Saturday, July 25, 2009

Large vs Small LFTRs II: The Compromise

Various approaches to the building of the Liquid Fluoride Thorium Reactors (LFTR).

—The Continuing Discussion of the Developing the Physical Economy of Humanity's Thorium Future—

On the central clearinghouse for all things LFTR, we've had wide ranging discussions on every single conceivable aspects of LFTR and what it means:

1. How to build them?
2. Safety issues
3. Proliferation issues
4. Financing LFTR
5. Fueling LFTR
6. Deploying LFTR
7. LFTR applications
8. LFTR as a "Thorium Bullet" to solve 100% of our energy needs and the launching of the Thorium Century.

And that, folks, is a small list.

Point 2 above is what I want to focus here on.

The small scale size of the LFTR…maybe as little as 1/3 the size of an equivalent Light Water Reactor for the same MW output...and the ability to build LFTRs from as small as 5MWs up to 1.8 GWs (or bigger) gives LFTR siting a far more flexible deployable possibilities than any other source of energy except, perhaps, diesel electric generators used throughout the would for smaller grids and remote applications.

But the smaller intermediate units, from the 100 to 500 MWs range, used as a replacement for gas fired peaker units (site restricted for environmental reasons and access to natural gas lines) and baseload replacement of coal, allow a more creative approach to application of this, real Generation IV fission energy.

My own contribution to this in the past few years was the "Missile Silo" paradigm. A subsurface structure, with a removable, concrete reinforced 'lid' on top, making for barely any above ground profile.

Excavations can be made using standard industrial reinforced concrete for the floor and sides, much of that modularly cast above ground and installed below ground. The LFTR modules, turbine generator train, etc can be brought in and lowered into place and assembled. Only the control room and, the air/water coolers would be above ground (air cooled condensers or low profile cooling towers/once through cooling if located near surface water supplies).

LFTRs are small because they are operate at normal atmospheric pressure and don't require the huge containment domes and heavy piping you see around nuclear plants today.

But there is another, more fascinating, and perhaps much cheaper way to deal with LFTR sitings. Build them on barges in shipyards and ship them whole to any site with navigable sitings…like existing coal plants, for example, many that have river or canal access.

The Russians are in the process now of building floating nuclear power plants of the pressurized water reactor style used on Russian maritime vessels and submarines. They are marketing them as being deliverable almost anywhere in the world. The LFTR can follow this paradigm but the floating LFTR is not what I'm proposing.

Secondly, Northrop Grumman Shipbuilding and nuclear giant Areva just started construction of their nuclear components factory at Grumman's Newport News Shipyard: to use the facilities, cranes and drydock to help build, assemble and ship their components around the globe.

The barge the LFTR would be sitting on would not be a temporary structure designed to either transport the LFTR or as a permanent floating lodge for the power plant.

Here is a generalized outline of how the construction/assembly/shipping/siting would work:

1. Factories and machine shops in the shipyard would upgraded, where needed, to nuclear specifications.
2. These factories and shop would forge, shape, assemble and finish components for the LFTR.
3. Additionally components manufactured elsewhere would be laid out in the shipyard.
4. A barge would be built big enough to transport, either for ocean going or inner-coastal transport, that would be towed to the siting.
5. The LFTR barge would be assembled in the dry dock using existing facilities at the shop yard.
6. As the barge is built from the bottom of the drydock up, the main decking would be jacked up over the keel of the barge and sub-assembly of the LFTR and it's main components would be assembled: reactor core, associated piping, heat exchangers, turbine, generator, lube oil and associated balance of plant equipment.
7. The barge would be built for permanent dry stationing at a prepared site.
8. The site would be excavated and prepared with a temporary caisson off the main navigable waterway. The caisson is like a dam used to block water from following into the dry dock.
9. After the LFTR barge is assembled and towed to the site the caisson would be put back in place and the barge/site temporary drydock would be drained.
10. The LFTR barge would settle on prepared pre-stressed concrete blocks.
11. The LFTR barge itself would be of steel and concreted design and completely self contained as a nuclear power plant.
12. 1 large LFTR could be transported and sited this way or numerous smaller 100 to 500MW LFTRs on one barge as needed-->All "Factory Assembled".
13. The areas around the barge and supports could then be filled in with spoil or clay or concrete depending on regulations.
14. Hooking up the LFTR to the site balance of plant would commence (station power, grid access, control room, etc).

Charles Barton and others at are noted for advocating that the smaller LFTRs be constructed in-lieu of a larger one because it could be completed basically in a small series of modules and easily trucked and then assembled on site. This would be next to impossible for the larger 1GW-plus reactors as even the smaller-per-MW LFTR of this size is way to big. The advantage of course of the smaller ones is that they could, in theory, be composed of all-assembly line built components mass produced for low price and high volume.

The shipyard metaphor, described above, combines both this concept of factory production with the "line production" of large air craft and ships using existing facilities that give LFTR manufacturers the flexibility of designing any number of sized LFTRs, from the smallest 5 MW (or smaller) which could be shipped on an air plane to multi-module larger sizes of the plus-GW capacity…all factor produced and assembled, ship whole and sited in one fell swoop.