This will be my last post on this matter.

Lotus, there are a lot of things said about nuclear power, radiation, etc, etc which is deliberately intended to scare and which has not scientific basis.

Certain types of Uranium has a half life of about 4.5 billion years - which means that when the earth formed, there was twice as much radiation just from Uranium as there is today. Yet with all the radioactive elements, at higher levels of radioactivity, life still somehow managed to survive. Funny eh?

Yet when man decides to dig it up, it suddenly becomes this deadly hot potato. We have been using refined Uranium for years, yellow cake. Take a look at the picture I attached. That is two guys, and a barrel full of Uranium. Amazed how they aren't dead?

Sparky

Is there any difference between naturally occurring radiation and the radiation from fukushima either from the melted cores or the used rods?

 

None at all, just like there is no difference between naturally occurring electricity- e.g. lightening, electric eels - and the electricity in your house.

 

Yes, there is a difference between naturally occurring radiation and artificial radiation.
What you really want to ask is "what are the effects of different types of radiation on living organisms, humans in particular?"

Naturally occurring radiation is what is known as background radiation, i.e. radioactivity emitted by typical surroundings.

Firstly, The effects of radiation will depend on the energy of the emitted radiation.
Different radioactive elements emit radiation of different kinds and different energies. The higher the energy, the greater the probability for DNA damage.

Secondly, the effects of the radioactivity will depend on the half-life of the radioisotope. A radioisotope with a long half-life has a lower probability of decay and thus exhibit lower activity.

Thirdly, the effects on the human body will depend on the type of exposure, external, internal, ingestion, absorption and body retention. Iodine-131 is particularly nasty because it is easily absorbed and accumulated in the thyroid gland.

Because of its short half-life (8 days), I-131 does not exist in the natural environment. Hence one does not get exposure to I-131 from natural radiation.

 

Radioactivity can last from any length of time from less than a second to millions of years depending on the specific radioisotope. The decay time is measured by a quantity known as the half-life, the length of time it takes for the radioactivity to decay to one half of its level from the time measurement begins.

Radioisotopes with short half-lives are as much a concern as longer half-lives since they will be emitting higher levels of radiation in the short term, i.e. the atoms are giving off their radioactivity at faster rates.

In the case of the Fukushima nuclear disaster, here are some examples of radioisotope half-lives of concern:

Iodine-131 half-life = 8 days
Strontium-90 half-life = 28 years
Cesium-137 half-life = 30 years
Plutonium-239 half-life = 24,000 years

http://en.wikipedia.org/wiki/Radiation_effects_from_the_Fukushima_Daiichi_nuclear_disaster

you have mentioned iodine as being a nasty one as it has a short half live. In the case of the the pollution getting into the food chain through the water pollution and being ingested how good/bad are
Strontium-90
Cesium-137
Plutonium-239

 

Is there any difference between naturally occurring radiation and the radiation from fukushima either from the melted cores or the used rods?

Depends on what you mean by "difference".

The radiation from a given radioisotope is identical whether that radioisotope is produced naturally or artificially.

The radiation from different radioisotopes is, in general, different. Not only might the two give off different types of radiation (alpha, beta, gamma, positron, neutron, ...) but the energy is also generally different.

Furthermore, even if you had two radioisotopes that decayed by emitting the same type of radiation at virtually the same energy, the daughter products would be different and hence the chain of radiation that you end up with will generally be very different.

In addition, a given radioisotope is also a chemical element and interacts chemically with its surroundings -- and that is true of its daughters as well. So not only is there the issue of the radiation, but also of the chemical toxicity.

 

When you say uranium ore is a crust product - does that mean it is some how created in the crust rather than already being part of the earth when it was still in a molten state?

From my understanding the earth's crust is similar to the slag crusts that form on top of a molten metal crucible. It is the lighter non-metal elements that must float to the top when the mass below is molten metals.

