Straight Talk On Radiation

To counter misinformation and confusion, radiation and radioisotopes are explained in a simple, straightforward, and accurate manner.

By Dr. J.H. Wakefield

From time-to-time I write on topics that are related to water and wastewater as a "backgrounder" so that those involved in the field can gain a wider perspective and have available to them a cogent explanation minus jargon on various topics. It is becoming readily apparent to those of us who have been intimately involved with the nuclear industry/radioactivity in one form or another over the years that water and wastewater professionals will encounter this increasingly in the performance of their duties now and in the future.

This is encountered as a result of nuclear accidents that have widespread and dire consequences (Chernobyl, Fukushima-Daiichi, the Waste Isolation Pilot Plant [WIPP] in New Mexico, the Three Mile Island nuclear facility, and various military installations including Hanford and Los Alamos among many other lesser-known occurrences) as well as "coming to grips" with previously unconsidered side issues from various industrial processes including mining, fracking, and fluoridation with radioisotopic contaminants.

Although many have heard of radiation dangers, some of these radioisotopes will become household words and concerns in the years to come: to wit, strontium (Sr⁹⁰), cesium (Cs¹³⁷), and naturally occurring radioactive elements such as thorium, polonium, radium, and radon. Most everyone has heard of the really bad boy, plutonium (Pu²³⁹), but there are several others out there waiting to be discovered by the public.

I've been noticing a whole slew of bogus information being put out in the media regarding radiation, the effects of radiation, and nuclear chemistry in general. So, with that as a motivator, I shall attempt to clarify, simplify, and correct what is essentially a straightforward subject. Too much of science is made a mystery by using technical jargon and abstruse and involved arguments that makes an actual understanding of what is transpiring more difficult. Let us now begin to examine this topic more closely and simply.

Understanding Atoms: Who’s In Charge?

I am sure that you all have heard the expression “nature abhors a vacuum.” Nature also isn't fond of stable structures that are not electrically neutral overall. If, by chance or design, such structures occur, they attract unlike charges so that the entire structure remains electrically neutral; otherwise the structure would be unstable. This means that unlike charges attract and like charges repel. Normally we use designations that are essentially arbitrary in that they exist as a pair. That is, positive charges and negative charges balance each other. For every positive there is a negative. By definition, positive is not negative, negative is not positive, they both exist as integral wholes, and the + and – signs that designate them are merely conventions that we choose in order to describe various natural phenomena.

Well, what does all this have to do with radiation and radioisotopes? It is the means by which we arrive at an understanding of the underlying order that governs atomic interactions. After all, radiation and radioisotopes are essentially phenomena of atomic systems, nuclear chemical systems, to be more precise. Now, let us delve into the basics of such systems.

All ordinary matter is composed of basic building blocks called atoms; these in turn are composed of atomic particles of a bewildering array. Only three of these are of import to anyone other than the frustrated nuclear scientists. They are protons, electrons, and neutrons. Protons are found in the nucleus and have an atomic mass of 1 and a positive charge (+ 1). Neutrons are also found in the nucleus and have an atomic mass of 1 and no charge (or a neutral charge, hence the name neutron). Electrons are found orbiting the nucleus in various paths, have a mass 1/1820^th of a proton, and a negative charge of 1 (-1). Although their masses are dissimilar, the charges on an electron and a proton are the same for a net effect of a zero charge on the atom. So, in an atom, each proton has a corresponding electron with an opposite charge orbiting the nucleus.

All chemical properties are caused by the loss or gain of electrons so that an atom has a charge (a process called ionization). Those elements that gain electrons are called non-metals, those that lose electrons are called metals, and those that may either gain or lose electrons, depending on the circumstance, are known as amphoteric. Many metals can exhibit amphoteric properties such as aluminum and zinc among others. Non-metals also may be amphoteric. Boron and carbon can be so considered, for example.

