A Brief History of Radioactivity

More than one hundred years ago, Henri Becquerel discovered that uranium emitted penetrating rays similar to those used by Wilhelm Röntgen to take the first X-ray image (of his wife’s hand), starting a new era of far-reaching applications. There are of course many dangers that come with the use of radioactivity, but there are also many beneficial uses for our society.

Continue reading “A Brief History of Radioactivity”

Low Background Steel — So Hot Right Now

The nuclear age changed steel, and for decades we had to pay the price for it. The first tests of the atomic bomb were a milestone in many ways, and have left a mark in history and in the surface of the Earth. The level of background radiation in the air increased, and this had an effect on the production of steel, so that steel produced since 1945 has had elevated levels of radioactivity. This can be a problem for sensitive instruments, so there was a demand for steel called low background steel, which was made before the trinity tests.

The Bessemer process pumps air through the iron to remove impurities. shropshirehistory.com

The production of steel is done with the Bessemer process, which takes the molten pig iron and blasts air through it. By pumping air through the steel, the oxygen reacts with impurities and oxidizes, and the impurities are drawn out either as gas or slag, which is then skimmed off. The problem is that the atmospheric air has radioactive impurities of its own, which are deposited into the steel, yielding a slightly radioactive material. Since the late 1960s steel production uses a slightly modified technique called the BOS, or Basic Oxygen Steelmaking, in which pure oxygen is pumped through the iron. This is better, but radioactive material can still slip through. In particular, we’re interested in cobalt, which dissolves very easily in steel, so it isn’t as affected by the Bessemer or BOS methods. Sometimes cobalt is intentionally added to steel, though not the radioactive isotope, and only for very specialized purposes.

Recycling is another reason that modern steel stays radioactive. We’ve been great about recycling steel, but the downside is that some of those impurities stick around.

Why Do We Need Low Background Steel?

Imagine you have a sensor that needs to be extremely sensitive to low levels of radiation. This could be Geiger counters, medical devices, or vehicles destined for space exploration. If they have a container that is slightly radioactive it creates an unacceptable noise floor. That’s where Low Background Steel comes in.

A person is placed into a low background steel container with sensitive equipment to measure the radioactivity of the body, which may be near the background level. Photo from orau.org

So where do you get steel, which is a man-made material, that was made before 1945? Primarily from the ocean, in sunken ships from WWII. They weren’t exposed to the atomic age air when they were made, and haven’t been recycled and mixed with newer radioactive steel. We literally cut the ships apart underwater, scrape off the barnacles, and reuse the steel.

Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a popular movie. After 1975, testing moved underground, reducing, but not eliminating, the amount of radiation pumped into the air. Since various treaties ending the testing of nuclear weapons, and thanks to the short half-life of some of the radioactive isotopes, the background radiation in the air has been decreasing. Cobalt-60 has a half-life of 5.26 years, which means that steel is getting less and less radioactive on its own (Cobalt-60 from 1945 would now be at .008% of original levels). The newer BOS technique exposes the steel to fewer impurities from the air, too. Eventually the need for special low background steel will be just a memory.

Oddly enough, steel isn’t the only thing that we’ve dragged from the bottom of the ocean. Ancient Roman lead has also had a part in modern sensing.

Soviet Era Smoke Detector Torn Down, Revealing Plutonium

It’s widely known that a smoke detector is a good ionizing radiation source, as they contain a small amount of americium-241, a side product of nuclear reactors. But what about other sources? [Carl Willis] got hold of an old Soviet era smoke detector and decided to tear it down and see what was inside. This, as he found out, isn’t something you should do lightly, as the one he used ended up containing an interesting mix of radioactive materials, including small amounts of plutonium-239, uranium-237, neptunium-237 and a selection of others. In true hacker fashion, he detected these with a gamma ray spectroscope he has in his spare bedroom, shielded from other sources with lead bricks and copper and tin sheets. Continue reading “Soviet Era Smoke Detector Torn Down, Revealing Plutonium”

Retrotechtacular: [Walt] Builds A Family Fallout Shelter

In the 1950s it seemed likely that the Cold War could at any minute take a turn for the worse, and we might all be consumed in the fiery conflagration of nuclear war. Fortunately neither the leaders on our side of the fence nor those on the other were the dangerous unpredictable lunatics their opponent’s propaganda might have portrayed them as, and instead we continued on our way uneasily gazing at each other over the Iron Curtain.

For civilian America, the Government created a series of promotional efforts to prepare them for the effects of nuclear war and equip them with the means to survive. Some of them like the infamous “Duck and cover” film seem quaint and woefully inadequate when viewed with several decades hindsight, but others tried hard to equip the 1950s American with what looked like the real means to survive.

Our film below the break today is part of one such effort. The Family Fallout Shelter was a booklet produced in 1959 by the Office of Civil and Defense Mobilization, and it described in detail the construction of a series of fallout shelters of differing designs.  There was a concrete underground shelter, a partially buried twin-wall shelter with infill, and the one shown in the film, a basement fallout shelter made from concrete blocks. Our narrator and protagonist is [Walt], a capable bespectacled middle-aged man in a check shirt who takes us through the shelter’s construction.

