Corrosion is the wrong word to use, but you are really just arguing semantics. Radiation can have quite a damaging effect on materials. Radiation interactng with structural materials in a reactor core can cause:
Ionization of materials- accelerating corrosion on the surface of the material and shifts within it Radio-activation of materials- which decay changing the chemical makeup of the material and therefore the disrupting the microscopic structure and weakening it Helium and production - some modes of decay of irradiated structural materials can produce helium (alpha particle) which displaces other atoms in the material and can produce voids within the material
In general the effect this has is mostly in the form of "embrittlement" and "swelling" of the material. While this is notably different than corrosion, it does increase the risk of microscopic cracks and fractures occuring in the pressure vessel. It is through these cracks that some leaks may form- though they are usually so small that it is mostly only the lightest elements like hydrogen that can escape in noteworthy quantity. Still, there the threat that this tritium poses is relatively minor even when released into the environment.
Tritium disperses rapidly in the environment since it diffuses exactly like normal hydrogen gas- this means the direct dose to individual people, plants, and animals in the area will be very low. Consequently, indirect exposure through livestock and produce will be even lower. Ground level exposure is generally exceptionally low compared to that from other potential byproduct releases due to the rapid and high (vertical) diffusion of both tritium gas and T2O. Exposure rates from tritium contamination, even from catastrophic accidents, is low enough to represent little threat to those in the immediate area and indirectly through affected food products and water supplies.
Even high levels of exposure, though unlikely, are generally not a significant threat. The mode of decay is a low energy beta-particle (electron) which is effectively attenuated by a sheet of paper or a thin layer of dead skin. This type of radiation is not particularly harmful, even when ingested. While very large doses over long periods of time can increase free radicals inside the body through ionization effects, the effect is so marginal that tritium is considered safe for use in exit signs. Even decay inside the body, from contaminated water, is unlikely to pose much of a statistical risk. In fact, a broken exit sign in a small movie theater would expose you to a greater dose than they these leaks from nuclear plants. That does is still low enough that, while caution is advised by manufacturers for the sake of prudence, that it does not amount to much more than your normal background dose. Tritium exposure is also considered to be a low enough risk that it is used in found in some gun sights and in some watches. Ingesting the tritium contents of one of these devices, while still far far greater than exposure from these plants, poses little to no real health risk.
In the case of the above story, the "well" described was a test well meant to monitor for releases of radioactive materials and not a drinkng water well- it was within the grounds of the power plant. It should be noted that the test well along the river showed no contamination. Now, even if you were to drink the water from this contaminated well for a year the increased exposure you would suffer beyond normal background radiation would be equivalent to about 1/1000th what you would get from a cross country flight in an aircraft. It is also slightly lower than what you would expect if you lived in an area with naturally elevated background radiation- which some studies have shown to actually produce a slight decrease in cancer rates. That might just be a statistical anomaly rather than an inoculative effect.
Aging power plants, in the US in particular, do pose some serious health and environmental challenges. Tritium leakage is not one of them and this all amounts to anti-nuclear scare mongering. The real worries stemming our unwillingness (not inability, we do have the ability and technology) to properly deal with nuclear waste as well as our reticence towards replacing our aging reactors are much more serious. They are however also much more complicated to explain and much less totally damning than "radiation leakage" sounds, so opponents do not necessarily fixate on the real issues. I find this to be sad and generally damaging to the discourse since it distracts from what would be a very interesting and important debate, were the points being brought up not so often disingenuous. Don't get me wrong, the anti-nuclear crowd does sometimes raise some good points they about how we handle nuclear power; this is not one of them
Not to say you can't produce SOME bomb grade Pu from a perfectly innocent electrical generation plant, but a real engineer would not do it.
That sort of thing would be a political decision weighing the perceived value of reliability with the great loss of efficiency involved in using the same reactor for both tasks. Not that it matters much, but the BN-600 in Beloyarsk is used for both power generation and plutonium production.
I never said this pictures were useful at all in developing a Pu reactor or that a reactor should be run as a power reactor. They are, in fact, irrelevant. I was pointing out that the idea that one could not use a conventional power reactor (such as a PWR, BWR, or unsafeguarded CANDU type design) to produce weapons grade material was erroneous.
You seem to have a misconception about just how much plutonium is produced from a conventional power reactor and just how suitable it is for weapons use. While a normal long fuel cycle does produce waste with about 20% of the plutonium in the form of Pu 240, if one is willing to sacrifie efficiency for the plausible deniability of running a power reactor then you can shorten the fuel cycle and get about 92-94% of the plutonium as Pu 239. That is suitable for weapons use. My point, once again, was that this is not an impossibility- hence the proliferation concerns over reprocessing of spent fuel and the PUREX method. That is preceisely why the UREX method was developed.
Now I should have made it clear when I moved on to talk about other types of reactor designs that I had begun to respond to the poster's argument that it takes more infrastructure than Iran has to make a nuclear weapon. Yes, they likely won't use a power reactor to produce their plutonium since a power reactor is much more expensive than a small heavy-water moderated breeder reactor and also less suited to the task. The argument that a power reactor is incapable of producing weapons grade material belies a complete lack of understanding of nuclear engineering and physics.
And yes, exactly as I had said, you don't want to use plutonium in a gun type bomb design.
