• Blog Stats

    • 85,337 hits
  • Archives

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 164 other followers

  • Copyright notice

    This blog entry and all other text on this blog is copyrighted, you are free to read it, discuss it with friends, co-workers and anyone else who will pay attention.

    If you want to cite this blog article or quote from it in a not for profit website or blog then please feel free to do so as long as you provide a link back to this blog article.

    If as a school teacher or university teacher you wish to use content from my blog for the education of students then you may do so as long as the teaching materials produced from my blogged writings are not distributed for profit to others. Also at University level I ask that you provide a link to my blog to the students.

    If you want to quote from this blog in an academic paper published in an academic journal then please contact me before you submit your paper to enable us to discuss the matter.

    If you wish to reuse my text in a way where you will be making a profit (however small) please contact me before you do so, and we can discuss the licensing of the content.

    If you want to contact me then please do so by e-mailing me at Chalmers University of Technology, I am quite easy to find there as I am the only person with the surname “foreman” working at Chalmers. An alternative method of contacting me is to leave a comment on a blog article. If you do not know which one to comment on then just pick one at random, please include your email in the comment so I can contact you.

  • Advertisements

Cleaning drinking water and what are carrier free radioisotopes

The last news which I have heard suggests that while some radioactive iodine has appeared in drinking water it is only at a low concentration. While it went over the limit for very young children it did not go over the limit for adults.

I have recently seen on the internet some advice issued by a person who was posting under a pen name whose real name or background is a mystery to me. In this advice the person suggests distillation of water as a means of removing the radioactivity, while distillation is able to remove some substances it is not a suitable treatment.

Firstly it is very energy intensive, you need a lot of energy to boil the water and then some means of cooling is needed.

Secondly distillation is not able to remove radioactive iodine from water. Iodine in the form of elemental iodine is volatile. It is likely to evaporate from the heated water.

While experiments with high chemical concentrations of iodine / iodide might suggest that the distillation works, these would be misleading. This is because elemental iodine (diiodine) reacts with iodide to form a triiodine anion (I3-). This is why iodine is soluble in potassium iodide solution but not in water. When dealing with low chemical concentrations of iodine (but can still be high radioactivity levels) it is important to understand chemicals can behave in a different way at super low concentrations.

Effects such as absorption onto the surfaces of filters, plastic and glass tubes can make carrier free radioisotopes vanish from solution. Carrier free means that the only atoms of the element present in the sample are radioactive. In real life it is often impossible to get perfectly carrier free radioisotopes but in real life it is possible to get radioisotopes where the “chemical concentration” of the radioisotope is close to zero. A 1960s book held the view that many strong stock solutions of radioisotopes have such low concentrations of the radioactive elements that all chemical tests would suggest that the stock solution was pure water.

When a stable isotope of the radioactive element is added then it is known as adding a carrier, for example if tube of sea water was spiked with a drop of sodium-22, then the radioactive sea water sample would contain a carrier in the form of stable sodium-23.

In the same way if sea water was neutron irradiated to form sodium-24 then because the sea water contains plenty of unchanged sodium-23 it is still a solution which has a sodium carrier.

In general if a radioisotope is formed by the neutron activation of a stable isotope of the same element as the wanted radioisotope then the radioisotope will have a carrier unless a radiation induced reaction can be used to separate the neutron activated atom from the bulk. Many neutron capture reactions are ones where the nucleus swallows up the neutron and then dumps its excess energy by gamma emission. This is a n-gamma reaction.

For example Co-59 + n gives an excited state of Co-60 which will emit a gamma ray and become ground state Co-60

However if the nuclear reaction forming the radioisotope causes a change of atomic number then the radioisotope can be carrier free, For example

n + Mo-98 –> Mo-99 –> Tc-99m

The Tc-99m can be separated from the Mo to give pure Tc-99m

Also when a np reaction occurs then we have the chance to form a carrier free radioisotope.

For example 32S + n –> p + 32P

is a reaction which makes phosphorus-32, the phosphorus-32 then decays by a beta decay back into sulphur-32

Also when nuclear fission occurs it is sometimes possible to get a radioisotope which is close to carrier free, the thing is that for many elements the fission process forms isotopes which decay very quickly into stable isotopes of many elements, so the iodine from the damaged fuel will contain stable iodine-127 in addition to the radioactive iodines. But the ratio of the number of the radioactive atoms to stable atoms is better in radioactive atoms than stable iodine which has been bombarded with neutrons.

The radioactive iodine in the environment is not perfectly carrier free it may be close to carrier free. I would expect when the chemical iodine concentration is low (carrier free) then any iodide which is oxidized to form iodine will be more volatile than in a system where the iodide concentration is high.

Cresson Kearny’s book “Nuclear War Survival Skills” in chapter eight (http://www.oism.org/nwss/s73p919.htm) explains that distillation does not remove radioactive iodine from water. (http://www.oism.org/nwss/)


3 Responses

  1. Hey this is kinda of off topic but I was wanting to know
    if blogs use WYSIWYG editors or if you have to manually code with HTML.
    I’m starting a blog soon but have no coding expertise so I wanted
    to get guidance from someone with experience. Any help would be greatly appreciated!

  2. I am sure this piece of writing has touched all the internet viewers, its really really pleasant post on building up new website.

  3. This design is steller! You definitely know how to keep a reader amused.

    Between your wit and your videos, I was almost moved to start my own blog (well, almost…HaHa!) Excellent job.
    I really enjoyed what you had to say, and more than that, how you presented it.
    Too cool!

Go on, Have your say !

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: