Dear RG Members,

Greetings.

ASME BPVC (nuclear code) uses the term 'Design lifetime' does it have a standard definition (Similarly section - VIII div-2 uses term useful life).

I want to understand it on 'day one' itself, so will not go in integrity assessment, in service inspection, NDT, RLA etc.

If during the design of a elevated temperature component, 1E5 Hours average creep rupture strength is used (in simplified way or say allowable stress - which is again based on different type of data from a 1E5 hours creep only) does it have a relation with 'design lifetime'? Is design lifetime is 1E5 hours. In general such components serve 20-30 years or even more.

One can further add fatigue , creep fatigue interaction, damage, fracture mechanics etc. and provide some numbers.

So the calculations carried out provide some numbers and a band of lifetime, with these how to tell conservatively the 'design lifetime'? Additionally how it will be defined to the user in physical terms? what will be the meaning of this time to designer? will the meaning vary from component to component? what if a crack appears on the component before the specified 'design lifetime'? etc.

I got some papers, you may find these useful:

1. https://www.sciencedirect.com/science/article/abs/pii/S0308016119303679

Article Quantification of conservatism in pressure vessel design sub...

2. https://unm.fr/wp-content/uploads/2022/10/862_FICHIER_0.pdf (page-16)

Advance wishes of Christmas and New year.

With regards

NC