What's in the steam coming from a nuclear reactor

I've hesitated to comment much on the ongoing Japanese tragedy, but I wish to talk a little about the output coming out from the reactor whenever they open the valves to reduce the pressure inside. In commerical nuclear reactors not using heavy-water for their coolant (aka most non-Canadian western reactors) the pure water coolant is exposed to the intense neutron flux as it passes through the reactor. The neutrons can interact with the oxygen nuclei in the water to form nitrogen-16, a very short lived radioisotope with a half-life of seven seconds. After a few minutes away from the core there is none of it left so the only hazard is near the output pipe, and there are places they store the output for just a little while to let all of the N-16 to decay back into oxygen-16.
The other common isotope coming out is tritium coming from the small amount of deuterium in normal water, leaking through the fuel rod cladding, and other spalling type nuclear reactions in the materials in the core. The tritium is a low radioactive hazard but has a 12-year half-life.

If the reactor is hot, water will decompose into hydrogen and oxygen, especially with the right catalysts.

So if you were to open the output valve on a reactor to relive the steam pressure inside (because the regular cooling is not working), you would get quite a bit of that nitrogen-16. It would be gone by the time a few minutes of wind-time, but it is quite the hazard to the plant. I wonder how much of the periodic bursts of site limit radioactivity is related to that.

The introduction of seawater into the cores introduces the possibility of neutron activation of a number of other elements (sodium, chlorine, etc.) into radioactive isotopes that last longer and can have more of an issue in life time and clean up.

None of this discussion is about the breaking or melting of the cladding and detection of fission products (like what you see when checking people on their clothing for particles), which seems to have occurred in some fashion.

A good primer on what might be going on, without hysteria is over at MIT.

The Magic numbers

"The magic numbers, as we know them now are :
2, 8, 20, 28, 50, 82, 126
and most importantly, they are the same for neutrons and protons."

Maria Goeppert-Mayer, The Nobel Lecture

The last female Nobel Laureate in Physics, 1963.

Granite counters: the claim of radiation risk

The New York Times has a surprising article today about the radiation risks of granite counters.

Granite is an intrusive rock--slowly cooled from magma several kilometers below the surface, the rock grows large crystals from the hundred-thousand to million year cooling period. It is also chemically more "continental"; that is, more quartz, more "felsic" minerals, as opposed to the "mafic" minerals that contain much olivine and pyroxene, two minerals rich in iron and magnesium. True granite is a chemically specific intrusive, and much of what is called granite isn't, but a cousin of it. Roughly you can say to expect quartz, feldspar (of some type, there are several), and a sheet silicate like mica or biotite.

Despite the popular image of the Earth's crust riding on an ocean of molten magma, there is little liquid under our feet. While it's hot, there is enough pressure to keep things solid. Occasionally something will upset that balance and allow the rock to melt, whether by bringing hot material up to a lower pressure (like at the mid-ocean ridges) or by adding a special ingredient to make it melt (like water released by ocean sediments subducting under a continent). Melting is complicated and rarely complete, and some minerals melt at a lower temperature than others, leaving behind and chemically changing what sort of rock it is. Granite is like this. It melts at a lower temperature than basaltic materials. It often contains more water. And it brings with it certain compatible elements including uranium and thorium. This is why granites are more radioactive than most rocks. They can contain 10-20x more uranium and thorium than the solid left behind. Some of the more exotic "granites" are pegmatites--the extremely large crystal remnants of the last little bits of liquid at the end of solidification--and they contain the highest amounts of these elements.

But is this a hazard? Granites I've encountered have rates ranging from nothing to about 10x background. This isn't that much. Time spent at cruising altitude is about 40x background at 500ft. It certainly wouldn't be worth the fuss of ripping up a kitchen, unless it was proven to be the source of elevated radon levels. After reading the literature about naturally occurring radon sources, I have difficulty assigning the radon to just a small granite piece. Any soil or rock within 4 gas-diffusion-days of the basement or slab can be a source of radon for a home, and the total amount of uranium in that quantity is going to exceed the amount in the countertop (especially the part of the countertop that is within radon's half-life time of the surface). If you covered your walls in granite it might be different.

