Webchat with nuclear physicist Paddy Regan


Prof Paddy ReganFollowing the earthquake-generated nuclear reactor crisis in Japan, and discussion on Talk, we invited Professor Paddy Regan on to Mumsnet for a webchat about nuclear power.

Professor Regan is professor of physics at the University of Surrey in Guildford, a Fellow of the Institute of Physics, and holds visiting researcher and teaching positions at Yale University and the University of Notre Dame. He's interested in measurements of naturally occurring radioactive materials (NORM) in the environment using gamma-ray spectroscopic techniques.


Fukushima crisis | Nuclear power | UK nuclear power | Science in the media | General

Fukushima crisis

Letter Q ChickensHaveNoEyebrows: What do you think is happening at Fukushima, and how dangerous is it?

Letter APaddy Regan: I think that the power is now back on to allow the pumps to work at the reactor, these should allow continual pumping of cooling water across the fuel rods and should 'fix the problem'. The issue from here is that we can't see how badly the engineering infrastructure has been damaged by the gas explosions, but as long as the rods are cooled the problem's over I think.

Letter QTheSkiingGardener: How accurate and reliable do you feel the information released by the Japanese authorities is? Are the readings reported by outside sources and the levels being found in plant matter consistent with the information given? And finally, how optimistic are you that the situation will be resolved without further escalation.

Letter A

"Even with this 'worst-case scenario', it is physically impossible for this to develop into a nuclear explosion."

Paddy Regan: I think that they are giving us the correct information. It is impossible to hide a radiation leak as we can measure the fingerprint radiation from many different places. I am also optimistic that, as long as they can keep getting the water in to cool the plant down, there will be no further escalation.

Letter QHereMeRoar: Why do the authorities keep insisting that even in a worst-case scenario lots of lives won't be at risk and the worst that can happen is local contamination? Is this right? Why is there no (even remotely possible) potential wider threat? 

Letter A

"The overall levels of radiation are very small compared to the known health effects of radiation."

Paddy Regan: Again, this is to do with numbers and rates. The 'worst-case scenario' that we are always asked about would be a full nuclear meltdown. This has not happened, but some of the fuel rods have been compromised and radioactivity released in the pressure vessels. Even with this 'worst-case scenario', it is physically impossible for this to develop into a nuclear explosion for all sorts of physics reasons including (a) the control rods went in as soon as the earthquake came, so there was no more fission production from that point on and (b) the enrichment of the fuel into the sort you need to make a nuclear explosion (ie like a nuclear weapon) is not sufficient (it never is in a reactor).

Letter Qsakura: What exactly are the risks for my children? If you lived in Japan now, would you stay? They're already saying the milk and vegetables have been affected by radiation.

Letter APaddy Regan: I have a number of friends in Tokyo who are academic nuclear physics researchers (at RIKEN) and they tell me that the main worry for them is the worry of more earthquakes. The radiation levels as measured from the releases at Fukushima so far certainly show up on their measuring equipment, but this really shows how sensitive this equipment is. The levels are now around 0.3 microsieverts per hour, which is higher than normal background, but still small. Also, the radionuclei in this are mostly radio-iodide, which has a half-life of approximately eight days, and will therefore drop significantly over the next two weeks.

The overall levels of radiation are very small compared to the known health effects of radiation. This website has a good chart of radiation doses, which I hope puts the radiation health risks into perspective.

Letter QObscureReference: I had heard that they were flooding the reactors with sea water to cool them and that this would cripple them, rendering them forever useless, but now there are reports that they are trying to 'fix' them? Any chance you could clear up this discrepancy? 

Letter A

"The main radiation risk for the workers at Fukushima would be exposure to 'whole body gamma doses', which they can reduce by getting further away from the radioactivity sources are they arrive."

Paddy Regan: The sea water was used as it was 'handy' when they needed it. Not all the reactors were flooded with sea water (four to six were out of use at the time, anyway).

I think that 'fixing them' refers to the cooling systems that should have kicked in following the earthquake (ie pumping regular water around using an electrical generator to cool the cores). The reactors with damaged fuel rods in the core are basically not useable for power generation anymore - for a start the outer building walls are missing.

Letter Qbrightpurplecow: Just wondered what you thought about Germany's reaction to the Fukushima crisis? Is this a massive overreaction or should we be taking a similar stance?

