ST Explains: How safe is nuclear power for Singapore?

02 Apr 2022

Straits Times, 2 Apr 2022, ST Explains: How safe is nuclear power for Singapore?
Nuclear energy could help to power Singapore by 2050, a report published last month had found.

The technology, once deemed unsuitable for the country, has already improved over the years, and greater progress lies ahead, said the Energy 50 Committee convened by the Energy Market Authority to chart a greener future for the country's power sector.

In particular, the report said that nuclear fusion technology and small modular reactors could be of interest for Singapore. The Straits Times speaks to experts about how nuclear technology works, and the recent developments in the space.

1. What is the difference between nuclear fusion and fission?
Both are physical processes that produce massive amounts of energy from atoms, said the United States Department of Energy on its website.

Fission involves the splitting of a heavy, unstable nucleus into two lighter nuclei, while fusion is the process where two light nuclei combine, releasing energy in the process.

All commercial nuclear plants now generate energy through fission.

But research groups worldwide are now looking into the feasibility of developing fusion plants.

Dr Valerian Hall-Chen, a scientist at the Agency for Science, Technology and Research's (A*Star) Institute of High Performance Computing, said: "The process of fission is easy to start and difficult to stop, while fusion is difficult to start but easy to stop."

He added that in fission reactors, several years of fuel is typically held in the reaction chamber, with various methods to ensure that it is "burnt" at a suitable rate. "There is a risk that the large quantities of fuel in fission reactors will be consumed quickly, potentially leading to a meltdown," he said.

Fusion, however, is less dangerous as there is no risk of a runaway chain reaction. But for fusion to occur, high temperatures several times hotter than the centre of the sun is required, he said.

2. Can nuclear energy technology be safer?
The two key safety concerns about nuclear technology are the possibilities of a nuclear meltdown - such as what happened at the Chernobyl nuclear power plant in 1986 - and the generation of radioactive waste.

Singapore University of Technology and Design (SUTD) research fellow Matthew Lloyd, whose work involves developing new metal alloys for nuclear fission and fusion industries, said that since the Chernobyl incident, there have been several generations of reactors with enhanced safety features, such as multiple independent backup cooling systems.

The development of nuclear fusion technology will also take away the risk of a nuclear meltdown, he added.

As for radioactive waste, Dr Hall-Chen said that in nuclear fission, " high-level and long-lived" nuclear waste is generated. This refers to spent fuel that is no longer efficient in producing electricity, and can take hundreds of years to decay.

Countries such as Sweden, Canada and the United States have taken to building disposal spaces underground as deep as 5,000m to store such nuclear waste.

Last year, construction for the world's first deep geologic nuclear waste repository to store spent fuel for 100,000 years began in Finland.

Nuclear fusion, on the other hand, produces "mid- and low-level short-lived nuclear waste", said Dr Hall-Chen.

Fusion products are not radioactive, although the reaction still produces some nuclear waste because some of the fusion products interact with the reactor walls to generate radioactive material, he said. "This can be minimised through designing the walls appropriately."

3. What are the obstacles to developing fusion energy?
There are challenges in science, engineering and economics, said Dr Hall-Chen.

For instance, one scientific challenge is how to make nuclear fusion more efficient.

Nuclear fusion is the process which makes energy in the sun.

But on earth, generating such high temperatures could cause heat to leak out of the reactor, reducing performance, he said.

In terms of engineering, a fusion reactor will also require walls that do not transform into radioactive elements after prolonged exposure to neutrons produced during fusion, added Dr Lloyd, whose work involves developing such materials.

Lastly, fusion power plants are still being optimised to become less costly.

4. How do smaller reactors help to reduce the chance of nuclear meltdown?
New small modular reactors which generate energy through fission technology can be mass-produced in a factory, and then trucked or shipped to the site of the power plant.

Since each unit is identical, they do not have to be designed from scratch and can be optimised with the best practices for safety, said Dr Hall-Chen.

He added: "In general, having each modular reactor produce less power makes it easier to cool them passively, that is, they cool themselves just by sitting there, without having to pump the coolant, thereby reducing the ways in which such a system can fail."

5. What is the timeline for fusion energy to come online?
Dr Hall-Chen said private fusion start-ups aim to prototype fusion power plants generating electricity by the early 2030s.

A few national state-funded fusion programmes aim to build their versions of such prototypes by the 2040s.

6. What are the latest developments in nuclear technology?
Across the world, new designs of fission power plants are being developed to enhance efficiency and improve safety.

One area of research, for example, is the design of thorium reactors.

"Unlike conventional nuclear reactors, which typically use uranium as fuel, they would use thorium which has comparably little proliferation risk associated, since neither thorium nor its products can be used for thermonuclear bombs," said Dr Hall-Chen.