "It is safe to walk on all of the islands ... although the residual radioactivity on islands in Bikini Atoll is still higher than on other atolls in the Marshall Islands, it is not hazardous to health at the levels measured ... The main radiation risk would be from the food: eating locally grown produce, such as fruit, could add significant radioactivity to the body...Eating coconuts or breadfruit from Bikini Island occasionally would be no cause for concern. But eating many over a long period of time without having taken remedial measures might result in radiation doses higher than internationally agreed safety levels.

The dose received from background radiation on the island was found to be between 2.4 mSv/year and 4.5 mSv/year (the lower rate is the same as natural background radiation) assuming that a diet of imported foods were available. But it was because of these food risks that the group eventually did not recommend fully resettling the island.

Howerver, if a potassium fertilizer remediation strategy consistent with international guidance on interventions to avoid dose in chronic exposure situations were undertaken , this strategy would provide a radiologically safe environment permitting early resettlement.

[IntLibber]

While our nuclear Navy has thrived with a continuing record of zero reactor accidents. . .

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Em, sorry but your definition of what constitutes a "reactor accident" is up for appraisal. I like the vast bulk of your post but it glosses over the fact we've lost not one but two nuclear vessels and the environmental hazards of this are formidable.

USS Scorpion was lost in 1968 and USS Thresher in 1963. There's all that atomic junk sitting on the bottom of the sea poisoning whatever is around it. Lets not pretend nukes are safe. They're not. We mitigate the risk through careful and hard work, but fission reactors with all their products are NOT safe. They have never been. Fusion will be much safer.

Actually, to correct your claims here, Capt Bob Ballard's surveys of the wreckage of both submarines confirmed that the reactor cores were secure and not leaking.

[cuddihy]

That would no longer be true if they were nuclear because of the security risk involved should a well organized band assault the ship and take it. A fission reactor is worth more than the ship in these instances so one expects they would not be put aboard things like cargo craft.

On the other hand, a Poly is so safe it could form the basis for an historic exception and not need such security as Navy fission reactors. What would/could a band of crazed fascists do with a Poly to gain power?

this is wildly incorrect. The non-propulsion plant costs of an Aegis destroyer are about twice the cost of a submarine reactor plant and about five times the cost of the nuclear core. So the propulsion plant of an Aegis nuke would be worth about 30% of the total ship cost.

And the scenario of a hostile takeover in a foreign port is just plain dumb, the nuke restrictions are all based on nuke disaster scenarios combined with pure anti- nuke policy reasons. Otherwise our subs wouldn't pull into Jakarta and Bahrain, which I can assure you they do.

[GIThruster]

Sorry but you seem to have missed the point. I was responding to the notion that all Navy ships ought to go nuke. My point is that this is not practical for things like cargo ships (which is just what I said) so your destroyer and sub illustrations do not come to the issue. I think subs and destroyers ought to use nukes. Cargo vessels. . .not bloody likely unless we have something much safer than fission. Seems to me a Poly would work just fine in cargo craft.

Fighting ships are filled with fighting men. Cargo ships are not. Fighting ships cost. . .em. . ."boat loads." Cargo ships do not.

[KitemanSA]

Personally, I'd kind of like to see super-tankers go Nuke with a Thorium fueled Augmented MSR. Just because you are delivering oil doesn't mean you need to USE oil.

And since tankers are on the go most of the time, the usage factor would be very high making it more cost efficient.

Also, if a typical AMSR produces significantly more power than now used in a super-tanker, maybe they could just run the ship faster and get a higher delivery rate too.

[WizWom]

As far as it goes, there were Nuclear Cruisers and Destroyers in the 60s.

And even a nuclear civilian vessel or 2, under The Soviet flag.

On the "power level" issue, it should be noted that Nuclear plants can be built incredibly tiny; a 1 MW fission plant is very possible. 1 MW heat is only about 400-500 HP shaft; that's a small yacht or a speedboat. A fission plant could be made for whatever power level was desired.

For civilian use, though, there is a LOT of red tape. Since it would operate anywhere, it would have to pass home country and IAEA scrutiny.

[KitemanSA]

And even a nuclear civilian vessel or 2, under The Soviet flag.

There was one under US flag too, NS Savannah if memory serves. It does. http://en.wikipedia.org/wiki/NS_Savannah

On the "power level" issue, it should be noted that Nuclear plants can be built incredibly tiny; a 1 MW fission plant is very possible. 1 MW heat is only about 400-500 HP shaft; that's a small yacht or a speedboat. A fission plant could be made for whatever power level was desired.

Perhaps, but due to the cube/square relationship, it is doubtful a small yacht or speedboat would float the sheilding needed for the power-plant. That is one of the main problems with using them on smaller US Navy ships. They get used on subs because, for a globe spanning navy, there is no real alternative.

