Local failures are defined here as those which cause local damage within a fuel assembly. The subject deals with the failure of individual fuel pins and the possible propagation of this failure from pin to pin and the sub­sequent possible failure propagation from assembly to assembly.

Section 3.1.1 dealt with fuel failure criteria arising from conditions within a fuel pin at the moment of failure, in particular for the case of fuel under­going a power transient. It also dealt with changes of fuel configuration within the pin during burn-up.

This section is concerned primarily with conditions following failure, especially with how neighboring pins might be affected.