Thursday, July 24, 2008

Post 59. Waste Needs not be a Barrier to Nuclear Energy Production.

( Reportage by the blogger from "Stumble Upon" ).
The “Problem” of Waste in Context
The low volume of nuclear waste as compared to wastes from coal-fired power production is what attracted the early conservationists who saw nuclear power as an ideal way to protect our ecosystem. A 1,000 Megawatt coal-fired power plant produces solid wastes at a rate of 1,800 pounds per minute, waste that includes 19 toxic metals such as arsenic, carcinogens such as benzopyrene, and mutagens from the respirable coal fly ash. A coal-fired plant also produces 50 times the radioactive emissions of an average nuclear power plant. For those concerned about such things, going nuclear even reduces CO2 emissions by 600 pounds per second.
The coal-fired plant also produces 30 pounds of sulfur dioxide per second (said to cause acid rain, amongst other problems) and as much nitrous oxide as 200,000 automobiles. Each year some 60,000 fellow citizens die early deaths from exposure to byproducts of coal combustion, according to studies by the Brookhaven National Laboratory, Divisions of Atmospheric Sciences and of Biomedical and Environmental Sciences. Note that unlike wastes from nuclear power plants, all products of coal combustion are either sent into the atmosphere or into landfills where they remain toxic forever.
Even with that extensive list of negatives, the danger from coal-fired power plants pales in comparison to a far more serious danger — a lack of access to electrical energy. If we opt for inconsistent sources of energy, such as wind power and solar generation instead of fossil or nuclear power, we have only to wait for the invariable brownouts and blackouts that will be the result. We see the toll from a lack of energy each time we have a natural disaster where people flee to the nearest place where the comfort, sanitation, and safety provided by electrical power is available. We also see this dramatically in countries where work is performed primarily by human labor and the combustion of wood is a primary source of energy — and the population lives in the squalor that we always see under such conditions. The surest way to a low standard of living is energy poverty.
What Are Nuclear Wastes?
There are many answers to this question, including smoke detectors in the landfill or gloves worn by a nuclear medicine physician. (A failed nuclear-waste disposal law proposed in the Colorado legislature would have made a trip to the restroom a criminal offense since urine is always radioactive with Potassium-40.) Here, however, we are addressing only the waste products from commercial nuclear power generating plants.
The fuel for a Light Water Reactor (LWR) as typically used in the United States is uranium — a relatively plentiful metal in the Earth’s crust averaging three grams per ton, which is three times that of mercury, 36 times the abundance of silver, and outstrips gold by a factor of 675. Once the ore is mined, the percentage of the fissionable U-235 isotope is “enriched” to some 3.5 percent compared to its natural occurrence of 0.7 percent within the predominant U-238 isotope. To fuel a reactor, finger-sized pellets of enriched uranium held in special tubing are inserted into the reactor core along with control rods of neutron-absorbing materials. Plain water is a critical component of any LWR as it serves as a coolant, a heat-transfer agent, and a moderator to slow down neutrons so they can be captured by the U-235 isotopes causing them to fission or split into a number of new elements.
The new elements created when the uranium atom “splits” are called the daughters* of the reaction and consist of a number of isotopes that run the gamut from being highly radioactive — hence spawning future radioactive disintegrations — to being stable and nonradioactive. The radioactive daughters and their progeny are considered high-level wastes. They consist of about 3 percent of the volume of spent fuel and amount to approximately 7.5 cubic feet (about a quarter of a cubic yard) from a year’s production from a 1,000 Megawatt power plant — considered to provide the electricity needs for 750,000 homes.
In rating the long-term dangers from these radioactive waste products, one must consider their half lives, i.e., the time required for an isotope to lose half its radioactivity. For example, radioactive iodine with an atomic weight of 131 (I-131) has a half life of about eight days, meaning a sample of I-131 will emit half of its initial radiation after eight days. In just over a month — 32 days — it will have lost 15/16th of its original intensity. After 30 half lives it is considered (by definition) to have completely disappeared.
The table below lists the half lives of significant radionuclides** found in spent nuclear fuel.
Gases
Kypton-85
10.7 years
Xenon-133
5.3 days
Solids
Strontium-90
28.1 years
Molybdenum-99
66.7 hours
Iodine-131
8.1 days
Cesium-137
30.2 years
Cerium-144
285 days
What About the Other 97 Percent?
We have addressed the 3 percent of spent fuel that can be considered extremely dangerous high-level waste, because of the intensity at which it releases its radiation. But we have also seen from the preceding table that the rapid decay of its components lessens its danger to relatively short periods of time. About 97 percent of spent fuel is not waste at all, but valuable uranium and plutonium that can and should be recycled for use as fuel. It seems odd that we are enjoined by “environmentalists” to recycle paper — a truly renewable resource — but be forbidden by government decree to recycle radioactive fuel that is many times more expensive than gold. After chemically removing the high-level wastes, the recoverable isotopes in spent fuels and their half lives are:
Uranium-235
710 million years
Uranium-238
4.5 billion years
Plutonium-239
24.4 thousand years†
Plutonium-240
6.6 thousand years†
