Canadian Coalition for Nuclear Responsibility |
 | Regroupement pour la surveillance du nucléaire |
Nuclear Wastes:
What, Me Worry?
Part Two
[ click here for the 1987 Addendum ]
3. SHORTCOMINGS OF THE GOVERNMENT REPORT (continued)
3.3. Third Shortcoming: Decommissioning Reactors
The metal structure of the reactor also becomes radioactive through neutron absorption or activation reactions. From the radioactive waste production viewpoint, the important neutron activation occurs in the small amount of corrosion products carried through the reactor by the hot water coolant.
(EMR Report, p. 10)
By the time a nuclear reactor has outlived its useful lifetime of approximately 30 years, many of the structural materials in the reactor building (particularly in the core area) have become so intensely radioactive that they will remain dangerous for a very long period of time many thousands of years. This makes the decommissioning of a nuclear reactor difficult, expensive, and dangerous. It also gives rise to large quantities of radioactive waste which must be disposed of in a geological repository along with the irradiated fuel. This waste problem, resulting from the decommissioning of nuclear reactors is far more important than "the small amount of corrosion products carried through the reactor by the hot water coolant."
It is an astonishing oversight that the study group did not even mention this problem, except for one sentence on page 10 and one line on page 48.
No power reactor has yet been dismantled, although the Oyster Creek power reactor in New Jersey has received an allocation of $100 million to cover the cost of its demise -- considerably more than the $65 million that it cost to build the reactor in the first place! The Elk River reactor (a small US. research reactor) was dismantled in 1971 at a cost of $57 million -- it cost $6 million to build. At the present time, a little reactor known as the Sodium Reactor Experiment, built in 1957 near Santa Susana, California and operated for only seven years, is being dismantled at an estimated cost of $56 million -- it took two years and $13 million to build it.
Radiation fields in the Elk River reactor were measured at 8,000 rads per hour two years after shutdown; but in a large power reactor, radiation fields of 100,000,000 rads per hour may be encountered shortly after shutdown. Because of these intense radiation fields, the radioactive structures will have to be flooded so that remote-controlled underwater cutting techniques can be used to cut them into pieces small enough to be placed in shielded canisters, thence to be transported to a geological waste repository.
(Current plans in the United States call for "mothballing" the reactor by removing the non-radioactive portions, sealing off the radioactive portions, and posting a guard for several decades -- 70 to 100 years -- thereby giving the reactor a chance to "cool down" so that workers engaged in disassembling the highly radioactive portions will not be overly exposed. Here in Canada, however -- according to the only study that AECL has published on the topic -- the cooling-off period has been eliminated.)
The volumes of waste resulting from decommissioning operations are considerable -- about 7,000 cubic metres per reactor. This quantity of waste could seriously influence the requirements for siting and operating a geological waste repository. To get some idea of the magnitude of the problem, Consider the projection of 75,000 megawatts in Canada without any further nuclear expansion beyond the year 2000; a scenario which is accepted by the study group as a likely one.
If we were to maintain 75,000 megawatts in Canada without any further nuclear expansion beyond the year 2000, we would have to decommission the equivalent of four 600 megawatt CANDU reactors each year, based on the assumption of a thirty-year lifetime for reactors. The committee can well appreciate the impact on waste disposal if we have to decommission four reactors per year; yet if nuclear expansion plans continue beyond the year 2000, the problem will be correspondingly greater.
Very little thought has been given to the problem of designing a reactor so that decommissioning it will be as easy as possible. In view of the time and expense involved (AECL estimates that dismantling a standard 600 megawatt CANDU would take six years and cost at least $30 million) it would make good sense to forego the licensing of any new reactors until this fundamental design problem has been addressed.
