Ionizing Radiation – Beginning with mining uranium

There are many different kinds of radiation: even sound waves are a form of very slow low energy radiation. Ionizing radiation is a particular class of its own; it has enough energy to break up molecules. It ionizes them, turning them into negatively and positively charged pieces of molecules (called ions).

There are several types of ionizing radiation: alpha radiation – slow-moving fat positively charged particles, beta radiation – faster moving negatively charged particles and gamma radiation – pulses of energy. X-radiation is very similar to gamma radiation but is machine-made. Neutron radiation occurs naturally only where there is uranium; only uranium spontaneously exudes neutrons.

No one disagrees that ionizing radiation is not good for living things. Breaking up molecules whether enzymes, structural proteins or genetic material requires repair - and biological repair may not always be accurate. There is a largely discredited belief that a little bit of ionizing radiation might be good for biological processes. This myth is largely propagated by supporters of the nuclear industry who seem continually to try to ease restrictions on industrial and environmental exposure. Most physicians believe in the precautionary principle; applied in this instance, less is best.

The largest proportion of an individual’s lifetime exposure, is from medical or clinical investigations. This exposure a person can, within some limits, control. Amounts of exposure to radiation from the sun, and that from flying at high altitudes is also largely under our personal control.

Background radiation is largely not under our control. Background radiation is around 3.1 mSv/yr on large areas of the Canadian Shield and in parts of the Rockies; the prairies are the lowest at around 2.1 mSv/yr. Winds from certain directions might bring higher levels of radiation. A location in India with a background radiation level of close to 5.0 mSv/yr has a definite increase in offspring with Down’s syndrome. There have been unusual anomalies documented in high numbers by physicians in the Ukraine near Chernobyl, amongst the Marshalleise Islanders, in the TRIANGLE in Kazackstan, and in the South of Iraq (exposed to excessive amounts of uranium-238). 

Uranium is really the start of the nuclear industrial chain since its unique properties made possible both the nuclear bomb and electricity from nuclear power. Its importance led to prospecting and mining, milling, transporting, refining, and enriching and thence to the end uses – bombs and nuclear power plants.

In nature, uranium appears as a black rock. The Dene people had traditions which told them to avoid the black rock. It is radioactive and contains traces of the entire uranium decay chain:

(Please note that the first bismuth in the chain should be bismuth-214 instead of bismuth-210)

 

Radioactive elements are continually giving off energy and as they release energy they change into another element. As this figure shows, uranium has at least fourteen decay steps between it and the stable, non-radioactive lead-208 at the end.

When uranium-238 decays to thorium-234, it gives off an alpha particle. The fat alpha particle can’t get through skin so for a long time it was not considered to be harmful. Inhaled or ingested, however, it is twenty times more destructive than any other radioactive emission.

Thorium-234, however, decays by beta particle emission. Whenever a beta particle is emitted, the atomic number goes up by one, illustrated by the positioning of the elements in the chain, and the atom becomes a new element. The new element in this decay step, protactinium-234, also decays by beta emission and becomes uranium-234.

The next series is the “alpha decay series” – the mass number going down by four with each decay step. Uranium-234 becomes thorium-230 with the release of an alpha particle and similarly, thorium-230 becomes radium-226.

Radium-226 is the first of the very energetically radioactive elements in the chain. It was discovered by Madame Curie in 1898. Because it was new and exciting and glowed in the dark, it was marketed as a cure-all and thousands of people drank radium water “for their health”. It was responsible for countless deaths because it is a bone-seeker, lodging in bones and causing cancers such as leukemias and osteosarcomas.

With a half-life of 1600 years, radium-226 becomes radon-222 which is a gas. In nature, the gas remains captured in rock for its short decay half life of three and a half days. In mine tailings, released from rock, it drifts into the atmosphere downwind as far as several thousand kilometers while it gradually becomes polonium-218 and settles onto plants and animals. Polonium is toxic to humans – like arsenic only much more so – an amount of polonium-210 no larger than the head of a pin killed the Russian spy, Litveninko.

Additionally, every decay step releases gamma radiation as well, lead-214 and bismuth-214 being the most biologically destructive.

Even prospecting can have an environmental impact. A group of people in Nova Scotia had their water supply affected when a driller went through their aquifer.  By mining uranium the surface radioactivity is affected forever. Where all of the elements in the uranium decay chain quietly went about their business of decaying in balanced synchronicity bound in granite, they are now a soup of radioactive elements that can be leached into water systems or even affect one another. They are no longer safely separated by inert granite.