So the lightweight ores that consist mainly of non-metals are a crust phenomenon and would not exist deep at the earth's "iron core". But like I said that's just my understanding.

 

you have mentioned iodine as being a nasty one as it has a short half live. In the case of the the pollution getting into the food chain through the water pollution and being ingested how good/bad are
Strontium-90
Cesium-137
Plutonium-239

Strontium is in the same group of elements as calcium and so can replace calcium in your bones. Once there it cannot easily be removed and will emit radiation into the surrounding tissue.

Cesium is perhaps the least concerning.

Plutonium is toxic and accumulates in bone marrow however people exposed to low levels have been followed over many years and have remained healthy.

 

excuse my for being very basic about this. I am just getting my head around radioisotopes.
In naturally occurring elements such as uranium - are they just much more stable or have less radioisotopes and so being ok to be around them - for instances like the yellow cake sparky49 mentioned.
and compared to this the used uranium rods are very unstable and have a much higher % of radioisotopes so the level of radio activity is higher and are far more dangerous?
Or is there a bit more to it than this.

 

Yes, that's pretty much it. Centrifuges are used to separate the isotopes by mass and hence "enrich" the uranium.

 

Yes, that's pretty much it. Centrifuges are used to separate the isotopes by mass and hence "enrich" the uranium.

is it still safe to be around enriched uranium and only when it gets activated in some way that the % of radioisotopes go up?
or in the enrichment process does the uranium automatically become more unstable or more radio active?

 

I have been to visit a nuclear fuel reprocessing plant and was given an enriched fuel pellet to hold - the only protection was a transparent plastic case.

Enrichment separates the isotopes so enriched fuel is more radioactive. But there are a few things to consider - quantity, time and can it get inside your body. The amount of radiation given off for a particular isotope is related to the amount of material you have (more material = more radiation) and the length of time you are exposed (longer = more radiation).

There are three types of radiation, alpha, beta and gamma. Alpha is slow and heavy - it will cause a lot of cell damage but is easily blocked by thin protection, beta is faster and lighter, gamma is like x-rays it is very fast and very light so it can go through a lot of material but has a smaller chance of interacting with molecules as it passes. The radiation is given off randomly, i.e. at random times but the more you have or the longer you are exposed the more radiation will hit you.

But the real problems start with things getting inside your body (or under eyelids etc.) and particularly elements such as Iodine and Strontium which are retained in your body. Because they are retained inside you they have a longer time period in which to emit radiation and so cause more damage.

I guess it's a bit like going out in the rain. Go out in light rain for a few minutes and you won't get very wet. Go out in light rain for a long time, or heavy rain for a short time and you will get wetter.

 

is it still safe to be around enriched uranium and only when it gets activated in some way that the % of radioisotopes go up?
or in the enrichment process does the uranium automatically become more unstable or more radio active?

The half-life of U-238 is 4.5 billion years and that of U-235 (the enriched kind) is 700 million years. This means that the probability of decay is very low in both cases and therefore they both exhibit very low activity.

U-235 has to be bombarded with neutrons first for it to fission and then produce more neutrons. This then triggers a neutron chain reaction.

 

Here is something to note about natural radiation. Humans are constantly receiving radiation from within our own bodies.

To put things in perspective, an adult human being receives about 4000 decays per second from natural potassium-40 in the body. 90% of the decays are beta particles and 10% are 1.46 MeV gamma rays. The latter tend to escape from the body leaving no energy or only partial energy.

 

Thank you for all this amazing information.
Trying to quantify this in relation ship to power stations is there a ready measurement in relationship to mass and time.
for instance radiation per gram per second -
1 gram of uranium in a live reactor gives this much radiation in 1 second
1 gram of a used uranium rod gives this much radiation in 1 second
1 gram of natural uranium gives this much radiation in 1 second
or do we just go by the half life as it is always in flux?

 

What you are asking for is called specific activity.