Such a postponement in reactor construction will also make the ultimate decommissioning burden that much less if the nuclear industry turns out to be a mere "flash in the pan". In a special report to the U.S. Congress by the Comptroller General of the United States, entitled "Cleaning up the Remains of Nuclear Facilities: A Multibillion Dollar Problem" (June 16 1977), this point is made very bluntly:
Obviously, light water reactors cannot be expected to continue indefinitely. If another generation of nuclear reactors cannot be developed or is not needed because another energy source, such as solar energy, has been introduced, the end of light water reactors could also be the end of the commercial nuclear power industry.Here, and henceforth, this report is identified as G.A.O. Report Number 1.The possibility of this industry ending raises questions as to whether there will be nuclear-related organizations, nuclear equipment, and individuals expert in the nuclear field that would be capable of dealing with the decommissioning and decontamination problems that could remain for about 100 years after the last reactor is shut down. (GAO Report#1, p.24)
[ DECOMISSIONING --1987 Addendum ]
3.4. Fourth Shortcoming: Uranium Tailings
To be safe, then, we believe that any wastes containing radioactivity above dangerous levels should be processed to reduce the volume, immobilized, and subsequently put into geological disposal. (EMR Report, p.24)
The study was specifically limited to radioactive material emanating from nuclear power stations and did not cover other aspect of the nuclear fuel cycle (i.e. mining, milling, & refining). (EMR Report, p.1)
People are often surprised to learn that the tailings are far more radioactive and far more dangerous than the uranium which is extracted from the ore. This is because the uranium "daughters" (radioactive byproducts of uranium) are more intensely radioactive than uranium itself, and they all end up in the tailings, accounting for about 85 percent of the initial radioactivity in the ore.
The principal radiological hazards from uranium tailings are due to two pernicious substances: radium-226 and radon-222.
3.4.1. Radium Contamination
Radium-226 is considered to be one of the most toxic radioactive substances known to man. When ingested through food or water, it is considerably more dangerous than either strontium-90 or plutonium-239. It accumulates in the bones, where it can cause bone cancer, head cancers, and other disorders, including leukemia. Chronic radium contamination may eventually prove to be an even more serious problem than mercury pollution is now.
When dispersed into the environment, radium (like mercury or DDT) is concentrated by biological organisms. River algae will typically show radium concentrations from 500 to 1000 times higher than the concentrations in the river itself. Crops irrigated with contaminated water will often concentrate the radium by a factor of 100 or more. In Colorado, in the 1950s, significant quantities of radium were found in the milk of cows, who had grazed on alfalfa, which was irrigated with water from the Animas River, which was polluted with radium from deserted uranium tailings piles further upstream. (For more details, see The Atomic Establishment by Dr. Peter Metzger -- an excellent historical sourcebook on radioactive pollution in the United States.)
It is sobering to realize that the quantities of radium contained in the tailings will be essentially undiminished for the next 10,000 years, and will not reach innocuous levels for several hundreds of thousands of years. Although radium-226 has a half-life of only 1,620 years, it is continually replenished by another radioactive substance called thorium-230, which has a half-life of 80,000 years. That is why the radium hazard is so persistent,
3.4.2. Radon Gas Emissions
Another hazard associated with uranium tailings is the radon gas being continuously emitted from the tailings piles. Radon-222 is a daughter of radium-226. It has a half-life of only 3.8 days, whereupon it in turn produces daughters -- the infamous "radon daughters" -- which are responsible for so many fatal lung cancers in uranium miners.
When radon gas is produced in the hard rock ore deep underground, it is relatively harmless, since most of it disintegrates long before it can escape from the rock formation in which it is trapped. However, once the rocks are brought to the surface and ground to the consistency of fine sand (which is what happens in the milling process), the radon gas can then percolate out of the tailings quite freely and enter the atmosphere.
Despite its relatively short half-life, radon can migrate through the air for hundreds, even thousands, of kilometres. According to a recent study done in the United States by the Environmental Protection Agency, it is estimated that between 60 and 200 people can be expected to die every century for the next 10,000 years and more all over North America -- in Canada, the United States, and Mexico -- as a direct result of inhaling the radon gas and the radon daughters given off by uranium tailings in the Southwest United States.
It has bean suspected for a long time that there is no safe level of radiation with regard to cancer production, but recent scientific evidence from the United States has shown that both radium and radon are even more hazardous at low dose rates than at high dose rates. (For more information, see the Congressional Seminar on Low-Level Ionizing Radiation of May l976, reprinted by the Environmental Policy Institute, 317 Pennsylvania Ave SE, Washington DC, 20003 USA.) This means that the health effects from chronic low-level radioactive pollution from uranium tailings may be far worse than was previously thought.
