Could Small Be Beautiful?

When I was compiling my list of reactors being marketed as of early 2011, I ignored a number of small designs that I felt were unlikely to be built.  There are more than a few such proposals, with many of them coming from various state-owned design bureaus in Russia.  During the early days of nuclear power, in the 1950s and 1960s, various national governments put money into building small reactors of interesting designs.  Some of those include Hallam, Piqua, Fort St. Vrain, Niederaichbach, Jülich, and the Steam-Generating Heavy Water Reactor.  None of these worked well enough to be cost-effective, and the nuclear power industry has come to be dominated by large light water reactors.

More recently, governments have been supporting research and development of small reactors, but only two examples of one model from Russia have been built.  Some private corporations are also working on new reactor designs with their own funds, but none have completed licensing.  Generically, these new designs are called SMRs, which stands either for small modular reactors or, less often, small and medium reactors.  The International Atomic Energy Agency defines small reactors as less than 300 MWe, and medium reactors as 300-700 MWe.  The word modular refers to how proponents see these reactors as being deployed, which would be at power plants with 4 to 20 units.

The main appeal of these reactors is the capital cost of any one of them.  Large nuclear reactors have a long history of enormous cost overruns on the initial estimates, which are also enormous.  The 1600 MWe European Pressurized Reactor (EPR) currently being built at Olkiluoto in Finland was sold as a turnkey contract for €3.3B, but cost overruns have pushed the price to over €6B - so far.  SMR proponents are projecting costs of their reactors from $50M to $1B, depending on the design.  But almost all of the designs haven't reached the final detailed design stage, so it is possible (and quite likely) that the estimates could turn out to be as wrong as ones for large reactors.  However, even if the estimates are wrong, the smaller reactors would be less risky for utilities to build because an overrun with any one reactor wouldn't threaten to bankrupt the company.

According to proponents, there are several other positive aspects to SMRs, though they don't all have the same ones.  For most, the smaller size would allow large sections to be mass manufactured off-site in controlled factory conditions, with only final assembly done on site.  This has the potential (in theory) to improve quality assurance over large reactors, which are largely custom built on-site of essentially one-off parts.  Some designs are small enough that they would be delivered as pre-fueled packages and then sent back to the factor when the fuel is exhausted.  That could significantly reduce the amount of waste generated at the power plant site, eliminate complicated on-site refueling operations, and potentially reduce the chances of fuel theft or proliferation.  It would not eliminate the chance of accidents or theft during transit, however, though the latter would be difficult.  Most of the designs call for the reactors to be housed underground, which basically eliminates the chance of damage from missiles or airplanes.  However, the crisis at Fukushima Dai-ichi has shown that backup systems can be critical.  Some of the new designs still require active cooling by a backup system after shutdown, and most leave these systems exposed.  Finally, depending on the size, some of the new reactors could be deployed in rural or remote locations where only a moderate amount of power is needed and a large reactor would overwhelm the local grid.

The main question about these designs is whether or not they would, when deployed en mass, end up being safer.  Clearly, if there was an accident with any one reactor, it would make less of a mess than a larger reactor would.  But I doubt whether 1000 reactors each of 100 MWe would be monitored and inspected as carefully as a set of 100 reactors of 1000 MWe.  That means each small reactor deployed has to have a radically lower probability of having its containment breached to make up for poorer monitoring and greater numbers.  Some of the designs may actually be that much safer, but until a plant goes through a rigorous licensing process, we have no way of knowing how good any of them are.

Most of the reactors listed below were pulled from two documents from the IAEA (1, 2), with others coming from Wikipedia or general web surfing.  Because there are so many of them, I may have missed a few.  I've classified some reactors as "abandoned" in the status field if I was unable to find them on the originating organization's website, though the lack of public information doesn't necessarily mean a project has been ended.  The converse is true as well.