You can calculate the specific activity of any radioisotope if you know the half-life and the atomic weight.

For example, U-238 has a half-life of 4.5 billion years and an atomic weight of 238.

The specific activity = 1.32 x 10^16 /(half-life x atomic weight) [Bq/g]

= 1.32 x 10^16 /(4.5 x 10^9 x 238) = 12300 Bq/g

 

That's great, thank you for this.
I am unsure how to calculate the specific activity for uranium in a reactor or for used uranium rods as the whole process has been accelerated?

 

Here is something to note about natural radiation. Humans are constantly receiving radiation from within our own bodies.

To put things in perspective, an adult human being receives about 4000 decays per second from natural potassium-40 in the body. 90% of the decays are beta particles and 10% are 1.46 MeV gamma rays. The latter tend to escape from the body leaving no energy or only partial energy.

I've been on Potassium pills for 15+ years now.

But, too much will kill a guy.

 

That's great, thank you for this.
I am unsure how to calculate the specific activity for uranium in a reactor or for used uranium rods as the whole process has been accelerated?

The radioactivity of uranium in a reactor is different from naturally occurring uranium.

Naturally occurring uranium consists of mainly U-238 that decays to radium and radon. See Radium series.

The fission products from a nuclear reactor are very different.

 

The radioactivity of uranium in a reactor is different from naturally occurring uranium.

Naturally occurring uranium consists of mainly U-238 that decays to radium and radon. See Radium series.

The fission products from a nuclear reactor are very different.

I think something might have gotten left out along the way (or maybe not, but I don't recall seeing it).

When a hunk of uranium is sitting on the table and we say that it has a half life of 4.5 billion years for U-238 or 700 million years for U-235. That is the half life not for spontaneous nuclear fission, but for spontaneous nuclear decay of any type. The probability that a given decay event will be a fission event (as opposed to an alpha, beta, gamma, positron, K-capture, etc) is an altogether different matter. In U235, only about 2 in one billion (10^9) decay events are due to fission, while in U238 it is over 500 per billion. So even though U238 is less radioactive than U235, it actually undergoes spontaneous fission at a rate that is nearly 50 times greater. It is this higher fission rate that makes U238 a problem for gun-type nuclear weapons as the probability of a spontaneous fission even occurring during the roughly 1ms long critical insertion window is unacceptably high.

The main point, however, is that "natural" radioactive decay is overwhelmingly dominated by non-fission decays while "artificial" radioactive decay is overwhelmingly by fission decays. But fission decays are completely natural (both spontaneous and neutron-induced), they just happen at a very low rate. In a reactor, we simply create an environment that results in neutron-induced fission events occurring at a much higher rate.

As MrChips says, the daughter products are very different, but that is not because one is natural and the other is artificial. It is because the daughter products are a direct result of the type of decay a particular isotope undergoes.


The "difference", as I understand it, it the difference between spontaneous fission and induced fission due to neutron bombardment. But neutron-induced fission happens in nature, too. Just not very often. In a reactor, we simply create the situation for this to happen a lot -- a whole lot.

 

From all of the comments I am coming to understand that there is natural radio activity around us and being created in us all of the time. which to me, we have evolved with, and our bodies interact with, as part of the whole eco system.
Then we have artificially generated radiation, generated by fission and I was trying to find the differences between the two.
To me the main difference seemed to be the depth of intensity of the radiation being created by artificially produced fission.
And I wanted to some how quantify that difference. that is why I was looking for a measurement to compare levels of natural radiation from uranium to that being created by fission with in a power station or emanating from used uranium rods.

I am not really at a point where I can come to any conclusions.
But at the moment my feeling is that we are used to radio activity at a certain back ground level and that that actually aids us in ways that science may know about but also in ways science may not know about. And that when we come in contact with radiation, and radio active particles in ways and levels of intensity that we have not evolved with, then the body has no history of this or ways to deal with it.