Letter APaddy Regan: I personally think it's an overreaction and more based on the fact that there are important local elections coming up in Germany and the Green Party there often hold a sway in power. Nuclear in Germany is still controversial, I think as a follow-on from its position as the 'border state' during the cold war, but again, just my personal view.

Letter Qexexpat: What would you say were the most reliable public sources of information about this incident and the local/regional/international impact? There are several people in Japan posting live updates of Geiger counter readings - they seem mostly reassuring, but is that useful information, or should I be more interested in radiation levels in the water, food chain, air etc? 

Letter APaddy Regan: I have a number of mates in Tokyo who are working in their main (academic) nuclear physics labs in RIKEN. There has been a small, but measurable rise in the background radiation levels in Tokyo which is associated with the release of material from the Fukushima plant, but the level is (a) very small and reflects the sensitivity of the detection system and (b) the main radioisotopes which were identified (iodine) only remain radioactive for approximately two weeks. At these levels, the increased radiation dose is about the same (for a brief period) as it might be if someone visited their friends in Cornwall for a couple of weeks.

Letter QZenyattadottir: When the various plumes from Japan waft over the UK, what radioactive particles will they contain, and will those particles stay high up in the atmosphere if it doesn't rain? If the various particles do come down to earth in rain, how long will their radioactive life be?

Letter APaddy Regan: This depends on what the particles are: iodine (approximately eight days); caesium and strontium (approximately 30 years); plutonium (approximately 20,000 years). The half-life is a property of the nucleus itself and different for each nuclear species. The activity (ie number of decays per second) is given by the number of radionuclei of that type presentdivided by the average time that it takes a single nucleus to decay (called the 'mean-life', which is like the half-life, sort of).


Nuclear power and radiation

Letter QLeninGrad: I read recently that 29,000 Americans will develop cancer as a direct result of radiation exposure from CT scans, and that is thought to be an underestimate. That can't be right, can it? No one warns you of that risk when having a procedure like this.

Letter APaddy Regan: This sounds about right to me, but it has to be taken into the context of the number of people who have cancer every year anyway (in the UK the lifetime risk of death from cancer is around 25% across the population. 25% of Americans is approximately 75m people across their lifetimes, so we might estimate a rough death rate from cancer in the US of 1m a year. The CT scans might be used in the treatment of people who are ill anyway - as with all such statistics, the numbers have to be taken in context.

Letter QIndelible: Do you think there is a future for thorium reactors?


Letter APaddy Regan: Yes, very much so, in particular in India (1 billion people who all need power and lots of thorium). There are a few technical issues (such as the need for a plutonium or 235U blanket needed to 'fire the reactor up' but it has many advantages in terms nuclear proliferation fears (ie you can't really use it covertly to make nuclear fuel for a weapon etc). I think (personally), that at least in India, these are the future.

Letter Qmoonbells: I have been reading about thorium/molten salt reactors today; their safety features seem to be quite good, especially in the case of an emergency shutdown. Admittedly, what I've read does come initially via a newspaper, backed up by Wikipedia (I don't have time to check journals this week) but could you speculate why these seem to have been quietly ignored? I never heard about this type in my degree course!

Letter APaddy Regan: These are very interesting - it's quite a long read, but one of my excellent MSc students did a project on thorium reactors a few years ago for his dissertation

There was also a recent full edition of Physics World on these (this is the professional magazine of the Institute of Physics), see these articles on thorium reactors.

Letter QCuppaTeaJanice: Please could you explain the different types of radiation simply, and also explain which form of radiation the people near Fukushima are at risk from and whether it will be relatively easy for them to protect themselves, or is it inevitable that if they are in the area they will be affected?

Letter APaddy Regan: I think you mean alpha, beta and gamma radiation. Basically, alphas and beta particles are 'particulate radiation' and gamma rays are a form of light which is too high in frequency for our eyes to pick it out.

They all have different properties, but alphas and betas can do quite a lot of biological damage, but only if they are in contact with the body. This is why you sometimes see the guys in suits and breathing apparatus, these are to stop alpha and beta particles being breathed in etc.

Gamma rays are like X-rays at the hospital. They can do some biological harm and travel further through air. The main radiation risk for the workers at Fukushima would be exposure to 'whole body gamma doses', which they can reduce by getting further away from the radioactivity sources.

