Radiation: How it Works and What it Does

Exposure to even minuscule amounts of radiation is enough to spark deep, gut fear in most people in the modern world. Our fear of radiation is not unfounded. In the wrong doses, it does heinous things to people. We have seen this in the bombing of Hiroshima and Nagasaki, in various nuclear accidents, in the Chernobyl disaster, and in the effects on the natives of Rongelap and their descendants.

This has been embedded in our subconscious over the last century, and for good reason... It makes us take precautions which typically allow us to play with god's building blocks and not fatally irradiate ourselves. That instinct is also a contributing factor to our lack of a nuclear holocaust, despite having the required number of weapons and vicious primate urges to create one. However, as evidenced in the previous days with the Fukushima nuclear accident, sometimes the worst does happen, and all of our well engineered precautions fail.

After that point, most people are still in the dark about what radiation is, how it damages tissue, and how to avoid or mitigate exposure.

Defining Radiation



To quote the dictionary, radiation in the broadest sense is "the process in which energy is emitted as particles or waves." That's pretty simple. Turn on a lightbulb to witness a form of radiation, if you'd like.

Further, radiation comes in two flavors: ionizing, and non-ionizing. Ionizing radiation is radiation which is powerful enough to rip electrons off of atoms. This is the bad and dangerous kind of radiation, and it can destroy body tissues on a microscopic level. When most people say radiation, this is the kind they're talking about. For the rest of this post, you can assume that I'm of the same mind.

Non-ionizing radiation is typically less dangerous. I say typically, because major contenders in the non-ionizing radiation class are sunlight and radio waves, both of which are (mostly) our friends. It will not be dealt with here.

Ionizing Radiation

Ionization occurs when radiation rips off an electron from an atom.

Ionizing radiation comes in several further flavors. The ones of concern in the context of this post are alpha, beta, gamma, and neutron radiation.

Alpha and beta radiation are similar in that they are a byproduct of radioactive decay in which high energy, short-ranged (milimeters or less) particles are emitted. Alpha decay releases alpha particles, which are identical to helium nuclei. Beta decay releases electrons and certain antimatter particles. Alpha radiation is less dangerous than beta radiation, as an external source does not penetrate the skin. An external source of beta radiation can cause burns if it makes contact with skin. Both can be harmful or fatal if the sources of radiation are in some way ingested, as the radioactive material can become concentrated in the tissues of vital organs.

Gamma radiation is different from Alpha and beta radiation in that it is not a particle per se, but a wave frequency in the electromagnetic spectrum, similar to x-rays. In nuclear bombings and accidents, gamma radiation is released after radioactive materials have undergone alpha or beta decay. High energy gamma radiation is more penetrating than alpha and beta radiation, which means that the whole body and its tissues can be irradiated by an external source.

High energy neutrons can make other matter into sources of radiation via a process called neutron activation, which can turn otherwise well-intentioned matter into unstable, radioactive matter. They also have the ability to ionize atoms. Neutron radiation is more penetrating than alpha and beta radiation. It is sometimes more penetrating than gamma radiation as well.

How Radiation Harms

Radiation does damage to tissue by ionizing some of the atoms in the tissue cells' molecular structures. It is kind of like the cell is being shot up with an atomic machine gun with radiation bullets. As the energetic particles and rays bombard a cell, bonds in the cell's molecular structures are ripped apart and the molecules come unglued; molecule mangling free radicals can also be produced by ionization of water molecules in cells with the same result.

Many structures in the cell can be repaired, even if damaged by radiation. However, some damage done to the cell's vital structures (including DNA) cannot be repaired or there is too much damage, and this is where the problems start.

When damage occurs to a part of the cell, the cell either repairs the damage to the best of its ability, or it dies. If the cell survives to divide again, incorrectly repaired DNA can lead to cancers and abnormal tissue growths in the irradiated organism, or deformities in the organism's offspring. Most of the time, the cell can successfully repair radiation damage without mutations. This is the common effect of low occupational and environmental doses.

