Nuclear Power and its Waste

The disposal of radioactive waste from nuclear power operations is an intractable problem which does not appear to have any solution. The Nuclear Regulatory Commission (NRC) has promulgated a draft Generic Environmental Impact Statement for public comment which outlines their plans and assurances for the continuing ability to safely deal with spent nuclear reactor waste. Their term is “waste confidence.” These are some of my comments concerning the accuracy and credibility of that draft which I submitted during their public comment period.

Fuel rod storage under water in fuel pools also has the problem of radiolytic hydrogen generation which can react with the zirconium cladding and other metallic components to cause hydride embrittlement. This creates problems for the future handling of the rods in the dry cask systems because the fuel elements become fragile and can break during transfer or repackaging, thereby releasing their contents. It is unclear whether the embrittlement gets worse with continued aging in dry storage. The NRC states that the Fukushima disaster proves the design strength of spent fuel pools, in that all pools survived the tsunami and reactor explosions virtually intact. They do not mention the fact that these pools are now perched precariously six stories above the destroyed reactors and are almost impossible to access. Removing the spent fuel to a safer location would expose workers to high ambient, perhaps lethal, radiation levels. Photos of the pools in news reports from the site appear to show debris lying in the pools although the water level seems to be maintained. Two and a half years after the accident TEPCO has only just now begun to deal with this spent fuel and the outcome is still far from certain.

As for dry cask storage, the NRC has proposed basically two scenarios to deal with the political impasse over the Yucca Mountain repository; and to inspire “confidence” that nuclear power plants will be able to continue to produce and dispose of their nuclear waste into the foreseeable future. These scenarios are: (1) continued on-site storage of spent fuel in cooling pools for the first 60 years after reactor shutdown, after which the fuel will be transferred to dry cask storage on-site, placed on concrete pads in the open air where they are effectively parked for the next 100 years or indefinitely with pad and cask replacement each additional 100 years; and (2) away-from-reactor dry cask storage at independent spent fuel storage facilities yet to be determined, on concrete pads in the open air, with the possibility of indefinite storage by replacing the pad and containers every 50 to 100 years. Facilities for dry transfer of fuel assemblies between casks would need to be constructed in both of the above scenarios.

The away-from-reactor analysis in the case of scenario (2) smacks a bit of desperation as the NRC repeatedly uses another politically failed depository as an example of and “proof of concept” that an away-from-reactor consolidated independent fuel storage facility is both feasible and practical. The example used is that of a withdrawn license application by Private Fuel Storage, Ltd., to build a depository on the Goshute Indian reservation in Skull Valley, Utah. Basically, the proposal amounted to relocation of the politically failed national underground repository at Yucca Mountain to an above-ground, open-air, indefinite, storage facility, built to accommodate 40,000 metric tons of the nation’s accumulated high level nuclear waste, just 35 miles from Salt Lake City. Not surprisingly this proposal met with considerable resistance. PFS, Ltd. wanted the Goshute land because it was not subject to state environmental regulations. They approached the tribal leaders and made them an “offer they couldn’t refuse,” namely, give every member of the tribe a million dollars and let them all move away from their reservation, en masse. Some members of the tribe declined the recommendation of their elders and because they refused to leave the reservation, the deal fell through. The Governor of Utah also weighed in on this controversy and threatened to block road and rail transport of high level waste across State transportation corridors into the depository. The proposal became a poster-child for environmental injustice, until it was eventually abandoned.

It is disingenuous on the part of the NRC to pretend that spent nuclear fuel storage is just like any other industrial enterprise with similar land and water use characteristics. Nuclear waste lasts “forever” and so will permanently alter the use possibilities of any affected site. It also bears a stigma in the public mind, largely because of its association with nuclear weapons and the proliferation problems that association represents. This perception will psychologically limit proposed future uses of any such site and will attract other equally obnoxious industrial operations. Thus the land must be considered a “sacrifice zone” from the beginning with no pretense that it will ever be reclaimed for general use. The long duration of spent fuel storage presents another problem, that of securing the fissionable material from misappropriation and misuse. As the fuel ages and the radioactivity decreases it becomes more attractive as a target for theft and extraction of its plutonium content. The USA is less than 240 years old so that is all the experience we have as a republic. Over the next few centuries, while the fuel remains “hot,” I submit that we have no way of predicting what sorts of situations might occur. We cannot, therefore, be “confident” that the current political and economic systems will continue to provide the physical security, in perpetuity, needed to keep the fissionable materials safe.
Other reasons aside, it is not a good idea to concentrate such a large amount of waste in one place especially if it is stored above ground. This makes it a target for aerial and surface terrorism and creates the potential for a huge accident with widespread contamination of the air, land and water.

