Objective
To obtain experimental data on the formation of molten fuel pools, on the quenching of fuel jets in the reactor coolant and on the interaction of molten reactor fuel for geometries and conditions simulating in-vessel and ex-vessel severe accident situations. These data obtained from the FARO facility, which uses real reactor materials at relatively large scale (up to 150 kg of molten fuel) are then used to improve and validate the analytical models applied for safety evaluation. The facility can be adapted to LMFBR and LWR severe accident studies.
Progress to end 1990
During 1990 in the FARO test facility two experiments of the BLOKKER II test series have been performed. In these tests the melt penetration and freezing in rectangular cavities (simulating LMFBR inter-subassembly gaps) were investigated at 400 and 900C initial structure temperatures.
The limited number of tests in 1990 was due to the preparation of the facility for its new utilization in the field of LWR safety, which was recommended by the Member States and discussed also with non EC organizations (USNRC, EPRI, PSI-CH). Necessary modifications of the plant have been studied and designed and new main components ordered. This includes also the order of a new MF (medium frequency) furnace for the melting of about 200 Kg stainless steel, zirconium and oxide mixture to produce LWR corium for future interaction experiments.
A first scoping test using the existing TERMOS test section and a fuel mass of 50 Kg mixed oxides has been prepared. Various back-up tests on electrical heating of UO2/ZrO2 mixtures and on fuel jet break-up have been performed.
The implementation of a new version of the computer code TEXAS, developed by Prof. Corradini (University of Wisconsin) for the description of the molten fuel/coolant interaction in the FARO-LWR configurations has been achieved. Several test scenarios have been precalculated. Preliminary thermohydraulic calculations using the computer codes RELAP5-EUR and SAFIRE for FARO-LWR vent sizing have been performed. In addition, the FARO-BLOKKER II tests have been interpreted with the new version of the CEA code BUCOGEL.
In September 1990 a Technical Exchange Arrangement between US-NRC and STI-JRC has been signed: this arrangement foresees cooperation in the field of severe accident analysis and in particular for the execution of at least five FARO tests in the next three years.
The test programme for LWR severe accidents in FARO is also extensively discussed with the experts of EC Member States.
Detailed description of work foreseen in 1991 (expected results)
1. Execution of the "scoping test" with 50 Kg of melt (TERMOS configuration).
2. Preparation of the FARO facility for the LWR test programme: assembly, installation of new components (e.g. modified TERMOS test section, condenser) and instrumentation.
3. Preparation and execution of a first experiment with larger fuel mass in water at 50 bars initial (system) pressure in the modified TERMOS test section.
4. FARO test interpretation using the already developed computer codes will be continued. Safety analysis assessments for the FARO-LWR project including thermal explosion effects, will be performed and also the execution of numerous pre-test calculations and post-test interpretations.
Short description of evolution of work in 1992
Continuation of the experimental and analytical programme on LWR Severe Accident Research in collaboration with USNRC and EPRI and with EC partners.
Topic(s)
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21020 Ispra
Italy