ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

Year 1995

• 1Heat and Mass Transfer in Severe Nuclear Reactor Accidents Proceedings of International Symposium - 22 -26 May, 1995, Kusadasi, Turkey

708 pages

Volume price - $176.00

J. Bestele
Gesellschaft fur Anlagen und Reaktorsicherheit (GRS) mbH Forschungsgelande, D-85748 Garching

K. Trambauer
Gesellschaft fur Anlagen und Reaktorsicherheit (GRS) mbH Forschungsgelande, D-85748 Garching

The Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) mbH is developing in cooperation with the Institut fur Kernenergetik und Energiesysteme (IKE) of the University of Stuttgart the system code ATHLET—CD (Analysis of Thermalhydraulics of Leaks and Transients with Core Degradation) with financial support of the Federal Ministry of Education, Science, Research and Technology. The code consists of detailed models for the thermalhydraulics of the reactor coolant system. It is based on a lumped parameter approach for the five equation system of the two phase flow with drift-flux model. This thermofluiddynamics module is coupled with modules describing the early phase of the core degradation, like cladding deformation, oxidation and melt relocation, and the release and transport of fission products. The validation of the code is being done by the analysis of separate effect tests, integral tests and plant events. The code will be applied to the verification of accident management procedures.
The test LOFT-FP-2 was conducted under the auspices of the Organization for Economic Cooperation and Development (OECD) at the Loss-of-Fluid-Test (LOFT) facility, a 1 : 50 volumetrically scaled pressurized water test reactor, of the Idaho National Engineering Laboratory(INEL) on July 9,1985. The objective of the test was the examination of fission product release and transport during a small break loss of coolant accident (LOCA). The temperature in a specially designed fuel element in the center of the nuclear core exceeded 2100 K for several minutes.
The high temperature caused the degradation of the fuel element and the release of fission products and aerosols. The test was terminated by flooding the reactor pressure vessel (RPV) with water. At the beginning of the flooding phase the temperature in the core increased again due to the exothermal metal—water—reaction of the rod cladding and caused further damage of the core with extensive hydrogen generation and fission product release.
The test was calculated from reactor scram until the end of the quenching of the hot core with the system code ATHLET—CD in order to validate the code for reactor case. All important phenomena which occurred during the transient, like loss of coolant, core uncovery, heat-up and degradation, release and transport of fission products and aerosols and the final flooding were calculated well. The approach of coupling the modules which describe core degradation, fission product release and transport with the modules which describe thermalhydraulics and neutron kinetics turned out to be successful.

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