More on the New York Geiger Counter law

From the report of the committee on public safety:

However, the emergence and commercialization of new and highly sophisticated technology developed for the purpose of detecting weapons of mass destruction brings with it the possibility that the private sector will acquire detection capabilities which were previously used only by properly trained military and law enforcement officials.

I love how science and education had nothing to do with the invention or previous use of this technology. Geiger counters must have sprung from the forehead of the Police Commissioner! They couldn't have been invented in 1911, because the government says they're new.

P.S. No more Cloud Chamber experiments either, because those would detect radiation. Can't alarm the masses.

End of the year non-review, #1

A non-review, since I didn't post about things I saved in "starred items" in Google Reader. So, some quick posts about them.

Grist complains Senator Harry Reid is defending the 1872 Mining Law, which is still on the books. Parts of it are stupid; we should hold profitable companies to clean up their messes and begin to increase the tiny rates charged for minerals on public lands. But in parts of Nevada mining is all that keeps the area inhabited. Reid comes from a down and out mining town to the south of Las Vegas that I've spent plenty of time in; and no one would argue it was having a too-hot economy. Reid also gets re-elected by the will of the people of Nevada every six years, and to be honest, it can be a close vote every time. Reid is not perfect; a true politician as I found when I talked with him years ago; but he's fantastic for Nevada--holding off the results of the "Screw Nevada" bill and deflecting the Yucca Mountain nuclear waste dump as long as possible, despite the efforts of many in both parties. He works well with Senator Ensign on nonpartisan issues for the state like smart planning on wilderness and auctioning federal lands in southern Nevada. All these things would be much worse off if he were defeated--there would be no Mining Law reform, no wilderness declarations, no effective attempt at ending the bureaucratic environmental disaster that Yucca Mountain will be.

Radiation doses from above ground nuclear testing

Estimated gamma-ray radiation doses from above-ground nuclear testing in Nevada, as of 1957. Above-ground testing continued, at a higher pace, until 1962.

This doesn't include radiation from non-gamma sources, including iodine-131, as shown here.

I personally spent a lot of time in the 2-4 Roentgen range as a kid.

A simple ion chamber to measure radioactivity

I built Charles Wenzel's simple ion chamber. It creates an electric field inside the can via a battery. A wire in the center of the can, isolated from the can, is connected to a transistor pair called a Darlington, essentially a pair of amplifiers. When ionizing radiation creates an ion in the can, the electric field drives the ion towards either the can or the wire, depending on the charge of the ion. This creates a very small current which barely turns on the darlington to allow the voltmeter to measure a small change in voltage.






I could easily up the voltage on the chamber by snapping in more 9V batteries.


You can also light things up nicely: I had 122V DC at my disposal, although I wouldn't recommend running it for very long. Based on a rough calculation, the 40W lamp would run for an hour on this battery set, but the batteries aren't meant to source this much current (about 1/3 Amp).



I had an easy way of changing the chamber voltage, 9 volts at a time, so I measured the quiescent voltage and the voltage with a smoke detector alpha particle source in the chamber. I sealed the chamber by placing it on a sheet of aluminum foil.

Voltage	Null voltage	alpha source
36V	4.8mV	9.1mV
45V	7.1mV	14.9mV
54V	11.3mV	20.6mV
63V	23.4mV	41.5mV
72V	1230mV	1915mV
81V	12000mV	12000mV

Dear Blogger, why do you mess my table so?

Radioactive Bananas?

Are bananas radioactive? We've all heard they are rich in potassium, good to eat to restore electrolyte balance in the human body, but since they have potassium they're bound to have some potassium-40 in them, like our own bodies do.

How much ⁴⁰K? Bananas have 400-450mg of potassium; interestingly the state of Colorado says potatoes are a better source (750mg per medium potato). Potassium-40 is isotopically 0.01177% of natural potassium, so that's 0.05mg or 50ug of ⁴⁰K.

***This sentence was the error in the original post:
The specific activity of potassium-40 is about 30Bq/g (A Becquerel is one radioactive event per second), so there is only 1.5 Bq in a single banana. ***

In fact, the specific activity of potassium-40 is 258,000 Bq/g. 30Bq/g is the specific activity of generic potassium; that is, potassium that has 0.01177% K-40.
So, the banana actually has 13.5Bq.

