PROBABILISTIC EVALUATION OF TURBINE MISSILE DAMAGE POTENTIAL.

The generation and consequences of turbine missiles have been getting considerable attention recently in the nuclear industry. The fracture mechanism of the turbine wheel and the physical processes of those missiles damaging safety-related structures are extremely complicated in a deterministic sense. In this paper, an overall evaluation of the turbine missile problem is made. The complexities in separating high and low trajectory missiles and the damage potential associated with them when applied to a real nuclear power plant is discussed in detail with the help of examples. A detailed discussion is made on the parameters commonly known in the industry as P//1, P//2, P//3, and P//4. A statistical evaluation of the parameter P//1 is made. Some of the important aspects that need to be considered in the calculation of P//2 are considered. Moreover, the damage criteria, namely, spallation or back face scabbing, penetration, and perforation and the influence of using different equations (NDRC, BRL, etc. ) with their associated variabilities in the calculation of P//3 are discussed. Finally, a probabilistic methodology is developed for the calculation of the P//4-value considering high speed and normal speed failure, and the number and the locations of the wheels in an LP turbine unit, for the whole power plant.