Thread by @james_acton32

Let's do math on the Taishan fuel leak!

Chinese authorities estimate that around five fuel rods have leaked, but basically says this is unremarkable. No biggie.

But, actually, this many rods leaking is very unusual. Let's work out how unusual. (1/n)

world-nuclear-news.org/Articles/Fuel-…

China's nuclear regulator, NNSA (NOT the same organization as @NNSANews), says the reactor contains more than 60,000 fuel rods. Based on the following IAEA doc, I believe the exact number is 63,865. (241 assemblies, each containing 265 rods). (2/n)

aris.iaea.org/PDF/EPR.pdf

Now, the @W_Nuclear_News article linked above cites the @iaeaorg as saying that there are ~14 leaks per 1,000,000 rods. (3/n)

So, using the binomial distribution, we can estimate that the probability of at least five rods leaking is just 0.2%.

In fact, given that not all of the fuel may have fully irradiated, this is just an upper bound. The real number is probably much smaller. (4/n)

In other words, there's *at most* a 0.2% probability that five rods would leak by chance. Which means that there's very likely some kind of common mode failure at play. (5/n)

What that failure is, I have no idea... Could be to do with fuel design, manufacture or handling, or with reactor operation. China's opacity is weak evidence (and only weak evidence, IMO) that it's more likely to do with handling or operations, than design or manufacture. (6/n)

But the big point is this: Given the leakage is almost certainly the result of some kind of abnormal event, it's incredibly important to understand it--both for reactor safety in China and elsewhere. China's opacity is very worrying from that perspective. (7/n)

To be clear, though, I very much doubt that there has been or will be a serious accident.

Now, back to my day job. Was there some kind of a summit going on today? (8/8)