The Ship Model Forum

by **Werner** » Tue May 29, 2007 10:08 am

Is six feet or so of water not an ideal neutron moderator?

If I had a litre of Radon and a litre of water and mixed them in a 2 litre jar, what would the result be? Surely the material with the heaviest weight per volume would occupy the bottom layer. No magic will occur.

I think the fact that Radon is a gas at room temperature would not inhibit it's sinking under the much lighter sea water. Nor would it inhibit Radon entering solution with the water.

Would not (in the abstract) a Radon atom (weight 222) sink much more quickly than, say a mere atom of lead at 82? I had always heard the molecular weights of the isotopes would greatly discourage their mixing in the water column, and will instead be buried under sediment in a few years, especially at benthic temperatures and pressures.

The Russians have always used this excuse when dumping surplus nuclear materials in the Arctic Sea.

by **Pieter** » Tue May 29, 2007 3:54 am

You're absolutely right. The flow model for the coaean is very different, so is the atmospeheric model for the air above it. We are talking about some kind of catastrophic hull failure in a surface warship, very close to the atmosphere. And as chuck remarked the molecular weight of radon (and some other decay products) does not matter. And you did not take note of the rest of the primary cycle materials. Some people do not seem to understand that any reactor which is depending neutron flux for keeping up the chain reaction will contaminate everything in the structure around it. This is the main reason for the eleborate shielding you can see around shore based nuclear reactors. I don't see why a catastrophic failure of the hull of a nuclear surface warship would somehow magically contain all radio active matarials and bury itself in a few miles of ocean. Aside from the fact that nuclear surface warships have mainly been fighting in wars in relatively shallow waters like the Persian Gulf and the Adriatic (which does have ocean depth parts but which is mainly very shallow) over the past 20 years.
[Radon has a molecular weight of 222 and will sink into the ocean substrate like a hot knife in butter.

The flow model for the ocean would be quite different.[/quote]

by **chuck** » Tue May 29, 2007 3:14 am

Werner wrote:Your reactor-generated Radon has a molecular weight of 222 and will sink into the ocean substrate like a hot knife in butter.

t.

While I hate to be the intractabe pedantic, I feel obliged to play the role you assign me.

Since we are talking about sinking in the ocean, I think we can presume that we are not talking about an ideal gaseous substance. Therefore the density does not depend directly on molecular weight.

by **Werner** » Mon May 28, 2007 11:46 am

Your reactor-generated Radon has a molecular weight of 222 and will sink into the ocean substrate like a hot knife in butter.

Natural Radon was rarely a problem in houses with basements where the Radon is kept within millimeters of the floor and transfers some radiation to dust motes which are light enough to be drawn into the heating/cooling system.

The flow model for the ocean would be quite different.

by **Pieter** » Mon May 28, 2007 6:35 am

No Godzilla, just some nice and friendly cases of radiation sickness , cancer and birth defects in a large number of people, including military . Godzilla's inspiration may have been the very real story of a japanese fishing boat which came into contact with fallout from a nuke test in the pacific in the 1950's. The ban on atmospheric testing of 1962 between the US and the SU had nothing to do with public misconceptions about radiation safety (both US and SU public were still in their atoms for peace phase) and a lot with 17 years of hard experience with the effects of radiation on their own personnel.
Back to the original subject, we don't know the effects of a nuke warship being destroyed in war at sea as it has not happened yet. Most submarines sunk either had their reactors switched off or a very heavy shielding mechanism in a hull designed to take a lot of pressure. The hull structure of a surfcae warship is very defferent and depending on how many air is left when leaving the surface will of will not break up during the sinking.
One thing about Werners' remarks, most radioactive elements in a reactor core are heavier than water but not all of them. Lightwater reactors like the ones used in nuclear surface warships create a lot of lighter radioactive elements by neutron flux on parts of the reactor and which are part of the primary cycle (the parts of the reactor that are in contact with the core). Many of these like radioactive radon are carcinogenic. This becomes worse with time so if any nuke carrier is to be sunk it had better not be Enterprise.
[quote="Jack Ray"[/quote]

Do you mean that the radioactive fallout from American nuclear testing in the Pacific did not help give birth to Godzilla??!!?[/quote]

by **Gerarddm** » Sun May 27, 2007 6:13 pm

Uh, what does a nearby nuke generating EMP do to an all electric ship? Blooey, I'd say... what does it cost to shield a ship from EMP?

by **chuck** » Mon May 14, 2007 1:26 pm

Werner wrote:
Specific production of a specie of water from radioactive isotopes would be the kind of thought experiment only of interest to intractable pedantics like Chuck.