By neutron speed, there are:

• 38 thermal reactors
• 26 fast reactors

By major type, there are:

• 14 pressurized water reactors (PWR)
• 13 lead-cooled fast reactors (LMFR or LFR)
• 10 light water reactors (LWR - light water reactors that are not typical BWRs or PWRs)
• 8 sodium-cooled fast reactors (LMFR or SFR)
• 6 high temperature gas-cooled reactors (GCR or HTGR)
• 4 boiling water reactors (BWR)
• 2 molten salt-cooled reactors (? - no common acronym)
• 2 gas-cooled fast reactor (GFR)
• 2 lead-bismuth-cooled fast reactor (LMFR or LFR)
• 1 lithium-cooled fast reactor (? - no common acronym)
• 1 heavy water-moderated pressurized water reactor (HWBWR)
• 1 molten salt reactor (MSR)

Reactor	Type	MWt	MWe	Country	Company	Status	Refuelling
4S	Sodium-cooled fast reactor	30	10	Japan	Toshiba Power Systems	US pre-licensing	factory
4S-LMR	Sodium-cooled fast reactor	135	50	Japan	CRIEPI	concept	factory
ABV-6	Pressurized water reactor	60	12	Russia	OKBM	concept	on-site
ACACIA	High temperature gas-cooled reactor	60	23	Netherlands	NRG	abandoned	on-site
AFPR-100	Light water reactor	300	100	USA	PNNL	abandoned	factory
AFR-300	Sodium-cooled fast reactor	800	300	USA	ANL	concept	on-site
AHTR	Molten salt-cooled reactor	600	300	USA	ORNL / UCB	concept	on-site
AHWR	heavy water-moderated boiling water reactor	260	100	India	NPCIL	detailed design	on-site
ARC-100	Sodium-cooled fast reactor	920	300	USA	Advanced Reactor Concepts	concept	on-site
BGR-300	Gas-cooled fast reactor	300	130	Russia	RRC Kurchatov	concept	factory
BMN-170	Sodium-cooled fast reactor	400	170	Russia	OKBM	abandoned	on-site
BN GT-300	Sodium-cooled fast reactor	730	300	Russia	IPPE	concept	on-site
BREST	Lead-cooled fast reactor	?	300	Russia	NIKIET	concept	on-site
CAREM	Light water reactor	100	27	Argentina	INVAP / CNEA	Argentina pre-licensing	on-site
CCR	Boiling water reactor	900	300	Japan	Toshiba Power Systems	abandoned	on-site
CHTR	Lead-buismuth-cooled fast reactor	0.1	0.02	India	BARC	concept	factory
DRX	Pressurized water reactor	0.75	0.15	Japan	JAERI	abandoned	on-site
ELENA NTEP	Light water reactor	3.3	0.07	Russia	RRC Kurchatov	abandoned	factory
EM2	Gas-cooled fast reactor	500	240	USA	General Atomics	concept	factory
ENHS	Lead-cooled fast reactor	125	50	USA	LLNL / UCB	concept	factory
FBNR	Pressurized water reactor	134	40	Brazil	FURGS	concept	factory
GT-MHR	High temperature gas-cooled reactor	600	287	USA	General Atomics	concept	on-site
GTHTR-300	High temperature gas-cooled reactor	600	274	Japan	JAERI	abandoned	on-site
HTGR	High temperature gas-cooled reactor	220	100	Japan	First Atomic Power Industry Group	concept	on-site
HTR-PM	High temperature gas-cooled reactor	380	160	China	CNNC	prototype construction	on-site
IRIS	Pressurized water reactor	?	335	USA	Westinghouse (Toshiba)	US pre-licensing	on-site
ISIS	Pressurized water reactor	650	200	Italy	Ansaldo Nucleare	abandoned	on-site
KALIMER	Lead-cooled fast reactor	392	150	Korea	KAERI	concept	on-site
KAMADO	Light water reactor	1000	300	Japan	CRIEPI	abandoned	on-site