[MSimon]

The real problem is the cost of operating personnel. And liability in case of an accident issues.

[jnaujok]

USS Scorpion was lost in 1968 and USS Thresher in 1963. There's all that atomic junk sitting on the bottom of the sea poisoning whatever is around it. Lets not pretend nukes are safe. They're not.

From Wikipedia:
"The Navy has also released information about the nuclear testing performed in and around the Scorpion site. The Navy reports no significant release of nuclear material from the sub." The likely cause of the Scorpion's sinking was a fire from a torpedo battery, not the nuclear pile. The scorpion sank in two miles of water, and sits on a muddy plain, with no measurable amount of inherent life in the area (i.e. it landed in the ocean equivalent of a barren desert.)

And the USS Thresher was sunk by a faulty pipe fitting that caused the engine room to flood. In fact, the SCRAMing of the reactor by the crew probably contributed to its rapid sinking, since it relied on it's nuclear power to maintain depth. When the emergency blow valves failed (they iced up, preventing the ballast from blowing) the Thresher sank and imploded. No evidence of leakage from the reactor has been found at that site either. To this day, the nuclear fuel remains intact in the reactor and radiation remains typical of worldwide background levels.

So, as the prior poster said, there have been no reactor accidents with US Naval vessels. Period.

Your kneejerk post is equivalent to claiming that all internal combustion engines are unsafe, because a car had a flat tire.

[GIThruster]

Your kneejerk post is equivalent to claiming that all internal combustion engines are unsafe, because a car had a flat tire.

No. When someone says that gasoline is perfectly safe and there's never been a gasoline accident, I point out that there are accidents with people in cars all the time. When someone says that the Navy has a perfect record in nuke safety and I point out it has lost not one but two nukes on the ocean floor, there is nothing "knee-jerk" about it. The Navy does not have a "perfect record". It has not one but two reactors sitting on the ocean floor. That's hardly a perfect record.

[MSimon]

Your kneejerk post is equivalent to claiming that all internal combustion engines are unsafe, because a car had a flat tire.

No. When someone says that gasoline is perfectly safe and there's never been a gasoline accident, I point out that there are accidents with people in cars all the time. When someone says that the Navy has a perfect record in nuke safety and I point out it has lost not one but two nukes on the ocean floor, there is nothing "knee-jerk" about it. The Navy does not have a "perfect record". It has not one but two reactors sitting on the ocean floor. That's hardly a perfect record.

I try not to confuse drive train failure with engine failure.

[jnaujok]

When someone says that the Navy has a perfect record in nuke safety and I point out it has lost not one but two nukes on the ocean floor, there is nothing "knee-jerk" about it. The Navy does not have a "perfect record". It has not one but two reactors sitting on the ocean floor. That's hardly a perfect record.

Sorry, but the U.S. Navy has hundreds of ships on the ocean floor. By your measure that any accident is a problem with the power source, then clearly diesel engines, coal fired steam engines, and even sails are far more dangerous than nuclear power.

The fact is, both the Thresher and the Scorpion were sunk, not because they were Nuclear submarines, but because of human error of poor engineering in the non-nuclear parts of the submarine.

So it would be far more accurate to say that the Human part of the Navy failed, and to get rid of them.

There is nothing, nothing other than the crushing pressure of two miles of water, that prevents the Navy from recovering those two nuclear power plants and using their materials to build a new reactor. Seriously.

Did you ever wonder why the only nuclear plants lost are on submarines? It's because submarines are inherently dangerous. Face it, when they're running as planned, they're already sunken. That's the very worst fate a normal ship can face. Now add in that they're also under tens of atmospheres of pressure, and that the slightest flaw in the hull or hatches will cause them to sink all the way, and you're asking for trouble.

The Thresher sank while being tested after a refit. The refit was flawed, the sub leaked, and sank. The Scorpion was known as a "bad-luck" ship with dozens of recorded problems and near-failures.

If the Titanic had been nuclear powered, then you'd refer to it's sinking as a nuclear accident?

[TheSeeker]

Almost all of the engineering of a LFTR has been demonstrated already (decades ago) and there's enough Thorium to last for thousands of years, even if the entire world had the USA's level of energy consumption per capita.

I want to see fusion as much as anyone here, but I think Thorium is a great stepping-stone while we wait for science to catch up to our imaginations. Lets just hope we don't run out of Thorum before we get fusion right.

[ladajo]

The Thresher sank while being tested after a refit. The refit was flawed, the sub leaked, and sank.

The sub's issue was freezing up of the emergency blow supply valves cutting off air to the tanks while attempting to surface. Bad design.

As I recall reading in the public domain, they tried to blow tanks after a SCRAM and issues making a recovery.