New ‘safer’ nuclear reactor offers hopes for waste disposal

British scientists are to research whether a new type of supposedly safer, smaller, cheaper nuclear reactor could help reduce the UK’s radioactive waste stocks.

A team from Cambridge will investigate the potential for using thorium-based fuel in a new reactor under development in the US that would be small enough to manufacture in a factory but produce as much energy as current power plants.

Using a combination of the abundant material thorium and plutonium from the UK’s waste stocks to power a nuclear reactor could theoretically reduce reliance on the rarer element uranium and produce waste that was dangerously radioactive for a much shorter period.

The Cambridge team, led by Dr Geoff Parks, plan to use computer models to research how well this thorium fuel-cycle would work in the “integral inherently safe light water reactor” (I2S-LWR) being developed by the Georgia Institute of Technology.

‘This is a change of paradigm for light water reactors, which attempts to produce the output from a conventional reactor but with the footprint of a small modular reactor,’ Parks told The Engineer, adding that smaller reactors would be quicker and cheaper to build.

‘[We’re] looking at potential uses for that reactor technology both short term – as a means of getting rid of plutonium in a useful way rather than simply treating it as a waste – but also establishing a way forward for a longer-term view for the potential use of thorium in the future when uranium begins to run out.’

The designers of the I2S claim it is safer and smaller than current reactor designs because it incorporates its heat exchangers inside its main pressure vessel rather than relying on an external system.

It also features a number of passive safety features, such as a cooling system that relies on naturally circulating air rather than pumped air or water, which won’t stop working without a power supply.

The Cambridge research will explore the pros and cons of different fuel combinations, including thorium, plutonium and the main material the designers are focusing on, uranium silicide, which is more power dense and so more cost-effective than the uranium oxide currently used.

Parks said that because the I2S is an evolution of existing light water reactor designs it could be brought to market more quickly than other reactors proposed for use with a thorium fuel-cycle, suggesting it could even be deployed within a decade and be installed in old nuclear power stations such as Sizewell B.

However, he also admitted that with current uranium stocks there was no major economic necessity to move to a thorium fuel-cycle at the moment and that such a transition would only happen if the government committed to thorium through a long-term flagship research project.

A paper published by the UK’s National Nuclear Laboratory in March 2012 found that ‘the thorium fuel cycle at best has only limited relevance to the UK as an alternative plutonium disposition strategy and as a possible strategic option in the very long term,’ and recommended ‘a low level of engagement in thorium fuel cycle R&D’.