WhiteBlue wrote:Edis, you are conveniently forgetting the real risks of the nuclear power industry. They start with the fact that uranium mining is one of the dirtiest forms of energy mining known to man. The mines in Russia and other countries are environmental disasters poisoning the countryside and the drinking water for miles around. Russian uranium miners and their families have extremely short life expectancies and are likely to die of radiation exposure illnesses very quickly. Those practices have been common in the industry as claims of Australian aborigines show. The federal republic of Germany just spend € 6 billion of tax payer's money to clean up the Wismut Uranium mining operation which was primarily exploited by Russia for weapons and energy use.
WhiteBlue, I'm not forgetting anything, but unlike you my arguments are based on facts rather than emotional opinions and various unsupported claims.
Uranium mining
is generally not significantly different than any other mining operation of heavy metals. There are some extra controls with regard
to radiation levels, but radioactivity can be a concern even for other types of mining and
is generally not a problem when mining most uranium ores. For most underground mines ordinary ventilation prevent high radiation doses for
the workers. Very high grade ores can require automated equipement and radiation protection work workers
to ensure safe radiation levels of workers, but such ore
is rare.
At
the Olympic Dam mine in Australia
the annual radiation dose
to workers have been measured
to less than 1 mSv and
the average annual radiation dose for
the mine workers subjected
to the highest doses have been measured at 3.6 mSv (
http://www.arpansa.gov.au/pubs/rps/rps9_ris_final.pdf ). People living near
the Ranger uranium mine in Australia are subjected
to 0.04-0.2 mSv/year, and radiation
to locals due
to water contamination
is 0.01-0.02 mSv/year. Workers in Canadian uranium mines are subjected
to 0.45-3.71 depending on
the mine and
the work carried out by
the worker. As a comparison
the annual radiation dose by natural background radiation
is typically in
the range 1-10 mSv depending on location,
the average being 2.4 mSv. There are however extreme cases of natural background radiation of up
to 250 mSv/year. Similar,
the radiation dose received by a Swedish iron ore mine worker during
the seventies could be a round 70 mSv/year, far more than what uranium mine workers are subjected
to today.
Uranium oxide have a chemical toxicity comparable
to lead oxide, and
the precautions for handing it are similar too. Clothes, gloves and in some cases
the use of respirators.
Modern mines in OECD countries are typically forced
to pay
the costs it takes
to restore a mining area. How uranium mining was done in
the past isn't of concern for modern
nuclear power. But uranium mining can certainly be done safely.
WhiteBlue wrote:Plutonium is not the stuff you use lightheartedly for power like gasoline. It is illegal to transport it by air in many states including the US because of it's poisonous character and the extreme duration of contaminations. Half life time is ten thousands of years which makes contaminated sites unsafe for periods that extend the time frame of written history. Of course open contaminated sites tend to be "cleaned up" by dilution but that only means that the radiation gets carried away and is spread over wider areas than the initial accident or bomb release site. It is known that very few inhaled micro particles of plutonium oxide can cause cancer. This is one of the reasons that nuclear explosions for weapon research have been banned first for air and ground burst and then for under ground bursts as well.
No, plutonium
is only
the stuff you use
to power pacemakers and spacecraft, and another of
the actinide metals that are produced in reactors, americum can be found in household smoke detectors. Yikes...
The plutonium myths just never seem
to die. Most (but not all) of
the plutonium produced in
nuclear power reactors are Pu-239, a plutonium isotope that
is a weak alpha emitter much like natural uranium. It has a half life of 24,000 years and
the long half life
is the reason for
the low radioactivity (although much higher than for natural uranium which has a much longer half life). Since alpha radiation can't penetrate
the skin it
is only harmful if ingested.
Aside from radiological toxicity plutonium
is a toxic heavymetal much like lead and other similar metals. It
is considered safe
to ingest up
to 1 milligram plutoniumoxide.
The safe limit for air contamination are 0.1 Bq/m^3 (1 µm sized particles).
Plutonium
is not a significant handling issue; clothes, gloves and possebly a respirator if there
is a danger for plutonium particles in
the air. Inhaling particles
is where plutonium can do
the greatest damage. Since plutoniums discovery in 1941 there have however not been any deaths due
to plutonium exposure.