3.4.3. Methods of Disposal
Clearly, the problem of safely disposing of uranium tailings is one that must be attended to. As Dr. Hare told this committee on December 15, 1977, we need to have
A far more satisfactory position as regards the front end of the fuel cycle: the handling of the mining and milling operations, the wastes that come from these operations at the front end and from any refining that is done in the country. To me that is at least as great in importance as the back end ...
(The front end of the nuclear fuel cycle refers to everything that takes place before the uranium fuel is put into the reactor: the back end of the nuclear fuel cycle refers to everything that happens to the irradiated fuel that comes out of the reactor.)
To dispose of these dangerous wastes in shallow tailings ponds on the surface of the earth is quite unsatisfactory. Revegetation of old tailings ponds has proven to be unreliable in most cases, as the vegetation dies off due to acids which are generated in the wastes beneath. Even when revegetation appears successful, no one can guarantee stability for thousands of years -- it is at best a temporary measure.
If current plans are carried out, the tailings from the Cluff Lake uranium deposit in Saskatchewan will be stored in underground concrete vaults with domed asphalt roofs, because of their extraordinarily high degree of radioactivity. While this seems preferable to the method of dumping the wastes into tailings ponds, it must be borne in mind that each vault will have to be replaced about 2,500 times in the next 100,000 years (assuming a forty year lifetime for each vault). Who will pay for all these vaults, we wonder? And, incidentally, if the vaults only last for 40 years, how long will the containment structures for the tailings ponds last?
Some believe that uranium tailings should be disposed of geologically down the mine shafts from which the ore was extracted originally. It is hoped that this would greatly alleviate the problem of radon gas emissions as well as the problem of radium contamination of surface waters. To prevent groundwater contamination through gradual dissolution of the tailings, they should not be stored loosely underground, but immobilized (perhaps cemented in place) so as to resemble as closely as possible the hard rock environment from which they originally came.
Others have advocated the deep geological disposal of uranium tailings, similar to the deep geological disposal of spent fuel discussed in EP 77-6. On January 12, 1978, under cross-examination at the Porter Commission, Dr. Hare agreed that geological disposal of uranium tailings should be considered. In September 1977, during cross-examination at the Cluff Lake Board of Inquiry, the principle of geological disposal for uranium tailings was also supported by Dr. Peter Dyne. Dr. Dyne was the chief architect of AECL's current geological waste disposal policy before he became Director of Energy R&D under the Honourable Alastair Gillespie.
Here we have another very good reason for slowing the growth of the nuclear power industry in Canada until the waste disposal problem has been properly addressed. Wastes from uranium tailings are accumulating at a fantastic rate, and are already causing excessive contamination in Northern Ontario. If the Canadian government can use international marketing arrangements to boost the price of uranium for economic reasons, surely we can use the same basic mechanism to boost the international price of uranium in order to cover the cost of properly disposing of the radioactive wastes which are produced in uranium mining operations throughout the world.
To work out such agreements will take time. It will be time well spent. The cost of cleaning up the environmental degradation, the cost of paying for the public health burden, the cost of managing these uranium tailings piles into the indefinite future, will be much greater than any extra cost which might be incurred by disposing of the waste properly once and for all. But, we first have to find out whether we can do it, and if so, how we should go about it. This is the radioactive waste problem that should be given the top priority, rather than the problem of spent nuclear fuel -- which is not currently contaminating the environment the way the tailings are.
January 12 1978 Dr. Edwards: Is it your opinion that the geological disposal concept might advantageously be applied to uranium tailings?Dr. Hare: On page 4 we stressed the fact that we have been limited to the discussion of radioactive wastes produced by reactors which means that we have dealt with only part of the problem. "We are strongly of the opinion that the other parts of the cycle are just as significant from the waste management point of view and we recommend that they be studied also." We made that recommendation early on in our study and it is still my opinion that there should be widespread public discussion of the handling of uranium tailings in the same terms and along the arguments that we are having now. Dr. Edwards: In other words, is it your personal opinion that geological disposal should be seriously considered for uranium tailings? Dr. Hare: I have not looked at the problem sufficiently no answer the question authoritatively, but if it contains sufficient quantities of radium or actinide material capable of being released into the environment, then geological disposal should certainly be looked at in that context. But again that is a personal opinion; it is not in the report. |
September 1, 1977 I would be much happier with large amounts of radium if they were also put eventually underground in a geologic repository ... I don't want to create problems for the mining companies but ... I would myself much prefer to see all these radioactive wastes, and that includes the low level wastes, essentially put away into geologic storage so we don't get into these interim storage techniques and make a long-term commitment to these. I don't really like that idea.