Intractable pedantic? You wound me.

by **Lesforan** » Mon May 14, 2007 9:35 am

The gist of what I have been able to deduce from what I am hearing and reading indicates that the focus of future USN strategy will be on preparation for littoral warfare. If we are to continue to be the world's policeman, we need to be gearing up for close-in missions: amphibious landings, fire support, close-in patrols, etc.

In light of this, I cannot see the wisdom of using podded drive units 40' below the surface. Increasing the draft in this way would make the ships less suitable for this type of shallow-water combat. Imagine the problems if a warship were to hang up on a reef while under attack.

by **Jack Ray** » Mon May 14, 2007 8:03 am

Werner said:

The public's perception of the dangers of nuclear power are based on a deeply ingrained ignorance reinforced at nearly every opportunity by the press and other media, who seem specialized for getting the facts wrong in general, and on scientific facts in particular.

Do you mean that the radioactive fallout from American nuclear testing in the Pacific did not help give birth to Godzilla??!!?

by **Werner** » Sun May 13, 2007 1:06 pm

Anonymous wrote:
Werner wrote:Pure water does not become radioactive.

Water can be chemically pure and made from radioactive isotopes of hydrogen or oxygen.

Let's be realistic: for the purposes of this discussion, a reactor at the bottom of the sea does not make the sea water radioactive, nor do it's components or by-products represent a significant danger to the cultures who live on those waters or use them for commerce or industry unless they are determined to recover the wreck or work within a few meters of it for some purpose.

Specific production of a specie of water from radioactive isotopes would be the kind of thought experiment only of interest to intractable pedantics like Chuck.

The public's perception of the dangers of nuclear power are based on a deeply ingrained ignorance reinforced at nearly every opportunity by the press and other media, who seem specialized for getting the facts wrong in general, and on scientific facts in particular.

by **Lesforan** » Sun May 13, 2007 12:35 pm

I like the idea of turbo-electric drive. If you recall, this concept was used on USN battleships in the WWI era. It had some real advantages: eliminated the need for gearboxes to reduce shaft rpm. Eliminated the need for reverse-rotation turbines. Allowed better compartmentation of hull, better watertight integrity, shorter shaft runs, better distribution of boiler and engine rooms. Possibly reduction of vibration.

Disadvantages: Weight of generators and motors; use of high-voltage electricity in a moist, corrosive environment. Need for power-switching control equipment in a protected location.

If drive units are going to be located on pods (which I am not at all sure is even a good idea in a warship), electric drive is probably the only practical method. Long vertical driveshafts mechanically driven from within the hull would certainly be vulnerable to battle damage. This would also seriously increase the draft of the ship.

I always liked the Kirov hybrid drive: it would provide a redundancy in case of reactor failure.

The high-voltage side of the electric drive would of course need to be kept as physically small as possible. But even here, the potential exists for redundant, alternate hv. cable routes between generators and motors to circumvent battle damage.

My ideal concept: nuclear steam turbine-electric drive. Steam generator boosted by independent oil-fired boilers, separate from reactor system, that could also be used as an emergency power source for propelling ship at reduced speed. Multiple-shaft screw drive in conventional layout. Electrically-driven internal bow thrusters to aide docking and steering in case of rudder failure. Dual non-balanced rudders located in thrust current of inboard screws. Dual hydrodynamic stabilizers on each side of hull.

by **Guest** » Sun May 13, 2007 12:02 pm

Werner wrote:Pure water does not become radioactive.

Water can be chemically pure and made from radioactive isotopes of hydrogen or oxygen.

by **Werner** » Sun May 13, 2007 11:04 am

Pure water does not become radioactive. The reactor and it's by products are very heavy elements (2-3 times heavier than lead). The solids and solutions tend to sink into the soil directly below the ship.

by **Dustermaker** » Sun May 13, 2007 5:28 am

kennylibben wrote:i'm going to have to agree with the move for the moment, it sucks i know but we must stop our oil dependency at all costs - and solar panels are not going to work well on a ship.

by the way - has a nuclear powered vessel ever been sunk by enemy fire? what if the core was damaged - how catastrophic would it be to the environment - and how wide of a radius?

I think that if one of our CVN's goes down from enemy fire we have worse problems on our hands than environmental concerns.

by **Seasick** » Sun May 06, 2007 9:05 pm

Average Anual Unit Operating Cost as evaluated in 1996:

Average cost per unit in FY1996: (2006 estimate)
Ticonderoga CG class $28 million. ($35.8 million)
Kidd DDG class: $25 million. ($32 million)
Arleigh Burke DDG class $20 million. ($25.6 million)
OH Perry FFG class: $16 million. ($20.4 million)

Now for some nukes:

Average cost per unit in FY1996:
Virginia CGN class: $40 million. ($51.1 million)
California CGN class: $40 million. ($51.1 million)

by **Guest** » Sun May 06, 2007 9:00 am

Nuclear power requires trained personel and a large support infrastructure that noone wants to pay for or maintain. That and politics killed the Nuc cruiser in the USN.
Costs resulted in the Tico using a Spruance hull and propulsion vs a new design much less nuclear power. Result was a badly overloaded/crowded ship.