Plutonium-241
13.2 years†
Note that except for plutonium-240 and -241, these recyclable isotopes have very long half-lives and they emit their radiation slowly — so slowly, in fact, that they can safely be handled with bare hands. But there is no need for the public to come into contact with any of these since they can be used immediately as nuclear fuel. Already in LWRs, plutonium transmuted from U-238 provides nearly a third of the generated electrical energy. Stockpiled weapons-grade plutonium is being mixed with uranium in a “mixed oxide fuel” or MOX and “burned up” as fuel in the reactor. How better to beat a sword into a plowshare?
So why doesn’t the United States, like other countries possessing nuclear power, reprocess its fuel, removing the high-level radionuclides and reusing the uranium and plutonium isotopes? It is owing to the perceived — rather misperceived — dangers of the plutonium in the “spent fuel.” In 1977, the Carter administration canceled the Barnwell, South Carolina, reprocessing plant then nearing completion because of an exaggerated danger of terrorists stealing our nuclear fuel and chemically separating the plutonium from the uranium in order to build nuclear weapons with it.‡ France, Germany, Japan, and Russia continued with their reprocessing facilities and have assured themselves sources of readily available nuclear fuel for the foreseeable future. Our reprocessing efforts were limited to military purposes.
How Dangerous Are Nuclear Wastes?
Nuclear power plant wastes come in two distinct varieties: the dangerously radioactive daughters that are the remnants of the fission reaction, and the remaining recyclable isotopes that can be “burned” as fuel in the reactors to produce heat, steam, and electricity. Those opposed to nuclear power would have us confuse these two. A nuclear physics axiom is: “In general, the higher a radionuclide’s specific activity, the shorter its half life (decay rate), and the more ‘radioactive’ it is when compared to one with a lower specific activity.” If the “specific activity” stuff seems a bit confusing, you might think of short half-life isotopes to behave like gasoline thrown on the campfire, while the long half-life isotopes are analogous to the methane that seeps slowly up in the bayou and glows on those still, dark nights. High-level wastes give up their energy in a short period of time and then become stable and harmless, while the unused fuel (uranium and plutonium) are so weakly radioactive that their emanations are only dangerous in the minds of those who are dead set against nuclear power.
How long does it take for high-level wastes to become safe? For those interested in a definitive answer to this question, Bernard Cohen’s article “The Disposal of Radioactive Wastes From Fission Reactors” in the June 1977 issue of Scientific American is a classic that delves deeply in to the subject. However, there are ways to attack the question using logic. The daughters of fission reactions are not only radioactively hot but are also thermally hot, since the energy from the decay is converted into heat energy. These decay products begin very hot and cool as they lose radioactivity. The decrease in the heat produced can therefore be equated to the decrease in radioactivity. A canister of waste that produces 30,000 watts of heat energy when removed (after one year) from a power plant cooling pond would have dropped to about 3,000 watts in 10 years, to 300 watts in 100 years, and to a barely detectable 3 watts in 1,000 years. We can see then that the radioactivity of the waste canister has decreased to 1/10,000th its initial value and is not likely to require the services of armed guards 24/7 for 100,000 years, as the more vocal anti-nuclear activists would have one believe.
Where Do We Bury Virginia?
Another interesting way for us to assess the dangers of radiation is to compare the radiation levels found in nuclear plant wastes to those of material found in nature. Numerous studies dating from the 1970s show that ores from which the uranium for fuel was mined have the same amount of radioactivity that nuclear wastes will emit after being sequestered from 400 to 900 years, depending on the quality of the ores and the timing of a power plant’s refueling cycles. If we used the same philosophy about naturally occurring radioisotopes as we do nuclear power plant wastes, we would have to dig up, encase, and rebury the State of Virginia because of the large uranium deposits that have been found there. (And you can be certain Senator Harry Reid, whose fear-mongering about nuclear wastes knows no bounds, would not allow Virginia to be buried in Nevada!)
We don’t attempt to sequester naturally occurring radioactive pitchblende and similar ores to protect humans and animals from cancers and mutations, nor should we. They’ve always been there. Many states besides Virginia — e.g., New Mexico, Wyoming, Colorado, Utah, Texas, Arizona, Florida, Washington, and South Dakota — have ore deposits that are sufficiently concentrated for commercial mining, without harm to the population or causing radioactive pollution of the groundwater. And, for the record, these naturally occurring ores aren’t vitrified, encased in stainless steel, or stored in a dry environment.
Yucca Mountain
In the late 1950s, the National Academy of Science looked into the then-upcoming nuclear-waste disposal situation. At the time reprocessing of the fuel elements was a “given”; thus, it was just the high-level, short half-life decay products that were being considered as nuclear waste. Scientists decided that vitrifying them (making them into glass), encasing them in stainless-steel containers, and burying the canisters in geological formations that hadn’t seen moisture in millions of years was the best way to keep them out of the biosphere and eliminate the possibilities of groundwater contamination. This also allowed for retrieval of the valuable radionuclides if that became desirable in the future.