It is useful to note that as metal atoms get larger, they are more active. This is easily remembered since their electrons are farther from the nucleus than are lighter elements, and the nucleus has diminished “pull” on them as they get farther away; conversely, non-metals are more active as they get smaller. In this case, the nucleus has an increased “pull” as the atomic radius brings them closer to the oppositely charged nucleus. There are a group of elements known as the inert gases that do not form chemical compounds under ordinary conditions as their electron configurations are inherently stable with respect to their nuclei.

The nucleus/electron relationships determine the chemical reactivity of an atom (hence, an element). Just as a balance exists (more or less) between the nucleus and the orbiting electron cloud, the nucleus itself is also able to reach a state where it is inherently unstable. Remember that the nucleus consists of positively charged protons and neutrally charged neutrons. Also remember that like charges repel. So, how does a nucleus keep from flying apart by repulsion of the like charges? For that matter, how does the electron cloud also keep from flying apart with all the negatively charged electrons repelling each other?

The answer to this is abstract, complex, and changes with the times as we discover deeper levels of understanding and the mathematics to model the damn thing. So, if you're looking for definitive answers to the above questions, read no further and take up particle physics. If you are as bewildered as I am by all this, continue reading and hear me out as I attempt to make sense of it all.

Radionuclides

Regarding the stability of atomic nuclei, there are numbers of protons and neutrons that are inherently stable depending on the atom. There are also those that have too many or too few neutrons and become unstable. These nuclei of any particular element's atoms ALWAYS have the same number of protons; it is the number of neutrons that vary. Atomic nuclei of any atom that have differing numbers of neutrons are known as isotopes. If these isotopes have an unstable nuclear configuration, they are radioactive and are known as radionuclides. So, we now know what radioactive elements are on the atomic level. Now, let us examine them closer and determine what we really need to know to understand what's going on.

As we stated before, radioactive atoms (isotopes) are inherently unstable so that they are in a constant state of “decaying” to another element and giving off energy in the process. This usually involves the decay of a neutron. This spontaneous disintegration is orderly, and the end products are always other atoms; some of them may eventually be stable (not radioactive) while others may still be radioactive unless and until they are wholly transformed (transmuted) into non-radioactive elements. The amount of time before 50 percent of the isotope is changed (transmuted or decayed) is known as the half-life.

All atoms have a particular “shorthand” symbol in which they are presented.

Let us examine the simplest atom, that of the element HYDROGEN. There are three isotopes of hydrogen: ₁H¹ ; ₁H² ; ₁H³. Note that the first number is a 1. This is the Atomic Number (Z), which happens to be number of protons in the nucleus. All hydrogen isotopes have the same number of protons, but the neutron number is different and is reflected by the following superscript number. Normally it is a single proton in the large majority of hydrogen atoms; there are a small number of hydrogen atoms with one neutron (naturally occurring) and called deuterium. The third isotope of hydrogen is synthetic, unstable, and is known as tritium. It has two neutrons. Unlike the other hydrogen isotopes, tritium is radioactive with a half-life of 12.26 years. A rule of thumb is that a radionuclide has to undergo 10 half-lives before it effectively disappears. This makes tritium present in ever diminishing amounts for 122.6 years. By the way, tritium is a β^- emitter.

As these radionuclides decay, they have several modes of doing so:

• α (alpha with the emission of a Helium nucleus)
• β^- (beta with the emission of an electron)
• β⁺ (beta with the emission of a positron [antimatter electron])
• EC (orbital electron emission)
• IT (isomeric transition from a higher to a lower state)
• n (neutron)
• SF (spontaneous fission)

Of the aforementioned, only alpha, beta, and neutron particulate emissions are of interest with respect to radiation. Of course, gamma rays are too, but they are energy only — not particles. Whatever the decay mode of an atom is, the radiation can have adverse affects on living things, and the ingestion of radioactive particulates magnify these affects greatly. Gamma ray emitters and high-energy beta emitters can be dangerous without being inhaled and neutrons are always dangerous, but the most serious radiation risks comes from particulate inhalation, particularly those emitting alpha particles.