KLT-40S	Pressurized water reactor	150	35	Russia	OKBM/ Atomstroyexport	production	on-site
LSPR	Lead-cooled fast reactor	150	53	Japan	RLNR-TIT	abandoned	factory
MARS	Molten salt-cooled reactor	16	6	Russia	RRC Kurchatov	abandoned	factory
MARS	Pressurized water reactor	600	150	Italy	U. of Rome / ENEA	abandoned	on-site
MASLWR	Pressurized water reactor	150	45	USA	NuScale	US pre-licensing	factory
MBRU-12	Sodium-cooled fast reactor	48	12	Russia	OKBM	abandoned	factory
MDP	Sodium-cooled fast reactor	840	325	Japan	CRIEPI	abandoned	on-site
mPower	Pressurized water reactor	400	125	USA	Babcock & Wilcox	US pre-licensing	on-site
MRX	Pressurized water reactor	100		Japan	JAERI	abandoned	on-site
MSBWR	Boiling water reactor	?	50	USA	GE / Purdue	abandoned	on-site
MSR-FUJI	Molten salt reactor	450	200	Japan	ITHMSI	concept	continuous
NP-300	Pressurized water reactor	?	300	France	Areva NP	abandoned	on-site
Package Reactor	Light water reactor	25	?	Japan	Hitachi / Mitsubishi	abandoned	on-site
PBMR	High temperature gas-cooled reactor	400	165	South Africa	PBMR (ESKOM)	abandoned after starting US pre-licensing	on-site
PEACER-300	Lead-cooled fast reactor	850	300	Korea	Seoul Nat. U.	concept	on-site
PFPWR-50	Light water reactor	50	n/a	Japan	Hokkaido U.	concept	factory
Power Module	Lead-bismuth-cooled fast reactor	75	25	USA	Hyperion Power Generation	US pre-licensing	factory
PRISM	Lead-cooled fast reactor	840	311	USA	GE-Hitachi	US pre-licensing	on-site
PSRD	Light water reactor	100	31	Japan	JAEA	concept	factory
PWBWR	Lead-cooled fast reactor	450	150	Japan	RLNR-TIT	abandoned	on-site
RAPID	Lithium-cooled fast reactor	10	1.2	Japan	CRIEPI	abandoned	factory
RBEC-M	Lead-cooled fast reactor	900	340	Russia	RRC Kurchatov	abandoned	on-site
RMWR	Boiling water reactor	955	330	Japan	Hitachi / JAERI	concept	on-site
RUTA-70	Light water reactor	70	n/a	Russia	NIKIET / IPPE	concept	on-site
SMART	Pressurized water reactor	330	90	Korea	KAERI	Korea license	on-site
SPINNOR	Lead-cooled fast reactor	55	20	Indonesia	ITB	concept	factory
SSTAR	Lead-cooled fast reactor	45	20	USA	ANL / LLNL / LANL / INL / UCB	concept	factory
STAR-H2	Lead-cooled fast reactor	400	n/a	USA	ANL / OrSU / TA&M / OhSU	concept	factory
STAR-LM	Lead-bismuth-cooled fast reactor	400	178	USA	ANL	concept	factory
SVBR-75/100	Lead-cooled fast reactor	280	100	Russia	IPPE / OKB Gidropress	concept	factory
TPS	Light water reactor	64	16	USA	General Atomics	abandoned	on-site
UNITHERM	Pressurized water reactor	20	7	Russia	NIKIET	concept	factory
V-SPINNOR	Lead-cooled fast reactor	17	6	Indonesia	ITB	concept	factory
VBER-300	Pressurized water reactor	850	295	Russia	OKBM	concept	on-site
VK-300	Boiling water reactor	750	250	Russia	NIKIET	concept	on-site
VKR-MT	Light water reactor	890	300	Russia	RRC Kurchatov	abandoned	factory

Note: I'll probably edit this post frequently as I find more information.

Added 2011/06/08: The Union of Concerned Scientists has provided some testimony to Congress on SMRs.