Experts on Japanese nuclear power plant explosion

The Japanese Government is struggling to cool its Fukushima nuclear power plant following a dramatic explosion at the plant which authorities say neverthless failed to breach the reactor’s housing.

The explosion at the Fukushima nuclear power plant

A state of atomic emergency is in place as the threat of radiation leaks remains high and tens of thousands of people have been evacuated from the area within 20km of the power plant.

Our colleagues from the UK Science Media Centre gathered these comments from nuclear engineering and safety experts.

A briefing paper from the World Nuclear Association on nuclear power stations and earthquakes is available for download here.

Professor Malcolm Sperrin, Director Of Medical Physics And Clinical Engineering, Royal Berkshire Hospital, said:

“There is a lot we don’t know at the moment but this looks very serious. However, there are a number of things that we should remember. First of all the Western nuclear industry is very geared up for dealing with accidents and incidents. There are likely to be detailed procedures in place – Japan will have planned, prepared and practised for something like this.

“The big difference between something like this and previous accidents elsewhere in the world is that there will be mechanisms in place to deal with the explosion and any impacts it might have.

“Although there is a lot we don’t know, it is very unlikely that this was an explosion involving the core.

“If there is a nuclear leak that would be very serious, but as we can see there are plans in place to cope with such occurrences. We would need more information before we could comment further on the impact of a leak.”

(Malcolm has previous experience in the atomic energy sector – some years ago now)

Professor Andrew Sherry, Director, Dalton Nuclear Institute, The University of Manchester says:

“It is important to understand the details of what has happened before judging the severity of the Fukushima nuclear incident at resulting from the earthquake. The 40 year old BWR plant includes a multi-barrier approach to containment of nuclear materials that includes fuel cladding, reactor pressure vessel, containment vessel and the containment building. At this stage is not yet clear the cause of this morning’s explosion, nor the level of resulting damage.”

Professor Richard Wakeford, Visiting Professor in Epidemiology at the University of Manchester, said:

“If the explosion at the Fukushima nuclear power station has resulted in a significant release of radioactive material then this will soon be readily apparent from the radiation monitoring that is undoubtedly underway around the plant. Until we have reliable information on the results of such monitoring from Japan, some of the speculation in which some commentators have indulged is just that – speculation. We should have the information to allow an informed assessment of the situation soon enough.”

Professor Paddy Regan, Professor of Nuclear Physics at the University of Surrey, said:

“It looks as if the coolant pumps had initially stopped working. They shut down automatically when the reactor shuts down, but there is a backup system running off a diesel generarator – it looks as though that’s the bit that failed.

“As a result there is no way of pumping heat out of the reactor, so it has to cool naturally. If the reactor gets too hot, in principle this means the fuel rods can melt – but it looks unlikely this has happened to any great extent in this case.

“To reduce the pressure, you would have to release some steam into the atmosphere from the system. In that steam, there will be small but measurable amounts of radioactive nitrogen – nitrogen 16 (produced when neutrons hit water). This remains radioactive for only about 5 seconds, after which it decays to natural oxygen.

“But if any of the fuel rods have been compromised, there would be evidence of a small amount of other radioisotopes in the atmosphere called fission fragments (radio-caesium and radio-iodine). The amount that you measure would tell you to what degree the fuel rods have been compromised. Scientists in Japan should be able to establish this very quickly using gamma ray spectroscopy as the isotopes have characteristic decay signatures. Current reports seem consistent with a small leak to relieve pressure.

“But we still need to establish the cause and exact location of the explosion, which is a separate issue. So far it looks like it’s not the reactor core that’s affected which would be good news.

“We must remember that there are 55 reactors in Japan and this was a huge earthquake, and as a test of the resilience and robustness of nuclear plants it seems they have withstood the effects very well.”