Neutrons - "Obvious lack of Knowledge"

“Obvious lack of knowledge”, that is the criticism aimed by four retired nuclear physicists who have read my book. The basis for this claim has been (in all four cases) the characterization of a neutron as being “made up of a proton and an electron”.

Is a neutron “made up of a proton and an electron”?

Neutrons are large subatomic particles. Subatomic particles can be “fundamental” or “elementary” as we once thought atoms were or “composite”, being made up of other subatomic particles.

Neutrons are composite subatomic particles, made up of elementary particles, in this case quarks and gluons. Quarks are further characterized by “flavor” – up, down, strange, charm, bottom, and top. (I am not making this up!)

Both neutrons and protons have three quarks. This number cannot change. The neutron is made up of two down quarks and one up quark and is about 0.2% more massive than a proton. Neutrons decay with an average half life of 10.3 minutes. “Decay” in neutron terms involves one of the down quarks converting to an up quark; two up quarks and one down quark makes a proton. The difference in mass is given off as an electron plus an electron antineutrino.

Neutrinos and antineutrinos were completely omitted from From Hiroshima to Fukushima to You because they have no electrical charge and apparently don’t affect living tissue. They do account for the tiny bit of energy left over when the proton and electron are formed at the decay of a neutron.

So in summary: In relatively quick succession, the average lifetime of a neutron being 10.3 minutes, the down quark becomes an up quark and the neutron becomes a proton, now making up the greater part of the original mass. With the formation of a proton, the electron plus energy is released.

Is a neutron “made up of a proton and an electron”? Technically no but that’s what we get when neutrons decay. Shucks, I should have said "effectively made up of a proton and an electron".

There is also a tendency among the retired physicists to get their shirts in knots over calling neutrons “glue that holds a nucleus together”.

(One physicist whose real issue is about nuclear power used this to harass a professor using my book as text to indicate that I know nothing about which I speak.)

Let me quote Dr. Ken Mellendorf from Illinois Central College:  “Neutrons hold the nucleus together.”  His explanation is slightly different than mine.

Protons are positively charge and normally would repel one another. At the close range of a nucleus, something called the “Strong Force” takes over – it is more powerful than the existing electrical repulsion. However, except at “absolute zero”, protons still have a tendency to be a bit uneasy and move around. They need extra holding force.

Neutrons have no electrical charge and are similarly affected by the Strong Force so they are attracted to both the protons and other neutrons. As nuclei become larger for larger atoms, more and more neutrons are required to create the force to hold the collection of protons and neutrons together.

Sounds like “glue” to me!

Being Responsible: The Sign at the End of My Lane

A sign at the end of my lane reads “No Nuclear Waste Dump Anywhere”. Since the sign was on my deck for the summer, I know what questions people ask. 

FYI background information: Nuclear waste is made up of radioactive elements. Radioactive elements decay and as they “decay” they give off both radioactive particles and energy as they become a different element. For example: radium changes into radon gas when it decays. The release of the particles (or energy) can affect cells. Special radioactive elements are used in controlled circumstances to treat cancer because it kills cells that are rapidly dividing preferentially to normal cells. However, it also kills normal cells and can cause cancer, inheritable defects and developmental abnormalities.

The Nuclear Waste Management Organization (NWMO) proposes a Deep Geological Repository (DGR) which they claim to have the ability to monitor for a century - at which time they abandon it, so, in fact, NWMO is proposing a Deep Underground Dump (DUD). 

The questions: 

First: “Why not put the waste back in the ground where it came from?” Some time ago, that would have been my question too.

Bad idea.

First: it is not the same kind of thing. The waste is hundreds of times more radioactive than the ore that was taken out of Saskatchewan. It contains some 200 or more brand new radioactive elements, some more lethal than others. While computer models predict how each element will decay (and each decay chain is known), no one really knows how the combinations will chemically or physically inter-react as they change through time. At the one existing North American underground dump, the WIPP facility in Carlsbad, intended to last “thousands of years”, no one still knows why radioactivity was released because they cannot get close enough to examine it.

Second: Packaging the stuff doesn’t work. Radiation changes things over time – the iron and/or copper that makes up the containers is constantly barraged by nuclear particles that change the elements. If an iron atom is changed into an atom of a gas, salt or even different kind of metal, the container gradually “rots”. In fact, this is reason nuclear power plants “wear out” and need “refurbishment”. 

