SPLITTING the atom has joined the start-up scene.

Green energy firms have long been popular ventures for entrepreneurs, but nuclear power has largely been ignored, thanks to the extreme cost, safety issues and the worries about nuclear proliferation that are usually associated with such an undertaking.

But a small group of nuclear scientists believe they can change things. By building new types of reactors, some of which reuse spent fuel rods from massive – and often ageing – power plants, they aim to commercialise cheaper, safer replacements to transform the industry.

At the centre of conventional reactors are rods of uranium submerged in water. The rods contain about 5 per cent uranium-235, which readily sheds neutrons. As these neutrons fly into other uranium atoms, they knock loose more neutrons in a chain reaction that heats up the surrounding water. The steam this process creates is used to drive turbines to generate electricity.

These reactors make up the vast majority in service globally. The trouble is that, by the time the rods need replacing, only about one-twentieth of the radioactive material they contain has been used up, and so these power plants quickly accumulate highly radioactive waste. Enter the Waste Annihilating Molten Salt (WAMS) reactor, which is being developed by , Massachusetts. The design calls for uranium and plutonium in used fuel rods to be dissolved in a tank of liquid lithium-fluoride salts. Heat from the radioactive elements builds within the salt, which can then be circulated out of the reactor’s core to a heat exchanger, where water is turned into steam to drive a turbine.

The design should mean that a disaster like the one in Fukushima, Japan, is out of the question: in the case of a power outage, the unchecked heating of the molten salt would melt a plug below the core, draining the salt into a containment vessel that dissipates the heat. This would allow it to cool and solidify within a few hours, locking in any hazardous materials.

If all the nuclear waste currently in existence was reused in such reactors, they could supply the entire planet’s power needs for 72 years, carbon-free, claims Leslie Dewan, the company’s chief science officer.

“If all the nuclear waste in existence was reused, it could meet the planet’s power needs for 72 years”

WAMS is not the only game in town, though. With investment from Bill Gates, TerraPower of Bellevue, Washington, is designing a “travelling wave” reactor, which uses spent fuel to create a slowly expanding ring of fission in a reactor core that could sustain itself for decades.

The journey from the drawing board is long and expensive. Transatomic is currently looking to raise a “couple million dollars” to do materials testing, which will take about two years, says CEO Russ Wilcox. Then it would make a small demonstration plant, and finally a full-scale plant able to produce 500 megawatts. The whole process could take 15 to 20 years.

But if entrepreneurs don’t shoot for radical improvements to nuclear power, who will, says Jacob DeWitte, CEO of UPower Technologies in Boston. “Newer companies can help stimulate innovation in a traditional start-up sense,” he says. “Go hard, go fast, and try to make this a reality.”

Within five years, his firm hopes to commercialise what it calls a “nano-nuclear battery” that fits in a shipping container and generates 1 megawatt of power.

This article appeared in print under the headline “Atomic boom”

THE future of energy storage has taken root on an onion farm in southern California.

Seeking to offset its electricity bills, Gills Onions in Oxnard has installed a flow battery. When electricity prices from the grid peak, the farm can tap stores of energy created by processing agricultural waste. The battery can supply 600 kilowatts of electricity over six hours to run farm machinery for a fraction of the usual cost.

Flow batteries are centred around two aqueous electrolytes, which are held in separate tanks when the battery is idle. To get electricity from it, the liquids are pumped into a chamber separated by a membrane, sparking an electron-producing chemical reaction across the membrane. To store energy, an external current is applied across the membrane and the process works in reverse.

The batteries’ size – they can be as big as shipping containers – and ability to store large amounts of energy make them well suited to smoothing out the variable supply of wind, solar and other renewable energies. But they are expensive, and their pumps and tubes make them difficult to maintain.

Several firms are now coming to market with designs that they say address those concerns, opening the door to the possibility that battery backups for renewables could one day form a constellation of self-sufficient microgrids far more resilient than the present electrical infrastructure.

“The batteries can deliver large amounts of energy, making them suited to smoothing renewables”

, based in Hayward, California, has designed a zinc-bromine flow battery that does away with the membrane in favour of a porous metal electrode onto which zinc is plated when the battery discharges. , in Sunnyvale, has cut costs by improving the electrolyte pumping system and using iron chromium rather than the more expensive vanadium present in older designs, says Bret Adams of the company.

Flow batteries are also considered to be very safe, because unlike some lithium-ion designs, they are not prone to thermal runaway, which can cause battery fires. There have been growing pains, though, including anode failures, short membrane life and electrolyte leakage, says Steve Minnihan, an analyst at technology market research firm Lux Research. “It indicates to the market that flow batteries need a few more years in the lab before they can rival lithium-ion or lead-acid in high-volume deployment,” he says.

Nevertheless, they are finding their way into the field. In 2011 the Marine Corps Air Station in Miramar, California, learned the hard way how brittle today’s centralised grid is. When a massive blackout took out much of San Diego’s power, the base ground to a halt. There is a 230-kilowatt solar array on site, but it wasn’t designed to provide backup power. So they had to rely on fossil fuel generators that took hours to bring online. A microgrid like the one at Gills Onions is now being built on the base that will use a 250-kilowatt battery to store spare power generated by the solar panels.

Flow batteries could back up neighbourhoods, too. The Modesto irrigation district in central California is planning to put flow batteries at 45 electrical substations throughout the municipality so they provide power even if a transmission line is knocked out. “Power reliability – and microgrids are one example of that – will really be one of our killer apps,” says Primus Power CEO Tom Stepien.

This article appeared in print under the headline “Going with the flow”