Passive Advanced Light Water Reactor designs and the ALPHA program at the Paul Scherrer Institute

A number of passive Advanced Light Water Reactor designs have been proposed worldwide. The Paul Scherrer Institute has participated since 1991, via its ALPHA programs, together with a number of overseas and European partners, in several of these developments. The PANDA, LINX-2 and AIDA facilities were designed, constructed and extensively used to study containment cooling and aerosol retention aspects of passive Advanced Light Water Reactor designs. During the ALPHA-I phase of the program, the effort concentrated on the Simplified Boiling Water Reactor. Both, the boiling water reactor (ESBWR, SWR-1000) as well as the pressurized water reactor passive designs (in particular designs with double concrete containment, such as the European Passive Plant) are the focus of the current phase ALPHA-II. This second phase includes the TEPSS, IPSS and INCON projects conducted under the sponsorship of the European Commission. The paper describes briefly the PANDA and LINX-2 facilities, reviews the scope and accomplishments of the ALPHA project, and summarizes certain project findings to date. The emphasis here is on the long-term containment cooling aspects of the project.