- Dr. Peter Dyne, chief architect of |
[ TAILINGS --1987 Addendum ]
3.5. Fifth Shortcoming: Assessment of Risks
We conclude as follows: (1) the health hazard posed by disposed-of-irradiated fuel or reactor wastes will be virtually nil (2) the safe disposal of such fuel and wastes is essential for public health. (EMR Report, p.30)
It seems as if the authors are anticipating the conclusions of the research project which they are advocating. They have concluded in advance that such research can only produce favourable results. Obviously, they are entitled to their opinion. However, in a public information document such as this, it would seem that a special effort should have been made not to rush to judgment, but to describe all those potential mechanisms which could conceivably jeopardize the integrity of a geological waste repository.
The study group could have tried to communicate to the public just how toxic this material is, in order to help people appreciate the stringency of the requirements for radioactive waste disposal. They could have pointed out that a single medium-sized reactor produces more radioactive garbage in one year than would result from the fallout of a thousand Hiroshima bombs. They could have noted that there is more strontium-90 and caesium-137 created inside the four Pickering reactors each year than has been produced by all the atomic bomb tests conducted to date, including the underground tests. However, the study group chose not to do so, perhaps because such comparisons do not contribute to a positive public relations image for the nuclear industry.
But without an appreciation of the enormous toxicity of these nuclear wastes, it is impossible to arrive at a realistic assessment of the risks involved in trying to store them safely for a million years or so. To be safe, these wastes must be contained to the 99.99 percentage level, and beyond. Never, in the entire history of human civilization, has anything been contained to this degree of perfection.
What if nuclear power is allowed to expand, and yet no satisfactory solution to the waste problem has been found by the year 2000 ? What if geological disposal in granite is discovered to be unacceptable for reasons which are not yet known? What do we do then?
Wouldn't it be wiser to adopt a policy today of slow growth or no-growth in nuclear power until we have a solution to the waste problem "in the bag"? As Sir Brian Flowers said at the Porter Commission's Nuclear Seminar on September 26, 1977, the most sensible nuclear policy would seem to be "a constructive dragging of the feet".
The following points briefly outline some of the many factors which make radioactive waste disposal a risky business.
3.5.1. Overheating of the wastes
This irradiated fuel is highly radioactive, giving off both particle and penetrating radiations. These radiations are actually a form of energy, and, on absorption, become heat. (EMR Report, p.10)
If the heat is not dissipated fast enough, the temperature in the repository will rise. One of the objectives of the Canadian research program will be to determine just how hot the wastes should be allowed to get.
If they become too hot, then the glass containers may crack. Moreover, as Dr. Aikin pointed out at the Porter Commission on January 14, any glasses become soluble in water at temperatures above 250 o C. In addition, the thermal stresses caused by the heat buildup could cause serious fractures in the granite rock itself thereby establishing a path for water to enter the repository and dissolve the glass containers. For all these reasons and more, it is essential to guarantee that heat will be quickly dissipated through the rock so that the wastes do not get hot.
This seemingly simple and straightforward problem is complicated by several factors:
- There is no scientifically agreed-upon calculational model to predict what the temperature of the wastes or the rock will be at some future date. In one of the scientific references we checked, we found the following mathematical formula, accompanied by a cryptic comment:
here is the formula: 
here is the comment:
"There are probably as many approaches to this kind of heat problem
as there are variables."Somehow, such comments do not succeed in inspiring confidence in us! After decades of experimental and theoretical work on heat diffusion through rock strata, such processes are still not fully understood.
- The rock, which is not a good conductor of heat in the first place, may in tine become less and less efficient in dissipating heat as a result of "thermal fatigue" (analogous to the reduced conductivity of old electric wiring).
- There is a significant possibility that chemical reactions may take place between the stored wastes and the minerals in the rock, leading to a sudden unexpected rise in temperature.
- Some minerals exposed to radioactivity may "store up" the energy in their crystal structures, subsequently releasing the stored energy in a sudden burst called a "Wigner release" which could cause overheating of the wastes. This is precisely the mechanism which triggered the infamous Windscale reactor accident in 1957; a Wigner release from the graphite moderator led to a raging fire in the reactor core, spreading radioactive contamination over much of Northern Europe.
