The present research program on irradiation embrittlement and annealing of reactor pressure vessel (RPV) steels in Switzerland is carried out at the Paul Scherrer Institute for Reactor Research. The particular program structure and its relation to the concept for an improved surveillance program is described.

Based on past experience with surveillance programs, especially for older plants, the main goal of the research program is determined by an effort to overcome identified shortcomings.Therefore the following topics are discussed: 1. Obtaining additional data to supplement those from specific surveillance capsules. 2. Understanding the mechanisms of irradiation embrittlement by microstructural investigations of the materials. 3. Investigations of the annealing-recovery behavior of irradiated RPV steels. 4. Validation efforts concerned with the transferability of test reactor and surveillance program results to the real RPV.

Within the framework of bilateral research agreements, participation in research programs coordinated by the International Atomic Energy Agency (IAEA), and collaborative research with other Swiss and foreign institutions, a review of past and future activities is presented; the technical facilities (irradiations, mechanical testing, physical methods) and the advanced and new tools used in the investigations, especially those for the microstructural studies, are outlined and put into perspective. Finally, first results obtained in the research program are summarized.