Category Archives: nuclear power

A Natural Reaction

Uranium is, of course, the stuff of nuclear reactors and atomic weapons, but it is also part of an intriguing detective story from 1972 that traces back to events two billion years ago – actually 4.5 billion years but at that age who’s counting.

First a little background. For either nuclear reactors or bombs, Uranium 235 is required. This isotope of Uranium has fewer neutrons in the nucleus and is present in small concentrations with U238, the most common isotope. U235 with a natural concentration of 0.72 %, must be concentrated further to make a fissile material that is used in reactors and weapons.

In the early seventies, there was something of a panic in France. France, then as now provides the lion’s share of their electricity from nuclear reactors. At the time France was buying Uranium ore called yellow cake from a mining region in the Oklo River basin in Gabon, Africa. Assays of some shipments showed that the ore was unnaturally low in U235, sometimes by as much as half the expected concentration.

During this period there was much civil unrest as the continent slowly emerged from under the yoke of colonialism. It was feared that Uranium was being stolen by a local tribe with the intention of making a crude bomb. It turns out that the problem was a rather unnatural event in nature. When scientists looked at an analysis of the shipments low in U235 they found several unnatural elements such as Americium, Curium, and Polonium.

These so-called transuranic elements were not known to exist in nature until this discovery. The only place they had been observed was as part of the waste from nuclear reactions, both controlled reactors and bombs. The French had discovered an extremely rare event, a natural nuclear reactor.

When the U235 atoms draw too close together a chain reaction occurs which produces heat. That heat is used to produce steam in nuclear reactors. In the process, the U235 reacts to turn in to other elements. Exactly the same process occurred in the Oklo River basin.

Over two billion years ago there was scant free Oxygen in the air, then along came cyanobacteria. Gradually the atmosphere changed and many minerals reacted with Oxygen. All the rusty looking soil across the planet is due to Iron Oxide which formed during this period.

In the case of Uranium, it became more water-soluble as it oxidized. In locations with rich Uranium deposits such as the Oklo River basin, this allowed for the dissolved Uranium to accumulate in shallow lakes. Over time some of these lakes became isolated and as the lakes evaporated the Uranium was concentrated. Another bacteria capable of taking the Oxygen away from the Uranium Oxide reduced the solubility even further.

When the Uranium in these pools reached critical mass – the concentration necessary for a chain reaction – the U235 fissioned producing heat and forming the transuranic elements. As the reactions proceeded the U235 was depleted. Altogether sixteen different sites in the river basin have been found to have undergone fission reactions. To date this is the only known place on earth where a natural fission reaction has occurred.

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.

Environmental Stewardship

This time of year we tend to look back on the past year, resolve to do better next year, or at least think about what the future will bring. In terms of energy supplies, we have in past years continued our reliance on highly subsidized fossils fuels, the use of which endangers the environment and contributes to our spiraling health care costs. Will we in the future resolve to be less wasteful? Will we resolve to do better as stewards of the planet, for our children’s sake?

The twentieth century will be looked upon as the heyday of fossil fuels, first coal, then oil and now increasingly natural gas. The availability of these fuels produced in North America is increasing which is good for the economy, but bad because the increase utilization of fossil fuels. This is bad for the environment and our health. There are two broad alternative futures;

hard vs soft energy paths

hard vs soft energy paths

business as usual where we favor big solutions like increasing reliance on nuclear reactors and abundant coal reserves, or what Amory Lovins described as the “soft energy path”. In this alternate future energy will be supplied by sustainable, dispersed energy sources such as wind and solar.

The big solution is basically a supply side, large scale strategy which favors production to meet demand, rather than the management of demand to impact production. Nuclear power in one form or another is realistically the only long term solution in this pathway. Due to economy of scale issues, nuclear reactors are very large, when measured by energy output. And unlike the suggestions of the fifties, nuclear power is not and will never be “too cheap to meter.”