Thick metal/materials will stop gammas, a piece of paper will stop alphas and a thicker piece of paper will stop beta particles.

Letter Q

"I think the designs and safety protocols with modern, generation III+ reactors are very good. The issue of energy needs is not going away, neither is the need to reduce carbon emissions."

jenpet: Do you think, overall, that the nuclear industry is secretive and withholds information from the public wherever possible, as people tend to panic and assume the worst? 

Letter APaddy Regan: No, I don't think it is secretive per se, but it is arguably its own worst enemy when issues such as this arise. The nuclear industry was, in general, very slow to comment/discuss the Fukushima issue in the press and I think should have done more to really explain the engineering and scientific situation. 

Letter QDamnYouAutocorrect: Do you think nuclear power generation is basically safe? I mean, compared with other forms of power generation, and in context of the need to reduce carbon emissions? Or is that an impossible question to answer?

Letter APaddy Regan: What do we mean by safe? I think the designs and safety protocols with modern, generation III+ reactors are very good. The issue of energy needs is not going away, neither is the need to reduce carbon emissions.

Together, these (to me at least) point to a need to have at least some nuclear power in the grid/mix (again this is just a personal view, I am not a spokesperson for the nuclear industry, just a university academic).


Nuclear power in the UK

Letter QMistyMerkin: Do you think that the British government will now still go ahead with the planned 10 new reactors, despite the hype of it being clean energy and no inherent plans to deal with the waste generated (that being left up to our grandchildren to deal with), or is the deal already done with the "fat cat" business men?

Letter APaddy Regan: I do hope so, we need to get our energy from somewhere and we also need to develop enough technical skills to do this. Regardless of what people think, the stats say that nuclear power is at least as safe as any other in terms of accidents and health risks.

The idea that there is no plan to deal with the waste is not true. There are basic reprocessing ideas but the real question is whether we would have a single through fuel cycle and throw away the unused fuels, or reprocess and use the plutonium to make more fuel. The first solution would only give us around 100 years worth of uranium left to do this with; the reprocessing and usage in, for example, a thorium reactor or an energy amplifier (sometimes called an accelerator driven system) would increase this to thousands of years.

Nuclear waste is an issue really for the PR people to sort out. Gas and coal stations give out lots of chemical waste, which never decays (as it turns out, they also release radioactivity into the atmosphere from the natural uranium and thorium decay products in the coal).

Letter QLilymaid: In the light of what has happened in Japan, should we be over-engineering even more than in the past for the UK new build programme? Are there any other factors we should be taking into account?

Letter APaddy Regan: The reactors in the UK are getting quite old and if there is a decision for rebuild they will be newer designs. These would be the so-called 'generation III+' reactors, which have many passive safety systems in them. Reactors are really, in the simplest cases, big kettles - you need to get the heat out at some point or the element melts.

But, if we want to have these in the UK, I agree that we do need a better educated and trained staff of health and reactor physicists and scientists, who understand how you measure radiation accurately and who can give 'cold blooded' calculations and predictions on the potential health risk. These are known and can be found at the International Commission on Radiological Protection (ICRP) website. The ICRP is the world body that has collated all the data from the Japanese atomic weapons survivors, people exposed at Chernobyl and others, plus data on medical X-ray and radiotherapy treatments to give us our best estimates as to the biological effects of radiation on humans.

Letter QThisIsANiceCage: On a previous thread, a poster said: "I must admit that I'm pretty pro-nuclear power but I really don't want the Germans (RWE) nPower building power stations over here. They built a plant in Koblenz and, if I remember correctly, weren't allowed to operate it. I've heard some real horror stories about how their power stations are built and wouldn't want them in this country." I wonder if you could comment on that? 

Letter APaddy Regan: We don't have the manpower, training or political will at the moment to build our own (UK) nuclear power stations. The big guys are Westinghouse (who I think are now Japanese owned), ARRIVA and EDF I guess. Rolls Royce might be interested in bidding for some of the 'action', but the question is whether there is the political will in the UK to fund the training of engineers and scientists to do this, and also to back the industry.

I'm not sure there are many votes in it (until the lights go our and/or we are buying our electricity from the French nuclear reactors across the channel).

