OTHER ACHIEVEMENTS

In addition to the main project activities outlined above, several scientific achievements that helped better understanding of system behavior and containment phenomena also took place. These include:

ALPHA staff members have made significant contributions to the understanding of the modes of passive operation of the SBWR. Contributions include, for example, detailed mod-eling of the condensation of steam in the presence of non-condensables in the PCCS units used to remove the decay heat from the containment [21].

An example of sophisticated but small-scale experiments and analytical modelling are the study of plumes in small-scale water pools (LINX-1) [8,9] and of two-phase flows of mixtures of air and steam bubbles in water (LINX-1.5) [10].

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Development and testing of instrumentation has also taken place, triggered by the needs of the PANDA and LINX experiments (e.g., floating thermocouples for water surface tempera-ture measurement, testing of non-condensable fraction sensors [23], etc.).

8. CONCLUSIONS

In several countries, there is a general move towards the introduction of more passive systems for emergency core cooling and containment decay heat removal in future reactors. In the US, this trend has materialized with the certification effort related to the AP-600 and the SBWR. In Europe, certain recent concepts for new BWRs and PWRs also include long-term passive decay heat removal systems. In Japan, Canada, and other countries there is interest in adding such passive systems to either existing reactor designs or to new ones. The ALPHA project is situated in this international framework. Its long-term objectives are to contribute at the forefront of this research area worldwide, but in Europe in particular.

As stated, future reactor systems are likely to include some form of passive containment cooling systems. Although the designs of such systems may vary from one reactor concept to another, there is a need to provide basic scientific understanding of their performance under fairly large-scale prototypical conditions. The PANDA and LINX-2 facilities provide the ideal environment for long-term international collaboration in this area. For example, the LINX-2 facility will be used in the near future to test, in collaboration with the Italian ENEL, the design of an advanced PWR containment building condenser.

Although the present PANDA experiments constituted initially "confirmatory" research, the data that they will deliver has now become an essential part of the "certification" process for the SBWR.

ACKNOWLEDGMENTS

All the members of the ALPHA team in the Thermal-Hydraulics Laboratory and of the ABDA team at the Safety and Accident Research Laboratory have contributed to the progress of the ALPHA project and, therefore, indirectly to this article. Their particular contributions are too numerous to mention here but are gratefully acknowledged by the authors.

The ALPHA project receives financial support from the Nuclear Power Committee of the Swiss Utilities (UAK), the (former) Swiss National Energy Research Foundation (NEFF) and the General Electric Company. Particular contributions from international collaborations are mentioned in the text.

The authors wish to acknowledge the Toshiba Corporation for permission to use data from the GIRAFFE facility.

REFERENCES

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[12] DURY T.V., "Pre-Test Thermal-Hydraulic Analysis in Support of the AIDA Testing Design Using the ASTEC Code", PSI internal report TM-42-94-10, ALPHA-409.

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[14] DREffiR J., "PANDA-Versuchsanlage; Pflichtenheft fur Messung, Steuerung und Regelung", PSI internal report TM-42-92-21, ALPHA- 217.

[15] YADIGAROGLU G., "Scaling of the SBWR Related Tests", GE Nuclear Energy report NEDC-32288 (July 1994).

[16] CODDINGTON P., "A Procedure for Calculating Two-Phase Plume Entrainment and Temperature Rise as Applied to LINX and the SBWR", PSI internal report TM-42-94-01, ALPHA-401.

[17] CODDINGTON P., "A Review of the SBWR PCCS Venting Phenomena", PSI internal report TM-42-94-02, ALPHA-402.

[18] ANDREANI M., "Study of the Horizontal Spreading of Rising Two-Phase Plumes and its Effects on Pool Mixing", PSI internal report TM-42-94-05, ALPHA-404.

[19] ZUBER N., (1991), "Hierarchical, Two-Tiered Scaling Analysis" Appendix D to "An Integrated Structure and Scaling Methodology for Severe Accident Technical Issue Resolution", Nuclear Regulatory Commission Report NUREG/CR-5809, EGG-2659 (November 1991).

[20] ISHII M. and KATAOKA I., (1983), "Similarity Analysis and Scaling Criteria for LWR's Under Single-Phase and Two-Phase Natural Circulation," NUREG/CR-3267 (ANL-83-32).

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[21] MEffiR M, "SBWR-PCCS Numerical Integration Programme and Test Results", PSI in ternal report TM-42-94-08, ALPHA-406.

[22] S. GUNTAY, G. VARADI, J. DREIER, "ALPHA- The Long-Term Passive Decay Heat Removal and Aerosol Retention Program", IAEA Advisery Group Meeting on the Technical Feasibility and Reliability of Passive Safety Systems, November 21-24,1994, Jiilich, Germany.

[23] LOMPERSKI S., "High Temperature and Pressure Humidity Measurement Using an Oxygen Sensor", PSI internal report TM-42-94-03, ALPHA-403.

PREDICTED PERFORMANCE AND ANALYSIS OF ADVANCED