And of course there is the yet to be solved problem of high level nuclear waste. Because of these problems the industry is both highly regulated and highly subsidized. The nuclear industry of the future, if it has a future, will be regulated so that the consumer is protected somewhat from the economic and environmental vagaries of energy production, but that will result in a larger governmental role to oversee said industries. This is the classic big industry, big government system which has been the historical trend over several generations. And it has worked more or less in not only the energy industry specifically but the economy in general. OK, there is the problem with the rich getting richer and the poor getting poorer, but that has also been the trend of late.

The soft energy path envisions power production to be greatly decentralized. When power is coming from wind turbines or solar panels economies of scale are not nearly as significant. Solar and wind will be done on a much smaller scale, as suggested by Kirkpatrick Sale in his book “Human Scale”. Power will be produced by individuals or local coops, with less need of big government oversight as the risks are considerably less. Production will be controlled by demand management through more emphasis on efficiency. In this strategy there is less need for big government, and less likelihood of extremes in wealth accumulation, at least in the energy sector.

So these are our possible energy futures as viewed through two extremes. I prefer the latter, but we will see what the future brings.

reactor schematic

The Future of Nuclear Power?

There are discussions among members of the environmental community about nuclear power. Some have suggested that nuclear power can be part of the solution to curbing the release of greenhouse gases. Others disagree.
Dr Amory Lovins, noted physicist and sustainable energy guru, notes that “Each dollar spent on a new reactor buys about 2-10 times less carbon savings, 20-40 times slower, than spending that dollar on the cheaper, faster, safer solutions that make nuclear power unnecessary and uneconomic”. Then there is this:

In March 2011 a magnitude 8.9 earthquake and subsequent tsunami has initiated a crisis in northern Japan. Damage to several nuclear reactors has caused the leakage of three hundred tonnes of radionuclide containing water into the ground and nearby sea.

Four of the six reactors at the Fukushima Nuclear Power Plant were irreparably damaged.  Although the reactor cores may not have suffered any catastrophic failure of the containment vessels, partial meltdowns have occurred. Partial meltdowns occur when the fuel in the core gets so hot that the metallic cladding of the fuel rods melt. This means that the reactors will never be used again and in fact constitute a huge expense for cleanup.

Radiation due to fissile isotopes has been detected at levels some 400 times normal in the soil about 25 miles from the plant and traces of radiation have been detected in air as far away as Seattle, Washington. An ocean plume of radioactive water will reach the US in 2014.

ocean plume

Ocean Plume

The relative risk is unknown but simply calls attention to the magnitude of the damage which has occurred at the reactors in northern japan.

Much of the radiation must be coming from the on-site waste storage. The issue of nuclear waste continues to plague the nuclear industry in one form or another. We all want the power, but nobody wants the waste.

The problems at the Fukushima plant are due mainly due to the loss of power on site. The diesel generators which should have provided backup power to the site to maintain reactor coolant water failed because of the tsunami. Because of lack of coolant water, the fuel rods overheated, causing the metal cladding to melt, then react with steam in the reactor to produce Hydrogen. It was this Hydrogen which caused explosions in two or more of the reactor buildings. These explosions damaged the spent fuel pools which allowed water to leak out, thus precipitating radiation leaks.

The fuel rods in the spent fuel pools constitute high level nuclear waste. Unlike the fuel rods in the cores of the reactors, those in the spent fuel pool are not within any containment barrier. Rather they sit at the bottom of a swimming pool like structure. When coolant water is lost from these pools the rods overheat, melt and release radioactivity.

Every reactor in the United States stores its high level radioactive wastes in this relatively insecure fashion. The wastes are stored in the pools for five to ten years until cool enough to be moved to other storage locations. Severe weather events such as tornadoes, flooding, hurricanes, or even terrorists could damage the integrity of the fuel pools, unlike the much more secure reactor cores.

If nuclear power is to have a renaissance, there must be greater attention paid to the issue of on site waste storage. Of course more secure handling of wastes will only add to the cost and it is ultimately cost factors which will determine the fate of nuclear power here in the United States.