Live webchat with Professor Paddy Regan, nuclear physicist, tonight, 21 Mar, 8-9pm

[GeraldineMumsnet]

We're very pleased that Paddy Regan, professor of physics at the University of Surrey in Guildford, is our webchat guest this evening between 8pm and 9pm.

In the wake of the Fukushima crisis in Japan, you asked on this thread if we could get a nuclear physicist on. So thanks to Prof Regan for agreeing to come on to MN.

He's 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.

In his 'spare' time, he says he plays a poor game of squash, even worse golf and tries to do the occasional sponsored run for the Mental Health Charity MIND. He is married to Susie, a nurse, and they have four children.

@Cortina

"Also, the radionuclei in this are mostly radio-iodide which has a half-life of ~8 days and will therefore drop signficantly over the next two weeks."

It's the word 'mostly' in this sentence which I find worrying. What about the other types, what risk do they pose if any? I gather from the chat that Paddy thinks there isn't anything really to be concerned about (?)

Hi Cortina,
sorry I just got back from work and saw these.... it's true that the numbers seem alarming. The other types of radioactivity likely to be present are 137Cs (which is a beta and gamma-ray emitter and has a half-life of ~30 years) and possibly some 90Sr which is a pure beta emitter which also has a half-life of 30 years. There will also be some other Iodine isotopes (such as 129I which has a very long half-life of more than 10 million years....i.e., is so long lived that it basically emits very little radiaoctivity in anyones lifetime). Other possible radioactivities, depending on what was in the plume (i.e., if there was any uranium (and in the case of MoX, plutonium) are both mainly alpha emitters with rather long half-lives. These have basically no biological effect unless they are ingested in significant amounts.
The main issue from a radiobiology point of view is still the 131I (radioiodine) which has a half-life of 8 days...so assuming no more is emitted from the reactor, this will decay away naturally...after 24 days it will be at a level of 1/8 of what it current is.

@BeenBeta

The Japanese authorities ave announced today that Tokyo tap water is radioactive and may be dangerous to babies. That is likely to be due to radioactive iodine.

The plant is still intermittently on fire and at least one fo the reactors is now at over 500 degrees centigrade and getting hotter.

The reconnection of the electric supply is only to the control rooms and not the pumps. Reactor number 2 needs a new pump entirely.

Hi BeenBeta,
The levels reported for some of the water in Tokyo are at levels of a few hundred Bq per kg (i.e. litre) of water. This is below the dose that would be reportable for adults (for 131-iodine) but is above the (rightly conservative) low limit threshold for very small babies. There are studies from Chernobyl that the intake of (significant) amounts of 131I in the very young can result in an increased risk of thyroid cancer. It is however worth noting (a) that this risk is still very small (certainly the idea that all the babies in japan who have access to this water will get thyroid cancer is not at all correct) and (b) the reported measured levels are about a factor of 2 above the usual background levels (as of earlier today at least). This means, that assuming there is no further additional radio-iodine introduced into the water, the radiation levels from 131I should fall by a factor of 2 within 8 days (the half-life) and be 'back to normal'. 131Iodine is also a well know radio-pharmaceutical which is used to diagnose under and over active thyroid conditions, so we know quite a bit about the radiation health effects from it. The issue would be if the radiation levels in the water did not drop over the next week (in the regions which are being reported as being high), this would imply a continuing radioactive contamination of the water, which would keep the radio-iodine levels at there current high levels.
The amount of 131I can be measured directly by the emission of a characteristic gamma-ray of a know energy, so as with the other aspects of this case, any contamination can not be hidden, no matter what the level. it's also worth noting that there is usually an increased level of naturally occurring radiation in all sorts of types of 'mountain spring water', some of which have increased amounts of radium in them from passing through the granite rocks etc. As with all radiation and health physics, it all comes down to a case of measuring the ammount and type of radiation present and using the previous data on radiation effects on humans (which comes mostly from Nagasaki, Hiroshima and Chernobyl) and assigning a risk factor for that level of radiation exposure. Most of the literature which exists suggests that humans (radiation workers for a start) can be exposed to at least ~20mSv per year with no obviously statistical health effects. At the current time, all of the measured and reported of these doses for people in Tokyo are very, very much less than this.

@BeenBeta

sakura - I am trying not to be eternally depressIng on this issue and stick to facts but frankly it just is not getting better really at the plant.