Due to a process called apoptosis, highly damaged cells essentially self-destruct. Apoptosis is activated by damage to DNA and certain other cellular structures. This is of particular concern in tissues which require rapid cell division and production to maintain functionality, such as the bone marrow. This is the type of cell damage that leads to acute radiation sickness and often death after exposure to high doses of radiation. On the other side of the coin, it is this very process by which many cancers are destroyed using radiation therapy.

Modes of Exposure, Measurements, and Harmful Levels

Radiation exposure can occur from an external source, such as unshielded nuclear fuel or the radioactive isotipes found in fallout. External sources become internal sources of radiation if the unshielded source is somehow ingested. Internal exposure to radiation is more dangerous than external exposure.

Radiation is measured in a few different ways, each measure quantifying a different attribute of the radiation. The grays & rads and sieverts and rems are of primary focus in this post, as they are the measurements used when referring to how much radiation a person is getting.

Grays and rads measure the amount of energy absorbed by matter from radiation (absorbed dose). Sieverts and rems quantify the amount of damage done by the absorbed dose of different types of radiation (equivalent dose).

1 gray of radiation is equivalent to 100 rads. 1 sievert is equivalent to 100 rems.

The sievert is arrived at by multiplying the absorbed dose in grays by two different weighting factors. The first is the weighting factor that deals with the type of radiation. The other is the weighting factor that deals with the part of the body exposed to radiation.



weighting factors for converting grays to sieverts

Rem stands for roentgen equivalent in man. The rem is arrived at by multiplying the absorbed dose in rads by one weighting factor which deals with the type of radiation.


weighting factors for converting rads to rems

The following outlines various doses of radiation and their effects on a person if the person recieves a full body dose:

Nice thread, it's some very useful info considering the times. We're about to find out first hand what "worse than chernobyl" is like. Good luck to all of you, S&F.

AWESOME thread and very informative. I have been trying to explain this to people around me and this thread has just about covered all the important factors!

Well thank you very much for that much needed lesson. It was well written, and easy to understand. Learning new stuff is awesome!!

Thank you for the radiation lesson. It is highly possible that many people will be in a state of panic over recent events who don't fully understand the risks of exposure, other than the fact that they exist. It astounds me that reporters are in Japan and you see footage of people in the streets who may already be exposed to harmful levels of radiation.

Very informative thread, S&F!

Also useful to know would be how to interpret various readings. For example, we are getting reports from Japan referring to radiation levels in units called mSv (millisieverts). According to the following radiation detection equipment web site, SE International, mSv is a measurement of gamma and x-ray radiation, usually reported as mSv/hr (per hour). - Whereas the readings available at Radiation Network and at the Tokyo gieger counter site are in CPM (counts per minute), which is a measurement of apha and beta radiation. The two units of measurement are not interchangeable and they measure different things.

[edit] When I posted this, the radiation network (US radiation map) was still up and running. As of this moment, however, I am getting a 404 message for the entire domain. Now, this could simply mean that their servers were overwhelmed by traffic and crashed the site (which is a distinct possibility, given the circumstances). However, it could also mean that TPTB don't want us to know the radiation readings on the west coast, as reported by ordinary citizens with geiger counters. Make of it what you will.

Originally posted by OuttaHere
[edit] When I posted this, the radiation network (US radiation map) was still up and running. As of this moment, however, I am getting a 404 message for the entire domain.

I get a 404 for the link you posted, but not for the domain, this link works: www.radiationnetwork.com...

To the OP, good explanation. I used to be licensed to handle radioactive materials and it's pretty close to what I remember from my training.

I would add we are all exposed to ionizing radiation every day from miscellaneous sources. One big source that affects some people more than others is radon gas, but many soils are naturally radioactive and many people don't know this. Flying is another source, and since pilots do that for a living, they get a fair dose of radiation.

So if you get a little bit of radiation from a reactor drifting your way, one question to ask is, how does it compare to background radiation sources you already are exposed to every day. In the case of Three mile island, the exposure levels weren't significantly above background levels and routine activities like flying. The Japan incident has yet to play out fully so we'll have to keep monitoring what's released.

Great thread - S & F.

Particularly appropriate as the people of Japan try to cope with this disaster and the rest of the world waits and wonders if the radiation will also affect them.

Good job and thanks!!