WhiteBlue wrote:Processing nuclear waste from Plutonium breeding reactors involves a serious amount of transporting highly active nuclear materials. This is a high risk in densely populated areas like central Europe. It has been shown by activists that German castor rail transports exceeded the legal radiation limits by a factor of 100. People on railway stations have been exposed to illegal dosis of radiation regularly. This isn't even contemplating what happens in accidents during transportation and processing. There have been accidents in Plutonium processing plants in Germany before, where workers got contaminated. Luckily those were very early days and the released quantities were small.
The majority of
the radiation in used
nuclear fuel
is caused by short lived fission products and has very little
to do with plutonium. If
the used fuel
is from a breeder or light water reactor doesn't really matter, although MOX fuel have some special requirements in order
to avoid a criticality incident.
Used fuel
is shipped in forged steel shipping casks by road, rail or by sea. This have been done under 40 years without accidental release of radioactivity. There
is no danger
to the public during normal operation, it
is safe
to go near one of these casks and they are designed
to handle severe accidents without failure. They have for instance been dropped from 600 meters, run over by train and burned without failing. Should
the cask fail in for instance a very severe fire, this
is not a big disaster as
the zircalloy fuel cladding would handle
the temperatures caused by for instance a tunnel fire.
I don't think Germany have any "plutonium processing plants", they have uranium enrichment plants but that
is something else. Handling of uranium
is comparable
to many other toxic heavy metals some of which can be found in for instance
solar cells.
WhiteBlue wrote:Reprocessing produces large quantities of radioactive waste that needs to be stored away from the biosphere for a long time. Germany has been pioneering the deposition of radioactive waste materials for many years. We have used disused deep salt mines for the purpose. It now transpires that these depots are not safe. The initial geological surveys always predicted that the mines would stay bone dry. It is not true as we now know. The German depot Asse is flooded at increasing rates and only massive pumping keeps the water away from the radioactive materials. There are very serious concerns that we ever find a safe place to store our highly radioactive materials if we cannot control the medium radioactive stuff. A final depot isn't identified for the accumulated radioactive waste of all the German power plants. The Americans have similar problems with their nuclear test area in Nevada. Underground water gets contaminated by the bomb residue and it carries the radiating materials off site.
Current reprocessing plants like La Hague use
the PUREX process. Used fuel
is dissolved in acid, and plutonium and uranium are extracted from this solution separate.
The remainder, a few percent of
the total fuel mass,
is mixed into glass and poured into stainless steel containers.
A 1000 MW
nuclear reactor needs about 20 metric tons of new fuel each year. Equally, 20 metric tons of used fuel
is produced. When taken out of
the reactor this fuel
is highly active and produce heat due
to radioactive decay.
The fuel will have
to be cooled for many years. In Sweden
the used fuel
is first stored at
the powerplants in 9 months or more before taken
to a central underground storage facility where it will be stored under water in large pools. It will remain there for at least 40 years,
the longer one waits
the easier
the fuel will become
to handle as
the radioactivity levels rapidly decrease at first along with
the heat production. As
the volumes of used fuel are very small, there isn't really any need hurry
to build final repositories. Infact, there
is much energy still left in
the used fuel, it could be reused in a CANDU reactor (due
to its much better neutron economy) and/or reprocessed where
the uranium
is enriched for new fuel rods and
the plutonium
is blended with depleted uranium
to produce MOX fuel (
the reactor thus burns plutonium into fission products).
The best, but more long term solution
is however
to use
the plutonium and other actinides in fast reactors. Fast reactors with their high energy neutrons and good neutron economy are able
to burn
the long lived actinides into mostly short lived fission products.
Using fast reactors
to destroy long lived transuranics does however require modifications
to the reprocessing process and there are several such process under development. Short lived fission products would then
go to to a final repositories, transuranics are burned as fuel and
the few long lived fission products could potentially be dealt with by transmutation. Other valuable products could also be reused.