The supposed reconnection of the electric supply to the pumps is not happening and I have seen thermal images of each reactor building and they are very very hot indeed and well above design temperatures.

The radiation level at reatcor 2 is at it highest level ever according to this mornings reports and worst still Kyodo news is reporting a neutron beam has been observed 13 times coming from the plant up to 1.5 km away.

"But the measured neutron beam may be evidence that uranium and plutonium leaked from the plant's nuclear reactors and spent nuclear fuels have discharged a small amount of neutron beams through nuclear fission."

I dont care what anyone says - that is not good news. In my view, the plant and the nuclear fuel in it is beginning to seriously degrade and in severe danger of emitting mass quantities of radiation to the environment.

The 'neutron beams' would certainly not be a good sign...these might be evidence of ongoing fission, perhaps from some hotspots in some of the exposed fuel. I'm not sure what is mean by 'beams'. The fuels rods should not be able to get supercritical. I have no idea what the plant looks like in terms of its structural integrity...a full meltdown and large scale release of fission fragments would make the current situation far worse, but it seems, at present we are not at this stage. I guess, as with before, the radiation levels and types of radiation coming from the plant continue to need to be monitored. It is worth remembering that if a human being is exposed to a dose of ~8 Sv they collapse there and then (the Central Nervous System shuts down). Since the radiation workers are still working on site, they clearly have not recieved anything like this dose of radiation yet. Doses of 2 Sv would make the workers so ill ('radiation sickness') that they would not be physically able to work. The fact that there are people in the site and able to work means that their doses must by at most in the ~250mSv range (which represents a 1% lifetime increased in total cancer risk..i.e., rising from around 25% risk of a fatal cancer without the radiation exposure to 26% with this level of exposure). For doses of fractions of this (according to the 2007 International Commission on Radiological Protection (ICRP) stats) the numbers scale proportionally...so an extra dose of 25mSv would be a 0.1% increase cancer risk (from ~25.0% to 25.1% etc.)

@BeenBeta

The fuel rods in a reactor emit neutrons as a normal part of the nuclear fission process.

The fact that neutron emisisons are being detected in large quantities suggest that they are being emitted by fuel rods somewhere in the plant. Either because the reactor containment vessel has been ruptured and the core is exposed, or because the rods have melted and leaked out of the reactor or because rods are exposed to air in the spent rod pools and are getting hot and emitting a lot more radiation than would normally be allowed.

Note that there are also 'beta-delayed' neutrons which come from the fission some of the fission fragments themselves (these are actually utilised in the control of a 'normal working reactor'). It is possible that the neutrons come from these. What I am not sure about is how this 'beam' could get 1.5km from the reactor...neutrons from the reactor should be stopped/absorbed in air, concrete at a much shorter distance....as with all reports at the moment, this is puzzling and needs more information and clarification for a scientific analysis of what is actually going on.

Paddy - thank you for your reply.

All in all, yes I agree with your main point that if there was nothing more emitted from the plant then everything would be fine and very few extra cases of cancer would occur.

My worry and I suspect everyone living in tokyo is that this entire issue seems to just be dragging on and on and on with progress targets for shutting down the plant safely just seeming to come and going with no real progress and signs that the plant is getting hotter and hotter and radiation levels climbing.

In the end I think they will have to bury it in a concrete sarcophagus and create an exclusion zone around it. How they actually achieve that I have no idea.

@BeenBeta

Also Reuters which is reporting radiation at 500 milisieverts per hour at reactor 2 which is the danger zone.

I read that a dose of 10 sievert in one dose will usually kill through organ failure so standing next to the reactor for 20 hours will give a worker that big a dose.

Hence they have to keep withdrawing workers.

10 Sv will certainly kill most humans. I assume if the workers are withdrawing a specific distance from the plant this implies (to me at least) that the source of this radiation is gamma-radiation (perhaps from open spent fuel rods which are not covered with water which would attenuate the gamma-ray radiation). The radiation effect from gamma-rays falls off from a 'point source' very quickly with distance. I guess it would be good to know what the source of this radiation is and why is it localised (apparently) to reactor 2. Again though, the distance between this reactor issue and Tokyo is huge compared to teh typical range of gamma-rays coming directly from the reactor and the rods there...certainly gammas emitted at the plant can get anywhere near Tokyo.

