I think the Canadians have a design for a helium cooled reactor that is much closer to being fail safe.

The Canadian design (the Candu reactor) actually uses heavy water (deuterium based water) as a part of the reactor core/moderator as well as the heat transfer coolant. If the heavy water leaks out, the reaction stops. It is extremely safe, however, if is far more expensive to build and maintain due to the cost of the heavy water. They do make power efficiently, are profitable and nearly 100% safe.

 

What is likely to happen now is that the Japanese reactors that are failing are going to provide ammunition for the anti-nuclear types. Every one of those old pressurized water reactors needs to be taken out of service.

 

The Canadian design (the Candu reactor) actually uses heavy water (deuterium based water) as a part of the reactor core/moderator as well as the heat transfer coolant. If the heavy water leaks out, the reaction stops. It is extremely safe, however, if is far more expensive to build and maintain due to the cost of the heavy water. They do make power efficiently, are profitable and nearly 100% safe.

I don't understand why the decay of the uranium fuel will stop if the heavy water moderator is not present. Can you go into that part of the safety a bit more?

John

 

I don't understand why the decay of the uranium fuel will stop if the heavy water moderator is not present. Can you go into that part of the safety a bit more?

John

From a quick search:
http://canteach.candu.org/library/20040718.pdf

 

What is likely to happen now is that the Japanese reactors that are failing are going to provide ammunition for the anti-nuclear types.

rightly so.

 

@nsaspook,

Thanks, ¶18.4 answered my question. I guess I rely on Wikipedia too much.

John

 

There are more types of reactor than I had imagined - http://www.world-nuclear.org/info/inf77.html

 

@nsaspook,

Thanks, ¶18.4 answered my question. I guess I rely on Wikipedia too much.

John

Sorry John, went back out to the Glades but I see you got your answer. This is a natural result of using un-enriched, natural uranium, as the fuel. This is one way the Candu saves money too.

 

A couple of reasons why we shouldn't

1. Fermi I (1966)
2. Three Mile Island (1979)

For a bone chilling account, at odds with the official version, of the accident at Fermi I see

http://www.amazon.com/Almost-Lost-D...=sr_1_1?s=books&ie=UTF8&qid=1300063877&sr=1-1

 

As they say, necessity is the mother of invention. Wikipedia stressed the necessity part of Candu. That does not diminish the inventive part in the least. For another example, compare the MiG 21 to the F4. Of course, we all know the MiG 21 was first designed by a bunch of Germans. John

 

The talking heads today tossed out a scary sounding 'fact'. Some people have recieved as much as 20,000 times the normal dose of radiation for a day.

However without a basis of how much radiation that is and how it compares to a known lethal dose it is pretty useless and inflammitory language. The actual amounts that are dangerous was NOT EVEN MENTIONED.

So everyone is like, OMG - 20,000 TIMES THE NORMAL DOSE! OMG!

Turns out the normal dose is a small fraction of a MICRO REM. 20,000 times merely lifts the dose into the low low milli rem range.

Turns out ONE simple chest xray can expose a person to many thousands of millirems.

So, these people recieved less radiation than I did last year at the hospital with an xray for a broken toe bone.

G_D DA_M fear mongering asshats. Why wouldn't they want everyone to know that 20,000 times the background level is NOTHING even compared to a chest Xray.

 

As Candu demostrates it's possible to make a fail-safe system using un-enriched, natural uranium, as the fuel. Light water high pressure system are not fail-safe as they always need power for cooling so you see what's happening in Japan. SO the problem is not nuclear power but the fact that most current power reactors are just sized up models of US sub reactors where the goal was max power in a small space and not safety as the primary goal, with the operator acting as the fail-safe.

 

G_D DA_M fear mongering asshats. Why wouldn't they want everyone to know that 20,000 times the background level is NOTHING even compared to a chest Xray.

if it bleeds it leads as they say in 'the business'.

http://www.bbc.co.uk/news/world-asia-pacific-12729221
A second explosion has hit the nuclear plant in Japan which was damaged in Friday's earthquake.
...
The U.S. Seventh Fleet said Monday it had moved its ships and aircraft away from the quake-stricken Japanese nuclear power plant after discovering low-level radioactive contamination. The fleet said the radiation was from a plume of smoke and steam released from the crippled Fukushima Dai-Ichi nuclear power plant, where there have been two hydrogen explosions since Friday's devastating earthquake and tsunami. The fleet said the dose of radiation was about the same as one month's normal exposure to natural background radiation in the environment.

okay, fair enough. but they still got the hell out of there.

 

okay, one more,
http://www.youtube.com/watch?v=6UZuNI7Yk2k

 

It is a question of comparative risk and the extraordinary standards to which most nuclear plants comply. Nuclear power is a hot political topic, and the media, politicians, and interest groups are never hesitant to use fear mongering to promote their agenda.

However, as mentioned by Kermit2, the data rarely support such concerns, particularly when the risks of injury from nuclear power are compared to risks from other activities. For example, according to this article in Scientific American, coal ash is more radioactive than waste from our nuclear power plants, yet the former is used for roads and the latter must be buried as hazardous:

http://www.scientificamerican.com/article.cfm?id=coal-ash-is-more-radioactive-than-nuclear-waste

These data from the International Atomic Energy Agency for occupational exposure show that nuclear power workers have less exposure than civilian air crews or those who work in above ground buildings.

Source:http://www.iaea.org/Publications/Booklets/RadPeopleEnv/pdf/chapter_9.pdf
Occupation/Industry          Exposure (mSv/year)
Uranium mining                               4.5
Uranium milling                              3.3
Metal mining                                 2.7
Civilian aircrews                            3.0
Above ground buildings                       4.8*
Nuclear reactor                              1.4
Nuclear reprocessing                         1.5  

*The source article does not explain what is meant by this.  I suspect it may be a limit rather than an average.

As for the Seventh Fleet moving, there can be lots of reasons for that. One could be that the allowable radiation surveillance levels on nuclear-powered ships are so extremely low that the low level of contaminants they might be exposed to in the area of this disaster would create false alarms. I doubt it was an matter of imminent danger.

John

 

this article in Scientific American, coal ash is more radioactive than waste from our nuclear power plants, yet the former is used for roads and the latter must be buried as hazardous

yeah they kind of just failed to mention the waste part didn't they.

a deliberately misleading article...
and even more-so before their readership spoke up.

it's really more about perception / stereotype management than anything else.

 

Does anybody really believe there exists a "safe" level of ionizing radiation to which they would be willing to expose themselves?

 

Does anybody really believe there exists a "safe" level of ionizing radiation to which they would be willing to expose themselves?

In brief, yes. There is a level of ionizing radiation for which I am not willing, nor would I expect others to take additional risks necessary to reduce my exposure levels below it.

John

 

Well there are certainly consequences associated with that position, and we won't really know what they are until it is too late. Since I live not too far from Fermi I and TMI who is to say my chronic conditions are not related to environmental factors.

 

Since I live not too far from Fermi I and TMI who is to say my chronic conditions are not related to environmental factors.

How far is "not too far?"

More on point, no one can say what your conditions are not related to, even if Fermi and TMI never existed.

John