Thursday, March 17, 2011

Trust in Cheeses

The question I should be asking is: “what am I going to do with all this cheese?”. Instead I am transfixed by the slowly unfolding train wreck that is Japan's nuclear emergency. All my life I have been taught that radiation is terrifying; radiation in Japan doubly so. I have grown older and my radiation fears have tended towards imagining unexplainable cancers, and away from Mothra and Godzilla; still the fears persist. One good reason for the fear's persistence across the many year's changing perceptions of risk is that there are some good reasons to fear radiation exposure.

I have been told that the coverage of the nuclear emergency in Japan is dangerous in-and-of itself. People have told me that when they watch the news they can feel information being sucked out of their brains. They feel more ignorant than before they turned on their TV. Despite the fact that I do not have a TV I am worried about this uncontrolled proliferation of FOX news technology. I have decided to write a couple of entries on radiation in response; this piece is the first. I am eating a grilled Camembert sandwich while writing it.

I have extensively studied the effects of many persistent toxins in the environment, and radioactive toxins have a uniquely advantageous feature; that they are radioactive. The radiation provides a signal that screams out the presence of these toxins. Many toxins can only be detected after samples have been properly taken, often carefully preserved, and sent back to a lab for expert analysis. The radioactive toxins can be detected on-site with a magic wand.

Strangely, what we reveal with our magic Geiger-counter wand is the radioactive material disappearing. The more we detect the less is still there. The radioactive atoms are said to be disintegrating, and it is those atomic disintegrations that are the source of the radiation. In fact we measure the amount of radioactivity of a sample of material in number of disintegrations per minute. The standard unit of measure for this is a curie (3.7 X10^10 disintegrations/ minute). The curie is named after Marie Curie who won a couple of Nobel prizes, and then died of aplastic anemia caused by radiation exposure. Marie discovered radium, and a curie is about the amount of radioactivity you would find in a gram of pure radium-226.

The curie is a great unit of measurement for deciding downwind risk from a nuclear event. If someone was to say that a cloud containing 'X' number of curries was floating over your area you could get an idea of how much landmass could be contaminated at what concentration. If the Fukushima Dai-ichi power plant releases 'X' number of curies one could tally up where it all appeared to go to in order to determine our knowledge of the extent of the damage.

The curie can even be used to provide quantitative assessment of relative danger. For instance the Chernobyl nuclear disaster released between 51 and 324 billion curries of radioactive material; how much has Dai-ichi released so far? I have read comparisons between Chernobyl and Dai-ich in almost every press release and article, but what does anyone really mean by “not as bad as Chernobyl”? It is hard to find any mention at all of the curie unit of measurement in any of the Dai-ichi incident coverage.

One reason for this should be that the number of curies is a calculated quantity. Picture rats leaving a sinking ship. You look out into the harbor and see a bunch of rats swimming away from a floundering boat. You can immediately say “there are a bunch of rats in the water”. You can even count the rats. If you measure the amount of water around the boat that you can see, and you know the amount of water that could contain swimming rats around the boat, it is an easy calculation to determine the amount of rats leaving the sinking ship. More likely the observer will make the more immediate observation like this: “There are two hundred rats swimming this way! Lets move!”. We measure radiation in a surprisingly similar way. The Gieger-wand measures the number of radioactive “rays” that hit it. This measurement is given in counts-per-minute (CPM).

CPM is a measurement of the amount of radiation at a given location. We can calculate the amount of radioactivity in an area by knowing how the CPM at a location (or several locations) represents the radioactivity given off by the area. It is not a difficult calculation, but for radiation release from a nuclear event many assumptions must be made.

By varying some simple attributes of a detector we can gather very useful data about the type of radioactivity. There are three major types of radiation from nuclear material; those are alpha, beta, and gamma rays. I like to both simplify the discussion of radiation into these three divisions (because it does capture most important aspects of radiation), and to call the radiation “rays” (because it sounds much cooler that way). Alpha rays are the Cadillac of radiation; big, powerful, and slow. Beta rays are the -hmmm- Smartcar of radiation; small, light, and slow. Gamma rays are the rocket-powered skateboard of radiation; tiny, almost no mass, and fast.

