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PostPosted: Aug 16, 2017 8:16 pm 
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Well if an ESBWR sinks the IC condensers will be submerged forever,


This is true. Ditto for the spent fuel pools.

What's more difficult to claim is the containment. It's designed for 3 barg, so 100 barg of seawater is going to totally crush it. Then the question becomes does it fail in a bad weigh, ie structural collapse, then it would be hard to claim the IC works - ICS is attached to the containment top slab and there are various valves needing to be open that are in containment. Hard to claim if containment is crushed! Though if the containment fails in a more benign way which is more likely (probably penetration failure, drywell head rupture, equipment hatch rupture or some such) then the IC should be functional.

The primary loop is probably robust enough to deal with 100 barg, having something like 86 barg design pressure and being 180+mm thick nuclear grade steel. ICS has even higher design pressure. So these components would probably be ok at the bottom of a 1000 meter deep ocean.

Still, a huge and difficult analysis and test program would have to be conducted to prove all this. Might be better to just avoid.

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being two hundred miles from shore effectively eliminates any chance of ever needing a Fukushima and Chernobyl style exclusion zone.


Of course. But then the ESBWR isn't subject to the Fukushima style failures in the first place, having fail-open isolation condensers with a 7 day water supply (or infinite if moon pool). The design exclusion area boundary is 0.8 km only. You need to get into containment bypass or refuelling core damage events to need more than that boundary but now we're getting into <10-9 events.

as you know the main issue is the loss of heat sink, accidents that have heat sinks are really of no concern to the public because either there is no core damage or the containment will never fail or both.

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Apparently experience in the North Sea Oil industry has indicated that water at depth, like that off Norway, has a lower fouling potential than shallower water, apparently it has less biofilm forming bacteria and crustacean/coral formers.


I buy that. 1000 meters down it's getting up there in the marine equivalent of a desert. Still there are so many seawater cooled shore reactors and coal fired plants, having seawater cooled condensers, it must be a doable situation. Having sharks in the ICS pool will freak out workers though! :lol:

Quote:
Additionally turret moorings are quite problematic - the highest voltages available in modern electricity-transmission swivels for turret moorings are 66kV AC or 90kV DC [an example of the former].
You could put enough of the swivel rings in parallel to get the current capacity, but you would stil lhave to put HVDC systems or transformers on the swivel.

Which could get problematic, even though HVDC Light stations are relatively compact.

A spread moored or tension legged platform is in a fixed orientation so the cable can almost just be dropped over the side.


Isn't the line flexible enough to just drop it from the bottom of the ship with a few loopings/spirals for leeway?

Any ideas on what kind of tension loads you'd need to hold something like the Prelude in position? Any ideas on cost?

Spread mooring sounds a little easier perhaps. Dunno - not a marine engineer.


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PostPosted: Aug 17, 2017 12:20 am 
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I am a votary of floating or submerged nuclear power plants but am aware that it requires a new engineering design. It could include a thorium fuel cycle for long fuel cycle and still remain in an enrichment of civil nuclear plant range. RG plutonium or 20% leu with thorium could be a suitable fuel. A single clearance for continental shelf location could suffice for regulation for a previously approved design.
There is more space available on waterside of coasts than on land side due to nimby problems.


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PostPosted: Aug 17, 2017 9:40 am 
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China also has big plans regarding floating nuclear power plants, according to this recent NextBigFuture article:

https://www.nextbigfuture.com/2017/08/c ... ships.html


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PostPosted: Aug 17, 2017 10:17 am 
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Cyril R wrote:
What's more difficult to claim is the containment. It's designed for 3 barg, so 100 barg of seawater is going to totally crush it. Then the question becomes does it fail in a bad weigh, ie structural collapse, then it would be hard to claim the IC works - ICS is attached to the containment top slab and there are various valves needing to be open that are in containment. Hard to claim if containment is crushed! Though if the containment fails in a more benign way which is more likely (probably penetration failure, drywell head rupture, equipment hatch rupture or some such) then the IC should be functional.

The primary loop is probably robust enough to deal with 100 barg, having something like 86 barg design pressure and being 180+mm thick nuclear grade steel. ICS has even higher design pressure. So these components would probably be ok at the bottom of a 1000 meter deep ocean.

Still, a huge and difficult analysis and test program would have to be conducted to prove all this. Might be better to just avoid.

