Progress in Hardware Development for the SAFE Heatpipe Reactor System

摘要

Advanced Methods & Materials Company (AMM) previously fabricated the stainless steel modules for the SAFE 30 system. These earlier modules consisting of five fuel pins surrounding a heat pipe, were brazed together using a tricusp insert in the gaps between tubes to ensure maximum braze coverage. It was decided that if possible the next generations of modules, both stainless steel and refractory alloy, would be diffusion bonded together using a Hot Issostatic Pressing (HIP) process. This process was very successfully used in producing the bonded rhenium Nb-lZr fuel cladding and the heat exchanger for the SP-100 Nuclear Space System Ref 1& 2. In addition AMM have since refined the technology enabling them to produce very high temperature rocket thrust chambers. Despite this background the complex geometry required for the SAFE module was quite challenging. It was necessary to develop a method which could be applied for both stainless steel and refractory alloy systems. In addition the interstices between tubes had to be completely filled with the tricusp insert to avoid causing distortion of the tube shape during HIPing and provide thermal conductivity from the fuel tubes to the heat pipes. Nevertheless it was considered worth the effort since Hot Isostatic Pressing, if successful, will produce an assembly with the heat pipe completely embedded within the module such that the diffusion bonded assembly has the thermal conduction and strength equivalent to a solid structure.