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After seeing peoples' replies below, I did a little math. SoCal residential uses about 244 billion cf gas each year (ref and ref ) and let's assume that is what this inventory is used for. 244 billion cf gas = 20.2 billion pounds (using 12.076 cf per pound of standard gas ref).

So according to the article, 150 million pounds have been leaked, or 0.7% of the above annual usage.

If the rate of 110,000 pounds per hour continues for 2 months, making some assumptions from the article, then 158 million pounds more will leak, or another 0.8% of the stockpile.

Why can't anyone put it in terms like this for people to better visualize the issue...

All right here it is in SI with some rounding
http://www.uigi.com/UIGI_SI.PDF [uigi.com]

This tells you how much energy it takes to cool air from different states.
So lets take air at Death Valley. Right now it's about 21 C and 20% Humidity.
Looking on the chart you have:
Enthalpy 28.5 kJ/kg
Dew Point -2 C
1 kg of air you have 3 g of water

Take Orlando. Right now 27 C and 50% Humidity.
Looking on the chart you have:
Enthalpy 56 kJ/kg of air
Dew Point 16 C
1 kg of air you have 11 g of water

So the air in Orlando contains 3 times as much water per kg of air.
The energy required to cool it is 2 times as much per lb
You only have to cool 50% of the temperature difference (21 C-(-2 C)) = 23 C vs (27 C-16 C) = 11 C.

Now lets say you want to get 1000 liters = 1000 kg of water out of the air. Assume you will be able to reduce both to a humidity ratio of 1.5 g/kg

For Death Valley you will get 1.5 g/kg of air so you need to cool 6.7 x 10^5 kg of air.
Look on the chart for the before and after enthalpy and you get (28.5-(-6)) kJ/kg = 34.5 kJ/kg
You need about 2.3x10^6 kJ to make 1000 liters.
To make this in a day you need a power of 266 kW.

For Orlando you will get 9.5 g/kg of air so you need to cool 1.1 x 10^5 kg of air
Look on the chart for the before and after enthalpy and you get (56-(-6)) kJ/kg = 62 kJ/kg
You need about 6.5x10^6 kJ to make 1000 liters.
To make this in a day you need a power of 75 kW

Again you can get big efficiency gains from using the now -10 C air to prechill the incoming air so the actual power required will be less.

Here's an SI version.
http://www.uigi.com/UIGI_SI.PDF

A grain is .06 grams.

There goes my mods for the discussion. Anyway: See http://www.uigi.com/MSDS_gaseous_CO2.html (no explanation but a confirmation of the statement). See also http://www.sae.org/misc/aaf99/visteon.pdf for a report on what happens when a CO2-fueled cooling system leaks its contents into your car.

What I know is that when you inhale CO2 the acidity of your blood will increase. At a certain point your blood will be to acidic to sustain life. This is what happens when, for instance, you have a heart problem and your body starts to "compensate". I put that in quotes because the way it compensates keeps you alive for a bit longer but kills you in the long run and leads to a lot of damage to organs, especially the heart. But I digress.

The rising of the acidity in your blood (lower Ph) is also cited as an important cause for its lethality in a report from the Dutch ministry for public health and the environment, http://www.rivm.nl/milieuportaal/images/20091002_Evaluation_toxicity_CO2.pdf, that writes:

"It is generally believed that CO2 toxicity is caused by displacing oxygen, leading to asphyxiation, similar to the mode of action as inert gases. This is only partly true. The inhalation of high concentrations of CO2 can lower the pH of the blood and thus trigger effects on the respiratory, cardiovascular and central nervous systems (HSE, 2007)".

I'm wondering why they can't pump liquid nitrogen in there to cool it down. Didn't they do that at Chernobyl?

Water has a specific heat of 4.187 kJ/kgK and a heat of vaporization of 2,270 kJ/kg.

Liquid nitrogen has a specific heat of 2.042 kJ/kgK and a heat of vaporization of 199.1 kJ/kgK, and a specific heat of 1.04 kJ/kgK when gas.

So putting in 1 kg of water at 20 C and extracting it as steam at 100 C removes (4.187)*80 + 2270 = 2605 kJ of heat energy from the reactor.

Putting in 1 kg of liquid nitrogen at -200 C and extracting it at 100 C removes (2.042)*4 + 199.1 + (1.04)*296 = 515 kJ of heat energy from the reactor.

Per kg, water removes over 5x more heat energy than liquid nitrogen. The only reason to use liquid nitrogen is if you wanted to drop the temperature below the boiling point of water. AFAIK radioactive decay is not influenced by temperature, so there would be no benefit to doing that here.

If I had to guess, the Soviets had to encase an active pile in-situ with concrete. Concrete tends to be very temperature-sensitive when curing - too hot and it'll crack. So they probably used liquid nitrogen to drop the temperature to where the concrete which initially contacted the pile could cure without cracking.

"Surely it is conceivable to cool liquid nitrogen down a little below it's boiling point."

Well, yes, in theory you can do that. I haven't read up on my cryogenics, but the trick is to exchange heat efficiently in order to lower the temperature of the liquid nitrogen. One way to do that is to use an even colder medium and a heat exchanger, which is kind of futile, since the colder medium can be used directly. The other method is to use compressible phase-changing gases, such as found in refrigirators. At this moment I cannot think of a reason why that is impractical. Perhaps there is a lack of suitable elements/gases..

This website http://www.uigi.com/nitrogen.html, however, gives a very good reason:
"When liquid nitrogen is vaporized and warmed to ambient temperature, it absorbs a large quantity of heat. The combination of inertness and its intensely cold initial state makes liquid nitrogen an ideal coolant for certain applications such as food freezing."

So the energy/heat required for the phase change of nitrogen from liquid to gas is quite a respectable one, making operating with liquid nitrogen at that temperature (i.e. the b.p.) a preferable one.

I do know, however, that with special techniques, it is possible to cool liquid helium a little further towards the zero Kelvin point. This is used, for example, in MRI scanners to minimize the boiloff of helium. I believe they have now acheived zero (!) boiloff.

B.

  I should mention that just outside of town the local gas company has a tower where they compress air to extract oxygen, nitrogen, and argon for commercial sale.

The compression part of an air separation plant just provides the push to force the intake air through the whole process - the extraction is done cryogenically. In other words, the atmospheric air is cooled through heat exchangers to become a liquid where distillation can occur.

what you'd be giving up is the mostly unused nitrogen, which makes up about 78% of the atmosphere down here on Earth

http://www.uigi.com/nitrogen.html

Certainly, our bodies can do without breathing nitrogen for a while. Deep divers sometimes use breathing gases like heliox with little or no nitrogen (as it can cause the nitrogen narcosis and the bends.)

what you'd be giving up is the mostly unused nitrogen, which makes up about 78% of the atmosphere down here on Earth

http://www.uigi.com/nitrogen.html

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At low concentrations, the gas is odorless. At higher concentrations it has a sharp, acidic odor. It will act as an asphyxiant and an irritant.

Carbon Dioxide is a powerful cerebral dilator. At concentrations between 2 and 10%, Carbon Dioxide can cause nausea, dizziness, headache, mental confusion, increased blood pressure and respiratory rate. Above 8% nausea and vomiting appear. Above 10%, suffocation and death can occur within minutes. [source]