It's not detectable, by me at least. My body has 4000Bq of K-40, but the geiger counter doesn't change from background when I'm near it. The geiger counter didn't see the bunch of bananas either.

Sorry, Kristin, the counter didn't move.

It does move for pure potassium chloride though.

The Japan nuclear plant earthquake leak

Robert Merkel does the calculations on the leaks from the nuclear power plant in Japan and makes the point most media missed: the leak of water into the ocean wasn't anything. The media missed the much larger release into the atmosphere--nearly 300 million becquerels, or about 3000x times the amount of radioactive material. (A becquerel is one atom disintegrating per second). But looking only at the total amount of radioactivity doesn't tell the whole story. A release of the noble gas krypton-85, for instance, does not really accumulate in organisms in any way; while a release of iodine-131 would concentrate and damage your thyroid. Half-lifes and the particular radiation emitted is also important in consideration: the weak beta electrons (~18keV) from tritium decay is considered not as hazardous as a multi-MeV alpha particle from polonium-210.

The reprocessing of nuclear fuel rods in France releases huge amounts of krypton-85 into the air: 1.8 × 10^17 Bq in 1994 alone.

The 90,000 becquerels of whatever went into the ocean (I am guessing it was tritium) is actually not that much: your own body has about 4000Bq of potassium-40 and 3000Bq of carbon-14 in it; in addition, at least here, tritium is allowed to be diluted by large amounts of river water in Illinois.

The end result is the release wasn't a lot; it sounded like a lot from the numbers, but that's due to the definition of a Becquerel more than anything else. The reality is most people don't have much of an education on radioactivity, and this affects how they irrationally perceive a risk.

All of this is really just a minor detail though, when the real issue is any delay or hiding of release information, which according to the press is endemic in the Japanese nuclear industry.

UPDATE: I've found descriptions of the leaks here. The spent fuel pool water sloshed onto the floor and leaked out via cabling. The second leak, to the atmosphere, was iodine and radioactive dust from a main exhaust line.

weird battery chemistry

A computer UPS status report.

On seeing this, my first thought was, "I really hope there is no actinium in this UPS."

My second thought was, "I wonder what sort of electrochemical potential a Pb-Ac battery would have."

Geiger counter clicker schematic

By long-delayed request, a schematic of the geiger counter clicker unit I built to supplement the Aware Electronics RM-70. I'm not very good at creating electrical schematics, so please be gentle.

Schematic in TinyCAD.


Schematic as PNG.

Online Geiger counter: off

The online Geiger counter is temporarily off while I deal with power issues in my office. I've also been thinking of taking it and a GPS on a tour around campus--there are a few places with exotic granites/other intrusives (like the Henry Moore sculpture not a few hundred feet away from my very desk) that have decent Uranium/Thorium concentrations.

Description of the counter

Groom Lake aka Area 51 aka The Ranch

Be amused that a 1989 report on the containment of radiation from underground nuclear tests from the Office of Technology Assessment, a moribund Congressional office, casually mentioned that there was a monitoring station for accidental radioactive releases from the Nevada Test Site at a classified non-existent location. They also mention the sensitive Tonopah Test Range on the map. Those wacky Congressional Reports!

The Containment of Underground Nuclear Explosions (PDF)
It's on page 69.

You can visit any of the community monitoring stations, and I recommend it if you are ever in any of the towns. In Las Vegas it's located in the parking lot of the Atomic Testing Museum, at Flamingo and Swenson.

ABC Primetime: Radioactive Road Trip

What a piece of alarmist drivel. ABC Primetime "exposed" the security of university teaching and research reactors.

"Oh my god! Tours of reactors without background checks!"

"40kg of highly-enriched weapons-grade uranium in the reactor--without security!"
It might be 40kg, but it's sitting in rods with so highly radioactive nuclides it would kill them in a second. No one could handle it at all, and could never actually process it to get the uranium out.

"Big backpacks on campus--they could be full of books--I mean bombs!"

"Building plans on-line! of buildings on campus!" Wouldn't want students to find where their classes were or anything.

"Two nuclear bombs worth of uranium--to make topazes more blue." Yes, again, completely untouchable uranium.

Yes, journalism students looking like, I don't know, students, got tours of university facilities. God forbid!