Well it might be easier to simply have blow-in panels that cause the containment to allow material in if the pressure differential over the containment wall exceeds ~1.2 bar (so it physically can't trigger unless the containment is sinking).
If the panels are big enough the contianment should flood fast enough that it will avoid a huge pressure spike in all practical sinking scenarios.

I wonder if the evidence from the monitoring the wrecks of Thresher and Scorpion are useful here?


The advantage of a controlled mechanism is that it avoids having to work out what closure fails in all starting conditions.
Cyril R wrote:
Of course. But then the ESBWR isn't subject to the Fukushima style failures in the first place, having fail-open isolation condensers with a 7 day water supply (or infinite if moon pool). The design exclusion area boundary is 0.8 km only. You need to get into containment bypass or refuelling core damage events to need more than that boundary but now we're getting into <10-9 events.

as you know the main issue is the loss of heat sink, accidents that have heat sinks are really of no concern to the public because either there is no core damage or the containment will never fail or both.


Well yeah, but the idea of saying "even if it goes Chernobyl there are no people to be evacuated" is probably useful to the political argument.

Cyril R wrote:
Isn't the line flexible enough to just drop it from the bottom of the ship with a few loopings/spirals for leeway?

Problem is since a turret moored vessel can windmill around the mooring an unlimited number of times, it is quite possible that over the life of the plant that the cable will wrap itself around the mooring line or the platform itself and could be damaged.
Cyril R wrote:
Any ideas on what kind of tension loads you'd need to hold something like the Prelude in position? Any ideas on cost?

Spread mooring sounds a little easier perhaps. Dunno - not a marine engineer.


An awful lot as apparnetly the Prelude's reference storm exceeds a Category Five Cyclone.

EDIT:

The advantage of deep water is that it makes the use of microchannel seawater heat exchangers far more practical - as they won't need cleaning so often.
Which allows very compact direct contact condensers exchanging heat through even more compact PCHEs/FPHEs.
Which saves volume, and volume is critically important in a floating application.


Last edited by E Ireland on Aug 17, 2017 10:36 am, edited 1 time in total.

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PostPosted: Aug 17, 2017 10:26 am 
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Thorcon is also offering a ship based reactor:

Image

Though they propose to island (sink) it once it reaches destination.


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PostPosted: Aug 17, 2017 10:39 am 
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I think the big advantage is that despite its very large size there exist multiple docks that could build such a vessel.
For example Harland and Wolff in Belfast can build a 556m long and 93m beam vessel, and although they only have one dock that big with an 8m draught, you could build the hull there and move it someplace else for fitting out.

There are several places to dock and work on a 556m long hull, for examples the closed Refineries in Milford Haven or the Anchorage at Scapa Flow, both have ample draught for a fully massed, if not ballasted platform.

And if you had a half dozen or more such docking locations you could rotate the platforms through them as if it was a pseudo-production line.

So it is likely far more efficient.


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PostPosted: Aug 17, 2017 12:35 pm 
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Quote:
Well it might be easier to simply have blow-in panels that cause the containment to allow material in if the pressure differential over the containment wall exceeds ~1.2 bar (so it physically can't trigger unless the containment is sinking).
If the panels are big enough the contianment should flood fast enough that it will avoid a huge pressure spike in all practical sinking scenarios.


This is true. Years ago I came up with a passive overpressure-vacuum relief method that is suitable for over/under pressure protection of any closed system. It consists simply of a U tube shaped pipe with both ends open. One end open to the pressurized device, the other open to the atmosphere. The lower half of the U pipe is filled with liquid (typically water). Overpressurizing or underpressurizing would blow the water seal and produce pressure and vacuum relief. Only moving part is the liquid so it is highly reliable.

This system could be used for the ESBWR as well. For a ship reactor you could even have the U be open to the sea water (ie a J pipe with lower end open to ocean). It would flood the containment with seawater upon sinking and compress the air in the containment to a pressure nearly equal to the seawater hydrostatic, so failure would not occur.

Quote:
Well yeah, but the idea of saying "even if it goes Chernobyl there are no people to be evacuated" is probably useful to the political argument.


Sure, but how much space are you counting on needing? Looking at Fukushima, 20-30 km is really enough even if you set very strict standards on dose. Is it worth the extra costs to go to hundreds of km?