Third: The Cost. Federal government has already spent more than $700 million on the six year long Seaborn Panel that recommended against a Deep Geological Repository. The Nuclear Waste Management Organization (NWMO) has spent millions and plans to spend millions more. And then there is the cost of building the dump site, creating the containers and shipping them across Canada – there exists already enough waste that it will take trucks driving continually a couple of hours apart for a couple of decades to get the current waste to Saskatchewan – is practically unfathomable. Virtually all of these eventually billions of dollars will come out of the public purse. Creighton is still under consideration for a DUD.

Second question: "What do you propose? Saskatchewan may as well make money from the waste?"

The Candian Coalition for Nuclear Responsibility and the US Environmental Protection Agency propose that the stuff remain in the containers in which it is currently stored where it can be monitored – after the six to ten years that it spends under water until it is “cool” enough to be stored. The containers regularly assessed and breaches repaired early. The waste would be readily accessible if a technology were developed that sustainably recycled them.

The EPA called it “Rolling Stewardship”. The beauty of the plan would be that when the nuclear power plants are decommissioned, they can virtually be decommissioned on the spot! There would be jobs into the future as far as humans exist. 

We’ve created the waste, for our children and our children's children, we need to manage it responsibly. 

Typos, Errors and Clarifications (Updated Version)

We opened ourselves to receiving comments on the book, From Hiroshima to Fukushima to You, and did we ever receive them! From physicists, mechanical and nuclear engineers to doctors and lay people, most of the letters have been complementary. Unfortunately, a few errors or misunderstandings have occurred.

Typos: 

Page 26: Bismuth-208 should be bismuth-209.

Page 31: Astatine-219 should be astatine-218. Its half-life is actually about

                        1.5 seconds.

 Page 32: Figure 2.4 the first mentioned bismuth-210 should be

bismuth-214.

Page 86 & 90:  Plutonium-249 should be Plutonium 239.

Page 89: “Moderate” should be used instead of “modulate” and a

            “modulator” should be a “moderator”.

Page 177: Heavy water is deuterium oxide, not deuterium dioxide.

Downright Errors:

Page 30: The text erroneously says that neutrons don’t occur naturally – of course they do. Uranium-235 releases neutrons when it fissions.

Page 85: Figure 6.2 shows one U-235 fission producing three U-235 fissions and then possibly six U-235 fissions. This would not be a “controlled nuclear reaction”. Each generation should have the same number of fissions.

There are a number of areas where our readers and we differ on some of our interpretations of “how things work”.  We have enjoyed the discussions and look forward to more feedback.

Clarifications:

Page 2 and page 31:  We refer to “cosmic rays” and “gamma rays”. There is reason to be confused about the exact nature of the ionizing radiation reaching the surface of the earth from outside the atmosphere; see the Canadian Nuclear Safety Commission backgrounder at http://www.nuclearsafety.gc.ca/eng/resources/fact-sheets/natural-background-radiation.cfm 

Page 25: The damage to organic material when a neutron decays is done by the resulting proton and electron but technically, a neutron is not “made up of a proton and an electron”.

Both neutrons and protons are composed of quarks – a neutron is composed of two “down quarks” and one “up quark”. (http://www.youtube.com/watch?v=_nky2XQGQ3k) The decay of 10.3 minutes actually involves the transformation of one of the “down quarks” into an “up quark” turning the bulk of the neutron into a proton. The rest of the decay involves the emission of an electron and an antineutrino. (See http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html)  We chose not to introduce new subatomic particles to the reader; a neutron’s damage results from its ability to penetrate and from the resulting proton and the electron. 

Page 29: Several readers have pointed out to us that in Figure 2.3 “If the plastic or wood is thin enough, it won’t stop beta particles.” Correct. In fact, beta particles have a wide range of energies (however specific for specific radioisotopes) and the thickness required to stop them varies with their individual energies. Wood could be as thin as a centimeter and as thick as 31 cm (1 foot) or more!

Page 31: Astatine was not shown in the decay chain but mentioned in the text: It was omitted from figure 2.4 for simplicity. Polonium-218 decays to lead-214 and also to astatine-218. Astatine-218 decays two different ways: by alpha emission to bismuth-214 and by beta emission to radon-218 (which then decays to polonium-214 by alpha emission).

We continue to welcome your input.