On 15/04/2011 05:06 PM, Jim Henderson wrote:

> Where it becomes problematic is when they say "I don't need to know how
> this works, as long as someone else does and it works" and then argue
> with the science of how it works with no understanding of it.

FULL CIRCLE!

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Le 2011/04/15 12:00, Darren New a écrit :
> On 4/15/2011 8:49, Invisible wrote:

>  > Or somebody flies a passenger jet into it. Or...
>
> They're designed to resist that one.
Or a jet fighter going at full after burner speed with maximum ammo.

>
>> Uranium-235 has a halflife is 700 million years.
>
> U-235 isn't that dangerous, tho, unless you pile up enough to interact.
>
> What it also means is that if you spill 100 pounds of U-235 somewhere,
> it's going to take 700 million years for even 50 pounds of it to have
> emitted radiation. That's a very low level of radiation.
>
> The actual chemical properties are probably more dangerous than the
> radioactive properties if you spread it out widely enough.

True!
Uranium is a heavy metal, and is toxic the same way as lead or arsenide, 
but somewhat more reactive.
Plutonium is lso much more dangerous based on it's extreeme chemical 
toxicity than it's radiation, and it's much more radioactive than uranium.

>
>  > That's /halflife/, not the
>> time it takes to degrade completely, just the time for *half* of it to go
>> away. 700 million years is longer than that oil has been in the
>> ground. ;-)
>
> Which tells you that it isn't *that* dangerous or there wouldn't be any
> life in the ground.
>

And during all that time, the rate of emission steadily goes down.

The most dangerous radioactive materials are those with short half-life.
Then, if that material emmits almost all of it's radiation as alpha 
particles, you may dismiss it (twice ionised helium). It's stopped by 
any sheet of paper. They can only cause damage if they are inside your body.

Then, there is the beta particles (electrons). Not to penetrating. A 
plank of wood, almost any thickness of any metal, or about 1m of air 
will stop it.

The real problem are gamma rays and neutron emissions. Gamma rays need 
thick lead shielding to stop.
Neutrons can make other materials become radioactive. They can also 
travel prety far. But water, and several other materials, does stop them 
effeciently.


Alain

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Le 2011/04/15 13:00, Orchid XP v8 a écrit :
>>> That doesn't mean that the cooling system can't overload and explode.
>>
>> Right. But if you knock down a thorium salt reactor, it just gets cold.
>> It's basically a big stack of pool-ball sized balls that heat up if you
>> get a bunch of them close enough. So if something goes wrong and knocks
>> down the wall, it cools off and you send in people in lead-lined
>> bulldozers to scoop the stuff up.
>
> If it's so simple and easy, why isn't everyone doing it?
>
>>> Uranium-235 has a halflife is 700 million years.
>>
>> U-235 isn't that dangerous, tho, unless you pile up enough to interact.
>>
>> What it also means is that if you spill 100 pounds of U-235 somewhere,
>> it's going to take 700 million years for even 50 pounds of it to have
>> emitted radiation. That's a very low level of radiation.
>
> How do you work that one out?

Halflife is defined as "the time it takes for half of the original 
amount to degrade". So, it takes 700 millions years for half of your 
uranium's atoms to deckay, and thus, emit radiation. After 1400 millions 
years, 75% of the original amount will have deckayed.
It apply to radioactive materials. It also apply to medication in your 
body, and many other things.

>
>> The actual chemical properties are probably more dangerous than the
>> radioactive properties if you spread it out widely enough.
>
> Well, yeah, that's probably true enough.
>
>>> That's /halflife/, not the
>>> time it takes to degrade completely, just the time for *half* of it
>>> to go
>>> away. 700 million years is longer than that oil has been in the
>>> ground. ;-)
>>
>> Which tells you that it isn't *that* dangerous or there wouldn't be any
>> life in the ground.
>
> It's also an extremely rare element. Not like a reactor core, which is
> make out of pure Uranium...
>

A reactor core is NEVER "pure uranium".
The uranium is contained in "fuel canisters" incerted into fuel 
channels, then there is the moderator medium, then the cooling system, 
then the controll rods channels.



Alain

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>>>> Uranium-235 has a halflife is 700 million years.
>>>
>>> U-235 isn't that dangerous, tho, unless you pile up enough to interact.
>>>
>>> What it also means is that if you spill 100 pounds of U-235 somewhere,
>>> it's going to take 700 million years for even 50 pounds of it to have
>>> emitted radiation. That's a very low level of radiation.
>>
>> How do you work that one out?
>
> Halflife is defined as "the time it takes for half of the original
> amount to degrade". So, it takes 700 millions years for half of your
> uranium's atoms to deckay, and thus, emit radiation. After 1400 millions
> years, 75% of the original amount will have deckayed.
> It apply to radioactive materials. It also apply to medication in your
> body, and many other things.

