The Guardian newspaper’s Environment Facebook page recently put the following to their readers:
Ask the Global Energy Prize‘s expert panel your toughest energy questions and they’ll be back here on Friday with their answers. What should power our cities, homes and industry in the future — renewable energy, nuclear power, or fossil fuels? How significant will shale gas be? And what role will oil play in our energy future? Just post your energy Qs here. 5 experts will answer the 10 best questions: Harry Fair (US), Tom Blees (US), Thorsteinn Sigfusson (Iceland), Barry Brook (Australia) and Klaus Riedle (Germany).
Below are the six questions put to me (Barry Brook) and Tom Blees — and our answers, of course! The original answers were not hyperlinked, but if you are curious about anything we mention here, try searching for the keywords on this website (e.g. type bravenewclimate.com/?s=thorium in your browser address bar), or on Google (e.g. type ”ammonia site:bravenewclimate.com” in your search box).
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BARRY W. BROOK
Q1. Do you agree that Thorium power is a safe, plentiful, and viable energy source that should be investigated as a matter of urgency?
Yes, thorium power is an attractive prospect for the next generation of nuclear reactors, but then surprisingly enough, so is uranium.
For today’s reactors, it takes about 150 tonnes of natural uranium to fuel a 1 gigawatt (GW) power plant for an entire year (the total energy produced is called a gigawatt year, or GWyr). One GWe of power (the ‘e’ stands for electrical power rather than ‘t’ for thermal power, or heat) is a huge amount. It’s enough to run 65 million desk lamps (assuming they used 15 W compact fluorescent globes), or more practically, to satisfy today’s electricity demand of a typical UK city of more than half a million people. For comparison, to deliver a GWyr of energy using a coal-fired power station, about 4 million tonnes of coal must be burned (the amount can vary depending on the grade of coal).
Most of the nuclear power stations in use today are called ‘thermal reactors’, or ‘light water reactors’ (LWR). They use ordinary (‘light’) water as a coolant, which take heat away from the reactor core. The water also acts as a ‘moderator’, slowing down subatomic particles called neutrons, which shoot out of the atom’s nucleus when a nuclear chain reaction is underway. These neutrons are responsible for causing unstable heavy atomic nuclei to split apart and release energy. Other reactor designs use heavy water (enriched in ‘heavy hydrogen’: deuterium) or graphite (a form of carbon found in pencils) to moderate the neutrons (the latter is used in the UK’s gas-cooled Magnox reactors, for instance), but the effect is similar. These nuclear power plants need, as fuel, a form (isotope) of uranium that has 143 neutrons in its nucleus, called 235U (or ‘uranium 235’). Yet natural uranium contains 0.7% 235U; the other 99.3% is composed of an isotope that has 3 additional neutrons, called 238U (or ‘uranium 238’). As a result, today’s LWRs are able to extract less than 1% of the atomic energy content of uranium. The rest is discarded, unused, either as spent fuel (‘nuclear waste’) or as depleted tails (the leftovers, composed mostly of 238U, after the fuel has been ‘enriched’ to raise the concentration of 235U to 3 – 5%).
Filed under: Emissions, Nuclear, Renewables | 34 Comments »
