Specific Risk = 1 – (1 – Total Risk)^{Years of Service}

 

This would mean that the specific risk that a nuclear reactor would experience a meltdown is:

1 – (1 – 0,000029)⁴⁰ = 0,001 or 0,1%

If this still sounds like an acceptable risk, then one should keep in mind that there’s not one, but actually 150 nuclear power reactors in operation in Europe (2004). Of course you cannot just multiply the risk of one reactor experiencing a meltdown by 150. Instead, you have to calculate the risk in terms of service-years:

 

Specific Risk = 1 – (1 – Total Risk)^{Years of Service x Number of reactors}

This would mean that the specific risk that a nuclear meltdown in Europe within 40 years is:

1 – (1 – 0,000029)^{40 x 150} = 0,01597 or 16%

Now, one might say that not all reactors in Europe are as un-safe as the German ones with their “steel caskets”, the “high amount of zirconium in their core”, the “lacking heat removal by containment spray” and their “higher risk of hydrogen combustion” (all comments from the 1997 OECD report on severe accident management²), which is true. But then again, there’s a lot that are still less safe. The calculation above simply assumes that the German power plants represent the average power plant in Europe and while this might not be entirely correct and the actual cumulative risk might deviate by some percent points, the main message stays true: there is a significantly higher risk of a nuclear meltdown in Europe than the nuclear industry wants us to believe.

A risk of 0,1% is like rolling a 6 on a die with 1000 sides. If you have only one die, this might seem like a long shot, but when there are 150 dice, the chance of rolling a 6 on one of them seems a lot more probable – 16%. In fact, it’s the same probability as rolling a 6 on a regular, 6-sides die – or playing Russian roulette with a 6-barrel gun!

If you look at the chance of a nuclear meltdown worldwide (again assuming that German nuclear power plants represent the average risk type), just insert the total number of reactors (440 in 2004) into the above equation and you get a risk of 39.9%. With the nuclear meltdown in Chernobyl, this event has already taken place. The gun has gone off once already – let’s not risk finding out how many bullets are still left…

by Henrik Paulitz
German IPPNW

Sources:

1 GRS 1980: Deutsche Risikostudie Kernkraftwerke. Fachband 5. Untersuchung von Kernschmelzunfällen. (German Risk Study of Nuclear Power Plants – Volume 5 – Examination of nuclear meltdowns). Study commissioned by the German Federal Ministry for Science and Technology. TÜV Rheinland, 1980.

2 OECD 1997: Level 2 PSA methodology and severe accident management. Prepared by the CNRA Working Group on Inspection Practices (WGIP). Organisation for Economic Co-operation and Development. Paris. Unclassified. OCDE/GD(97)198.