Wednesday, November 18, 2015

My father's reactor, Not my father's Reactor Industry: 4

Back in 2008 when I was looking at the question of how nuclear manufacturing costs could be lowered.  Nuclear costs could be lowered bu decreasing materials and labor costs in the initial manufacturing phase.  Factory assembly of parts modules would lower initial manufacturing costs.  The use of the cost lowering, highly efficient and safe Molten Salt Reactor would also help lower manufacturing costs.  By building smaller reactors, investment costs could be lowered.   Smaller cores meant that reactor construction modules would be easier to transport, and decreasing transportation difficulties would also lower transportation costs.  Frially on site assembly eof a complete nuclear power facilities.  Thus we have three distinct arenas for lowering nuclear costs. First the Nuclear design, secondly modular manufacture and third facility set up.  These three arenas oought to be thought through together.  However only ThorCon among MSR designers is looking at production vinues, and indeed the ThorCon production vinue is very important to understanding the reactor's design and its problems.

ThorCon has as I have noted not posted a Product Description for the United States DoE.  The Principle of ThorCon, Jack Devanney is by training a ship architect and business man, who has comissioned the construction of very large tankers from Korean ship builders as well as buying and selling more tankers than I could shake a stick at.  Now in retirement, he as taken up as a hobby of building Molten salt Reactors at ship yards.  He has gathered around him a group of Energy from Thorium old hands, pruse several who could be counted MSR/Thorium prophets.  The Prophets are the ones who first saw the revolutionary potential of the MSR.    Some ike the ThorCon Reactor designer, Lars Jorgensen were earlkly EfT recruits, But Ralph Moir had coauthored along with famous (or infamous( Edward Teller, a paper published after Teller's death on the potential of MSRs. Moir was not in the EfT crew, but robert hargraqves was.  Robert Hargraves who influanced my thinking about factory production of small nuclear power plants even before Robert became on of the EfT gang is another ThorCon advisor.  FiniHargravesalong with EfT  Lsrs Jorgensen, an electrical engineer and self taught reactor designer is the chief technology officer of ThorCon.  Lars is a very bright person, and he has studied the ORNL literature, and spent many hours in tghe EgT comment forum, where many MSR and LFTR design issues were hashed out, by some really smart people who were engaged in a collective self education project.  Let us think of the ORNL MSR research literature as the Torah of the EfT movement, and the EfT Comment Forum as its Talmud, then Lars would be classified as a MSR Rabbie.  Actually he is a Thorium fanboy as well, since he plands to kick up the conversion ratio of the ThorCon Reactor, by turning to thorium, although we are going to have Plutonium preoduced and burnt as well.  The ThorCon is not a breeder, but iI suspect it woukd produce a respectable conversion ratio.  This is at the very least a pious hope.

There is a fly in the ointment, that is the core graphite problem.  Like most ORNL technology reactors, excluding Transatomic's nuclear waste burner, the ThorCon Reactor uses graphite as a moderator.  The one exception is the Transatomic which has developed an interesting, innovative but also controversial approach to neutron moderation, that may notoffer superior life expectancy to graphite.   U have suggested in my discussion of The University og California Mark One Reactor, that pur Graphite pebbles might offer a solution to the core graphite problem, since the pebbles may be removed and replaced after the have been beaten up by neutrons.  Thus the solution to the core moderation problem wight well be core pebbles.  Like most of the current generation of MSR designers Lars has not thought about pebbles.  Per Peterso of course has, but n his pebbles are fuel carriers.

So why is a ship archetect, and retired tanker fleet operator, like Jack Devanney interested in building Molten Salt Reactors?  The answer, in short, is that he still wants to make money by building reactors in shipyards.  This would necessitate building big reactors on a ship that has been parked in the ship yard.  Once the reactors are assembled, the ship carries them off to various ports where they off loaded and set up.  Not a whole lot of attention has been paid to the offloading.  Final setup is interesting, because the core, or can as ThorCon calls it, is only expected to last 8 years, because of the graphite problem.  Then a new can is dropped into the site, and the old core is shut down and then removed and then replaced in due time with nother can.

Why follows next is an example of why I can never win a popularity contest.  This all strikes me as a really bad idea.  No doubt this oppenion will upset some of my friends.  Replacing the cans every 8 years amounts to a business risk.  No one yet knows how much it will cost to remove the cans and transport them away.   It may be cheap, but we don't know enough about it to say that yet.

We find the same limited core lifetime in David LeBlance's IMSR, but their is a difference.  David's IMSR can be used to provide a number of grid services, that do not require constant operatrion at peak power, because Molten Salt Reactors can be throttled.  The MSR proves that the anti-nuclear argument that reactors cannot provide elecrity on demand.  In fact mSRs can respond to energy demand as quickly as its power turbines can ramp up.  In fact one way to shut fission in a MSRdown, is to allow its core heat to rise, until it reaches the maximum allowable core heat level.  As the core heat rises, the fuel carrier salt expands, and as it expands it flows out of the core.  At maximum heat enough nuclear fuel flows out of the core, to bring the remaining core fuel below the criticality.  The chain reactor automatically hot, while decay heat keeps keeps the core salt at top temperature.  Once power demand is increased, heat flows out of the core, to the turbine, which turns an electrical generator.  As the heat leaves the core, core salt temperature dropps, and the fuel carrier salt is drawn back into the core, where fission recommences.   Thus the MSR is a perfect peak demand power plant.

Not only can IMSRs preform peak power production roles, but they can also serve as backup or reserve power units.  Backup is required to maintain grid stability.  If a power facility undergoes
 a sudden shutdown, reserve plants must be available to pickup the slack quickly, or the grid crashes. Finally, sudden alterations in electrical demand, or in electrical alteration because of generator characteristics require load balancing, that is a generation facility that can quickly alter power output, in order to stabilize the grid load. The advantage for Molten Salt Reactors is that none of them require that the generation facility operate at a high capacity factor, but all of them are essential for tghe operartion of the grid.  Lower capacity factor means longer graphite life.  If trhe capacity factor is 25%, not unusuual for units that operas in these roles, then iMSR core life is going to be 28 years, not the seven that full time operation yields.

So why does ThorCon have to build big MSRs, and why can't the big MSRs beoperated as peak, reserve, and load leveling capacities as I suggest the iMSR can?  Well ging big and requiring a lump sume capitalization of the 1 Gwe capacity it offers, the operators need to keep it runing to pay off interest and principle.  This begins to look like a risk to the bnkers when they learn that the reactor core will have to be replaced after 8 years.   But in order for the project to be profitabler to a ship yard, they have to sell their reactors at a respectable price.  Hence we have a squize, that looks like risks for everyone.

The Shipyard is the tail that threatens to wag the MSR dog.  I am sorry to say this, it looked like such a beautiful idea.  Maybe it can be carried off at an aircraft factory, or at a small ship yard, that is a yard that builds small ships.  

2 comments:

Steen Larsen said...

Hello Charles,

In this and other articles you mention the "the core graphite problem". Are you aware that this has been solved in the European/French design called the Molten Salt Fast Reactor?

See: https://www.iaea.org/NuclearPower/Downloadable/Meetings/2013/2013-03-04-03-07-CF-NPTD/T1.5/T1.5.merlelucotte.pdf

IMHO this is an extremely elegant and simple design and has no graphite in the core. Actually the core only contains molten salt fuel.

Best regards
Steen Larsen

Charles Barton said...

I am aware of it, i was put off by the word fast, which I understand to mean, not very scalable. I will look further.

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