Radiation Contamination

Plazaman

Along with everyone else I'm closely following the ongoing news stories about the Nuclear Reactor malfunctions in Fukushima.

I'm curious to find out how a person can be irradiated? A lot of the workers in the plant and in the surrounding area wear protective suits and those in the surrounding 20k area have been told to stay indoors and close all windows and doors.

Is it simply a matter or ensuring radioactive particles do not come in direct contact with your skin? I'm assuming at some stage, if high enough, these can penetrate protective wear? Also the fact that they want to spray water above this power plant to prevent the spread of radiation, it this like "keeping the dust down"? Many thanks for your patience - reply in laymans terms please.

Just for clarity, irradiated means treated with radiation. I think strawberries tend to be/used to be irradiated, to kill micro organisms.

Staying indoors and wearing protective suits (called hazmat suits meaning hazardous materials) doesn't protect from radiation but it does as you said stop potentially radioactive particles from touching your skin or entering your lungs. Radiation is around us all the time, it's high levels of it which are dangerous, so by staying indoors and not touching any radioactive particles, you're seriously lowering the level you're in contact with. Radiation can penetrate most things, but the people within the zone where the radiation from the plant would be dangerous were evacuated I think. Those outside the zone mainly just had to worry about the potentially dangerous radioactive particles that were free in the atomosphere/on surfaces, as the level of radiation in a particle of radioactive dust isn't likely to kill you if you're inside, far away from it.

To get a tad more sciency, there are different types of radiation, alpha, beta, gamma, etc. which aren't all protected against in the same way, but in general a heavy metal like lead would be needed to protect against it. Radiation is pretty much when an atom breaks down spontaneously and releases a sub-atomic particle. What particle that is determines what kind of radiation it is. Since it isn't just emitted in one direction, the farther away form it you are from the atom, the less chance you have of coming into contact with the radiation. So distance is key, and it's very important that direct contact is avoided.

DailyBlaa

As true-or-false correctly stated above distance and limiting contact with surfaces which have could potentially have radioactive particles in them is key. The Japanese situation is different from what happened in Chernobyl. In Chernobyl a massive explosion due to steam build up blew up the reactor housing which allowed vast amounts of radiation and radioactive dust escape to the atmosphere. Luckily in the Japanese case at Fukushima the core has remained intact some the radiation is much lower.

As it stands at the moment only the workers in the immediate area are at risk of having radiation related illness. As it stands at the moment the doses at the plant range from 350-500 millisieverts per hour which itself would not leave to radiation sickness but a prolonged exposure will increase the likelihood of cancer developing. Typically for that level of dose it would increase your risk of getting cancer by 3-5%. This doesn't happen over night it may take years for the effects to show.

Quiet you

DailyBlaa wrote: »

As it stands at the moment the doses at the plant range from 350-500 millisieverts per hour which itself would not leave to radiation sickness but a prolonged exposure will increase the likelihood of cancer developing. Typically for that level of dose it would increase your risk of getting cancer by 3-5%. This doesn't happen over night it may take years for the effects to show.

I remembered this from a year or two ago and it stuck with me. I found it an eye opening documentary but as I've no scientific background I'm stuck in the position of not knowing whether what they're saying is accurate and un-biased or that they've missread the information and have gone down the wrong road.

Basically, what they're saying is this. The linear no threshold (LNT) is used to determine how much radiation a human can be exposed to before it's harmful. It was devised after studying those who survived the atomic blasts in Hiroshima and Nagasaki. These people were exposed to extremely high levels of radiation but for a very short period.
The scientists and doctors working in Chernobyl say that no evidence exists that low level radiation poses health risks, in fact in certain circumstances it could be benificial.

Like I said, I have no scientific background but seeing as this was a BBC Horizon documentary I couldn't just dismiss it outright as I would have if it was some discovery channel deal.


http://news.bbc.co.uk/2/hi/science/nature/5173310.stm

Capt'n Midnight

In 1958, using data largely drawn from these bomb studies, scientists came up with an answer. It was called the Linear No Threshold (LNT) model and suggested all radiation, no matter how small, was dangerous.

IIRC it was back in 1947 when they first ruled out "safe" levels of radiation. The idea that the body could repair itself so that there would be no damage below a certain level. Though I'd have to look up that level to compare it with the BBC link.

It also depends on the type of radiation. Alpha particles will be blocked by the skin or even a few cm of air. But they are very bad news if they get in to the body

Quiet you

Capt'n Midnight wrote: »

IIRC it was back in 1947 when they first ruled out "safe" levels of radiation. The idea that the body could repair itself so that there would be no damage below a certain level. Though I'd have to look up that level to compare it with the BBC link.

It also depends on the type of radiation. Alpha particles will be blocked by the skin or even a few cm of air. But they are very bad news if they get in to the body

I realise that but am I wrong in thinking that since uranium has such a long half-life the levels of Alpha particles emitted (in a worst case Chernobyl scenario) would be so low as to not cause any real issues?

In an atomic explosion I assume there is a large and sudden release of Alpha particles as opposed to the slower process involved in natural decay?

darjeeling

Quiet you wrote: »

I realise that but am I wrong in thinking that since uranium has such a long half-life the levels of Alpha particles emitted (in a worst case Chernobyl scenario) would be so low as to not cause any real issues?

In an atomic explosion I assume there is a large and sudden release of Alpha particles as opposed to the slower process involved in natural decay?

Fission chain reactions are indeed greatly accelerated relative to spontaneous decay. Uranium 235 (the principal fuel in most nuclear power plants) has a half-life of 700 million years when decaying spontaneously. When bombarded with neutrons of the correct energy, though, very rapid fission occurs. This is what happens in fission reactors, where Uranium 235 absorbs a neutron, then splits to release daughter nuclei, gamma radiation and more neutrons that continue the chain reaction.