Originally posted by OuttaHere
Also useful to know would be how to interpret various readings. For example, we are getting reports from Japan referring to radiation levels in units called mSv (millisieverts). According to the following radiation detection equipment web site, SE International, mSv is a measurement of gamma and x-ray radiation, usually reported as mSv/hr (per hour). - Whereas the readings available at Radiation Network and at the Tokyo gieger counter site are in CPM (counts per minute), which is a measurement of apha and beta radiation. The two units of measurement are not interchangeable and they measure different things.

[edit] When I posted this, the radiation network (US radiation map) was still up and running. As of this moment, however, I am getting a 404 message for the entire domain. Now, this could simply mean that their servers were overwhelmed by traffic and crashed the site (which is a distinct possibility, given the circumstances). However, it could also mean that TPTB don't want us to know the radiation readings on the west coast, as reported by ordinary citizens with geiger counters. Make of it what you will.

edit on 15-3-2011 by OuttaHere because: new information

Millisieverts are simply a derivative of the sievert. To figure out what the measurement is in sieverts, move the decimal point left three places. Sieverts can measure gamma and x-rays, and without a weighting factor in the gray to sievert conversion, I believe gamma is the basic measure. Other types of radiation can also be measured in sieverts.

The most useful thing I can contribute regarding counts per minute is that anything over 100 seems to indicate something beyond background radiation, although higher readings are typical at high altitude, over 300 cpm, such as during a typical airplane trip.

EDIT: I found this in a different thread. It seems to indicate that 1 cpm=.01 microsieverts/hour, though I am not sure that is correct, given that different detectors have different sensitivities as to how many of the actual decays per minute they will count from a radiation source.

I guarantee you my gonads command a 'tissue weighting factor' of greater than 0.08.

But, thanks for the charts

Great post and very informative .
Many thanks S + F

A test meant for fun they gave out when I worked in a nuclear plant was this.......

You have 4 cookies ( for the types of radiation)

A an Alpha cookie
B. A Beta cookie
C. A gamma cookie
D. A neutron cookie

You have to hold one in your hand
Put one in your pocket
Eat one
Throw one away

What do you do with each one?

The Tokyo site was reporting 16.64 CPM. I did the math, doesn't SEEM harmful. But what about continuous exposure?

Japan UPDATE?

Yeah, no info at all.

Generally speaking - the Japanese issue is hyped considerably.

That's not to undermine the importance of it - but the number of people who have died and who are -still- dying due to the aftermath of a wave of every-day water will outnumber the dead and injured from any kind of radiation-related disaster that could plausibly come from this chain of events.

Sure - "if the containment were to fail..." bad things would happen, yes. That's why it has a containment vessel - and it's built - specifically - for instances like this, and to make sure that reactor core never sees the open air. That's not to say it's impossible for that to happen - but there are trained professionals working to keep that from happening - between their expertise and the original design of the reactor - even so much as a mild breech of containment is so remote as to not be worth worrying about - particularly when there is still thousands of tons of wreckage to sift through and potentially living people to still be found buried.

At the end of the day - more radiation is released from the burning of fossil fuels than has ever been released by nuclear disasters (unless you start counting radioactive fallout from deliberate nuclear tests - ... which aren't related to nuclear power in this context). You're exposed to all kinds of nasties from coal and oil plants that you will - in all plausible likelihood - never be exposed to from a fission power plant.

reply to post by nithaiah
Here's an important article. Alex Jones of infowars fame says if you read this you will be the knowledgeble person in the county.
www.bestmetalresearch.com...

Originally posted by redgreen
reply to post by nithaiah

 

Here's an important article. Alex Jones of infowars fame says if you read this you will be the knowledgeble person in the county.
www.bestmetalresearch.com...

I'm not getting the illustrations at that link.

I found another link with the same article plus the illustrations:

www.ki4u.com...

The illustrations are the best part, some of those I hadn't seen before. But I was pretty familiar with the rest of it already.

Thanks OP for this very informative thread ;-) A lot of knowledge from school lessons in physics cam beack after reading it, so thanks for this! S+F for you!

reply to post by nithaiah


get away from the effected area and dont forget to take a good bath . soap and water can remove some of the radiation from you as well. but wont help you if you are still in effected area