[ HEAT --1987 Addendum ]
3.5.2. Disintegration of the Waste Containers
They also allowed for the eventual breakdown of the glass in which the wastes were embedded.
(EMR Report, p.33)
- Intense radiation has a noticeable weakening effect on almost all structural materials, causing then to become brittle and increasing the likelihood of their undergoing spontaneous disintegration by crumbling into tiny pieces. In particular, glass is known to "age" over time, and radiation effects in old glass may be substantially worse than they are in "young" glass.
- It is known that radiation damages crystal and crypto-crystalline structures (such as glass) by knocking individual atoms out of place, leading to a marked deterioration in the physical properties of the substance. (For example, quartz becomes more aqueous or jelly-like after intense or prolonged radiation exposures).
- According to the California Interim Report, "the recrystallized form of the waste-containing glass which results after short storage periods has been noted to be more leachable than the original glass. Examination of naturally-occurring uranium- and thorium-containing glasses has also shown alterations over time which may make the glass more susceptible to leaching." (California Report, p. 81)
- The slow unremitting buildup of helium gas over thousands of years within the stored wastes (due to alpha radiation) may contribute to the possibility of the containers crumbling or shattering into a million pieces when disturbed by earthquakes.
U.S. nuclear authorities are now operating under the assumption that their canisters for stored wastes will completely disintegrate in a relatively short period of time -- within a century. EMR Report EP 77-6 refers to a French study which also allows for the eventual breakdown of the glass in which the wastes are to be embedded (EMR Report, p. 33). AECL considers this possibility unlikely and is not prepared to accept it in the calculations. However, it would seem to be prudent to assume that the containers will disintegrate, no matter how unlikely this may seem to AECL scientists.
After all, if this radioactive garbage ever gets out into the environment, the damage will be irreversible. We could no more clean it up than we can presently clean up the mercury contamination that fouls our waters today.
[ CONTAINERS --1987 Addendum ]
3.5.3. Chemical Reactions in the waste Repository
This radiation can cause electrical effects in the materials they pass through, frequently resulting in chemical change. (EMR Report, p.25)
- Chemical reactions are more easily triggered under the influence of heat (which stimulates the molecules) and radiation (which causes ionization). It is important to remember that the glass blocks buried at Chalk River 15 years ago contained only very small amounts of radioactive waste material, so that the glasses were not subjected to significant heat or radiation. Indeed, the small amount of heat that was produced inside these experimental blocks was carried away by subterranean cooling waters. Conditions will be very different in a geological repository, and chemical reactions will be much more likely.
- Chemical reactions between the hot glass containers and the host rock are a distinct possibility, especially in the presence of small amounts of water. The resulting chemical decomposition of the rocks may well lead to the evolution of hydrogen, oxygen. and other gases, possibly creating an explosive situation, especially if there is a significant heat buildup.
- In subterranean salt depositories, it has been found that hot radioactive wastes will actually cause small pockets of brine to migrate through the salt to the wastes, thus providing water for possible chemical reactions. It is not yet known whether a similar mechanism may cause water to migrate toward the wastes in granite formations.
Special attention should be focused on this question of possible chemical reactions when siting a waste repository, It would make most sense to search for a rock formation which involves relatively few minerals, since the possible chemical reactions are then so much more restricted that they can be investigated one at a time on a laboratory scale. Site approval should not be given until the entire series of chemical experiments has been concluded. Further significant expansion of the nuclear power program may have to be delayed pending the outcome of such experiments.
[ CHEMISTRY --1987 Addendum ]
3.5.4. Integrity of the Waste Repository
The main question then arising is clearly this: can one dispose safely of high-level, long-lived wastes or irradiated fuel so as to isolate them from the environment for very long periods? How secure, in other words, will be the radioactive materials committed to the disposal sites? (EMR Report, p.31)
There are three fundamental objections to this line of reasoning.
The first objection has to do with our predictive abilities -- do we really know what the future will bring? After all, the planet was once lifeless, but it did not remain lifeless forever. The continents were once joined together, but at some point in time they separated. The great western plains were produced by the scraping of gigantic glaciers across the surface of the earth, and no one can tell us what was there before the glaciers came. Our knowledge of earthquakes is still in its infancy; seismic maps are still being redrawn after every major quake that doesn't fit the current theory. As one pundit said, "predictions are always uncertain, especially when they deal with the future."