Are you saying there's some sort of relationship between the halflife of 
a substance and how much radiation it emits?

>>> Which tells you that it isn't *that* dangerous or there wouldn't be any
>>> life in the ground.
>>
>> It's also an extremely rare element. Not like a reactor core, which is
>> make out of pure Uranium...
>>
>
> A reactor core is NEVER "pure uranium".

It's far nearer to being pure than anything in nature.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On Fri, 15 Apr 2011 18:48:14 +0100, Orchid XP v8 wrote:

>>>> Which tells you that it isn't *that* dangerous or there wouldn't be
>>>> any life in the ground.
>>>
>>> It's also an extremely rare element. Not like a reactor core, which is
>>> make out of pure Uranium...
>>>
>>>
>> A reactor core is NEVER "pure uranium".
> 
> It's far nearer to being pure than anything in nature.

Would you like me to have a bona-fide nuclear physicist refute this?  I 
have a very close friend who has a doctorate in nuclear physics (and two 
others who hold advanced degrees, one doctorate and one masters), and 
after he stopped laughing, I'm sure he'd be more than happy to give you 
all the nitty-gritty details about what is wrong about that statement. ;)

Jim

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Le 2011/04/15 13:48, Orchid XP v8 a écrit :

>> Halflife is defined as "the time it takes for half of the original
>> amount to degrade". So, it takes 700 millions years for half of your
>> uranium's atoms to deckay, and thus, emit radiation. After 1400 millions
>> years, 75% of the original amount will have deckayed.
>> It apply to radioactive materials. It also apply to medication in your
>> body, and many other things.
>
> Are you saying there's some sort of relationship between the halflife of
> a substance and how much radiation it emits?
>

Not some sort of relation. Direct relation.
The rate of emission is directly proportional to the amount and invertly 
proportional to the halflife.

A substance that have a halflife of 1 year is 700 millions times more 
radioactive than uranium. Some radioactive materials have halflife of 
much less than a second, like about 1e-10s. This makes them 
extraordinary radioactive, but you can never accumulate more than a few 
femtograms of them at any given time...


Alain

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On Fri, 15 Apr 2011 18:04:24 +0100, Orchid XP v8 wrote:

>> http://www.scientificamerican.com/article.cfm?id=electric-cars-cost-
per-charge
>>
>> How come I do your googling for you?
> 
> And now we have to sit down and figure out who funded them to publish
> that, where they got their data from, what methods they actually used,
> etc. It's not as simple as "it's true, because this random website says
> so".

Scientific American is a reputable journal, not "some random website".

Jim

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On Fri, 15 Apr 2011 18:05:09 +0100, Orchid XP v8 wrote:

> On 15/04/2011 05:01 PM, Jim Henderson wrote:
>> On Fri, 15 Apr 2011 10:21:37 +0100, Invisible wrote:
>>
>>> Wind power is great. But... do you really want the whole country to go
>>> black every time the wind stops blowing? Similarly, solar power. You
>>> realise that the sun is below the horizon for hours at a time, right?
>>> And some days, it's just not very sunny. For either of these things to
>>> work, you seriously need high-efficiency power storage, so you can
>>> collect power when it's there, and store it for when it's not.
>>
>> And most solar collection and all wind powered systems I've seen
>> actually include that storage subsystem.
> 
> Last time I heard, storing electricity efficiently is an unsolved
> problem.
> 
> (Apparently current battery solutions aren't very efficient.)

And yet they're in common usage and working fairly well.  How about that?

Just because it's not 100% efficient doesn't mean you can't do it.

Jim

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On Fri, 15 Apr 2011 18:06:45 +0100, Orchid XP v8 wrote:

> On 15/04/2011 05:06 PM, Jim Henderson wrote:
> 
>> Where it becomes problematic is when they say "I don't need to know how
>> this works, as long as someone else does and it works" and then argue
>> with the science of how it works with no understanding of it.
> 
> FULL CIRCLE!

Indeed, but those who use that kind of logic don't even realise they're 
doing it.

Jim

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On 4/15/2011 10:00, Orchid XP v8 wrote:
> If it's so simple and easy, why isn't everyone doing it?

Hey, 3GHz 4-core processors only cost like $200. Why didn't we have those 
back in the original PC?

>> That's a very low level of radiation.
>
> How do you work that one out?

Put it this way. You have a chemical that will react and release enough 
energy to boil 10 gallons of water. If you spend 20 minutes reacting it to 
boil ten gallons of water, is that safer or more dangerous than releasing it 
all in three milliseconds?  Would you rather be standing next to an 
automobile that's idling or an automobile where the gas tank is exploding? 
It's the same amount of total energy.

The longer the half life, the less radiation is being emitted per pound of 
material. That just falls out of the definition of half life.

-- 
Darren New, San Diego CA, USA (PST)
   "Coding without comments is like
    driving without turn signals."

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