NRC Statistician Comments on Nuclear Reactor Risk Assessment Models
I had a long chat with an NRC statistician to discuss their methods for estimating the probability of a reactor accident. He confirmed what I already knew: no existing statistical methods can accurately predict such events. Rather, their theoretical mathematical models only indicate which parameters, out of hundreds, have the most influence on net risk (sensitivity analysis); but the models do not supply accurate net estimates for the risk of a critical reactor incident.
Bottom line: nobody really knows the probability of a meltdown or major radiation release at Diablo Canyon.
Historical evidence (number of actual reactor failures) might suggest a probability somewhere between 1/100 and 1/500 during its term of operation.
Two revealing quotes:
Kaiser 2012, Empirical Risk Analysis of Severe Reactor Accidents.
time to the next accident among the world’s 441 reactors … is estimated to 11 years.
Raju 2014, Estimating the Risk of Nuclear Accidents
The existing record of accidents … [and] their probability distribution is sufficient to rule out the validity of the industry’s analyses at a very high confidence level.”
A database (Excel spreadsheet format) on all US reactors is here: http://www.globalnucleardata.org/