Quote:
Problem is since a turret moored vessel can windmill around the mooring an unlimited number of times, it is quite possible that over the life of the plant that the cable will wrap itself around the mooring line or the platform itself and could be damaged.


I thought that there would be at least 2 turrets, one on the stern and one on the prow, for a long ship doesn't that restrict movement to a lot less than 360 degrees? Can't you restrict it to say 90 degrees like that?

Quote:
The advantage of deep water is that it makes the use of microchannel seawater heat exchangers far more practical - as they won't need cleaning so often.
Which allows very compact direct contact condensers exchanging heat through even more compact PCHEs/FPHEs.


I'm not sold yet on PCHE for seawater cooling and condensing steam on the other side, the fouling problem looks substantial. Pretty serious provisions would have to be taken I guess - maybe pre-cycloning the water, then pre-filtering, and powerful UV lights to kill bacteria so they don't biofilm all over the exchanger. Probably also want to design for a relatively high velocity through the PCHE channels on the seawater side. Or have some high velocity backblow pump.

Using PCHE for the feedwater heaters is going to be pretty sweet, and only clean steam and clean feedwater in it.


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PostPosted: Aug 17, 2017 1:09 pm 
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I ended up going into MSc 'Nuclear Science and Technology' this year (from September), and right now I am pondering ways to use PCHEs for steam cycle improvements.

I have a module where most of the marks are designing a steam cycle for a reactor, and I am pondering writing a dissertation on such things.
Right now I am thinking about an intermediate Dowtherm loop to the reheaters, and dropping moisture seperators entirely in favour of a double reheat.

But anyway, the advantage of using a DCC is since the steam is not in the heat exchanger, you can position the exchanger several metres below the seawater max-level, which means that potentially the water in the exchanger could be at higher pressure than the seawater, and as such any leaks would be from the feedwater side into the seawater side.

Since our turbine hall is the highest element in the plant, it will certainly be above the waterline.....


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PostPosted: Aug 17, 2017 1:59 pm 
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Quote:
I ended up going into MSc 'Nuclear Science and Technology' this year (from September), and right now I am pondering ways to use PCHEs for steam cycle improvements.


Excellent! I can already say, you've made the right choices!

Quote:
I have a module where most of the marks are designing a steam cycle for a reactor, and I am pondering writing a dissertation on such things.


There is much to improve, clearly. Here's a paper on steam injectors:

Attachment:
Steam Injector driven Passive Cooling.pdf [1.72 MiB]
Downloaded 15 times


Bigger last stage blades would be especially useful, especially if you can get low condenser pressures.

Quote:
But anyway, the advantage of using a DCC is since the steam is not in the heat exchanger, you can position the exchanger several metres below the seawater max-level, which means that potentially the water in the exchanger could be at higher pressure than the seawater, and as such any leaks would be from the feedwater side into the seawater side.


This is true. And the total cost may be lower too, with vacuum equipment restricted to just a small chamber, that can be made of steel plates/steel-concrete instead of hundreds of thousands of vacuum tubes. For the heat sink exchanger, you can probably consider different plates type exchangers too, they may be cheaper than PCHE. We're only talking about a few atmospheres of pressure here and its low temperature. I'm sure standard plate type exchangers are going to be cheaper than PCHE for this application. I think PCHE for feedwater heating and for reheaters is going to be more interesting, anywhere where you have high pressure and clean steam/clean water this is going to be attractive. There used to be just one supplier but these days there is more than one making these things so the situation has improved also from the business and market viewpoint.

Are you going to be looking at this big ship LWR?


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PostPosted: Aug 17, 2017 2:42 pm 
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Cyril R wrote:
This is true. And the total cost may be lower too, with vacuum equipment restricted to just a small chamber, that can be made of steel plates/steel-concrete instead of hundreds of thousands of vacuum tubes. For the heat sink exchanger, you can probably consider different plates type exchangers too, they may be cheaper than PCHE. We're only talking about a few atmospheres of pressure here and its low temperature. I'm sure standard plate type exchangers are going to be cheaper than PCHE for this application.


I thought about conventional plate type heat exchangers, but the problem is that they have much less surface area per unit volume - which means that the exchangers end up enormous.
Cyril R wrote:
I think PCHE for feedwater heating and for reheaters is going to be more interesting, anywhere where you have high pressure and clean steam/clean water this is going to be attractive. There used to be just one supplier but these days there is more than one making these things so the situation has improved also from the business and market viewpoint.