Danger Zone

At this point, we will digress into what makes for a dangerous radiation hazard from a particular isotope. There are several points that, taken as a whole, determine the hazard of a particular isotope. The first is the actual nature of the radiation emitted (alpha, beta, or gamma); the second is the energy of the waves/particles emitted; or, perhaps it's the other way around with the energy output via wave/particle actually the more important.

Now, let us consider what manner of protection may be required from any emitted radiation. One may block (or shield) the radiation; and, this blocking or shielding depends on the energy transmitted by the isotope and the type of energy transmission. We normally shield gamma and beta radiation, but are unconcerned with alpha shielding. In alpha radiation, containment is all important as a sheet of paper or the skin is sufficient to shield one from its affects. Gamma rays are the most penetrating, and heavy shielding such as lead, is required depending on the amount and energy levels of the gamma rays emitted. Gamma rays are actually high-energy X-rays; or rather X-rays are lower energy gamma rays. In either case lead, and sometimes lots of it, and distance provide the best shielding. Beta rays are easier to shield, but they require metal plates (as a minimum) to protect from the radiation; they are actually waves/particles (electrons) known as wavicles. An interesting point to note is that beta radiation may require a minimal degree of containment, especially if it is used in quantitative analysis. Containment is required if, and only if, the parent isotopes exhibits movement. Because gamma rays have no mass, and electrons have very little mass, the parent isotope does not exhibit movement; therefore, little or no containment is required. On the other hand, alpha emitters need containment primarily as opposed to shielding, but many of them require both. Containment is required because an isotope emitting alpha particles (which are actually helium nuclei) is emitting a particle with significant mass. This, naturally, results in a “recoil” (remember for each action there is a separate and opposite reaction), and the end result of all this is that the alpha-emitting isotope moves randomly to contain whatever space it is in. Naturally, the smaller the space, the less the problem is. So, for that reason, it is absolutely essential to confine its potential for movement. Another point worth remembering is that alpha particles are highly charged (+2) because they contain two protons and two neutrons. Their mass is therefore 4. This fact gives rise to all kind of deleterious effects should any of these alpha-emitters get inside the body. And, as an extra-added attraction, they are weak with respect to ionization potential of dry air, unlike the gamma and some beta emitters, and are therefore not detectable with Geiger counters.

Another aspect of danger from these radionuclides is their propensity to gain entrance into the body via inhalation or other modes such as entering a cut/abrasion or anywhere the integument is compromised or by being taken in with contaminated food. Once inside the body, they are really a major problem. This is actually more of a problem with alpha emitters (because of their high delivered energy within the body where they are essentially unshielded) and some of the medium energy beta emitters. Gamma emitters, on the other hand, do not require entrance into the body to cause their deleterious effects nor do high-energy beta sources.

All of these dangerous risks are interrelated in the case of chemical activity and targeted locations within the body. Some isotopes, though easily shielded, target body locations which make them particularly hazardous. Included is the poster bad boy strontium-90 (Sr⁹⁰), the equally dangerous isotopes of cesium-134 (Cs¹³⁴)and cesium-137 (Cs¹³⁷), our ol' pal iodine-131 (I¹³¹), and the baddest of the bad boys, plutonium-239 (Pu²³⁹). There are also a whole slew of them produced by the military/industrial complex and the nuclear power industry that also give rise to major problems at different times.

One way to understand this danger of a particular isotope is to see how other members of its chemical “family” that are not radioactive are structured in the body. For example, strontium is closely related to calcium but more active. Therefore, strontium tends to replace calcium. This is a very bad thing when the strontium is strontium-90 (Sr⁹⁰) and replaces the calcium in the bones. This gives rise to bone cancers and to leukemia as that is where blood cells are generated in the body. Being irradiated by beta particles is not a good thing. Cesium is in the same family as potassium and is even more active. Replacement of potassium by cesium in the muscles and in nerves is most assuredly not a good thing with either of the radioactive cesium isotopes, cesium-134 (Cs¹³⁴) or cesium-137 (Cs¹³⁷). Iodine, on the other hand, is concentrated in the thyroid gland/tissue and is a natural uptake point for the radioactive isotope iodine-131 (I¹³¹). Plutonium is a highly-active metal, forms a variety of different compounds, and is taken up all over the body.