Paddy - yes again I agree with you the threat to Tokyo is still minimal but I liken the situation to the 'boiling frog' problem. At first the situation is manageable and very very slowly gets worse until the tipping point when the temperature gets hot enough to kill the frog.

To me the situation at the Fukushima plant is slowly, very slowly slipping into a more and more precarious state. We were promised it would be getting better by now. It does not appear to be getting better and with radiation levels so high at the plant that makes getting it under control ever harder.

It just seems unstoppable - at least for now. Which is worrying.

@BeenBeta

Paddy - thank you for your reply.

All in all, yes I agree with your main point that if there was nothing more emitted from the plant then everything would be fine and very few extra cases of cancer would occur.

My worry and I suspect everyone living in tokyo is that this entire issue seems to just be dragging on and on and on with progress targets for shutting down the plant safely just seeming to come and going with no real progress and signs that the plant is getting hotter and hotter and radiation levels climbing.

In the end I think they will have to bury it in a concrete sarcophagus and create an exclusion zone around it. How they actually achieve that I have no idea.

Hi again,
I agree, the additional stories of continuiing puffs of radiation are a concern...again, this is something that has to be monitored and measured, specifically in determining the size and type of radiation which is being measured and also over what area (i.e. are these simply single, localised high doses or wider spread plumes?)...From this distance away and with the measurements we keep getting on a seemingly random basis, it is hard to make an accurate evaluation, but common sense and experience tells us that a massive radiation leak from Fukushima to Tokyo is very, very unlikely.
The famous Windscale fire of ~1957 threw lots of radioisotopes in the surrounding environment with little obvious additional health deteriments. For my taste, there is a good discussion on the risks by Michael Hanlon of the UK Daily Mail which is on the web at
www.dailymail.co.uk/debate/article-1369140/Japan-nuclear-crisis-Disaster-proves-value-safety-nuclear-power.html

hope the additional comments/discussion helped a bit. I really have to go now and get my 'real work done'....I enjoyed the discussions for sure. All the best mumsnet,
Paddy

Thank you Paddy. It was nice talking to you too.

Hear, hear. Thankyou Prof. Regan for your diligence!

Thanks again very much Paddy.

Is anyone else trying to imagine Bounty or Netmums having a nuclear physicist for a webchat?

Sorry. Back to the serious stuff!

@washnomore
Yes, thanks for coming back, Paddy.
On behalf of those of us living in/planning to visit Japan, could I put in a special request for you to come and update us if you think there are any significant changes in the situation at Fukushima? It's hard to get a proper perspective on all the dribs and drabs of information coming out from other places....

The comments on that Daily Mail article are interesting.

Good heavens! I never thought I would have a good word for the Daily Mail!

THe problem is that although not every, single baby that ingests the water will get thyroid cancer, a lot of babies who wouldn't otherwise have got caner will get it.

Breaking news from NHK.

Steam rising from 4 reactors at Fukushima plant

Apparenlty the pumps failed on ractor 5 as well.

There are Sky News reports thsi morning saying that three workers were taken to hospital with radiation related injuries this mornng.

If you have time please do look at the story of the Fukushima Fifty plant workers and the photographs showing how they are working in the dark in heavy protective clothing with torches.

I read that Japan turned down an offer of help from the US at the start. I can't understand it. Surely they should be throwing everything at the plant to stop further radioactive emissions. And why not send in the army as extra manpower? Or fly in teams of nuclear reactor workers from around the world? There should certainly be an international effort to put an end to the emissions.

Wrt to the neutron beam, I think the term "neutron beam" is a translation error. What they were really reporting was the results from a fixed neutron monitor in that position, which is located at a plant boundary, hence the low (ie normal) reading .

There is an internationl response in operation: RANET, operated by the IAEA.

This is interesting. The amateur videos are clunky and awkward, but if you bear with them the maps are particularly informative.

BeenBeta, you should watch the Three Mile Island video in my link above.

ambivelent - I looked at the animated maps. I have seen them elsewhere in an earlier version but they are compelling/worrying.

I did read that the 'run rate' of emissions at Fukushima is now actually ahead of where Chernobyl was at the same stage.

The website is a bit confusing though. Where is the Three Mile Island video link?

Click on the pink link which says "Two half-hour videos..." That takes you to the Chernobyl one. In a box to the right are two picture links - the lower one is Three Mile Island Revisited. Click on that and the video comes up.

OK. I got it now. I will watch tomorrow morning.