Among short lived low and mid activity waste, which account for
the largest volume of radioactive waste but only a small part of
the radioactivity, some of it can be cleaned and recycled (PWR steam generators for instance). Among mid level waste, what can't be cleaned and recycled
is put in steel or concrete containers along with radioactive waste from healthcare, research and industry and filled with concrete. This can then be stored in several ways.
Low level waste needs
to be safely stored for 50 years and mid level waste for 500 years.
WhiteBlue wrote:Personally I do not believe in the claims that all consequences of nuclear accidents are now covered by insurance. It certainly wasn't the case in Chernobyl. That accident is a good example how the long term damages by radiation will be denied by the operators, the insurers and the authorities. Ukraine and Belorussia are experiencing a flood of genetic defectively born babies that is predicted to continue for many generations. Insurance firms will deny most of the consequences and blame it on "natural" radiation. They typically pay only for the most obvious like death by measurable over exposure. The side effects of low level contamination of huge areas are completely ignored although they cause much human suffering as well. Increased cancer and birth defects are argued away as always. There are indisputable scientific studies about child leukemia being significantly increased in the immediate surroundings of German nuclear power plants. These result show that the legal level of nuclear release that we achieve in some of the safest nuclear plants on earth is still problematic. Hence I do not believe in claims that all risks of operating nuclear power plants are economically insurable. We should not forget that many countries like Russia have nowhere near the safety standards that would be applicable in Germany, Sweden, France or Switzerland. Nevertheless the fallout from accidents will still be our problem to deal with to some extend.
Western
nuclear reactors have today accumulated more than 10,000 reactor years with only one significant
nuclear accident, one that did not cause any deaths.
The cost for cleanup after that accident was one billion dollar. Today
the probabiliby for such an accident
is probably more like one in a million reactor years.
The costs for Chernobyl have been estimated at $15-20 billion. Costs of an very extreme accidents have in some cases been cited as $100 billion, however, such as accident
is however only expected
to happen once in one billion reactor years.
Of course, there are no such things as unlimited insurance cover. It would not be economically possible cover an unlimited amount, there
is simply not an insurance company that have unlimited resources. So industries which potentially could cause large damage such as
nuclear, hydro and petrochemical are forced
to sign an insurance with a limited coverage required by law. We have
the Paris convention and in
the U.S. they have
the Price-Anderson
nuclear industries indemnity act. Both require
the nuclear industry
to have a no fault insurance up
to a certain amount and a system
to cover costs above that.
The top risk
is taken by
the state in case there would be a very severe
nuclear accident much like
the top risk for a very severe dam failure
is also taken by
the state.
The costs for
the states carrying
the top risk
is the costs for all
the hypothetical accidents which
the state will have
to pay for adjusted by
the probability for each accident. This cost have been estimated
to be $0.5-5.0 per reactor and year.
Chernobyl was operated by a communist state, so they probably didn't have any insurance.
The state probably acted as its own insurance company so
to speak, combined with other states that have payed some of
the costs. As I mentioned earlier
the costs have been estimated
to be in
the region $15-20 billion. Of couse, a reactor of
the kind used in Chernobyl wouldn't have been allowed
to be built and operated in any of
the OECD countries.
In any case, there aren't any "flood of genetic defectively born babies that
is predicted
to continue for many generations". Overall,
the effects on
the part of
the population that received
the highest doses have been smaller than expected. Cancer fatality rates among those subjected
to the highest doses are just a few percent higher than what you expect among a population. Infact,
the Chernobyl Forum report state that
the risk
to mental health caused by exaggerated fears about radiation are a greater risk than
the long term effects of radiation exposure.
The Chernobyl Forum report can be found here:
http://www.iaea.org/Publications/Bookle ... rnobyl.pdf
"There are indisputable scientific studies about child leukemia being significantly increased in
the immediate surroundings of German
nuclear power plants." Well, those studies have already been disputed. While so called cancerclusters can be found around
nuclear powerplants aswell as around other power plants and industries increased radiation levels near a
nuclear power plant can't explain
the increase in cancer rates. Someone living near a
nuclear power plant receives around 0.02 mSv/year due
to the plant, in addition
to the 1-10 mSv/year in natural background radiation. 0.02 mSv
is less than you would receive on a transatlantic flight (0.04 mSv) or a dental x-ray (0.09 mSv) and
is only about a tenth of what you would receive by living a house with radon. So, where you live and what you do will be much more significant which yearly radiation dose you receive than if you live near
to a
nuclear powerplant or not. There
is simply not a correlation beween cancer rates and radiation levels near
nuclear powerplants (Baker, P.J. and D.G. Hoel, "Meta-analysis of standardized incidence and mortality rates of childhood leukaemia in proximity
to nuclear facilities").
