Exit Sign Tritium

Are Safer Reactors Possible?

Critics of nuclear power argue that all reactors are inherently dangerous, and point to nuclear accidents such as Three Mile Island, Chernobyl and Fukushima as evidence of the danger. The primary worry about nuclear power stems from the release of radioactive fission products, and other radioactive materials that are produced inside reactor cores. Among those materials Plutonium which is produced by a nuclear process which occurs when Uranium-235 and U-238 fail to fission following the absorption of neutrons inside reactor cores. Tritium a hydrogen isotope is also viewed with concern, although in practice tritium is viewed as so safe that it is used to illuminate the hands and dials of some wrist watches. The Nuclear Regulatory Commission (NRC) explains,

In fact, if there were any significant danger from tritium, the NRC would outlaw using it in wrist watches. Just how dangerous is tritium? Recently a very small tritium leak from the Vermont Yankee power and was the subject of a big todo in Vermont. Nuclear critics insisted that the tritium represented a huge danger to the people of Vermont. The My conclusion from all this is that the present tritium leak at Vermont Yankee is no small thing. The material is dangerous at low concentrations, persistent in the human body, impossible to filter, and hard to contain. The leak is limited to the area in and around the plant for now, but I can’t imagine the isolation and cleanup is going to be easy. Based on reading a number of different articles and checking through the tables provided by the Vermont Department of Health, the fluid that was leaking into the ground contained tritium at a concentration of approximately 2.5 million picocuries per liter. That is equal to 2.5 x 10^-6 curies per liter. The rate that it was leaving the pipe was roughly 100 gallons (370 liters) per day. If the leak had been going on for a year before being detected and stopped, the total quantity of fluid that left the pipe would equal 138,000 liters. The total activity released would be 0.35 curies. If a single person consumed every drop of that water, their whole body radiation dose would equal roughly 30 rem. According to a 1977 UNSCEAR study, the LD-50 (lethal dose for 50% of the population receiving the exposure) for tritium in adult rats was determined to be 1000 Rad. For the kind of low energy beta emissions that are produced by tritium, a rem is equal to a Rad. A dose of 30 rem received over a 1 year period would be unlikely to cause any immediate health effects, though it might add an additional risk of developing cancer sometime during the person's life. The magnitude of that risk could be computed using the conservative linear, no-threshold dose assumption. On the other hand no one doubts that the escape of plutonium from a reactor can be a dangerous matter. Yet unlike tritium which is less dangerous than salt, but likely to escape from a reactor, Plutonium os very dangerous, but very unlikely to escape from a reactor. Nuclear critics love to recited how dangerous plutonium is. For example, journalist David McNeill stated In conventional Light Water Reactors plutonium is produced inside fuel pellets. The fuel pellet is a ceramic and in almost every case the fuel plutonium will remain there. The only way the plutonium might escape the fuel pellet, would require that the reactor core overheat to such an extent that the ceramic fuel pellets start to melt. Once the plutonium escapes the fuel pellet, it faces a further barrier, the pressure vessel, which contains the reactor core inside a thick steel wall. If the plutonium managed to get past the wall of the pressure vessel, it would face one or more cement barriers, and then the forces of gravity as it pulled the plutonium to the outside grounds of the nuclear power plant. So how did the plutonium manage to travel a mile away from the Fukushima reactors? The answer is probably because it was ejected from the reactor building by a hydrogen explosion. More likely the plutonium was contained inside the spent fuel pellets that were housed in a pool above the Fukushima reactors. It is far from satisfactory that any plutonium managed to escape from the beyond the grounds of the Fukushima reactors, but in fact the amount that escaped was so tiny that it could do no harm. . A 1 GW LFTR would produce about 40 Pounds of Plutonium a year. If the goal is to minimize plutonium production this can be easily done. If the goal is to destroy plutonium, the presence of thorium in a reactor core facilitates the burning of plutonium. Finally if the goal is to produce no plutonium, then the use of fluid fuel thorium breeders (LFTRs) is highly recommended, because Neptunium-237, a plutonium predecessor isotope can be cleaned from a molten salt coolant before it can be converted from neptunium into plutonium by absorbing a neutron. Cleaning NP-237 from molten salt fluid is a relatively easy and low cost procedure. Once out of the LFTR core the neptunium can be destroyed in a burner reactor. An important feature of our proposal is to locate every- thing that is radioactive at least 10 m underground—where all fissions occur—while the electric generators are located in the open, being fed by hot, nonradioactive liquids. The reactor’s heat-producing core is constructed to operate with a minimum of human interaction and limited fuel additions for decades. . . . Under- grounding will preclude the possibility of radioactive contam- ination in case of airplane disasters. A combination of 10 m of concrete and soil is enough mass to stop most objects. It would eliminate tornado hazards and, most particularly, contribute to defense against terrorist activities. In case of accidents, under- grounding, in addition to the usual containment structures, en- hances containment of radioactive material. The 10-m figure is a compromise between safety and plant construction ex- pense. We anticipate the cost to construct underground with only 10 m of overburden using the berm technique will add ,10% to the cost. Plutonium is very heavy. In order for plutonium to overcome the "gravity barrier" some force would have to transport it to the surface. That force cannot be an explosion, because there is nothing in the reactor or its fluid salts that can explode. Nor can it be a fire, because no fire is possible. Thus the plutonium is trapped underground. In " Migration Paths for Oklo Reactor Products and Applications to the Problem of Geological Storage of Nuclear Wastes ," G. A. Gowan repotted that plutonium along with many fission products including Zr, Nb, Ru, Pd, Ag, Te, Bi, and the rare earths, were immobile the the Oklo natural reactors core areas over a period of time of well over a billion years. In fact it appears that less than 10% of the actinides present when the original Oklo deposit was laid down had been lost to natural causes over a nearly two billion year period of time. Thus we can have a high degree of certainty that plutonium would be contained in underground reactor chambers, following the very unlikely event of the release of plutonium carrying salt inside the underground reactor chamber. As noted what holds true for Plutonium also holds true for many fission products. The Oklo Reactors "natural experiment," that an underground reactor accident would not lead the the release of most fission products and actinides in a reactor or in a nuclear cool down storage. Neptunium would be a potential exception and for that reason it should be removed from long term storage of nuclear wast and disposed of by nuclear burning. The fission products that are likely to escape in the event of a nuclear accident are well known and their behavior is well understood. They are noble radioactive gases, and volatile fission products. In fact the noble gases appear to pose little danger, and while volatile fission products are more dangerous, that danger can easily be mitigated. However, in Molten Salt Reactors it is easy to prevent the escape of fission products from the core fluid simply be removing them by simple and well understood processes. Reactor researcher, David LeBlanc states , The molten salt reactor that operated in the 1960s had a big advantage in the removal of many fission products without much effort. Gases ~Kr and Xe! simply bubble off aided by helium gas bubbling, where these gases are separated from the helium and stored in sealed tanks to decay. Noble and semi noble metals precipitated. In the planned reactor, the old method of removing the gases may be repeated. Clearly then if the public wishes to be assured that it will never be exposed to radioactive isotopes from reactor cores that can be accomplished at a relatively trivial cost without sacrificing any of the advantages offered by nuclear power. I can not assess how much safety the public will want or view necessary in order to be comfortable with nuclear safety, but the technology to provide the public with safety that would assure no human deaths due to accidental releases of radioactive isotopes in a reactor core accident. This standard may not be rational, but the Oklo Natural reactors demonstrate that such a standard is obtainable, and with Molten Salt Reactor technology it is obtainable without paying a high financial cost.