The second objection to the concept of geological disposal is simply this: how do you get the wastes into an undisturbed geological formation without disturbing it? Is it possible that the heat, radioactivity, and chemical activity of the stored wastes may threaten the integrity of the rock formation from within? What guarantees do we have that the plug that we put in the mine shaft will be as strong as the rock itself? The rock is of course a hard nut to crack, but the sealed mine shaft will be the product of human engineering. What evidence do we have that any human engineering project will remain intact for a million years, or even ten thousand years?
The third objection has to do with future human intervention which may bring the buried wastes back into contact with the biosphere again. A comparison may be helpful in this context with the pyramids of Egypt, which are only about five thousand years old. These mammoth structures were built to be burglar-proof, and to last forever; yet every single pyramid had been vandalized before the twentieth century, with one exception: the underground tomb of King Tutenkhamon, which was discovered intact in l922. (In other words, WE were the vandals who broke into King Tut's tomb and carted the treasures away!) Now just suppose that the ancient Egyptians had discovered nuclear power, and that King Tut's tomb had been a radioactive waste repository. The question is: would we have been able to decipher the hieroglyphics in time to realize the danger that might be involved in opening up the tomb? And even if we did decipher the message, would we not simply dismiss the warning as some kind of primitive superstition or curse?
Here are a few factors which may affect the integrity of a granite repository for radioactive wastes:
- Granite is a brittle substance, especially prone to fracturing and faulting. The very act of sinking a shaft and excavating chambers will likely cause significant fracturing of the rock. Even if this fracturing is not sufficient to jeopardize the safe containment of the wastes, subsequent earthquake activity may greatly extend the damage and expose fractured pathways to and from the stored wastes.
- No sensible relationship exists between earthquake activity and geology in the Canadian shield. The present quiescence in earthquake activity cannot be taken as evidence for forecasting seismic inactivity for the next 1000 years or more. In the case of Madoc, for example, there are two very active regions nearby: the Ottawa-Bonnechere Graben and the St. Lawrence Rift System. The proximity of these seismically unstable areas makes the entire region vulnerable to the future occurrence of earthquakes of greater magnitude than those previously recorded.
- Most of the minerals found in granite rocks are considered to be in a "metastable" state due to their low temperature of crystallization. These minerals are subject to damages at temperatures and radiation asset expected from the buried wastes over a long period of time. In particular, these metastable minerals are easily dissolved by natural waters, especially between 25 o C and 200o C.
- Glaciers are capable of depressing the surface of the earth by more than 1000 metres. In the case of a granite formation which is already weakened and partially fractured by excavation, the resulting stress may cause massive cracking or crumbling of the rock, thereby establishing a pathway to the environment for the buried waste.
[ INTEGRITY --1987 Addendum ]
3.5.5. Pathways to the Environment
Conclusion 17: from a carefully selected repository, with suitable immobilization techniques, it will be at least many centuries before such released radionuclides would reach the surface, and then in great dilution. (EMR Report, p.1)
The only obvious pathway whereby radionuclides might find their way back to the biosphere would be via solution or suspension in circulating groundwater. (EMR Report, p.32)
Conclusion 16: If unforeseen groundwater movement invades the repository, radionuclides may be carried outwards, but at rates very much slower than the groundwater movement itself, with the possible exception of Iodine-129 and Technetium-99.
Having made these rather sweeping assertions, the report goes on to express great confidence in a new and unproven technique called "pathways analysis". This technique uses complicated mathematical equations which are programmed into a computer in an attempt to calculate how long it will take for the radioactive waste to be carried by the water to the outside world, and then to trace the pathways of these dangerous substances through the food chains, and finally to calculate the ultimate health and environmental effects in the real world.
However, our knowledge of such pathways is still in its infancy, and the sources of error are numerous. Although pathways analysis is undoubtedly useful, it is only a mathematical exercise and may turn out to have little connection with reality. Nature can be very capricious; she does not always behave as expected.
We all hope that the wastes will never return to the environment of living things once they are buried. If they do return, however, it may be by a totally unanticipated pathway -- one which was not even considered in the "pathways analysis" conducted before its burial.