Misinformation

So, as a general rule, particulate contamination is far more dangerous than is atmospheric exposure. Unfortunately, our powers-that-be (PTB) are providing us with a lot of useless, and frequently incorrect, information. The danger of ANY radioisotope is its gaining entrance INTO our body. Once in, unless we can somehow get it out, there it will remain wreaking havoc of various sorts. IT DOESN'T TAKE MUCH. Talking about acceptable levels of radioisotopes in the air is nonsensical. THERE ARE NO SAFE LEVELS OF RADIATION WITHIN THE BODY. Accepting a level in the air is idiotic. What that does is basically throw the dice with your life. You may encounter it, and depending on the isotope, it may gain entrance into your body in a very minute amount. A millionth of a gram of plutonium WILL cause cancer somewhere in your body.

With respect to particulates, how aerosols of these are formed (smoke, by the way, is an aerosol of solid particulates) and how chemically reactive these are, are of overriding importance. Some isotopes form aerosols readily. Several good examples are iodine-131 (I¹³¹), cesium-134 (Cs¹³⁴) and 137(Cs¹³⁷), and strontium-90 (Sr⁹⁰). These aerosols have the propensity for smaller particles which are transported much further from the source (Fukushima, for example). Some are also highly soluble so that they can be present in rain or snow. Iodine-131 (I¹³¹) is a classic one of these as are the cesium-134 (Cs¹³⁴) and 137 (Cs¹³⁷) isotopes. A further consideration is the half-life of the isotope. Those with the longest half-lives are usually those disseminated most widely. Plutonium-239 (Pu²³⁹) has a half life of 24,110 years; strontium-90 (Sr⁹⁰) has a half-life of 29 years; cesium-134 (Cs¹³⁴) has a half-life of 2.065 years, and cesium-137 (Cs¹³⁷) has a half-life of 30.17 years; iodine-131 (I¹³¹) has a half-life of 8.04 days. Although iodine-131 (I¹³¹) is dangerous from several standpoints, it will be gone in 80.4 days after its creation. Why aren't the PTBs addressing the cesium-137 (Cs¹³⁷) and strontium-90 (Sr⁹⁰) issues? They are as easily monitored by Geiger counters as is iodine-131 (I¹³¹).

Human Health Hazard Analysis

So, now you have a rough idea what radiation is all about. Now let us turn our attention to measuring it. This is where the greatest confusion comes in both from the standpoint of the particular measuring technology; to the nature of what it is we're measuring; to what all these units mean, and how they are related to hazard.

Some units (Curies [Ci] and Becquerels [Bq]) used are applicable to actual measures of radioactivity as transformations per unit of time. Others (Roentgens [R]) are used to measure delivered ionization (remember radioactivity is ionizing radiation, by definition) in electrostatic units per mass. There are two units that measure absorbed dosage, the RAD (Radiation Absorbed Dosage) and the Gray (Gy) which is another way of measuring absorbed radiation dosage. The RAD is defined in the CGS system (ergs/gram), and the Gray (Gy) is defined in the MKS system (joules/kilogram). There are likewise two related units widely used which measure the equivalent dosage to give rise to a measure of the biological effects of radiation on human tissue. These are the REM (Roentgen Equivalent Man) and the Sievert (Sv).

It is these latter two units that are most relevant to measuring human hazards from ionizing radiation. Let us re-examine what they are and what they are useful for.

The REM is used to derive equivalent dosage which relates in human tissue to the degree of biological damage of the radiation. It is a fact that not all radiation has the same effect even for the same amount of absorbed dosage. The difference between alpha and beta radiation is a case in point. Many current radiologists deal in REMs. Sieverts (Sv) are currently more widely used as they are MKS-derived units and actually have a more current basis for their equivalent dosage values as the earlier REMs had a minor problem with their derived equivalent dosage. Of course, as in most scientific issues, there continues to be controversy as those schooled in REMs hang onto them tenaciously — and, the difference is actually minor in the whole scheme of things.

