What's going on in that Japanese nuclear power plant, and how should it be explained to an audience of non-scientists?
As was pointed out at a College of Journalism panel discussion on the subject, the word "explosion" in the context of a nuclear reactor "gets an emotional reaction in a script".
And yet, as Professor Laurence Williams explained, what we're seeing is a release of contaminated hydrogen from water that's been injected as coolant, maybe even as a deliberate response to the build up of pressure in the reactors. His phrase "hydrogen bang" might be more appropriate than the emotive "explosion".
Then there's "meltdown". The BBC environment correspondent Richard Black admitted that, if he had the chance to go back a couple of days, he might have reconsidered the word. Because in the context of nuclear accidents it has two meanings: in the film The China Syndrome (1979), it meant a molten mass of radioactive material that can burrow its way unstoppably down into the earth - to China! But it also means, less threateningly, any melting in the core of a reactor as it overheats, which need not trigger an epic disaster.
Laurence Williams, Professor of Nuclear Safety at the University of Central Lancashire, admitted there is a "dread factor" in nuclear accident stories, but reminded us, reassuringly, that "at the end of the day, we're all radioactive, everything is radioactive".
What's needed to assess a threat is detail. And while he commended the Japanese authorities for releasing more information about the Fukushima plant (seen the day after the earthquake, left) than they would have a decade ago, Professor Williams was still frustrated because "we don't know what and where, or what kind of radiation".
Richard Black was more positive about official communications. He said the Japanese prime minister had been "an excellent source of information", much more so than the nuclear power company Tokyo Electric Power.
The power company is in everybody's sights: Alex Wood, a former Tokyo-based Japan business reporter, said with astonishment that he had just heard that a right-wing paper in Japan had called for it to be nationalised.
As to how the story might develop, Professor Williams explained that the reactors had all been switched off as planned when the earthquake began. The problem had been that the power supply to operate the coolers had failed during the tsunami.
But the reactor is still cooling, so, the longer the time since shutdown, the closer to controllable the situation is. "If we haven't seen anything significant in the next few days," he said, "we're probably through the worst."
As to the long-term impact of the disaster, Richard Black said the plant had been designed to cope with a tsunami of 6.5 metres but this one had been 7 metres. That half metre, he mused, may have a big effect on the future of nuclear power in Japan and elsewhere.
You can watch the discussion on the College of Journalism's YouTube channel here.