Since no one wants a high-level nuclear dump in their backyard, or the transport of high-level nuclear waste through their neighborhood, the acceptance of a “Yucca Mountain” in the backyard scenario is unlikely to happen anywhere in America. Also the very concept of away-from-reactor consolidated interim storage does not meet with the strictures of ALARA, since transporting the waste twice or more in its lifetime greatly increases the risk of accidents and exposure to bystanders. It also unnecessarily contaminates virgin land not currently radioactive. The transport of nuclear waste is also not well controlled. For example, I personally measured radiation emanating from a transport truck on Interstate-40 near Amarillo, TX of several hundred CPM (50 times background) in just the few seconds it took to pass the truck. One can only imagine the exposure level to the driver and anyone parked next to the truck at a café, fueling stop, rest area or motel. The transport also exposes the fuel to the possibility of theft or traffic accidents which is clearly not a trivial risk. For the above reasons I believe that the entire Section 5 of the Generic Waste Confidence draft should be discarded as both imprudent and impractical. There may, however, be some situations where continued dry storage at the original reactor site is so dangerous that moving the spent fuel to an alternate, safer site is possibly justified, but risk versus benefit must be evaluated for each individual situation. Moving the fuel should never be merely for the convenience of the operators.

The NRC analysis of dry cask storage of spent fuel, for decades if not centuries, is totally inadequate. The description of how the fuel canisters are hermetically sealed is not sufficient for the reader to assess risk. The report states that “fuel is loaded into canisters, (presumably steel); the air and water are pumped out; the canister is filled with “inert gas” (what inert gas?); and the top is welded in place” to seal-in the spent fuel and isolate it from the environment. In another section, describing the long-term maintenance of casks at the facility, a comment is made that, during replacement activities, “around 10% of the casks and support pads will need to be disposed of as low-level radioactive waste.” There is no explanation as to how the casks and pads can become contaminated since they are supposed to be hermetically sealed. There are two obvious possibilities: (1) there is a failure of containment in the canister with the escape of the “inert gas” and the entry of air and water into the fuel canister with subsequent corrosion. This would compromise the integrity of the containment vessel and result in leakage. Continuous exposure of the canister metal to radiation from the enclosed fuel could also weaken its physical integrity and result in metal failure, corrosion and leakage; and (2) there is neutron activation of casks, canister components and the pads themselves.

In case (1) the NRC presents no history of dry cask storage to support its contention that the risk from loss-of-containment accidents is small, particularly over the super long time frames envisioned. In case (2) we are informed by the statement that “casks are placed 15 feet apart to avoid criticality events.” This would seem to indicate that spent fuel in dry casks still emits neutrons at a measurable rate, which are not absorbed by the cask shielding. This presents a problem for evaluation of dose to workers since neutrons have a biological effectiveness 20 to 50 times greater than an equivalent exposure to the same quantity of gamma or X-rays. Also since dry casks are cooled by circulating ambient air through the casks, inside the concrete shield, there is a significant potential for activation of atmospheric nitrogen by neutrons to form carbon-14-carbon dioxide. Since the earth’s life forms are carbon based, carbon-14 is a particularly noxious toxicant. Carbon-14-carbon dioxide has a long half-life and is also readily incorporated into the biome by photosynthesis, where it can be assimilated into bio-molecules such as DNA which are vital to life. Carbon-14 decays by beta emission and can cause disruption and mutation of bio-molecules in three different ways: (1) the emitted beta particle can ionize and disrupt adjacent bonds in the molecule; (2) the beta decay can cause the source nucleus to recoil and be expelled from its position in the bio-molecule causing bond recombination in deleterious ways; and (3) the decaying carbon nucleus can transform itself into a different element with different chemical properties and thus compromise the chemical integrity of the bio-molecule. The NRC does not state how much carbon-14 would be produced and released into the atmosphere by the air cooling of dry casks over decades or centuries or how this would affect future generations. This is not a question of a dose distributed uniformly over the planet affecting everyone equally; but rather the effect of a widespread random distribution of discrete biological disrupter molecules into the biosphere, (the biochemical equivalent of “land mines” or “time bombs” in the macroscopic world) each with the potential to cause random disease, mutation or premature death. During the atmospheric nuclear test era the concentration of carbon-14 in the biosphere more than doubled. This is one likely explanation for the large increase in the cancer rate during that same time frame.

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