FNST project explores viability of powering low voltage batteries using beta radiation from tritium
Most of us that work in the nuclear industry have a basic understanding of how a nuclear power reactor works – nuclear fission is used to produce heat, which is used to produce steam to turn a turbine that generates electricity. But there is another way that we can apply nuclear science and technology to produce energy, and CNL is currently exploring the viability of this technology as part of a project administered though Atomic Energy of Canada Limited’s (AECL) Federal Nuclear Science & Technology (FNST) Work Plan.
The technology is a betavoltaic device, and more specifically, a tritium battery. Tritium is a radioactive isotope of hydrogen, a by-product of CANDU® reactors, and something that CNL is very familiar with. The Chalk River Laboratories is home to a tritium research facility that was originally built to support research related to the safe operation of Canada’s nuclear fleet and the Canadian fusion program, but which has expanded to involve other research and development activities.
Tritium decays via beta emission, which means that it releases a spectrum of low energy electrons from its nucleus. In turn, that radiation can be harnessed to generate small amounts of power, a conversion process known as betavoltaics. The process is very similar to other energy conversion technologies we are all familiar with, though it also has some important differences.
“Betavoltaics work in much the same way that a solar panel does,” explained Jayeshkumar Patel, a research scientist in CNL’s Hydrogen Technologies branch. “In that example, solar cells absorb light and transform it into energy using a semiconductor. For a tritium battery, we use a similar semiconductor, but we use the beta radiation emitted from tritium instead of sunlight to serve as the energy source.”
While the energy emitted from tritium is modest – we’re talking about microwatts – it does have its advantages. Compared to a solar cell, which only produces energy during the daytime, the radiation emitted from tritium is consistent day and night. And with a half-life of approximately 12.5 years, tritium batteries could generate uninterrupted a low-power for more than 20 years.
There are many applications where this type of technology could be very useful. Patel believes that these batteries could be used to power wireless sensors in Small Modular Reactor (SMR) applications in remote locations that aren’t easily accessible, for example. This technology also has a great potential for defense, space and other remote applications (such as deep oceans) where the power source replacement is not possible frequently. With enhanced power outputs, another interesting function could be the use of tritium batteries to power pacemakers, a small device that is used to steady the heartbeat of arrhythmia patients.
“Pacemakers have to be surgically implanted into a patient’s chest, so it’s ideal to power these devices with a reliable source of power that will operate safely for decades,” commented Patel. “A lot of people at CNL already know this, but beta electrons don’t travel very far – they can be stopped with something as thin as a piece of paper. So tritium can be safely contained in these devices, and potentially serve as a suitable source of energy to power them.”
“We are exploring the use of beta radiation to directly produce electricity through a semiconductor, as just described, but there is another methodology that is also being studied,” explained Patel. “In this approach, we convert beta radiation into light, and then we use the light to power a solar cell, which generates electricity. It’s an added step to the process, but addresses some of the technical challenges that come with direct conversion.”
To perform this testing, CNL has developed a closed vessel where researchers have stored these devices and subjected them to tritium radiation, allowing them to conduct in-situ measurements. This gives them the capability to accurately measure the degradation of the materials, and to assess how they hold up under these conditions. After a few years, Patel believes that the data can be used alongside modeling to determine the battery’s viability over its lifetime.