Generating power with ‘miniature suns’

It’s car­bon-free, con­tributes to a green­er future and has effec­tive­ly inex­haustible fuel from sea­wa­ter and lithi­um. So says Pro­fes­sor Ian Chap­man, chief exec­u­tive of the UK Atom­ic Ener­gy Author­i­ty (UKAEA), back­ing nuclear fusion.

“It’s very low land use, so it does­n’t take up a lot of space, and it’s base­load, so you don’t have the inter­mit­ten­cy you might with renew­ables,” he enthus­es.

Nuclear fusion has long been her­ald­ed as the holy grail of pow­er gen­er­a­tion. So long, in fact, the indus­try jokes that suc­cess is per­ma­nent­ly 30 years away.

Recent­ly, though, all that has start­ed to change. Now, around the world, inter­na­tion­al col­lab­o­ra­tions and pri­vate com­pa­nies are mak­ing sig­nif­i­cant progress and claim­ing we could see the first com­mer­cial pow­er sta­tions come into oper­a­tion by 2040.

How fusion works

Unlike nuclear fis­sion, which gen­er­ates ener­gy through split­ting atoms, fusion involves smash­ing two atom­ic nuclei – gen­er­al­ly deu­teri­um and tri­tium, both forms of hydro­gen – togeth­er under great pres­sure, in a process that cre­ates a heav­ier nucle­us and releas­es ener­gy. It’s the same process that goes on in the sun.

“And the impor­tant thing is that, unlike fis­sion, it does­n’t have the same long-lived lega­cy waste or chain reac­tion,” says Chap­man. “You can’t have a Cher­nobyl; it just can’t hap­pen.”

In the UK, the gov­ern­ment is cur­rent­ly look­ing for a site to tri­al a pro­to­type fusion ener­gy pow­er plant, with coun­cils and local author­i­ties bid­ding to play host.

The design for STEP, Spher­i­cal Toka­mak for Ener­gy Pro­duc­tion, should be com­plet­ed by 2024. It will build on exist­ing UKAEA work with toka­maks, which are com­pact fusion devices that use mag­net­ic fields to con­tain plas­ma and cre­ate the high pres­sures required.

Finding new ways to channel waste heat

The lat­est step for­ward has been the fir­ing up of Mast‑U, a new spher­i­cal toka­mak that includes a new way of exhaust­ing the enor­mous amounts of waste heat.

“You must have seen videos of erup­tions com­ing out of the sun; solar flares or mass ejec­tions, big spi­rals of gas, which are thrown out,” says Chap­man. “Well, we have a minia­ture sun and, in the same way there are events which hap­pen at the edge where heat is thrown out, so you need to make sure none of that heat dam­ages the wall.”

The usu­al way of deal­ing with this is to allow the heat to flow to a sac­ri­fi­cial sur­face that’s con­sumed. How­ev­er, the new sys­tem allows mate­ri­als to last much longer by chan­nelling the heat over a longer dis­tance.

“By the time the mate­r­i­al gets out to the met­al at the edge it’s a lot cool­er, as it’s radi­at­ed heat along the path,” says Chap­man. “And that takes the heat flux down from a lev­el that’s at the melt lim­its of the mate­ri­als that we have, down to a heat flux that’s real­ly what would hap­pen in a car engine.” 

Mast‑U was turned on last Octo­ber and pow­er is now being ramped up. Results should be in by the sum­mer and, if suc­cess­ful, it should cut the heat which hits the wall by 90 per cent.

But STEP is by no means the only fusion project in town. ITER, the Inter­na­tion­al Ther­monu­clear Exper­i­men­tal Reac­tor, is a fusion project involv­ing 35 coun­tries. Already three-quar­ters built, it’s due to fire up in 2025.

ITER is all about proof of con­cept, demon­strat­ing that fusion can take place on a com­mer­cial scale. The find­ings will feed into oth­er nation­al ini­tia­tives around the world, includ­ing STEP and the pow­er sta­tions that will lat­er be based on it.

“Despite the onset of the pan­dem­ic in 2020, the ITER project has man­aged to stay large­ly on track,” says a spokesper­son. “2020 was a deci­sive year, with the arrival of ITER’s mas­sive first-of-a-kind com­po­nents, for exam­ple mag­nets weigh­ing sev­er­al hun­dred tonnes each, from all over the world and the start of machine assem­bly in mid-year.” 

Fusion in the private sector

Mean­while, a num­ber of inde­pen­dent com­pa­nies are work­ing on fusion tech­nolo­gies of their own. One such is First Light Fusion, spun out from the Uni­ver­si­ty of Oxford in 2011.

First Light has a dif­fer­ent approach to STEP or ITER, using iner­tial, rather than mag­net­ic, fusion. This involves fir­ing a pro­jec­tile at around 20 kilo­me­tres per sec­ond – 50 times faster than a bul­let – at a tar­get con­tain­ing deu­teri­um and tri­tium. The force gen­er­at­ed is pow­er­ful enough for fusion to occur.

How­ev­er, accord­ing to co-founder and chief exec­u­tive Nick Hawk­er, the com­pa­ny has no plans to move into pow­er gen­er­a­tion direct­ly, but instead will sell its tar­gets and tech­nol­o­gy. 

“We don’t think it’s cred­i­ble for a start­up to build a pow­er plant,” he says. “But we want to pro­duce some­thing that’s a phys­i­cal prod­uct, the ulti­mate espres­so cap­sule, a con­sum­able. Each one is equiv­a­lent in ener­gy terms to a bar­rel of oil.”

Chap­man wel­comes such ini­tia­tives, sug­gest­ing they all add pieces to the puz­zle. “I think it’s also a sign that the mar­ket has an appetite for fusion and wants to invest, and that’s a real­ly good thing,” he says. 

“These pri­vate com­pa­nies are now lever­ag­ing mon­ey from oil and gas majors and ven­ture cap­i­tal­ists, so that shows the mar­ket has an appetite for invest­ment.”

In the long term, fusion is unlike­ly to dis­place oth­er forms of pow­er gen­er­a­tion entire­ly; in many geo­graph­i­cal areas, wind or solar pow­er is a bet­ter bet. How­ev­er, it’s wide­ly seen as a poten­tial major play­er with­in a port­fo­lio of pow­er gen­er­a­tion tech­niques.

It’s also like­ly to need a fair lev­el of sub­sidy at first, says Chap­man. “To start with, with any dis­rup­tive tech­nol­o­gy, you need some sub­sidi­s­a­tion to begin with, just as we’ve seen with off­shore wind, which was sub­sidised 20 years ago,” he says. “But now the price has come down and down, and it’s cheap­er than oth­er ener­gy sources.”