Now picture trying to run some of these rays through a WalMart parking lot on Christmas day...while blindfolded. There are no cars (the only day of the year that WalMart is closed), but the huge expanse of asphalt is littered with abandoned shopping carts. The Cadillac does OK. It hits a bunch of carts, which bounce right off it, then a couple get jammed up underneath the lumbering beast of a vehicle. The trapped carts rip open the Cadilac's differential, and it comes to a halt. The Smartcar makes it a little further across the parking lot, but just because it does not hit so many carts; eventually it hits one just right and it too comes to a halt. The daredevil on the gamma ray zooms at incredible speed almost all the way across the parking lot, missing all the carts, then he barely clips one, and is toast. There is a wide path of destruction leading up to the alpha particle. There is a longer but much less defined trail of destruction leading up to the beta particle, and someplace in the parking lot lies a shattered skateboarder.

Knowing what type of radiation one is counting provides vital information about what type of radioactive contamination is causing it. A breakdown of CPM types also provides an idea of the type and amount of damage the radiation can cause. We do not, however, hear much talk of CPMs in the Dai-ichi coverage. Instead the radiation is mostly (when given a number at all) given in units called sieverts.

Sieverts are a measurement of radiation dosage received by biological tissue. They are a modification of the non-biological dosage measurement which is given in units called “the gray”. If we were to go back to the rats leaving the ship example the gray would kinda measure how many escaping rats climbed out of the water onto your particular boat. Sieverts take into account the amount of damage each type of radiation causes. The energy from each particle is multiplied by a Q(uality) factor to weigh its contribution to the total dosage. Alpha particles have a Q factor of 20. Gamma particles have a Q factor of 1. In the Walmart parking lot example the Q factor would give information both about how many damaged carts and the amount of damage the carts received. The Cadillac-crushed carts would be much more severely damaged than the Smartcar-dented-carts.

Picture the Walmart manager arriving to work at midnight on Christmas. He surveys the damage as he drives around the parking lot: “There were quite a few grays of vandalism here yesterday” he says. Then he has his minions collect the damaged carts: “There were quite a few sieverts of damage from the vandalism yesterday” he says. Then he is taken to the three broken vehicles that caused the cart-pocalypse: “There are three counts of vandalism that impacted the lot” he says. If he knew that all three vehicles drove across in one minute he could have said that there were 3CPM of vandalism for one minute on Christmas; if he knew that the vehicles drove across sometime in a five hour window he would instead say: “There was an average of 0.01 CPM of vandalism over Christmas”.

I bet somewhere there is an action movie where a vehicle is caught in slow-motion while barreling through a parking lot smashing carts. As the carts go flying through the air one can see the effect of the seivers it has absorbed knocking bits off. Inspired lighting could catch the chromed cart fragments glinting like precious stones in sunlight. I would watch such a scene with great enjoyment. I would eat popcorn while watching it; cheese flavored popcorn.

It may seem that sievers can be translated into direct risk assessments better than any other number. Unfortunately absorbed doses are moderated by shielding and protective measures. Alpha rays penetrate so poorly that thin sheets of cardboard effectively shield them. Sieverts are a great unit of measurement for determining X-ray risks or normal occupational exposure risks. In taking into account the factors limiting immediate exposure sievert measurements can significantly minimize the extent of damage in a large-scale disaster. The reason for this is that once radioactive material is released it becomes a toxin, and the assumptions used to determine the sievert dosage from CPM can significantly downplay the effect of unshielded exposure; one does not come close to describing the risks with ingested or inhaled radioactive particles.

There you have it. I've gone well over 1600 words and have not touched upon what happens to the biological system insulted with a radiation dose. That is why I planed on running this in two parts. This first part is important for without reasoned quantitative measurements of the extent of risk it is impossible to get any warm fuzzies about one's own safety. The news media thinks that you cannot understand the measurements of radiation, and so they begin to pride themselves in having little understanding themselves. Real knowledge is reduced to assumption-riddled misinterpretations which can be of less value than silence.

I have been told that as far away as Chicago many people have begun stockpiling cherry pop-tarts and potassium iodide. How many curies need to be released for there to be a risk to Chicago? How many curries have been released? How many curries might be released? It would be nice to have these questions answered; wouldn't it.

It appears, with my 15 pounds of really good cheese in my fridge, that I am hording for a potential nuclear apocalypse. Even though I live between Japan and Chicago I am not really worried. I live A LOT closer to Chicago than Japan.

I have, however, tried to calculate the number of curies of plutonium-239 that would be needed to manufacture a nuclear fondue pot.

REM - Shiny Happy People by damned78

No comments: