Costa Concordia disaster - what if it had been a polywell?

ANTIcarrot · Post by **ANTIcarrot** » Fri Jan 20, 2012 11:38 pm

Shipping has been touted as one of the major applications of polywell reactors; both for military and civilian appications. Assuming they're still viable (fingers crossed) what woudl have been the implications of the Costa Concordia had been fitted with a polywell?

The ship sank comparatively quickly, and there's plenty of evidence pointing to crew incompetence. What would the worst case scenario be?

hanelyp · Post by **hanelyp** » Sat Jan 21, 2012 2:36 am

Presuming a boron-proton reactor, I don't see a big problem from the engine. The quantity of fusion fuel carried would be small, though boranes are noted for some toxicity, more so the lighter varieties if memory serves. Fusion products are safe to vent, though helium has enough market value that you may not want to. Worst case of a cracked reactor vessel, I don't expect enough radioisotopes being washed out to be a long term problem.

All together, the fuel oil leak from a conventional engine may be more of a problem.

kunkmiester · Post by **kunkmiester** » Sat Jan 21, 2012 5:54 am

People in the reactor room would get a spectacular light show, but I'd imagine engine rooms would be designed to make sure that any kind of random failure would not get out.

The most energetic thing would be the superconducting magnets letting go, but that would be contained in a properly designed/modified ship, so a bit of leakage would be all you could expect.

ANTIcarrot · Post by **ANTIcarrot** » Sat Jan 21, 2012 2:24 pm

kunkmiester wrote:The most energetic thing would be the superconducting magnets letting go, but that would be contained in a properly designed/modified ship, so a bit of leakage would be all you could expect.

On the other hand, a properly designed ship would have been monitored via transponder, and alarm bells should have sounded within minutes of significant course deviation - hours before it got near the island. The captain also appears to have tried to repeat a sail-past he did before (possibly under different tidal conditions?) and passengers were at one point given the highly questionable advice to return to their cabins.

I know good design is designed to assume people are idiots, but sometimes those people are designers.

So the biggest problem would be a 'small' explosion, maybe a hundred kilos of TNT or so, which even a conventional ship's structure would contain anyway? And some boron leakage?

What about neutron-activated naterials? Even a pB11 reactor produces 0.2% of its power as neutrons. Operating for 6 years at 75MW the ship woudl have produced ~3.45 *10^13 joules of neutrons. Is there likely to be anything within the radiation shield that could turn nasty?

How strong should the vacuum chamber be? On land, you'd presumably build for 45PSI pressure for safety and reliability. On a sinking ship you'll hit 45PSI very quickly. How hot would be insides get? Any chance of a steam explosion?

If it seems like I'm reaching here, I am. But only because the worse case scenario is te most interesting case. And the one that will (I assume) be of greatest benifit to our glorious cause if it turns out polywell is a good idea after all.

kunkmiester · Post by **kunkmiester** » Sat Jan 21, 2012 3:42 pm

I did of course skip over most of the other issues with a sinking ship, but the focus on the issues of having a polywell on a ship.

I would imagine there would be a "scram" system, so that on a ship in such a situation the engineer would hit a big red button and the magnets would be dumped into a resistor bank and the chamber flooded with air or perhaps an inert gas. With nothing of serious energy present after that, any radioisotopes would stay in the structure of the vacuum chamber, and not be any concern.

D Tibbets · Post by **D Tibbets** » Sun Jan 22, 2012 7:19 pm

I don't know where the 0.2 % energy out as neutrons came from. My understanding is that it is more in the neighborhood of ~ 0.00001% or less (~ 1 part per ~ 40,000,000) Gamma radiation may be ~ 0.1 to 0.01%. [EDIT- referring to a P-B11 reactor]

The major concerns would be those related to the cooling fluid- possible steam , liquid nitrogen or helium. Failure of the superconductors might result in an explosion- similar to what happened to the LHC- destructive to the reactor- but little if any damage outside the engine room or vacuum vessel itself. The borane pressurized tanks might be toxic if ruptured, but the quantity should be tiny (~ 1 millionth of the equivalent diesel fuel quantity).

I suspect hot water/ steam concerns may be the major concern. There would be somewhere around 10-100 MW of waste/ process steam to deal with (or at least hot water).

In short, the concerns would probably be less than a conventionally fueled steam engine but more than a diesel or jet turbine power plant. Pollution concerns would be minimal, much less than concerns with thousands of tons of diesel fuel leaks in a conventional power plant.
Radiation concerns would be nearly nonexistent with a P-B11 reactor. With a D-D reactor, induced radiation would be mostly associated with solid structures, and would decay to small values within a few weeks, and almost completely decay within 100 years. Even with D-D Polywells the radiation concerns are very much less than with a fission reactor. There are no actinides decay chains that cause lingering heat problems or long term high level radiation concerns.

Roger · Post by **Roger** » Tue Jan 24, 2012 4:26 am

I'm going to assume the reactor room is sealed. Once the rocks are struck, Aux power goes on, Polywell goes off.

D Tibbets · Post by **D Tibbets** » Wed Jan 25, 2012 1:40 am

Why turn the reactor off, when a lot of power may be needed for steerage, firefighting, lighting, etc. The P-B11 Polywell should be at least as robust as any other kind of steam plant, and have less quantity of stored energy to deal with. The apparatus outside the Polywell- the high voltage DC handling equipment may be more critical. The induced radiation in the reactor walls, are trivial from a heat energy perspective once the fusion process is stopped- which would probably take a small fraction of a second. The latent heat capacity of the structures should (if designed well) easily handle any mild persistent heat generation decay products. The exception may be in a D-D reactor where the neutrons are captured in a layer of Boron 10. The neutrons reaction would yield an excited boron 11 which decays in seconds(?) to a lithium isotope and a tritium (if I remember right). Some heat is generated along with the tritium. This is part of Bussard's proposed 1/2 cat D-D fusion scheme to supplement the power balance from a D-D reactor. Tritium and He3 are produced in the two D-D branches. One or both of these 'waste' products can be fed back into the reactor to produce more fusion. The tritium component may be very important in a D-D Polywell that is only producing marginal amounts of D-D fusion. The Boron 10 blanket to capture and utilize the neutrons is a further method of boosting the net results. Of course in a P-B11 Polywell this issue is moot.

The issue of the superconductors is hopefully addressed by rapid switching equipment to ground. This issue has been argued in another thread, but the major concern would be in Tokamaks which would presumably have much larger superconducting magnets and thus much larger stored energy. Presumably in a well designed Polywell power plant there would be protocols for handling various fault modes. A ship hitting a reef need not trigger a "scram" unless the engine room is compromised. And such action would be designed to save costly repairs to the magnets, vacuum vessel, high voltage handling systems, etc. There would be no danger of blowing a hole through the side of the ship, or concern of exposing crew or passengers to lethal radiation dangers. Burns from hot coolent fluids or steam would be the major concern. There could be some radiation, but not at dangerous levels so long as the engine room was evacuated on a timely basis and the mostly metal structures that carried the induced radiation were not heated to vaporizing or burning temperatures by external fires. At that point the radiation contribution to the catastrophe is irrelevant. You are not talking about remote risk of exposure to radioactive iodine , cesium (?) and others that are released with fission fuel rod meltdowns.

Dan Tibbets

Roger · Post by **Roger** » Wed Jan 25, 2012 2:14 am

Ahem

Once the rocks are struck

One won't be needing steering. Emergency lighting on cruise ships IIRC are battery powered. Escalators-etc, Lifeboat deployment and communications covers the basics.

Why turn the reactor off

Because the Concordia was listing and going down fast.

D Tibbets · Post by **D Tibbets** » Thu Jan 26, 2012 8:55 pm

Roger wrote:Ahem

Once the rocks are struck
One won't be needing steering. Emergency lighting on cruise ships IIRC are battery powered. Escalators-etc, Lifeboat deployment and communications covers the basics.
....

Actually,after hitting the rocks, the Concordia made a dash for shore in an effort to beach the ship. How successful they were is uncertain. lives were lost as the ship settled and listed onto it's side. But, without this 'beaching', the ship may have capsized completely and sank in deeper water. Many more lives may have been lost.Admittedly I have no idea at which point the engines failed or were turned off in the Concordia. Also, a oot of power would be needed to power the lights, steerage, hoists, etc. Probably at least several megawatts (it was a big ship) The battery capacity would need to be large. As a comparison, the cruise ship that lost power near Britten a year or two ago, quickly developed problems and sank. I don't think there was any problem with the hull in this case. The Yorktown was abandoned in WWII after they lost power and could no longer manage fire control, and other necessary efforts to save the ship. And in the Titanic the power was kept on (running engines I'm guessing) for a relatively long time as it was sinking.

