Littl(er) Fat Man

Last week, the Tennessee Valley Authority and engineering firm Babcock & Wilcox signed an agreement to work towards small nuclear reactors.  The issue is that, unlike other forms of generation, nuclear hasn’t been scalable.  One nuclear reactor, to say nothing of an entire nuclear facility, simply is not cost-effective in a time of tight financing.  Large reactors are practically custom-built to their individual sites.  Meanwhile, wind, gas, and especially solar come from factories, where they’re cranked out on an assembly line.  The factory can be accelerated to produce more, then still more, then upgraded to produce even more.  Individual upgrades don’t require one big outlay, and thus, expensive financing terms.

The new reactor concepts are a fraction of the size of today’s reactors, and more like coal generators.  The point is to produce more of the reactor in a factory, and less in the field.  Once a site is running, adding one more reactor is then more scalable and less granular than it is today.  In other words, the ante is lower each time the nuclear industry tries to play a hand.

Nuclear proponents like to point out that two new reactors are being built.  They don’t like to point out the Wisconsin reactor that’s being closed down.  Due to the site containing just one reactor, it’s less economical than multi-reactor sites, with the same team running much more output.  Thus, nuclear power has been treading water compared to other sources in the portfolio; the two new reactors are simply allowing nuclear to keep up, instead of falling further behind.

Small reactors may also increase dispatchability.  Existing, huge reactors cannot heat up and cool down on timescales of hours.  It is thus difficult for them to throttle up and down to satisfy demand.  Instead, they are run as flat as possible, with downtimes scheduled for periods of low demand (like winter weekends).  A smaller reactor may give more operating flexibility, allowing dispatchability over more weekends and possibly the diurnal cycle.

The new design will likely be tall and skinny; the size reduction will come from a narrower diameter, but the height will stay similar.  This is for two reasons.  A narrower diameter might just fit on a barge, or possibly a custom, oversized road carrier.  Again, this is to allow factory production as much as possible, then shipment to the site.  A tall, skinny reactor will also be safer, probably.  In case of pump failure, coolant is more likely to circulate naturally via convection.  Coal plants have also grown taller, for related reasons.  Even in case of circulation failure, a backup cooling system can be mounted atop the reactor, “powered” by gravity feed.  Tall thermal plants are simply smarter designs.

The future requires scalable power, and flexible deployments.  Heck, the present requires agile financing.  Nuclear plants- at least, as in the ’60s- are none of these.  The industry sees it needs to adapt to the future to survive.  Even with this design, a start today won’t mean any actual operating revenue until maybe a decade from now.  Hardly what I call agile; more like a gamble.


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  1. Pingback: Receptacle Roundup X: Renault Caméléon | cableflux

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