Radioactive fly ash from coal fired power plants also tend
to be a bigger problem than radiation caused by normal operation of a
nuclear power plant. A 1000 MW coal fired powerplant can release 5.2 tons of uranium and 12.8 tons of thorium annually. This
is due
to uranium and thorium traces in
the coal that
the powerplant burns.
WhiteBlue wrote:I also do not share the optimism that new breeding reactor types will reach the safety level of low pressure water reactors for uranium processing quickly. The development history of new reactor types is littered with serious accidents due to unforeseen technical problems. Why should that be different when the level of technical complication is increased by using much higher pressure or heat or using combustible cooling agents like liquid metals? People have rightly expressed concerns over all these aspects and mostly improvements of safety and industry practices have only been achieved by public pressure. The people in this country do not trust the nuclear industry because they have been lied to too many times. Personally I do not trust people who claim that there are no problems with a wide industrial use of Plutonium for electric energy production. There are too many examples of the past that show the dangers are real and that they usually get understated. For me to believe in the promotion of breeding reactors I would require a solid expert opinion that covers the negative points as well. Until I read such a balanced opinion I will always suspect that the promoters are only serving their personal agenda or are repeating the propaganda of the nuclear industry lobby.
A liquid metal cooled reactor
is by design naturally safe. A lightwater reactor operate at a high pressure, a boiling water reactor (BWR) do for instance operate at around 70 bar,
the pressure that raises
the boiling point of water
to approx. 280 degC.
The water will thus boil at 280 degC inside
the reactor vessel at a pressure of 70 bar. Of couse, should one of
the main feeds
to the reactor break,
the result would be a pressure loss inside
the reactor which would lead
to boiling and a rapid loss of coolant inside
the reactor. Becuase of that risc all reactors are equipped with separate emergency core cooling systems which keeps
the reactor core cool.
To improve safety, later reactor design have all feedwater pipes above
the core.
A liquid metal reactor can on
the other hand operate at low pressures since
the boiling point of
the liquid metal
is very high.
The pressure
is therefore atmoshperic or just slightly above, of course oxygen free and inert.
The reason for using metal as a coolant
is because it doesn't act as a moderator and slow down
the neutrons; a fast neutron reactor. As a coolant there are two common metals/alloys sodium/potassium and lead/bismuth. As sodium react with water and become radioactive when irradiated it
is commonly used with a primary and secondary sodium coolant loop.
The sodium in
the primary loop
is heated by fission,
the sodium in
the primary loop then heats
the sodium in
the secondary loop which
is then used
to boil water. That
way water can safely be kept away from
the sodium that passes through
the reactor. Lead and lead-bismuth cooled reactors on
the other hand use only one cooling loop and boil
the water directly. Often liquid metal reactors are of
the pool type where pumps, heat exchangers, steam generators and everything
is built into
the reactor vessel. Combined with
the low pressure, that makes coolant leaks very unlikely compared
to lightwater reactors.
Liquid metal reactors also tend
to respond with reduced reactivity when
the temperature
is increased. So if
the reactor
is overheating its power output will be decreased without any operator intervention. Tests have been conduced on sodiumcooled reactors where
the primary coolant pumps have been stopped and
the reactor have stabilized itself.
If a core damage after all should occur, there isn't any water in
the reactor that separated into oxygen and hydrogen by
the temperature and cause an explosion. During
the Three Mile Island meltdown a hydrogen bubble formed in
the top of
the reactor that was of some concern, it was however later shown that
the oxygen had reacted with
the zirconium cladding around
the fuel pellets and formed zirconia so no free oxygen was availible. Of course, without water, this wouldn't be a possebility at all.
Experimental fast breeder reactors have been around since
the 1950'ties and
the most common types have many reactor years behind them.
