TEPSS—Technology enhancement for passive safety systems

The objective of the technology enhancement for passive safety systems (TEPSS) project TEPSS Final Report, INNO-TEPSS(99)-D21 (1999)) was to make significant additions to the technology base of the European simplified boiling water reactor (ESBWR). The project focused on mixing and stratification phenomena in large water pools, passive decay heat removal from containments, and effects of aerosol deposition inside a passive heat exchanger. The Paul Scherrer Institut (PSI) experimental facility—large-scale investigation of natural circulation and mixing—has been used to investigate venting of steam and steam/non-condensable gas mixtures into water pools. The test revealed that no significant steam bypass could be detected when injecting a mixture of steam or air and that mixing was very efficient. In addition to the tests, 3-D numerical computations and initial model development have been performed to study the behaviour of bubble plumes in water pools. The major part of the TEPSS project studied selective aspects of the response technology of modern pressure-suppression-type containment designs and of passive-type decay heat removal systems. The work included an experimental phase using the large-scale experimental facility—Passive Nachwarmeabbfuhr und DruckAbbau (PANDA), operated by PSI, where eight experiments successfully have been executed to test the performance of the ESBWR containment configuration. The PANDA tests have been analysed successfully using thermal-hydraulic system analysis codes and 3-D CFD codes. The aerosol impaction and depositionʹ analysis experimental facility of PSI has been used to investigate the degradation of passive decay heat removal due to fission product aerosols deposited on the inside surfaces of the passive containment cooler (PCC) heat exchanger tubes. One test performed revealed that the degradation of the heat transfer in the PCC tubes due to the deposition of aerosols reached about 20%. The test has been analysed using the MELCOR severe accident analysis code