Right now I am pondering a chain using Dowtherm A as a heat transfer fluid for an intermediate loop, allowing 325C heat (PWR outlet temperature) to be made available at reheaters, and then suborning the feedwater heating chain (which I reckon should be with open feedwater headers) to have a load of stages in the reheat lines with PCHEs.

Currently at 67 bar 283C steam (using the APWR and Sizewell B as reference reactors for conditions), with superheat to 325C, with double reheat at 32 bar and 7.5 bar. This means we don't need moisture seperators because the steam is still marginally superheated at turbine outlet.
Cyril R wrote:
Are you going to be looking at this big ship LWR?

I will add to the list of things on the long long list.
So many interesting ideas, so little time.


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PostPosted: Aug 17, 2017 2:58 pm 
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This is a bit of an aside and not meant to derail the existing conversation but I'm curious about where you think the best chance of siting these things would be.

Given what we know now the current stretch goal for a floating nuclear plant would be a VBER-300 in a barge which is Russian obviously and produces around 325MW electric, 917MW thermal.

The Russians seem to view this primarily as a way of powering their remote arctic-ocean facing settlements but I think we'd all like to see a broader application then just that. The basic requirements are:

1. Ocean accessible

2. Able to co-operate with the Russians

3. High power and/or construction costs

The first two are fairly evident but the third can be pretty complex due to the sheer number of reasons why you could end up with high power and/or construction costs, isolated in the high arctic is pretty clearly one but Hawaii might also fit the bill even if it misses out on requirement 2. Palawan island in the Philippines also seems pretty appropriate in terms of power costs at least. Sakhalin may also have some promising sites given it's isolation with enough people around to support such a power plant.

The purpose of this is to get an idea what low-hanging fruit might be out there for the floating reactors to expand into over time before trying to tackle big urban centers which could build a PWR reasonably.


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PostPosted: Oct 09, 2017 5:22 pm 
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Puerto Rico could use one just exactly right now.


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PostPosted: Oct 09, 2017 7:08 pm 
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rgvandewalker wrote:
Puerto Rico could use one just exactly right now.


Well, adding a powerplant won't do much if the grid is screwed. At that point you would be more interested in port power (smaller load), and probably freshwater production. A parkable disaster aid ship, similar to the Hope-class ships but nuclear would seem to be a better bet. Which leads to interesting sizing issues if you intend to enter and occupy a wharf long term in most ports.


That said, is there something resembling a standard for shipbourne power sources that can be interchangably connected to shore grids?

I remember there is the Powerships group, which has what appear to be self-propelled powerplants

http://www.karadenizenergy.com/en/Web/Page/56

and these guys seem to do straight up barges

http://www.powerbargecorp.com/

Is the assumption here that there is a shore HVAC grid substation within reasonable distance of a dock/wharf (such dock often colocated with an existing shore based powerplant)? That the ship based system must supply adjustable/variable substation equipment to adapt to local conditions?


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PostPosted: Oct 10, 2017 4:02 am 
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I remembered a video of a presentation on a floating combined fuel and power facility.

https://www.youtube.com/watch?v=G8zOHZINyG8

It's less than 15 minutes and worth every minute. The video is also a couple years old so it would be interesting to see how much further they've got in scaling up this process.

rgvandewalker wrote:
Puerto Rico could use one just exactly right now.


I agree. A ship off shore that can provide electricity, fuel (for vehicles, heat, cooking, generators, etc.), and drinking water would be be quite helpful. Even if the power grid is down and there's no real ability to send the power to shore the electricity could be sent to other ships capable of drawing shore power so they don't have to burn fuel in their own generators.

I read that USNS Comfort is deployed to Puerto Rico right now. If this is like past hurricane recovery deployments it will be providing food, medical care, drinking water, and oxygen, among other things to the people there. This seawater to fuel process must have oxygen as a byproduct, just bottle that up too. Oxygen is not only useful for medical purposes but if you just had a hurricane blow through I'd think some bottled oxygen for cutting torches would come in handy. Oxygen generators are pretty trivial now so that might not mean much as far as energy/fuel saving but every little bit would help, at least I'd think so.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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