SESAR Group: Thermal Hydraulics Outcomes

The present report deals with the perspectives in nuclear thermal hydraulics envisaged by a Senior Group of Experts (SESAR) of the Committee on the Safety of Nuclear Installations (CSNI) of the Nuclear Energy Agency (NEA) of Organization for Economic Cooperation and Development (OECD). Around each dozen years a SESAR is convened inviting specialists of member Countries in different areas of nuclear reactor safety and design. The main conclusions derived by the group in relation to thermal hydraulics in 2019 (the final report is not yet published at the time of writing this paper) are discussed in the present paper. Among the phenomena in relation to which additional research investigations are recommended, one may note reflood, and in particular the heat transfer situations where radiation heat transfer is relevant, natural circulation and sub-cooled nucleate boiling in the conditions of fast local power excursions; emphasis is given to the need to reduce the error in predicting pressure drops at geometric discontinuity. Furthermore, the importance of connecting the thermal hydraulics with the nuclear fuel material science is stressed, namely focusing on the conditions of high burn-up. In relation to experimental programs and facilities in the area, it is recommended that NEA/CSNI makes proper effort to keep the operability of PKL (full height, 1/100 volume scaling, four loops, 4 MPa maximum operating pressure) installed in Germany, PANDA (suitable for coupled Reactor Coolant Systems – Containment research) installed in Switzerland and LSTF (full height, 1/50 volume scaling, two loops, full pressure) installed in Japan.