Letter QilovemydogandMrObama: My mother lives in California, on the coast, and they have been advised that the radiation from Japan will not be a factor. How accurate is this, keeping in mind that the reactors, according to my understanding, haven't been cooled yet? How can anyone predict the future location of radiation as it seems so unpredictable?

Letter APaddy Regan: No one who lives in California will be affected by any radiation leak in Japan. The amount of radiation released and the distance it would have to travel mean that any risks from it are virtually unmeasurable, certainly compared to the lifetime risk of dying in a car accident, which for a Californian is around 1%, I think.


Science and nuclear power in the media

Letter QMrsKwazii: What is your view on the reporting of the Fukushima nuclear situation so far? In Germany, people were apparently stocking up on iodine tablets and Geiger counters - do you think that the media is irresponsible when it comes to nuclear?

Letter APaddy Regan: Yes, and in many ways it is ignorant. The newspapers' job is to sell newspapers - I learnt that a long time ago on my 'scientists meet the media' course ran by the science media centre (the Royal Institution). This does not mean that the individual journalists do not understand, but a sensationalist headline is there to draw in the eye so you buy the paper/watch the rest of the programme. I really think Germans (or Americans, as I was asked on CNN on Friday) buying iodine tablets for this particular incident is ridiculous. I assume it was started by someone with shares in an 'iodine-making factory'

Letter Qdawntigga: What is the question you've been asked recently that has annoyed you most? 


Letter APaddy Regan: I get a bit hot under the collar at continually being asked/reported on by 'other independent websites' that I would say that "I am funded by the nuclear industry" and am somehow in their pocket - I am not!

I am simply a university-based academic who does research into how the elements are formed in stars and uses his knowledge in this area to teach/train future radiation protection/measurement experts. The 'I'm in the industry's pocket' line shows a real ignorance of how nuclear physics research is funded in the UK (research councils etc) and I am never really given a chance to rebut it.

People forget that if they want 'independent experts' in such times of 'crisis' (such as this), the UK government has a responsibility to fund basic research at a sensible level. This was a massive issue last year, but is now forgotten in all the cuts. For example, in this open letter to the Times from members of the academic nuclear physics community. 

Letter QMrsKwazii: Of the media interviews you've been doing, how many have been with science correspondents? I know that this is a bugbear of Ben Goldacre, and probably shared by many scientists, and it really does have a knock-on effect on the general public's understanding of the actual situation. Shocking, really.

Letter APaddy Regan: Most of the journalists I speak to are science correspondents (in the papers at least) but few have science backgrounds. That said, they are usually very impressive. I think that Hannah Devlin and Mark Henderson at the Times, David Derbyshire and Fiona McCrae at the Daily Mail, Roger Highfield from the New Scientist and formerly from the Telegraph (he does have a PhD) and others besides, are all very good journalists, but the paper's thread is usually decided by the editors/subeditors who I never meet.

One thing from this experience and others I have had dealing with the London press, at least, is that the journalists themselves are a pretty good and impressive (intellectually speaking) bunch. I don't know either way about editors etc. 



Letter Q

"My experience is that actually most people are interested in science but have been put off by dull school classes."

Donki: How do you think we can encourage the uptake of science (and physics) amongst 16 year olds?

Letter APaddy Regan: Good question. There are some excellent TV programmes on (including my great Surrey pal Professor Jim Al-Khalili's new series starting tonight on BBC4, on Everything and Nothing), plus of course Brian Cox's stuff.

I think the main 'trick' is to get people not 'scared' of numbers. My experience is that actually most people are interested in science but have been put off by dull school classes. Show kids the real usefulness of science in modern society, even at the level of the 'little red light thing which makes your CD player work' (better known as the 'strained layer semi-conductor' invented by Professor Alf Adams FRS, also from Surrey) and they are usually more keen to get more into it. Enthusiasm and usefulness are, I guess, the keys to this one.

Letter Qjonicomelately: Who would win in a fight between you and Professor Brian Cox?


Letter APaddy Regan: I'm in the (super) heavyweight division and he's nice and slim. We are the same age actually, but my decay half-life sadly seems to be much faster than Brian's. We'd both be able to take Jim Al-Khalili though, I reckon.

Letter APaddy Regan: For general information on the issues discussed here, check out these useful physics links:



Last updated: 7 months ago