Sunday, October 25, 2020

Is San Onofre's plan to inspect the dry cask nuclear waste storage sufficient? NO! 


Is long-term dry-cask storage of nuclear waste in a salty environment safe? Probably not!

According to San Onofre's PR department, only 1 in 8 canisters will be randomly inspected for cracking -- about 12.5% of the total.

But how much of each canister will actually be inspected? Let's do some simple math:

San Onofre's 3D camera system (see photo) supposedly can see scratches down to 1/1,000th of an inch.

But that requires only being able to "see" only a small portion at one time.

The surface area of a dry cask is approximately 50,809 square inches (352.85 square feet). The bottom (about 26.5 square feet) of which is unavailable for inspecting with the current system (possibly the most important area since the entire weight of the cask rests on about 6 small metal plates underneath the cask).

If the inspection system can view one entire square inch in one second (humanly impossible in this author's opinion!) it would take approximately 47,000 seconds (~13 hours) to inspect one canister (not including the bottom at all). This would include zero overlap as the equipment moves up and down.

In any case, cracks can also form from the inside, which cannot be inspected at all. A crack forming from the inside could go completely around the canister and be 99.999% of the way through the thin (5/8ths inch) wall of the canister, and still would not be visible at all.

When lifting a canister out of the hole (perhaps 100 to 300 years from now) a circular crack would not need to be nearly that well formed to cause the canister to crack as it is being lifted, immediately releasing enormous amounts of radioactivity to the workers and the environment. Canisters are designed to be lifted from hooks at the top, such that the entire weight of the canister is supported by a couple of hooks at the top. The bottom of the canister and the sides support almost the entire weight since the contents rest on the bottom of the canister.

In this author's opinion, there is nothing safe about the inspection system or the eventual plan to lift and remove the canisters for transport to a permanent repository or secondary temporary repository, or to a reprocessing facility.

Ace Hoffman
Carlsbad, CA


Typical dry cask dimensions at SanO:
 69.75 inches wide and 197.0 inches in length.

area of a "right cylinder" (assumes square edges):
Calculated on Google:
((2 * (3.14159 * (69.75 / 2)) * 197) + (2 * 3.14159 * ((69.75 / 2) ^2))) = ~50809.82 square inches (about 352.85 square feet).
Calculated from:

radius r = 34.875 in
height h = 197 in
volume V = 752739.197 in3
lateral surface area L = 43167.8393 in2
top surface area T = 3821.01115 in2
base surface area B = 3821.01115 in2
total surface area A = 50809.8616 in2


"The 3-D camera system can see scratches down to one-thousandth of an inch, and has been able to document scratches that are about 26/1000 of an inch on canisters, Morris and Howell said. If those are the deepest scratches, they are well within tolerance, they said.

"Scratches are no more than the thickness of a credit card, said Edison’s Tom Palmisano at the San Onofre Community Engagement Panel meeting Thursday, March 28. The oxide layer on the exterior of the canisters reforms quickly, he said, so there’s no risk from corrosion in the short or long term."

"Stress corrosion cracking is an insidious form of corrosion since an applied stress and a corrosive environment can work together and cause complete failure of a component, when neither the stress nor the environment would be a problem on their own. The stress level may be very low, possibly only residual, and the corrosion may be initiated at a microscopic crack tip that does not repassivate rapidly. Incremental crack growth may then occur, resulting in fracture of the implant. Industrial uses of stainless steels in saline environments have shown susceptibility to stress corrosion cracking and therefore it is a potential source of failure for implanted devices."


"Deliquescence of these salts in a humid environment could create a chloride-rich brine on the canister surface. This, in addition to the presence of residual tensile stresses, could make the canister susceptible to chloride-induced stress corrosion cracking. "



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