A One-Dimensional Thermal Model of a TOPAZ-II TFE
Abstract
The TOPAZ-II space nuclear reactor, Ya-21u, was tested as part of the Topaz International Program in Albuquerque, NM during the period August 93 to March 95. It was also tested in Russia prior to its arrival in the U.S. Thermal testing was carried out using tungsten electrical heaters (TISA heaters) to simulate the nuclear fuel. No nuclear testing has been carried out on this system. Details of the TOPAZ-II reactor are given by the U.S. TOPAZ-II Flight Safety Team (1992), Wold et. al. (1994) and Paramonov and El-Genk (1994). During the testing of Ya-21u, the reactor was subjected to a variety of extreme conditions, including a shake and vibration test, air leaks into the TFEs and thermal shocks. Details of U.S. testing of Ya-21u are given by Schmidt et. al. (1995). Over the duration of these tests the electrical output parameters of the reactor changed significantly, presumably as a result of changes to internal TFE parameters such as effective emissivity of the inter-electrode gap, emitter and collector work functions and gap dimensions. The individual TFE characteristics depend sensitively on these parameters and the final electrical output is the result of a delicate balance between a number of competing effects. In order to better understand the factors resulting in the output degradation it proved necessary to develop computer models of the various internal TFE processes. An additional need arose to determine the effect of changes in NaK coolant temperature, such as occurred when the reactor was run without the radiator thermal shield. The computer codes described in this report were developed to meet these needs. Their primary function is to model heat transfer and thermionic emission within a single TFE. The theoretical treatment is exclusively one dimensional. This limitation is not thought to be particularly important for our primary applications.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 13, 1995
- Accession Number
- ADA360083
Entities
People
- J. L. Ing
- P. Agnew