Tag Archives: nuclear

Bhangmeter

,

A bhangmeter is a radiometer, a device that measures the power of electromagnetic radiation. Most people are already familiar with one type of radiometer, the Crooke’s radiometer, which detects infrared radiation.

crookes-radiometer

A Crooke’s radiometer. The higher the flux of infrared radiation the faster it spins.

Bhangmeters are placed on reconnaissance satellites* in order to detect nuclear weapon detonations and to measure their yield. Bhangmeters are designed to look for the characteristic “double flash” created when nuclear weapons detonate: the first initial bright flash being caused by the actual detonation of the weapon and the second being caused when the ionised gas shock wave cools enough to allow light from the fireball to escape.

The name “bhangmeter” was created by Frederick Reines (who later won the Nobel Prize for Physics for his work on detecting neutrinos), who suggested that one would have to be on bhang (an Indian drink made from marijuana) to believe that the detector would work.

* The US Department of Defense’s GPS satellites also carry bhangmeters.

Energy density of coal

, , ,

One kilogram of coal contains between fourteen and thirty-three megajoules of chemical potential energy, depending on the type of coal (lignite, bitumous or anthracite).

Coal also contains trace amounts of uranium, ranging from one to ten parts per million; in a worst-case scenario one kilogram of coal could therefore be expected to contain one thousandth of one gram of uranium. As uranium has an energy density of 79.5 trillion joules per kilogram that means that one kilogram of coal contains 79.5 megajoules of energy as nuclear potential energy.

Or in graph format (and remember, this is the best-case scenario for coal and the worst-case scenario for uranium):

energy-density-graph

So there you have it: you can get more energy out of coal by grinding it up and extracting the uranium than you can from actually burning it in a coal-fired power station.*

(It’s also worth noting that coal contains about two-and-a-half times as much thorium as it does uranium, and that thorium is also a nuclear fuel.)

* You could of course burn the coal first, and then extract the uranium from the ash produced, but unlike nuclear power, burning coal is bad for the environment.

Gravel Gertie

,

A Gravel Gertie is a structure specially designed for use when handling nuclear weapons. It is not designed to contain the force of a nuclear explosion, but rather to reduce the damage and contamination caused by a non-nuclear explosion – for example if the explosive lenses used in a compression-type thermonuclear weapon detonated prematurely during inspection or maintenance.

gravel-gertie

A Gravel Gertie has thick reinforced walls, but is “open” at the top with the roof being a seven-metre layer of gravel, held back by a thick waterproof membrane. In the event of an explosion expanding gas vents out through the gravel, but this gravel also acts to trap radioactive contaminants. In tests at Sandia National Laboratories a Gravel Gertie reduced airborne contamination after an explosion by a factor of ten.


View Larger Map

Four Gravel Gerties are visible in this aerial map of the Royal Ordnance Factory in Burghfield where the UK’s nuclear weapons are assembled; ROF Burghfield is part of the UK’s Atomic Weapons Establishment.

How are mushroom clouds formed?

, ,

Mushroom clouds (perhaps more properly known as pyrocumulus clouds) are traditionally associated with nuclear explosions, but any sufficiently large explosion (for example, a volcanic eruption) will create a mushroom cloud.

The mushroom cloud resulting from the Priscilla test of Operation Plumbbob.

When a large explosion occurs a cloud of very hot gas is created. This hot gas, being less dense than the surrounding air, rises rapidly upwards. As this cloud of hot gas rises it pushes against the air above it and this air resistance causes the top layer to move sideways whilst the hotter gas below continues rising upwards, creating a swirling doughnut-shaped vortex (in the photograph above a very hot “filament” is visible at the centre of this vortex). As the “cap” rises this swirling vortex pulls in cooler air from ground level, creating the “stalk” on which the cap sits.

The formation of a mushroom cloud during the Tumbler-Snapper series of nuclear tests.

The shape of a mushroom cloud is the result of a Rayleigh-Taylor instability at the interface between the hot less-dense and cold more-dense air. These instabilities occur in a number of different situations, and can be easily demonstrated at home by dropping coloured oil into water, creating tiny upside-down mushroom clouds as shown below in photographs by James Riordon of AIP.

The simulated formation of a Rayleigh-Taylor instability.

Nuclear art forgery

, ,

Nuclear weapons* are triggered by neutron initiators, devices that produce a sudden burst of neutrons on activation. They are most often constructed from a mixture of beryllium-9 and polonium-210. The polonium emits high-energy alpha particles, and when brought into contact with the beryllium it causes the beryllium to transmute into carbon with the release of a neutron. This neutrons causes an atom of uranium-235 to split (to fission) and in the process release a huge amount of energy and more neutrons that go on to cause further fissions.

This uncontrolled chain reaction results in the production of many exotic isotopes, as the uranium atoms split to form “chunks” of other elements. For example, it was in the aftermath of the ‘Ivy Mike’ test of the first thermonuclear bomb that the elements einsteinium and fermium were discovered.

The existence of rare isotopes can be used to demonstrate that a painting or other work of art was not produced before the 1940s or 1950s, when nuclear weapons testing was at its peak. Strontium-90 and caesium-137 are isotopes that did not exist in nature before the age of nuclear weapons and which permeate soils and are taken up by plants and other living things as they are very soluble in water. If these organic materials are used in the production of paints, or binders for paint, or in other ways in a piece of art then the presence of Sr-90 or Cs-137 can be used to prove that the item in question was created after the beginning of the nuclear age.

* This paragraph details the operation of a fission bomb. Fusion (thermonuclear) bombs work differently, but all use a fission stage to initiate the fusion process.