Now, we arrive at the confusing part. There are prefixes affixed to the various units, and we simply must be able to know what they designate and, hopefully, to convert from one to the other. The small letter m before a unit means milli- that is, a thousandth of the unit. A small Greek letter μ before a unit means micro — that is, a millionth of the unit. There are other commonly-used prefixes that designate multiples of the basic unit. A capital letter M refers to mega, that is, a million times larger (X 1,000,000); a capital letter K refers to kilo, that is a thousand times larger (X 1,000).

As a general rule Sieverts are 100 times larger than the corresponding REM units because of the basis used to set the equivalent values. REMs are set in the CGS (centimeter/gram/seconds) system and Sieverts are set in the MKS (meters/kilogram/seconds) system. The governing unit for comparison is the length unit, and meters are 100 times as large as centimeters.

Following are some useful conversion factors:

• 1 Sv = 100 REM
• 1 REM = 10 mSv (millisieverts)
• 1 mREM = 10 μSv (microsieverts)
• 1 mSv = 0.1 REM

Now that we have sort of established a base that will enable us to understand what is being purported, it's time to provide the technical data regarding the human exposure doses in Sieverts and what these effects are on individuals encountering these levels.

First off, REMEMBER that there is no safe level of radiation. The following is with respect to acute radiation, that is, dose received within a 24 hour period:

• 0 – 0.25 SV (0 – 250 mSv): No visible effects
• 0.25 – 1 Sv (250 – 1000 mSv): Some individuals feel a loss of appetite and concomitant nausea. The bone marrow, lymph nodes and spleen are damaged.
• 1 – 3 Sv (1000 – 3000 mSv): Individuals experience mild to severe nausea, loss of appetite, infection, and more severe bone marrow, lymph node, and spleen damage. Recovery is probable but by no means assured.
• 3 – 6 Sv (3000 – 6000 mSv): Individuals experience severe nausea and lack of appetite. There is hemorrhaging, infection, diarrhea, peeling of skin, and sterility. Death results if untreated.
• 6 – 10 Sv (6000 – 10,000 mSv): Individuals experience all of the above symptoms plus central nervous system impairment. Death is the expected result.
• Above 10 Sv (10,000 mSv): Individuals are incapacitated and die.

My Charge

Now is the time for a little perspective into what the various “experts” and media-types are trying to “sell you” as well as the outright misleading data and information provided by the government.

As you are aware, you have heard that a certain exposure is, say, equivalent to a cross-country sojourn via commercial airliners. THIS IS ABSOLUTELY FALSE AND, IN MY OPINION, CRIMINALLY MISLEADING. Following are some reported radiation exposures in units (millisieverts) that are a measure of radiation effects on human tissue:

• Dental Radiography: 0.005 mSv (millisieverts)
• Mammograms: 3 mSv (millisieverts)
• Brain CT Scan: 0.8 – 5 mSv (millisieverts)
• Chest CT Scan: 6 – 18 mSv (millisieverts)
• Background radiation dose for an individual in the U.S.: 3 mSv/year
• Average total radiation dose for an individual American: 6.2 mSv/year

Note that all of these are reported in units related to biological damage, and that the variance (though they don't mention it) depends on where the radiation is directed. But, it's all “smoke and mirrors” because it is based on EXTERNAL radiation. It is NOT based on the internal particulate radiation that an individual would encounter from fall-out such as in a nuclear bomb test or an industrial accident. What it all means is that external radiation detected is dependent on the detector(s) used and the type of radiation and is not relevant to INTERNAL RADIATION resulting from the ingestion of radioactive particulates from eating, breathing, or otherwise introducing them into the internal environment of the body.

So, be aware and don't be fooled by misleading analogies by those with agendas. Now you know more than they do for the most part.

Dr. J.H. Wakefield is a consulting scientist/engineer with more than 30 years of experience in water/wastewater treatment. He holds advanced degrees in microbiology and physical/analytical chemistry, and has been a practicing chemical and environmental engineer for many years.