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EducationWhat form of radiation from uraninite?

23rd Sep 2018 15:14 UTCEd Clopton 🌟 Expert

Is there a simple answer to the question of what type(s) of radiation (alpha, beta, gamma, other) radioactive minerals such as uraninite emit? I definitely am NOT hyper-paranoid about having the odd radioactive mineral in my collection--I just want to be able to answer in case someone asks.

23rd Sep 2018 15:29 UTCReiner Mielke Expert

All three and the amount depends on how old it is. Recently formed uranium minerals are less radioactive than billion year old ones (assuming U and Th content is equal).

23rd Sep 2018 18:15 UTCTravis Olds Expert

Reiner is absolutely correct. Age, as well as some other geologic factors, like oxidation+alteration, can change the relative amounts of alpha/beta/gamma emitters in your uraninite. But uraninite is also very dense and so is somewhat more self absorbing than a less dense uranyl-hydrate mineral.

Antony Glauser has prepared a really nice calculation for the surface beta dose from uraninite:

https://www.mindat.org/article.php/918/Estimating+the+beta+radiation+dose+rate+from+uranium+minerals

23rd Sep 2018 19:08 UTCDavid Von Bargen Manager

You get either an alpha particle or a beta particle in radioactive decay, but you don't decay from uranium to lead in one step. There are a number of intermediate products with different half lives.

https://en.wikipedia.org/wiki/Decay_chain

23rd Sep 2018 19:17 UTCŁukasz Kruszewski Expert

Mainly alpha, wtih some beta and tiny amount of gamma.

24th Sep 2018 01:38 UTCDoug Daniels

Agree with all others, you get all three. However, depending on how you measure the radiation (distance, things in between the specimen [a far example - uraninite in the ground]) will dictate what you measure. Even when buried in the ground, you'll get a good bit of gamma (the other two will be largely attenuated); unless you have a spectral meter, you won't know whether the gamma is from uranium, thorium, or potassium (or something even more oddball).

3rd Oct 2018 20:53 UTCRonald J. Pellar Expert

There is actually more than three types of radiation from some of the daughter elements. Neutrons from spontaneous fission, and of course neutrinos. However these are in very small numbers and not a problem.

4th Oct 2018 10:13 UTCAlysson Rowan Expert

Here is just about everything you want/need to know about radioactive minerals:

https://drive.google.com/open?id=1ROFLQVpRSzT4Oym77h2FtE77OwNtF2W0

or:

https://www.academia.edu/31501150/Here_be_Dragons_The_Care_and_Feeding_of_Radioactive_Mineral_Species_Feb_2017_

and

https://www.academia.edu/31507928/Here_be_Dragons_The_Care_and_Feeding_of_Radioactive_Mineral_Species_-_Mineral_Data_Feb_2017_

You may also find this useful:

https://www.academia.edu/36969379/Undoing_the_demonisation_of_radioactive_minerals

Alysson

4th Oct 2018 14:12 UTCEd Clopton 🌟 Expert

Thanks for the reference to Here Be Dragons! It contains a lot of useful info in an accessible form and should be widely circulated. I will be mentioning it and linking to it in our club's newsletter in the near future.

5th Oct 2018 18:27 UTCMartin Jára 🌟

A convenient way is to take a look if you have a pixel detector at hand. Here is for example my uraninite from Joachimsthal showing a little prevalence of beta in term of particle count.

Or at least of something that was classified as beta (the counter plugin is not very smart yet as it is intended for educative purposes only).

6th Oct 2018 10:32 UTCAlysson Rowan Expert

Martin Jara Wrote:

-------------------------------------------------------

> A convenient way is to take a look if you have a

> pixel detector at hand. Here is for example my

> uraninite from Joachimsthal showing a little

> prevalence of beta in term of particle count.

> Or at least of something that was classified as

> beta (the counter plugin is not very smart yet as

> it is intended for educative purposes only).

>

Now that is a nice piece of software. Is there a link for it?

I would imagine that the majority of the alpha is ²³⁸U and ²¹⁰Po (which is an incredibly energetic alpha emission).

Beta and gamma radiations from small samples of uranium minerals (i.e. not too thick) will usually be similar since, as a general rule, a beta emission is always accompanied by a gamma emission. Beyond that generalisation, things start to get complicated. For large specimens, the gamma rate will outstrip the beta.

For massive specimens, neutrons from spontaneous fission may be detected (maybe 2 or 3 neutrons per second - which is waaaaay above background in most places) - but that requires specialist instrumentation.

@ Ed.

Thanks. Here be Dragons has been around for a few years now, though I have had to move it a couple of times :(

The whole text is overdue a complete revision, but the supplement (radioactive minerals' computed activity & dose-rate tables) is revised occasionally (i.e. when I think it's due).

6th Oct 2018 10:38 UTCAlysson Rowan Expert

Ronald J. Pellar Wrote:

-------------------------------------------------------

> There is actually more than three types of

> radiation from some of the daughter elements.

> Neutrons from spontaneous fission, and of course

> neutrinos. However these are in very small numbers

> and not a problem.

True, though (and for academic interest only):

Almost every beta emission is accompanied by a gamma photon and the betas are invariably accompanied by an anti-neutrino travelling in the opposite direction to the beta.

Good luck to anybody trying to detect anti-neutrinos - they are relatavistic and tend to ignore the presence of matter altogether.

6th Oct 2018 19:22 UTCRonald J. Pellar Expert

True! Neutrinos and anti-neutrinos are nothing to worry about. Trillions of them pass through our bodies ever minute. However, neutrons from spontaneous fission can be worrisome as they can generate secondary radiation at the site of absorption by means of a neutron activation process. Fortunately, spontaneous fission is a rare event. The neutrons can be detected with an appropriate sensor.

6th Oct 2018 19:43 UTCAlysson Rowan Expert

A BF₃ detector close to a typical collection of uranium mineral specimens would probably pick up one to two neutrons per hour (if you were lucky).

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