Table 5.

Summary of risk calculation using the first-order reliability method

Best estimateStandard deviation.CriticalU
LinearExponentialLinearExponentialLinear*ExponentialLinearExponential
Thermal conductivity dry (W m−1 °C−1)0.260.300.020.020.2560.263−0.15−1.81
Thermal conductivity wet (W m−1 °C−1)0.961.100.120.120.7150.915−1.99−1.48
Reliability index (β)2.02.34
Probability of failure
P* = Φ(−β)
0.0230.0097
  • U, Set of uncorrelated, standardized normal variables (see equation 4);

  • *A temperature of 150°C was reached after 2.91 years.

  • A temperature of 150°C was reached after 2.65 years.