Publications
Failures and Implications of Heat Pipe Systems
Under Department of Energy (DOE), Office of Nuclear Energy (NE), Gateway for Accelerated Innovation in Nuclear (GAIN), Sandia National Laboratories (SNL) was awarded DOE-NE GAIN voucher GA-19SN020107, "Risk-informed mechanistic source term calculations for a sodium fast reactor." Under this GAIN voucher, SNL supported the industry partners development in preparation for licensing and commercialization by providing subject matter expertise on heat pipe technologies, providing computer code training and support, and perform first-of-a-kind experiments demonstrating the safety/risk impacts of heat pipe breach failures. The experiments that were performed had two primary goals: measure the peak heat fluxes that lead to heat pipe dry out and subsequent wall breach; and observe the consequences that result from catastrophic failure of a heat pipe wall. Intentional breaching of the heat pipe walls took advantage of heat pipe physics and operating limits. Large and nearly instantaneous heat fluxes were applied to the heat pipe to first cause localized dry out at the evaporator section which then leads to melting of the heat pipe wall. The hour glass heat pipe (Test 1) experienced dry out at 112 W/cm 2 and after 45 seconds, wall temperatures measure about 1,280degC and intentional failure of the heat pipe wall was achieved. The cylindrical heat pipe (Test 2) experienced dry out at 125 W/cm 2 and after 65 seconds, wall temperatures exceeded 1,400degC and intentional failure of the heat pipe wall was achieved. Both experiments characterize the parameters needed to lead to heat pipe wall failure. Furthermore, the failure of the heat pipes characterizes the safety/risk impacts from sodium-oxygen reactions that occur following the intentional failure. There were two major conclusions of these intentional failure tests: the heat pipes were able to continue operating beyond expected performance limits, and the failure behavior validated decades of operational experience. ii ACKNOWLEDGEMENTS First and foremost, many thanks to Daniel Ray (SNL, Dept. 8823) for the design and construction of the heat pipes, sodium fill operations, test apparatus, and many other experimental troubleshooting issues that arose over the course of this project. These experiments would not have been possible without the valuable efforts of Daniel. Second, thanks to Josh Christian and Benson Tso (both SNL, Dept. 8823) for the consultations and operation of the solar furnace. Third, thanks to Byron Demothenous and Anthony Tanbakuchi (both SNL, Dept. 1535) for the photometric setup. Also, thanks to Julius Yellowhair (SNL, Dept. 8823) for the processing, clipping, and presentation of the videos collected for these experiments. Fourth, thank you to current and separated SNL staff members that supported this project every step of the way. This includes Chuck Andraka, Matthew Denman, and Zachary Jankovsky. Additionally, thank you to the reviewers of this report. Last, and certainly not least, SNL would like to thank the DOE-NE GAIN for the support of this work under work-package GA-1951\1020107. Simply put, none of this work would be possible without their support. iii