In 1978, the Department of Energy began studying Yucca Mountain, a 4,950-foot ridge in the uninhabited desert 80 miles northwest of Las Vegas, as a site for the long-term storage of high-level nuclear wastes that by now were considered to include the recyclable fuel components. The facility, which has already been paid for by the nuclear power industry and its rate payers, was expected to begin accepting nuclear wastes in 1998. This did not happen due to a bitter fight over the issues of transportation dangers and the firm opposition by the anti-nuclear activists to even the most stringent safety measures to prevent migration of the waste products into the groundwater.
Yucca is now scheduled to begin receiving spent fuel in 2017, making it possible that some scientists and engineers will have spent their entire careers studying and constructing the repository. (In comparison, it took engineers and workers seven years to construct the 31-mile tunnel beneath the English Channel.) Yet even the 2017 start date is in jeopardy due to opposition from anti-nuclear activists and those who are swayed by their rhetoric.
Somehow we’re expected to believe that rains will suddenly come to the desert, with water rushing through 2,500 feet of solid rock, dissolving the stainless steel shells of the glassified waste, leaching radioactive materials from the glass, and then gushing through another 1,500 feet of rock to the water table. Fast forward 100,000 years where some civilization with the technology to drill wells through several thousands of feet of rock will drink that water — water that would be only a fraction as radioactive as well water in parts of Maine or in health spas all over Europe. As noted, in much less than 100,000 years — 400 to 900 years to be precise — the waste will be no more radioactive that the natural ores that were mined for nuclear fuel.
To even imagine that a stainless-steel canister encasing glassified wastes and stored in a dry environment that has been studied in every particular for over 30 years would deteriorate seems a foolish prediction when there are innumerable cases of unprotected iron fasteners and structural members dating from the Middle Ages that are still serviceable after hundreds of years of exposure to wear, tear, and the elements.
Statistical Deception
The underlying cause of the nuclear-waste “problem” is an exaggerated fear of radiation. We have been conditioned for many years to accept the premise that even the slightest bit of radiation is dangerous — a premise that is not borne out by any experimental evidence.
It is certainly true that high doses of radiation can sicken or kill, and lower but still very substantial exposures can increase one’s propensity for developing cancer. But contrary to “common knowledge,” examination of the data shows that low levels of ionizing radiation often have a beneficial effect on human health known as hormesis — a fact that many scientists are striving to make public with little help from an uninformed and generally anti-nuclear news media. There is a very close parallel between ultra-violet (non-ionizing) radiation from exposure to sunshine and nuclear (ionizing) radiation. While extreme exposure to sunlight can lead to sunstroke and death, and lesser amounts cause sunburn and increase chances of skin cancer, moderate sunshine stimulates our bodies to create vitamin D that is necessary for good health.
We see this same phenomenon with trace elements such as arsenic and many vitamins. It is not unexpected then to see the same human reaction to ionizing radiation.
We have been deceived into believing that all radiation is bad because of the United States’ policy reliance on the “linear no-threshold” theory, or LNT, which states that if large amounts of something cause death or sickness, fractional amounts of the same thing cause proportional amounts of death or sickness. If the LNT were applied to falling as it is to radiation, we might note that 100 percent of those falling onto concrete from 100 feet are killed, but only 50 percent of those falling from 50 feet die. With these data we would linearly extrapolate to say that 10 percent falling from 10 feet and one percent of those falling from one foot would die. Armed with this “linear no-threshold falling theory,” we could confidently assert that jumping rope should be banned on all school playgrounds since statistically anyone making 100 one-foot jumps would die.
Neither experience nor evidence supports LNT theory, yet this same statistical ploy is used to make very small exposures of radiation to large numbers of individuals appear deadly. In 2005, by unanimous vote, both the French Academy of Medicine and the French Academy of Science deplored the use of this dose-response methodology in predicting effects of low-dose radiation. It is high time that the radiation professionals in this country did likewise, and many are doing just that. Unfortunately, the fact that thousands of workers in nuclear industries are outliving their unexposed peers is not considered newsworthy, but a leak of three quarts of reactor coolant water with less radioactivity than salad dressing makes the front page as a catastrophe.
Radioactivity surrounds us. Human beings and all we come into contact with contain radioisotopes. Uranium in the soil will still be radioactive in 10 billion years when our sun runs out of hydrogen. It is a natural part in our universe. To fear it is like fearing the warmth of a fireplace just because fire can also burn down the house. Yet people are still paralyzed with fright because few in this country understand anything about the measurement of radiation or its effects. Until we do we are defenseless against the posturing of radical environmentalists and destined to eventually lose the most incredible source of clean, safe, and reliable energy that man has ever been fortunate enough to enjoy.