Again this is not a fission nuclear reactor. The advantages of keeping the engines running as long as possible makes sense, and the risks to the passengers and crew are trivial. The last hand off the ship could throw the switch, but that would be mostly meaningless.

To protect the environment some new ships may have automatic cutoff switches for the diesel tanks when the ship capsizes or sea water is detected in the engine room, etc. With a Polywell the P (hydrogen) is nonpolluting except as a fire hazard inside the ship. The decaborane (if a gasous form of boron compound is used). could have similar controls, and the volume of the tanks is ~ 1 millionth the size of corresponding diesel tanks. Auxillary power if needed- to start up the reactor, or to provide some power if the reactor fails would probably be a diesel generator , not a very large battery bank. The power output from this axillary generator may provide enough power for some ship functions, but not enough for steerage, as demonstrated in multiple ship accidents. Of course having a second main engine helps a lot. On a large ship like the Concordia, there are probably several engines- possibly gas turbines. These may cause just as much damage as a coolant failure of the superconducting magnets in a Polywell. If the ' jet' engine seizes it can do significant damage as it tears itself apart- which has happened multiple times in planes. So the decision to shut down the plant for safety concerns are probably no more stringent than for typical power plants (at least gas turbines).

And, finally, a fission pile that has a narrow operating range- it has to be on the edge of criticality to produce significant power - ie it is on full power or off, no other settings (and complicated by the significant latent heat due to decay products). A Polywell, like a gas turbine or diesel engine, will probably have a throttle that allows for a range of power outputs to meet demand. It could be idled, and with direct conversion, be throttled up to full power again within seconds if the power is needed.

Dan Tibbets

Roger · Post by **Roger** » Thu Jan 26, 2012 9:44 pm

D Tibbets wrote:
Actually,after hitting the rocks, the Concordia made a dash for shore in an effort to beach the ship. How successful they were is uncertain.

Uncertain?

http://resources0.news.com.au/images/20 ... saster.jpg

Successful?

Looks like the 955 ft ship might have made it 955 ft from the rocks. At most.

ladajo · Post by **ladajo** » Thu Jan 26, 2012 10:37 pm

a fission pile that has a narrow operating range- it has to be on the edge of criticality to produce significant power

Dan - What does this mean? Edge of criticality to produce significant power?

A core is either sub-critical, critical, or super critical, and none of these conditions relate to power capability, only in the sense that power is going down, staying the same, or going up. I guess Critical can be inferred to mean "self-sustaining" as well by some. I really do not get what you meant.

MSimon · Post by **MSimon** » Thu Jan 26, 2012 10:58 pm

And, finally, a fission pile that has a narrow operating range- it has to be on the edge of criticality to produce significant power - ie it is on full power or off, no other settings

The rod settings (determined somewhat empirically) for criticality are in a narrow range. Power settings for an operating reactor at temperature can run between 1% and 100%.

The reason for the 1% minimum has to do with the timings of the safety systems. Below 1% things can happen too fast. Above 1% the reactor is somewhat self regulating. By design.

And the 1% power level is in the range of power need for minimum aux systems.

ladajo · Post by **ladajo** » Fri Jan 27, 2012 12:56 am

And for non-steady state it requires rod motion to keep temps within parameters. This rod motion can be significant as you well know for a large transient or series. Once steady, and poisons burn off, no rod motion will be needed. But "critical" has nothing do do with power level outside of super and sub. A reactor is critical at 1% steady just as it is at 100% steady. The difference being a huge change in neutron flux, and being sub-crit or super-crit during the transient as flux falls or rises with the load change.

I still don't get what he meant.

cgray45 · Post by **cgray45** » Thu Mar 29, 2012 8:17 am

Biggest advantage? No oil. Clean up after a sinking can be a mess and a lot of that comes from having to clean up spilled fuel or draining the tanks (*which may not be conveniently placed).