Consider the following hypothetical scenario. Suppose that at some point in time, perhaps because of earthquake activity, a temporary pathway through the sealed shaft is created and flooding occurs in the waste repository. Suppose further that the shaft is then tightly blocked, sealing the water inside the repository. Now suppose chemical reactions take place between the stored wastes, the water, and the host rock, leading to the production of large quantities of steam and non-condensable gases. Pressure would be created and that pressure would continue to build up over a period of years or even decades in the underground repository, finally resulting in a violent explosion which could establish a pathway (perhaps through the shaft again) to the environment. If the waste containers have meanwhile disintegrated, you could have a radioactive geyser spreading contamination over a very large area.
This hypothetical scenario is not intended to be particularly realistic, though it is not impossible. It is intended merely to suggest that not all pathways may be predicted in advance. We must not be so foolishly arrogant as to suppose that we have anticipated all possible eventualities, when we come to site such a waste repository. There could be some nasty surprises.
Even in dealing with circulating groundwater, there is much that we do not know and much that we may never know. Within a rock environment, it is known that some radioactive substances can easily be carried along by slowly circulating groundwater, while other radioactive substances will move much more sluggishly because they tend to cling to the rock surfaces. The EMR report states:
A few of the fission products, notably technetium and iodine, are poorly sorbed and will hence move close to the rate of the water itself... (But) Strontium-90, which is poorly sorbed, and which moves at about one percent of the groundwater rate, would take 100,000 years to reach the surface, by which time it will have decayed to a non-radioactive nuclide. Strongly sorbed materials, like plutonium and most of the actinides, would take much longer. Such results are reassuring, but they would be misleading if the groundwater moves directly upwards, as it is believed to do in poorly permeable but fractured rocks. (pp.32-33)
- Just three months ago, new evidence was published in the United States which shows that some of the actinides can move hundreds of times faster than plutonium,
-
"... and thus plutonium is an unsuitable analog for the other actinides. This work strongly suggests each of the actinides must be treated as a separate entity ..." (Health Physics, Vol.33, No.77, p.316)
Since these other actinides (americium and neptunium) also have very long half-lives, they could conceivably reach the surface in dangerous amounts. We keep learning these new things -- how many more such surprises lie in store?
- Radionuclides may escape and travel at a much faster rate than the EMR report indicates. Iodine-129 is a gas: it will move much faster than the groundwater. Tritium and selenium-79 are also known to migrate very quickly. The EMR report fails to consider the possibility of water moving under pressure, which would cause radionuclides to be carried along very much faster and drastically reduce the opportunity for adsorption. There are other mechanisms by which radionuclides can travel at a much faster rate than anticipated -- for example, if they are carried along inside living micro-organisms.
- Not all scientists are convinced that "the key property in slowing the escape of the radionuclides to the surface [is] the sorption capacity of the rock." (p 13) According to the California Interim Report, "a panel of scientists under the auspices of the National Academy of Sciences concluded that the belief that plutonium and other transuranics are tightly held to soil particles and therefore not likely to move significant distances is not well founded. In addition, the scientists found that studies of marine and fresh water sediment columns as well as soil columns indicate unexpected vertical mobility of plutonium-239 and americium-241." (California Report, p.97)
Because of these difficulties, licensing actions on waste disposal are likely to take on a radically different tone. When required to provide expert opinions on geologic phenomena in the long time frame required, few if any reputable geologists are likely to insist that a particular depository selected by ERDA or industry will remain stable. Further, materials scientists may encounter the same difficulties when discussing very long-term leach rates, transport properties, or other phenomena important to safety issues. Finally, the experimental bases for conclusions drawn about the interaction of waste and environment will be essentially absent. Under these conditions, the licensing agencies will have to proceed on bases with which neither the public nor the agencies are particularly satisfied or familiar. Specifically, most evidence used to evaluate to safety issues will be based on extreme extrapolations of uncertain information, little of which will be subject to test. The normal, strongly redundant approaches which the public has come to expect from the nuclear industry will be absent.
