Nuclear fusion: the true, the false and the uncertain

TRUE — Fusion can generate net positive energy within a limited scope.

The Lawrence Liv­er­more Nation­al Lab Nation­al Igni­tion Facil­ity (NIF) in Cali­for­nia proved this in 2022 with its laser igni­tion fusion setup. The NIF setup uses 192 of the world’s highest-energy lasers to pulse up to 4 mil­lion joules of ultra­vi­olet energy onto a deu­teri­um and tri­ti­um tar­get. The tar­get, approx­im­ately as big as a pep­per­corn, is sus­pen­ded in a small x‑ray “oven” called a hohlraum, which can heat up to about 3 mil­lion degrees Celsi­us when hit by these power­ful lasers. This causes the fuel to implode, cre­at­ing the con­di­tions for fusion. On 5^th Decem­ber 2022, NIF achieved tar­get gain, mean­ing that 2.05 mega­joules of laser energy delivered to the tar­get gen­er­ated 3.15 mega­joules of fusion energy. More energy came out of the tar­get than was put in. This point, called “igni­tion”, was a breakthrough.

FALSE — That reaction created energy, but nowhere near enough to power the facility.

Over­all, the sys­tem still exper­i­enced a sub­stan­tial net energy loss. To give a sense of scale, the target’s 1.1 mega­joules of net energy is approx­im­ately 0.306 kWh. By com­par­is­on, that would only keep a small 5W LED light bulb on for 20 hours after con­vert­ing the heat to elec­tri­city. In addi­tion, NIF sci­ent­ists estim­ate the NIF laser facil­ity typ­ic­ally requires about 100 times more energy to run than the amount of energy delivered by the laser to the tar­get itself.

UNCERTAIN — It’s unclear when and how this crucial point, called the “engineering gain”, will be met.

At this point, engin­eers need to focus on find­ing addi­tion­al effi­cien­cies in the sys­tem to ensure it pro­duces more energy than it uses. One way to do this could be to reduce the system’s energy use rel­at­ive to out­put by mak­ing more energy-effi­cient com­pon­ents, such as lasers or super­con­duct­ors. Changes like tweak­ing the heat insu­la­tion or rolling out AI con­trols to oper­ate sys­tems faster than a human would also help. Oth­er gains can be made by improv­ing the machine’s mater­i­als and com­pon­ents to allow the sys­tem to oper­ate at high­er power levels. To do so, engin­eers could look to include mater­i­als that can with­stand extreme tem­per­at­ures and design even stronger mag­nets to bet­ter con­fine and con­trol the plasma used in fusion reac­tions. Anoth­er approach is to improve the pro­cess that cap­tures and con­verts the energy from the fusion reac­tion to electricity.

TRUE — Fusion is generally seen as “clean” energy.

It pro­duces sub­stan­tially less radio­act­ive “waste” than fis­sion – though it is pos­sible that with emer­ging tech­no­lo­gies, waste from fusion and fis­sion could be reused. Still, like oth­er nuc­le­ar fis­sion, fusion will require appro­pri­ate and com­pre­hens­ive over­sight. One con­cern is that the reac­tion could be used to gen­er­ate fis­sile mater­i­als usable in weapons. Fusion machines and related reac­tions do not dir­ectly pro­duce mater­i­al use­ful for weapons. The reac­tion does, how­ever, cre­ate an enorm­ous amount of neutrons.

On the bright side, these neut­rons could help gen­er­ate more fuel for the fusion reac­tion — many designs plan to incor­por­ate a “breed­ing blanket,” a lay­er of mater­i­als that acts as heat insu­la­tion, but is also lined with mater­i­als that can cap­ture the neut­rons to cre­ate more tri­ti­um. Urani­um or thori­um could also be placed in some breed­ing blanket designs. The con­cern is that these mater­i­als, once irra­di­ated, could gen­er­ate urani­um-235 that can be used in nuc­le­ar weapons. Phys­ic­al ways to deter this pro­cess exist, such as requir­ing the use of lithium‑6 in the blanket mod­ules. The IAEA will be import­ant in ensur­ing non-pro­lif­er­a­tion safe­guards and oversight.

FALSE — Fusion energy may be near limitless, but that doesn’t necessarily translate to unending energy.

Some fusion energy tech­no­lo­gies under devel­op­ment could the­or­et­ic­ally pro­duce more fuel than they con­sume and, there­fore, be essen­tially lim­it­less. But that does­n’t mean that this would provide the energy soci­ety needs. Most research­ers expect build­ing and oper­at­ing early fusion plants to be very expens­ive. Wheth­er soci­ety will be will­ing to pay to run costly fusion react­ors will depend on how fusion fits in with oth­er clean energy systems. 

UNCERTAIN — When fusion will start powering the world is still unclear.

I am optim­ist­ic that fusion will even­tu­ally provide clean energy to at least parts of the world. How­ever, the tech­no­logy is unlikely to be ready to entirely sup­port the trans­ition away from car­bon fuels in its own. This lag could put it at a dis­ad­vant­age com­pared to oth­er products adop­ted early on that could be deployed at a much lar­ger scale. Still, we could see a cas­cade of break­throughs that quickly accel­er­ates pro­gress for fusion. Or we may have to wait a long time before the next break­through arrives.

TRUE — Startups are saying they are ready to build commercial pilot plants.

Sev­er­al star­tups have announced very ambi­tious timelines. Heli­on, for instance, has prom­ised to start pro­du­cing energy from a fusion plant by 2028¹. In their 2023 report, the Fusion Industry Asso­ci­ation found that many oth­ers believe a fusion plant will deliv­er elec­tri­city to the grid before 2035². Fusion firms are indeed mak­ing iter­at­ive pro­gress and march­ing stead­ily toward suc­cess. The NIF, which proved fusion igni­tion, has provided cru­cial data that will help guide research programs—particularly for laser igni­tion type of fusion. Some firms have also star­ted rolling out arti­fi­cial intel­li­gence to optim­ise their approach to fusion, gen­er­at­ing some inter­est­ing res­ults. Still, mak­ing pro­gress is dif­fer­ent from hav­ing a product available.

FALSE — No startup has shown evidence that they reached the stage of development needed to roll out fusion to the market in the near term.

Star­tups still need to demon­strate their sys­tems’ net energy gain and over­all engin­eer­ing gain. They also have to learn how to run their fusion reac­tion on scales that can gen­er­ate a profit. As much as fusion com­pan­ies want to put a timeline on achiev­ing these tech­no­lo­gic­al mile­stones, these are break­throughs you can­’t schedule.

UNCERTAIN — There’s also a tricky commercial case to overcome.

Fusion is still a very high-risk invest­ment because the tech­no­logy has yet to be proven. It’s not like invest­ing in sol­ar cells 15 years ago when they were already at 20% effi­ciency. It’s more like invest­ing in sol­ar cells 40 years ago when they had 1% effi­ciency and a very small rol­lout. Star­tups will need to build pilot plants to prove their concept. Rais­ing enough cap­it­al to make those plants will likely be tricky. First-gen­er­a­tion sta­tions are likely to be costly and unreliable—that is just a part of innov­a­tion. Still, assum­ing we’re going to move away from fossil fuels, that pop­u­la­tion growth dra­mat­ic­ally increases, and devel­op­ing nations’ demand for energy con­tin­ues to grow, there’s a vast poten­tial mar­ket for all clean energy sources mov­ing forward.

Marianne Guenot