The main health risk in the case of the Fukushima plant, as with Chernobyl, comes from decay products generated during the reaction. These are normally contained within the nuclear fuel rods, but can be released if the rods become damaged due to heat. That is the main concern at Fukushima, where [edit] contaminated steam was released from the three damaged reactors during emergency cooling [/edit] and fairly recent spent fuel in storage is at risk of overheating and possible fire damage. In the case of Chernobyl, explosion of the reactor core and subsequent fire caused large amounts of decay products to be dispersed over hundreds of miles. The risk seems much smaller in the case of Fukushima.

One of the most dangerous decay products is Iodine 131, which is produced in large amounts, and decays via beta and gamma decay with an 8 day half-life. Uptake of radioactive iodine in the thyroid can lead to cancers, with children particularly at risk. A UN report found thousands of cases of children exposed to Chernobyl fallout later developing thyroid cancer, and concluded that a large proportion were caused by Chernobyl.

Caesium 134 (2 year half-life), Caesium 137 (30 year half-life) and Strontium 90 (29 year half-life) are longer-lived hazardous decay products from Uranium 235 fission. All were released in significant amounts in the Chernobyl explosion, and - at least close to the accident - some remain radiation hazards to this day.

The science programme Material World on BBC Radio 4 looked at the Fukushima inceident yesterday. You can find it here.

Quiet you

darjeeling wrote: »

The main health risk in the case of the Fukushima plant, as with Chernobyl, comes from decay products generated during the reaction. These are normally contained within the nuclear fuel rods, but can be released if the rods become damaged due to heat. That now seems to be the main concern at Fukushima, where fairly recent spent fuel in storage is at risk of overheating and possible fire damage. In the case of Chernobyl, explosion of the reactor core and subsequent fire caused large amounts of decay products to be dispersed over hundreds of miles. The risk seems much smaller in the case of Fukushima.

One of the most dangerous decay products is Iodine 131, which is produced in large amounts, and decays via beta and gamma decay with an 8 day half-life. Uptake of radioactive iodine in the thyroid can lead to cancers, with children particularly at risk. A UN report found thousands of cases of children exposed to Chernobyl fallout later developing thyroid cancer, and concluded that a large proportion were caused by Chernobyl.


The science programme Material World on BBC Radio 4 looked at the Fukushima inceident yesterday. You can find it here.

Much obliged, I hadn't thought of the radition that could be emmitted due to the reaction. I always thought that gamma radiation was only created by a nuclear explosion but seeing as that's a fission reaction I should have realised it would happen in a fission reactor. It's pretty obvious actually.

I sill don't get whether that UN report is still valid or not though. The link in one of my previous posts points towards lower levels of radiiation not being as harmful as first susspected seeing as the Linear No Threshold model was based on results taken from survivors of the bomb rather than a melt down.

Thyroid cancer in children apparently is common place but in most cases it goes into spontaneous remission. The UN report shows an increased level of thyroid cancer because they're looking for cancer in everyone but not an increase in deaths due to it.

I'm more then open to correction on this, it's just my understanding from reading what seems non biased information.




Also, thanks. I'll have a listen to that programme now

darjeeling

Quiet you wrote: »

I sill don't get whether that UN report is still valid or not though. The link in one of my previous posts points towards lower levels of radiiation not being as harmful as first susspected [...]

Thyroid cancer in children apparently is common place but in most cases it goes into spontaneous remission. The UN report shows an increased level of thyroid cancer because they're looking for cancer in everyone but not an increase in deaths due to it.

The broad conclusion of the UN report on Chernobyl is as you say. Effects on human health have been very low - much lower than initially feared.

In general, the people at the scene of the accident who were exposed to very high levels of radiation but did not die of acute radiation sickness have not died of long-term effects from the accident, though have suffered ill health.

People exposed to low levels of radiation have also not shown any long-term effects, with the exception of thyroid cancer, which shot up. Over six thousand cases of thyroid cancer were seen in people in Belarus, Ukraine and Russia who were exposed to I-131 as children. In children born after Chernobyl, incidence has fallen back to pre-accident levels. Thankfully, fatality has been very low - only 15 deaths by 2005.

Incidentally, first data from nuclear test ban monitoring stations is emerging. Iodine 131 and Barium 140 have been detected at two stations nearby. MET stations are modelling where radioactivity is likely to spread - happily it's mostly dispersing over the Pacific for now. (link: Nature blog)

Quiet you

darjeeling wrote: »

The broad conclusion of the UN report on Chernobyl is as you say. Effects on human health have been very low - much lower than initially feared.

In general, the people at the scene of the accident who were exposed to very high levels of radiation but did not die of acute radiation sickness have not died of long-term effects from the accident, though have suffered ill health.

People exposed to low levels of radiation have also not shown any long-term effects, with the exception of thyroid cancer, which shot up. Over six thousand cases of thyroid cancer were seen in people in Belarus, Ukraine and Russia who were exposed to I-131 as children. In children born after Chernobyl, incidence has fallen back to pre-accident levels. Thankfully, fatality has been very low - only 15 deaths by 2005.

Incidentally, first data from nuclear test ban monitoring stations is emerging. Iodine 131 and Barium 140 have been detected at two stations nearby. MET stations are modelling where radioactivity is likely to spread - happily it's mostly dispersing over the Pacific for now. (link: Nature blog)

Thanks, I've been having a bit of trouble trying to spot what is credible and what's misrepresentation of the information when it comes to this. Seems as if I was right in thinking the effects of radiation aren't as dire as commonly thought but alas, it's still more dangerous then I had thought.

Thanks again for your help.