While nucleate boiling does occur in pressurized water reactors, they are referred to as "Pressurized Water Reactors" or PWRs while reactors that employ lower pressure single coolant loops where steam is generated directly from the bulk-boiling of the coolant are referred to as "Boiling Water Reactors" or BWRs. While this might not seem to be a clear separation, among nuclear engineers it is almost universally understood what one means by BWR as opposed to a PWR. A nuclear engineer, nor most people even remotely associated with nuclear power and reactors, would refer to a PWR as a "boiling water reactor" as that would give the impression that they were talking about a very different reactor design and probably make them look foolish. Still, we tend to do it accidentally from time to time.
Also, departure from nucleate boiling is a term that is mostly referred to with regards to PWRs as opposed to BWRs. In a BWR, normal operation requires you move well past nucleate boiling. If you did not then the you would run into a lot of problems. Since the steam that is meant to pass through the turbines is that which is generated by boiling the water flowing through the reactor, you are going to have difficulty producing sufficient steam volume with only nucleate boiling. You also want to get a much higher exit quality (percent steam) in your center channel than you could through nucleate boiling. These two things are important to produce power efficiently and to protect the steam turbines. While steam dryers and separators can do a great job with 10+% saturated steam, but high velocity flows of "wetter" steam could overwhelm them and allow excessive amounts of water droplets into the turbines. Too many water droplets in the turbines equals multi-million dollar blade replacements much sooner. This is why departure from nucleate boiling is not really mentioned much when discussing BWRs. While the transition through the appropriate boiling regimes must be considered when calculating the thermal profile of a reactor, the phrase just doesn't come up. What it is used for is in the discussion of safety limits and accident conditions for PWRs. The maximum DNBR (departure from nuclear boiling ratio) is one of the key thermal limits one imposes on the operation of PWR. It is not however an item of concern when setting those limits for a BWR.
*blinks* You can't use a nuclear reactor to build a conventional nuclear device -- the best you'll get is a dirty bomb. You can use a breeder reactor to create fissionable material, but breeder reactors are also useful because they can take many different kinds of fuel and produce power from it, whereas conventional reactors can only use fissile uranium and it degrades to useless and highly toxic byproducts relatively quickly.
*blinks* Oh how you would have failed my fuel cycles class. Plutonium is present in spent fuel from even non-breeder reactors. Though it only represents 1% or so of the spent fuel, there are some potential advantages to using plutonium from spent fuel over highly enriched uranium. Plutonium can be extracted chemically from spent fuel while U235 can not be separated from U238 without enrichment facilities. The process of chemically removing the plutonium requires much less infustructure than enrichment of uranium. That being said, the byproducts are much more of a nuisance. Still, if a country wanted to claim to be using nuclear technology for power while steadily stockpiling weapons grade material, a power reactor and PUREX-like (Plutonium - URanium EXtraction ) reprocessing system would be one way to do it. That is why there have always been such large concerns over PUREX reprocessing.
One type of power reactor could be of particular interest to countries wishing to produce weapons grade material without performan ANY enrichment. Those are natural-uranium reactors which burn un-enriched uranium as their fuel. They require moderation by heavy water though, which tends to offset some of the cost benefits of not requiring enriched material. Still, being able to use only mechanical and chemical processing of uranium ore and leaving out the whole enrichment step does have its advantage. That is probably why India produced its plutonium through chemically reprocessed spent-fuel from a natural uranium reactor (CIRUS). That's also probably why Iran built a heavy water plant near Arak and is currently building a 40MW light-water moderated reactor as well. This is not a power reactor of course but is not particularly special. The reason a reactor like this would be used instead of a larger scale power reactor is because it is much cheaper if you leave off all those multi-million dollar power side components like tubrines and don't have to scale the system up to something that can light a city. To argue that "conventional" reactors can not be used to produce weapons grade fuel is incorrect. While most reactors used to do so are not power reactors, they are also not particularly unconventional in any way that makes them more difficult to build. In fact, they can be built much more cheaply than a power reactor and with a much smaller footprint.
requires exceptionally precise and expensive equipment and a lot of technical know-how to develop several key components to creating a conventional nuclear device.
This part is true enough for some of the more efficient bomb designs like those that evolved from "Fat Man." While one can use a technically simple gun-type bomb with highly-enriched uranium, this is not practical for a plutonium bomb. If a country wants to use plutonium from spent fuel then they must decide between a more technically challenging design with higher efficiency or a simple but low efficiency device like a two-point linear implosion bomb. The latter is not particularly appealing for a large scale and long term weapons program due to the relatively low yield, but has been considered a potential "suite-case nuke" design since it can be built to an extremely small diameter That definately doesn't sound like a design someone worried about terrorism would be concerned with, right?
India has the raw resources, but it's unlikely for cultural and economic reasons that they will develop a nuclear weapons program in the immediate future.
I think the main reason they are unlikely to develop a nuclear weapons program in the near future is that they had already conducted one test in 1974 and 5 more in 1998. They already have a nuclear weapons program, the nuclear infrastructure to produce the refined materials for them, and have built and tested nuclear weapons. They have, however, declared a moratorium on further testing.
Iran and most of the middle-east, for all its bravado and sabre-rattling lacks the infrastructure to make a serious attempt at nuclear weapons research.
A large scale heavy water plant and a 40MW research reactor sound like the infrastructure required to make a serious attempt. India was able to produce its initial plutonium stockpiles and conduct its 1974 "Smiling Buddha" nuclear test using the material output from its... 40MW research reactor and heavy water production facilities.