Wal-Mart's mysterious missing exit signs: A tritium health risk ...

What do Home Depot, the Mormon Church, and the U.S. Coast Guard have in common?

Answer: Radioactivity.

According to the Nuclear Regulatory Commission, the construction retailer, the church denomination, and the guardians of our coastline own hundreds of fluorescent exit signs containing the radioactive gas tritium. So, in fact, do various school districts, retail stores, and federal and state agencies. And if the signs are handled and disposed of improperly, tritium could make its way into our drinking water. The NRC was prompted to step in following Wal-Mart’s recent disclosure that 15,000 tritium exit signs have mysteriously disappeared from its stores nationwide.

On January 16, the NRC sent notices to 61 organizations that own 500 or more tritium signs to check the signs against their records and report any lost or missing signs to the agency. The recipients of the “demand for information” letter include the Department of the Navy, the Smithsonian Institution, the U.S. Postal Service, and the West Point Military Academy, as well as several pharmaceutical, defense, and aviation companies nationwide.

In all, more than two million tritium exit signs are estimated to be in use in the United States. The signs are popular because they do not require electricity and provide emergency light and direction during evacuations.

From 2001 to 2007, Wal-Mart bought 70,000 tritium exit signs to install in its stores and warehouses, according to the NRC. In 2007, after discovering that some signs had disappeared, the company started a nationwide audit of its facilities. The result: a staggering 15,000 signs were lost, missing, or otherwise unaccounted for.

An NRC advisory states that the tritium signs pose “little or no threat to the public health and safety and do not constitute a security risk.” Others are not so sure. “Fifteen thousand missing tritium exit signs at 20 trillion picocuries each means that 300 quadrillion picocuries of tritium could be making its way into people's drinking water,” warns David Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists. “Or, nearly four million gallons of water could be contaminated above the EPA's drinking water standards. And what if 15,000 missing tritium exit signs is a low estimate?”

Damage may already have been done. In January 2006, the Pennsylvania Department of Environmental Protection notified the NRC that more than half of the DEP’s water measurements downstream of landfills in the state showed tritium concentrations above the Environmental Protection Agency’s safety drinking water limit.

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