Is it Safe?
Fusion is inherently a fail-safe process. If the reaction is interrupted, fusion stops instantly. It is not possible for a nuclear fusion reaction to get out of control or for a chain reaction to occur.
Does it produce waste?
No nuclear fuel "waste" is produced as a result of nuclear fusion reaction - unlike traditional nuclear fission power which produces spent fuel rods and other waste - some of which stay radioactive for many thousands of years.
The deuterium fuel is not radioactive, however the tritium fuel generated by lithium would be radioactive, but this would be contained within the reactor. Tritium can be found in day-to-day life such as glow in the dark watches, emergency exit signs and similar radio-luminescent materials. However it is a very scarce material, which is why it is created within the fusion reactor from lithium. In a fusion power plant, the aim would be for fuel to be completely used up and should there be any leftover fuel in the reactor, due to it's high value it would be "scavenged" and re-injected into the process.
Due to the fusion reaction itself, a small number of internal parts of STEP would become radioactive - this is the case with any similar technology such as particle accelerators e.g. at the Large Hadron Collider in CERN. However this radioactivity would rapidly degrade after use and some of these parts could be fully recycled in around 50-100 years, compared to existing traditional fission power stations where reactor materials can be radioactive for thousands of years.
Could it harm the environment?
Fusion generation would convert a small amount of fuel into mostly energy, with by-products of the process being inert helium gas which can be collected and used for industrial purposes.
There is only a small amount of fuel in the plasma at any time, and overfuelling or overheating the plasma will lead to it being extinguished almost instantly. Extensive studies over the last two decades (for example the European Fusion Power Plant Conceptual Study) have shown that no plant failure or accident could result in the need to evacuate public from outside the site, and that the radioactive waste products from fusion power will not be as long-lived as those from nuclear fission.
More Questions?
If you have more questions please get in touch and we will do our best to help. Also please take a look at the excellent FAQ on the UKAEA website - https://ccfe.ukaea.uk/fusion-energy/faq/