We start with him giving some friends a tour of the finished shelter, and we see its cozy furnished interior with bunk beds and all mod cons. We’re told it would make a useful extra spare bedroom, or a darkroom. Then we flash back to construction as [Walt] takes us through all the steps required to build your own basement shelter. As he says, it’s a project that could be attempted by almost anyone, and what follows is a pretty good introduction to basic bricklaying. We can’t help being concerned about the security of those unmortared roof blocks in the face of a Tsar Bomba, but fortunately they were never put to the test. We do find it amusing that this is presented by the National Concrete Masonry Association — how better to boost sales than get the populace to build extra brick walls in every home?

The film and booklet provide a fascinating window into some of the culture surrounding preparations for nuclear war in the early Cold War era. The ideas that it would be survivable, and that two weeks in a home-made fallout shelter would be sufficient to ensure that civilians would be safe are in stark contrast to the then-secret deep shelters and long-term survival plans that the governments of the time created for themselves. It would be interesting to know how many of these home shelters were built, and how many survive. Did you ever spend a night in a basement spare bedroom with a blast wall?

We’ll leave you with the film’s closing words from the Director of the Office of Civil and Defense Mobilization.

No home in America is modern without a family fallout shelter. This is the nuclear age.

Continue reading “Retrotechtacular: [Walt] Builds A Family Fallout Shelter”

Retrotechtacular: Head Start On Tomorrow

In the 1950s and 1960s, the prospects for a future powered by nuclear energy were bright. There had been accidents at nuclear reactors, but they had not penetrated the public consciousness, or had conveniently happened far away. This was the age of “Too cheap to meter“, and The Jetsons, in which a future driven by technologies as yet undreamed of would free mankind from its problems. Names like Three Mile Island, Chernobyl, and Fukushima were unheard of, and it seemed that nuclear reactors would become the miracle power source for the second half of the twentieth century and beyond.

The first generation of nuclear power stations were thus accompanied by extremely optimistic public relations and news coverage. At the opening of the world’s first industrial-scale nuclear power station at Calder Hall, UK in 1956, the [Queen] gave a speech in which she praised it as for the common good of the community, and on the other side of the Atlantic the American nuclear industry commissioned slick public relations films to promote their work. Such a film is the subject of this piece, and though unlike the British they could not muster a monarch, had they but known it at the time they did employ the services of a President.

The Big Rock Point nuclear power plant was completed in 1962 on the shores of Lake Michigan. Its owners, Consumers Power Company, were proud of their new facility, and commissioned a short film about it. The reactor had been supplied by General Electric, and fronting the film was General Electric’s established spokesman and host of their General Electric Theater TV show, the Hollywood actor and future President [Ronald Reagan].

The film below the break starts by explaining nuclear power as a new heat source powering a conventional steam-driven generator, and stresses the safety aspect of reactor control rods. We are then treated to a fascinating view of the assembly of an early-1960s nuclear reactor, starting with the arrival of the pressure vessel and showing the assemblies within it that held the fuel and control rods. Fuel rods are shown at their factory in California, and being loaded onto a truck to be shipped across the continent, seemingly without the massive security that would nowadays accompany such an undertaking. The rods are loaded and the reactor is started, as [Reagan] puts it: “The atom has been put to work, on schedule”.

Continue reading “Retrotechtacular: Head Start On Tomorrow”

Lego Nuclear Reactor Uses Arduino

Before the NSA deletes this post, we’ll be clear: We’re talking about a model of a nuclear reactor, not the real thing. Using Legos, [wgurecky] built a point kinetic reactor model that interfaces with the reactor simulator, pyReactor.

Even without the Lego, the Python code demonstrates reactor control in several modes. In power control mode, the user sets a power output, and the reactor attempts to maintain it. In control rod mode, the user can adjust the position of the control rods and see the results.

If things get out of hand, there’s a SCRAM button to shut the reactor down in a hurry. The Lego model uses an Arduino to move the rods up and down (using a servo) and controls the simulated Cherenkov radiation (courtesy of blue LEDs).

We’ve been excited to see more high schools with significant engineering programs. This would be a good project for kids interested in nuclear engineering. It certainly is a lot safer than one of our previous reactor projects.

Lise Meitner: A Physicist who Never Lost her Humanity

It is said that the first casualty of war is the truth, and few wars have demonstrated that more than World War II. One scientist, whose insights would make the atomic age possible, would learn a harsh lesson at the outset of the war about how scientific truth can easily be trumped by politics and bigotry.

Lise Meitner was born into a prosperous Jewish family in Vienna in 1878. Her father, a lawyer and chess master, took the unusual step of encouraging his daughter’s education. In a time when women were not allowed to attend institutions of higher learning, Lise was able to pursue her interest in physics with a private education funded by her father. His continued support, both emotional and financial, would prove important throughout Lise’s early career. Continue reading “Lise Meitner: A Physicist who Never Lost her Humanity”