Universities are places far removed from the insanity that is the paranoia filled United States of today. They allow for actual learning free from irrational thought.

MIT got boned because ABC drove a moving truck near the containment vessel and then followed the clip with a shot of the Oklahama City Bombing. It's a frickin' containment vessel made of inches thick steel and feet of concrete. It can't be broken.

Did ABC show ANY ANY nuclear engineers on camera? Just the NRC head, who knew how to deal with media--apologize and promise to tighten things up. Ask an engineer about a reactor and learn about the safety features. You can't get bomb material from a reactor without industrial processes. Ask the US Government on the square miles of buildings they used to extract plutonium at Hanford.

Radioactive Krypton in the atmosphere

The radioactivity of atmospheric krypton in 1949–1950
Anthony Turkevich, Lester Winsberg, Howard Flotow, and Richard M. Adams
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=33711

Highlights:

"The work reported here was carried out in the old ruling engine room for grating production in the basement of the Ryerson Physics Laboratory of the University of Chicago."

"As mentioned earlier, atmospheric krypton in the 1990s has a radioactivity of tens of thousands of disintegrations per minute per liter. It is now about a hundred times more radioactive than the samples reported on here."

"The largest current producer of radioactive krypton is the French reprocessing plant at Cap-de-la-Hague, which released 1.8 × 10¹⁷ Bq of krypton radioactivity in 1994. If diluted by the whole world's atmosphere, this would produce a radioactivity of krypton of 2,400 dpm per liter (STP). Cap-de-la-Hague's output may represent about half of the present input into the atmosphere of this radioactive nuclide."

Geiger Counter

I bought a Geiger counter as a birthday present for myself. It is an Aware Electronics RM-70. It is cheaper than traditional Geiger counters because it is designed to work with a computer. By itself, it does nothing. I built a 'clicker' unit that can power and provide the standard click response to radiation events. I need to:
1. photograph clicker unit.
2. publish schematic.
3. enjoy the fun of graphs!

http://www.lib.uchicago.edu/~dean/MDWtoLAX-radiation.gif

Southwest Airlines flight to LAX. I turned on the detector at roughly 12,000ft, and turned it off at the official 10,000ft announcement. According to the pilot cruising altitude was at 39,000ft. The big drop at 3/4 of the way across the graph was a temporary disconnection.


http://www.lib.uchicago.edu/~dean/radon15min.gif
This is the decay of radioactive daughter products of radon-222 being captured on a coffee filter that filtered 15 minutes of air through a vacuum cleaner in someone's basement in Ohio.


If you graph this curve on a logarithmic scale, you get this:



It's not quite straight, but the slope of the line gives you the exponent of the equation far below. The unreadable timescale is the same as the graph above it.

Radon-222-> Po-218 + alpha
Polonium-218-> Pb-214 + alpha
Lead-214-> Bi-214 + e-
Bismuth-214-> Po-214 + e-
Polonium-214-> Pb-210 + alpha

Questions I have that I haven't answered: What exactly is the software recording? What are those numbers? If I listen to the pulses, it seems the software multiplies the number of pulses by 4 to get the observed numbers, which it claims are microRads/hr. If this were a singular nuclear decay, I could deal with it, but it's 5 different decays. So how do I convert into pCi/L of radon? Why does it appear the half-life of the graph is nearly 50 minutes, which just happens to be the half-lifes of the first five decay products added together? Am I recording both the alpha particles and electrons/positrons, AND the gamma rays?
http://hps.org/publicinformation/ate/cat1.html

Simple EPA primer on radon: http://www.epa.gov/radiation/radionuclides/radon.htm
Uranium-238 decay chain: http://www.atral.com/U2381.html

Radioactive decay follows A=A(o)e^-kt, where A(0) is the inital amount of material, A is the amount at time t, and k is the decay constant. k is related to the half-life (t 1/2) by the following: (ln 2)/k=t. To get this equation, set A=1/2 of A(0) in the first equation, remove the A(0), take the natural log of both sides, and you're done.

There are lots of fun projects associated with a Geiger counter. Cosmic radiation is one (remind me to graph my week-long Ryerson graph). Live web server graph of current levels is another.

I have another graph of a more recent trip to LAX here.