DEVELOPMENT OF TECHNIQUES FOR JOINING FUEL ROD SIMULATORS TO TEST ASSEMBLIES

摘要

We have developed a unique tubular electrode carrier for gas tungsten-arc welding small-diameter nuclear fuel rod simulators to the tubesheet of a test assembly. Both the close-packed geometry of the array of simulators and the extension of coaxial electrical conductors from each simulator hindered access to the weld joint. Consequently, a conventional gas tungsten-arc torch could not be used. Two seven-rod assemblies that were mockups of the simulator-totubesheet joint area were welded and successfully tested. Testing consisted of thermal cycling 500 times from 370°C (698°F) down to 100°C (212°F) with an internal pressure of 11.72 MPa (1700 psi). No leakage was detected by helium mass spectrometry, either before or after testing.