Dr. M.J.Steindler |
[ PATHWAYS --1987 Addendum ]
3.5.6. Biological Effects of Escaped Waste
They will run through the ecosystems like other soluble nutrients and may be locally reconcentrated by organisms. However, the dilution will be so great that they will not enter food chains in any appreciable quantities. (EMR Report, p.7)
Thus some release of certain radioactive materials is allowed, but it is such that no individual will receive a damaging amount of radiation. (EMR Report, p.25)
If radionuclides should escape into the biosphere from the repositories, it is virtually certain to arise from groundwater movement to the surface with subsequent possible movement through soils, plants and animals into human food and drink. (EMR Report, p.36)
The prompt effects are radiation sickness (nausea, loss of hair, drastic changes in blood cell composition, radical gastro-intestinal disturbances, etc.) and radiation burns (skin lesions which are very difficult to heal). These symptoms only occur when an individual is exposed to a massive dose of radiation, and then they are manifested promptly, within hours or days following exposure. At low dose rates, none of these symptoms is observed and the individual appears to be completely unharmed.
The delayed effects of radiation exposure include various types of cancer in the exposed individuals and a broad spectrum of genetic deficiencies in the offspring of the exposed individuals. These effects do not occur for many years after exposure, and there is apparently no such thing as a safe dose of radiation when it comes to these "delayed effects". In other words, there is no dose that is so low as to prevent any radiation-induced cancers or genetic defects to occur within the exposed population. This being so, it is indeed misleading to say that "no individual will receive a damaging amount of radiation". Such assurances can be given for the prompt effects, but not for the delayed effects of radiation.
The linear hypothesis, which is the cornerstone of modern regulatory philosophy, states that the number of radiation-caused cancers and genetic defects that will occur in a given population is proportional to the sum total of all the doses received by all the members of the population.
The implication of the linear hypothesis in terms of public health is that "dilution is not the solution to pollution". If a small groups is suffering from excess cancer as a result of large radiation exposures, it may be thought prudent to distribute the same total dose among a much larger population so that each individual receives only a tiny portion of the total dose. According to the linear hypothesis, however, there would be no reduction whatsoever in the number of cancers produced. The same applies to radiation-induced genetic defects. The increased incidence of these delayed health effects depends not on the size of the individual dose, but on the magnitude of the total population dose -- and it is largely chance that determines which individuals in the exposed population will suffer the ill effects...
The Hypothetical Individual
excerpted and rearranged |
P.J. Barry, IN ANSWER TO A QUESTION |
The escape of radioactive wastes into the environment could have very damaging long-term effects. Here are some of the factors which may make the situation much sore serious than is indicated in the EMR report:
- Radioactive materials can be concentrated be living organisms in surprising ways. Much is known, but there is still a great deal to be learned. Iodine-129 will concentrate in the thyroid gland and may cause thyroid cancer; but since it has a 17 million year half-life, the same amount of iodine can affect an awful lot of thyroid glands. Technetium-99 has recently been shown to be taken up by plants to a much greater degree than was believed two years ago. A 1975 symposium held by the IAEA on Transuranium Nuclides in the Environment showed that most of what we thought we knew about actinide pathways is probably wrong, because exceptions are more common than rules. The published proceedings refer to a "growing concern about man's ignorance of the biogeochemistry of [plutonium and other actinides] in relation to ... long-term buildup, availability, and transport in the environment."
- The health effects of low level radiation may be much worse than is currently believed. Strong evidence has been produced that the linear hypothesis systematically underestimates the risk from alpha radiation. Epidemiological evidence indicates that "the risk of radiation-induced cancer of almost every type [is] more, to an order of magnitude greater, than we considered them to be some time back." (Dr. Karl Morgan, in Proceedings of a Congressional seminar on low-level ionizing radiation, referred to previously on page 17.)
- Although there is some evidence to suggest that the genetic effects of radiation may not be as severe as previously thought, there are still great uncertainties. Many diseases such as heart disease, schizophrenia, arterioscleroses, mental retardation, cancer, diabetes, and early senility have genetic linkages and may be expected to increase in frequency with increased radiation exposures. Moreover, some of the genetic effects will be recessive traits and may not show up for several generations,
- There are many other delayed health effects which are suspected to be radiation-induced, including a generalized life-shortening and greater susceptibility to infectious diseases of all sorts. Details can be found in the Proceedings of the Congressional seminar on low-level ionizing radiation of May 1976, already referred to.
[ BIOLOGICAL EFFECTS --1987 Addendum ]