Personel and support costs aren't considered by the politicians when they are talking any ship/equipment program.

by **Werner** » Sun May 06, 2007 12:17 am

Don't forget: The USN plans to greatly complicate things by using podded electric motors 40 feet or so below the water line. In addition, they plan to use supercooled motors and generators. The plumbing for that will add an entirely different level of complexity to a combat system.

by **Guest** » Sun May 06, 2007 12:14 am

Seasick wrote:

My system is different. The combination is different. The electric motors run on electricity, the gas turbines generate electrical power seperatly. The electricity from the gas turbine generators goes onto the main bus and is pulled by all ship electrical systems the same way that electrical power from a third reactors steam turbine's generation would be added. The problem with the Kirov's system was that it was hopelessly complex and ill conceived.
Electricity is easier to combind.

The Kirov system works well enough in practice, and needing just one set of turbines is a big bonus.

The efficiency of electric motor demands very high voltage, and the main drive motor would preferably have tens of thousands of volts. So it would have to be isolated from the ship's system, which for the sake of damage control, should operate on low voltage, say 36 volts.

by **Seasick** » Sat May 05, 2007 11:45 pm

Your idea has been tried by the Soviets, in the form of the Kirov class CGN. The Soviet rationalized the propulsion even more. They noticed that nuclear engine requires a steam turbine to covert heat to usable power, and steam turbine is indifferent to whether the steam comes from the nuclear pile or a boiler. So rather than having 2 different sets of turbines, they used a single set of steam turbines that draws steam from the nuclear power plant through a heat exchanger for normal crusing, and they added an additional oil fired boost stage to the steam cycle to increased the energy contained in the steam in order to provide peak power. Certainly that seems to be a more rational system than one that would require two different turbines for cruising and boost.

The Kirov system is different. The Reactors supplied steam to the turbines which would be superheated by the boilers in a very complex pipeing nightmare.

My system is different. The combination is different. The electric motors run on electricity, the gas turbines generate electrical power seperatly. The electricity from the gas turbine generators goes onto the main bus and is pulled by all ship electrical systems the same way that electrical power from a third reactors steam turbine's generation would be added. The problem with the Kirov's system was that it was hopelessly complex and ill conceived.
Electricity is easier to combind.

by **Guest** » Sat May 05, 2007 10:32 pm

Seasick wrote:Chuck asked:
In an electrical warship, what is the base load requirement during normal operation, what is the peak load requirement during high maneuver and large electronic expenditure?
Nice thing about energy is that it can be measured in multiple unit types.

Ticonderogas for instance:

LM2500 gas turbines provide up to 100,000 SHP maximum, but the usual requirement is 86,000 SHP (USNI Combat fleets 2005-2006) and the electrical load is provided for by 7,500 kw (3 � 2,500 kw Allison 501K gas turbine sets).

100,000 SHP is the equivelent of 74.56 megawatts.
86,000 SHP is the equivelent of 64.1 megawatts.
7,500 kw is 7.5 megawatts.

The ordinary sepected load would be 71.6 megawatts for an all electric Tico and 82.06 megawatts maximum.

A reactor for a dual source ship like a Tico would most likely be about 65 megawatts and gas turbines to boost to 85 megawatts.

No, the idea arrangement for a Tyco from nuclear power persepctive would be for the nuclear engine to be just strong enough to power the ship at crusing speed and normal electric load, with everything else being boost. Nuclear engine's cost, capabilities and safety are all enhanced by reducing the need to throttle it to different operating levels in normal operation.

So if the ship requires 15,000 shp for normal crusing (not an unreasonable estimate for a 9,000 ton ship traveling at 20 knots), then 20,000 shp should be nuclear, the rest GT boost.

Your idea has been tried by the Soviets, in the form of the Kirov class CGN. The Soviet rationalized the propulsion even more. They noticed that nuclear engine requires a steam turbine to covert heat to usable power, and steam turbine is indifferent to whether the steam comes from the nuclear pile or a boiler. So rather than having 2 different sets of turbines, they used a single set of steam turbines that draws steam from the nuclear power plant through a heat exchanger for normal crusing, and they added an additional oil fired boost stage to the steam cycle to increased the energy contained in the steam in order to provide peak power. Certainly that seems to be a more rational system than one that would require two different turbines for cruising and boost.

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