Topical study on IRS events involving foreign material intrusion in plant systems. First issue. Report of a consultants meeting. Working material

Recent exchange of operational safety experience among countries, within the framework of the IRS, revealed a noticeable increase in incidents involving foreign material intrusion (FMI) in nuclear power plant systems. These incidents appeared to have safety impact, sometimes widespread, on many systems and components, including the reactor core, control rods, the secondary side, and other support systems such as the electrical, air, and water systems. Notwithstanding the economic penalties and the operational problems that can arise from the FMI, many events indicated severe component damages, challenges to safety systems and to fuel integrity. Difficulties encountered with the removal of foreign material present further challenges due to the long term effects of such material remaining in the system and interacting with either fuel cladding, with the potential of releasing fission products in coolant systems, or with the system pressure boundary with the potential for material wear and sudden failure of the pressure boundary. The FMI topic was, therefore, one of a number of topics that was recommended by the TCM in 1996 for investigation. A consultant meeting was held at the IAEA during the period 14-18 April 1997 to address this topic. Figs