Service life extension and safety enhancement of ship reactors

Abstract

The results of operation and the present state of the nuclear icebreaker fleet are presented. The fundamentals of service life extension of reactors on nuclear icebreakers are presented. The complex of research and development work performed on equipment and systems to secure reliability during the extension period is described. The main measures taken to increase the nuclear and radiation safety of nuclear icebreakers are shown and the economic impact of the work performed is evaluated. The nuclear icebreaker fleet plays a fundamental role in keeping the Northern Sea Route open. At present, this fleet contains four two-reactor open-sea nuclear icebreakers (Rossiya, Sovetskii Soyuz, Yamal, 50 Let Pobedy) and two singlereactor ships with limited draft (Taimyr, Vaigach). The reactor plants on the nuclear icebreakers Arktika, Rossiya, Taimyr, and Vaigach exhausted their surface life by 2006 (Table 1). One nuclear icebreaker was commissioned recently -50 Let Pobedy; additional ships are to be added to the fleet in 2017 at the earliest. For this reason, service life extension of nuclear icebreakers, first and foremost that of a reactor plant, the main irreplaceable part of a ship, is a necessary condition for keeping the Northern Sea Route open [1].The reactor plants on ships possess specific design features and unlike stationary plants operate under intense external forces. For this reason a complex of novel technologies for performing research and maintenance work is being implemented in order to extend the service life and increase the safety of nuclear icebreakers. Service Life Extension and Safety Enhanvement of Nuclear Icebreakers with Water Moderated and Cooled Reactors.A procedure for service life extension has been developed taking account of the requirements of regulatory legislation and normative government regulatory documents regulating safety in the use of atomic energy and taking account of the advances made in the mechanics of deformation and fracture of structural materials. The reactor plant on a nuclear icebreaker is characterized by smaller size and higher dynamical characteristics than stationary plants. As a result of these features, the reactor vessel and in-vessel facilities are exposed to higher levels of radiation and in the course of operation the equipment and pipelines are subjected to intense nonstationary thermomechanical and vibrational loads. Under such conditions, damage accumulates and develops in the structural materials. Most of this damage is hidden and located in equipment elements which are not accessible for diagnostics. The external form of the steam-generating block of a ship reactor plant is presented in Fig. 1. For this reason, the following were developed for service life extension: means for complex examination and diagnostics of the technical state of equipment and systems, physical-mathematical models, methods and computer programs for computational analysis of the processes leading to the degradation of the structural materials of equipment, methods for experimental-th...