* These daughters, if gathered together and weighed, would total a little less than the original uranium atom — and it is that “little less” that has been converted into energy according to Einstein’s famous E=mc2.
** Even these high-level “wastes” are valuable products for industry and medical diagnostics and treatment. Molybdenum-99 is the “cow” or source for producing Technetium-99 used in 30,000 “imagings” in European hospitals everyday.
† Not found in original fuel assemblies, only in recycled fuel.
‡ For why reactor-grade plutonium is not suitable for nuclear weapons, see “Iran and ‘the Bomb,’” October 16, 2006. This article is available online at www.thenewamerican.com/node/1749.
Transporting Wastes
Among the manufactured concerns of the anti-nuclear lobby is the hazard of used-fuel transportation. For those who haven’t driven on the interstate highway system lately, there are already (gasp) hazardous materials being shipped. Nuclear-fuel shipments would amount to less than one-thousandth of one percent of the 1.2 million daily shipments of hazardous materials.
Nuclear Energy Institute Executive Vice President Angie Howard points out that shipments of used nuclear fuel “have been completed safely since the mid-1960s and will continue to be conducted safely in the future. A proven record of 3,000 shipments covering 1.7 million miles with no impact on public safety or the environment demonstrates we can transfer this material safely.”
Used-fuel containers must pass rigorous tests by the Nuclear Regulatory Commission including:
A 30-foot free fall onto an unyielding surface, which would be equivalent to a head-on crash at 120 miles per hour into a concrete bridge abutment;
A puncture test allowing the container to fall 40 inches onto a steel rod six inches in diameter;
A 30-minute exposure to fire at 1,475 degrees Fahrenheit that engulfs the entire container; and
Submergence of the same container under three feet of water for eight hours.
If that’s not sufficiently comforting, there are also transportation tests to verify container integrity, consisting of:
Running a flatbed tractor-trailer carrying a container into a concrete wall at 84 miles per hour;
Placing a container on a rail car that was driven into a concrete wall at 81 miles per hour; and
Placing a container on a tractor-trailer that was broadsided by a train locomotive traveling at 80 miles per hour.
In all cases, post-crash assessments showed that the containers — although slightly dented and charred — would not have released their contents. One wonders how the thousands of tanker trucks transporting deadly chlorine and bromine gases would stand up to such conditions.

1 Comments:

At August 1, 2008 at 3:34 PM , Blogger Dr Gwynith Young said...

Dr Dave Warren, inventor of the aircraft flight recorder (black box) has been pro-nuclear for years. He would accept this argument. But he concedes that disposal is still the key sticking point, not least because of "not in my backyard" approaches. I believe myself that nuclear must now rise high on our country's agenda, but I await more specific disposal proposals.

 

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